By using ROS2 Lifecycle Nodes for each component of the Navigation stack, you
can ensure that the components start up and shut down in the correct order.
For example, **the map server and sensor topics need to be loaded before the
costmap and planner nodes.** With the ROS2 Lifecycle Node API, you can define
a lifecycle state machine for each component that includes the necessary
states for **starting up, shutting down, and transitioning between states** .
By defining the correct dependencies between the states of each node, you can
ensure that the Navigation stack components start up and shut down in the
correct order.


  * unconfigured
  * inactive
  * active
  * shutdown


_No plugins found._


  * Overview
  * 0  Assets
  * 7  Dependencies
  * 0  Tutorials
  * 0  Q & A


lifecycle_talker lifecycle_listener lifecycle_service_client


---

[
API Docs ](http://docs.ros.org/en/iron/p/lifecycle "View API documentation on
docs.ros.org") [
Browse Code ](https://github.com/ros2/demos/tree/iron/lifecycle "View source
code on repository")


#  The demo code


_See[ ROS Wiki Tutorials ](http://wiki.ros.org/lifecycle/Tutorials) for more
details. _


In order to trigger a transition, we call the ` change_state ` service


        }

        // We have an succesful answer. So let's print the current state.
        if (future_result.get()) {
          RCLCPP_INFO(
            get_logger(), "Node %s has current state %s.",
            lifecycle_node, future_result.get()->current_state.label.c_str());
          return future_result.get()->current_state.id;
        } else {
          RCLCPP_ERROR(
            get_logger(), "Failed to get current state for node %s", lifecycle_node);
          return lifecycle_msgs::msg::State::PRIMARY_STATE_UNKNOWN;
        }
      }

      bool
      change_state(std::uint8_t transition, std::chrono::seconds time_out = 3s)
      {
        auto request = std::make_shared<lifecycle_msgs::srv::ChangeState::Request>();
        request->transition.id = transition;

        if (!client_change_state_->wait_for_service(time_out)) {
          RCLCPP_ERROR(
            get_logger(),
            "Service %s is not available.",
            client_change_state_->get_service_name());
          return false;
        }

        auto future_result = client_change_state_->async_send_request(request);

        auto future_status = wait_for_result(future_result, time_out);

        if (future_status != std::future_status::ready) {
          RCLCPP_ERROR(
            get_logger(), "Server time out while getting current state for node %s", lifecycle_node);
          return false;
        }

        if (future_result.get()->success) {


###  Plugins


This service call takes a transition id. Only in the case, that this
transition ID is a valid transition of the current state, the transition is
fulfilled. All other cases are getting ignored.


_No message files found._


* Karsten Knese


Return either a primary or transition state.


At the same time, every lifecycle node has by default 5 different
communication interfaces.


CHANGELOG


An example of implementing the camera node using the Lifecycle interface is
provided, demonstrating how this interface provides greater control over the
state of the camera node and allows other components that depend on it to
watch its state and act accordingly. Overall, the use of the Lifecycle
interface in ROS2 can greatly simplify the management of software components
and improve the overall robustness and reliability of a ROS-based system.


Name  |  Repo  |  Deps  |  [ desktop ](/p/desktop/github-
ros2-variants#eloquent) |  [ github-ros2-variants ](/r/variants/github-
ros2-variants) |  [ ](/p/desktop/github-ros2-variants#eloquent-deps)
---|---|---

###  Launch files


This gives room for executing a custom error handling. Only (!) in the case
that this function returns ` CallbackReturn::SUCCESS ` , the state machine
transitions to the state ` unconfigured ` . By default, the ` on_error `
returns ` CallbackReturn::FAILURE ` and the state machine transitions into `
finalized ` .


[ API Docs ](http://docs.ros.org/en/bouncy/p/lifecycle "View API documentation
on docs.ros.org") [ Browse Code
](https://github.com/ros2/demos/tree/bouncy/lifecycle "View source code on
repository")


    [lc_talker] on_activate() is called.
    [lc_talker] Lifecycle publisher is active. Publishing: [Lifecycle HelloWorld #11]
    [lc_talker] Lifecycle publisher is active. Publishing: [Lifecycle HelloWorld #12]
    ...


Every child of LifecycleNodes have a set of callbacks provided. These
callbacks go along with the applied state machine attached to it. These
callbacks are:


  * Migrate std::bind calls to lambda expressions ( [ #659 ](https://github.com/ros2/demos/issues/659) )
  * Contributors: Felipe Gomes de Melo


In order to run this demo, we open three terminals and source our ROS2
environment variables either from the binary distributions or the workspace we
compiled from source.


In the following we assume that we are inside the namespace `
rclcpp_lifecycle::node_interfaces::LifecycleNodeInterface ` to shorten the
name of the return type. All these callbacks have a positive default return
value ( ` return CallbackReturn::SUCCESS ` ). This allows a lifecycle node to
change its state even though no explicit callback function was overridden.
There is one other callback function for error handling. Whenever a state
transition throws an uncaught exception, we call ` on_error ` :


##  Triggering transition 1 (configure)


    $ ros2 lifecycle set /lc_talker configure
    Transitioning successful


  * Replace ready_fn with ReadyToTest action ( [ #404 ](https://github.com/ros2/demos/issues/404) )
  * Contributors: Peter Baughman


_No CHANGELOG found._


####  Maintainers


**Checkout URI** |  [ https://github.com/ros2/demos.git
](https://github.com/ros2/demos.git)
---|---
**VCS Type** |  git
**VCS Version** |  iron
**Last Updated**

2023-05-19  |  **Dev Status** |  DEVELOPED
**CI status** |  No Continuous Integration
**Released** |  RELEASED
**Tags** |  _No category tags._
**Contributing** |  [ Help Wanted (  0  ) ](/r/demos/#iron-contribute-lists-
help-wanted)
[ Good First Issues (  0  ) ](/r/demos/#iron-contribute-lists-good-first-
issue)
[ Pull Requests to Review (  0  ) ](/r/demos/#iron-contribute-lists-pull-
requests)

###  Package Description


          RCLCPP_INFO(
            get_logger(), "Transition %d successfully triggered.", static_cast<int>(transition));
          return true;
        } else {
          RCLCPP_WARN(
            get_logger(), "Failed to trigger transition %u", static_cast<unsigned int>(transition));
          return false;
        }
      }

    private:
      std::shared_ptr<rclcpp::Client<lifecycle_msgs::srv::GetState>> client_get_state_;
      std::shared_ptr<rclcpp::Client<lifecycle_msgs::srv::ChangeState>> client_change_state_;
    };

    void
    callee_script(std::shared_ptr<LifecycleServiceClient> lc_client)
    {
      rclcpp::WallRate time_between_state_changes(0.1);  // 10s

      // configure
      {
        if (!lc_client->change_state(lifecycle_msgs::msg::Transition::TRANSITION_CONFIGURE)) {
          return;
        }
        if (!lc_client->get_state()) {
          return;
        }
      }

      // activate
      {
        time_between_state_changes.sleep();
        if (!rclcpp::ok()) {
          return;
        }
        if (!lc_client->change_state(lifecycle_msgs::msg::Transition::TRANSITION_ACTIVATE)) {
          return;
        }
        if (!lc_client->get_state()) {


##  0.9.3 (2020-06-01)


Update the CMakeLists.txt,


  * [ About ](/about)
  * Index
    * [ Package List ](/packages/page/1/time/)
    * [ Repository List ](/repos/page/1/time/)
    *     * [ Nodes ](/srvs/)
    * [ Messages ](/msgs/)
    * [ Services ](/srvs/)
    * [ Plugins ](/srvs/)
    *     * [ System Dependencies ](/deps/)
  * [ Contribute ](/contribute)
  * [ Stats ](/stats)


  * unconfigured
  * inactive
  * active
  * shutdown


###  Services


$ ros2 interface show lifecycle_msgs/msg/Transition


* Service ` <node_name>__get_available_states ` : This is meant to be an introspection tool. It returns a list of all possible states this node can be.


  * Aditya Pande
  * Audrow Nash


    [lc_talker] on_configure() is called.
    Lifecycle publisher is currently inactive. Messages are not published.
    ...


![](/assets/package.png) |


##  0.17.0 (2021-10-18)


_No service files found_


##  Triggering transition 2 (activate)


    [lc_listener]: notify callback: Transition from state inactive to activating
    [lc_listener]: notify callback: Transition from state activating to active


    $ ros2 lifecycle list lc_talker
    - configure [1]
      Start: unconfigured
      Goal: configuring
    - shutdown [5]
      Start: unconfigured
      Goal: shuttingdown


[ API Docs ](http://docs.ros.org/en/dashing/p/lifecycle "View API
documentation on docs.ros.org") [ Browse Code
](https://github.com/ros2/demos/tree/dashing/lifecycle "View source code on
repository")


ros2 pkg create --build-type ament_cmake camera_node --dependencies rclcpp sensor_msgs rcutils rclcpp_lifecycle lifecycle_msgs


_Not currently indexed._


##  0.7.4 (2019-05-20)


The possible transitions to invoke are:


  * Add lifecycle rostest ( [ #336 ](https://github.com/ros2/demos/issues/336) )
  * Contributors: Michel Hidalgo


##  Triggering transition 1 (configure)


##  0.9.2 (2020-05-26)


* ` CallbackReturn on_error(const rclcpp_lifecycle::State & previous_state) `


##  0.9.0 (2020-04-30)


This allows users to get notified of transition events within the network.


Return either a primary or transition state.


At the same time, every lifecycle node has by default 5 different
communication interfaces.


##  0.12.1 (2021-03-18)


This gives room for executing custom error handling. Only (!) in the case that
this function returns ` CallbackReturn::SUCCESS ` , the state machine
transitions to the state ` unconfigured ` . By default, the ` on_error `
returns ` CallbackReturn::FAILURE ` and the state machine transitions into `
finalized ` .


##  0.14.0 (2021-04-06)


_No service files found_


class LifecycleTalker : public rclcpp_lifecycle::LifecycleNode


ROS 2 introduces the concept of managed nodes, also called ` LifecycleNode `
s. In the following tutorial, we explain the purpose of these nodes, what
makes them different from regular nodes and how they comply to a lifecycle
management. Managed nodes contain a state machine with a set of predefined
states. These states can be changed by invoking a transition id which
indicates the succeeding consecutive state. The state machine is implemented
as described at the [ ROS 2 design page
](http://design.ros2.org/articles/node_lifecycle.html) .


lifecycle_talker lifecycle_listener lifecycle_service_client


  * configure
  * activate
  * deactivate
  * cleanup
  * shutdown


Basic concepts
Basic Concepts
How to use ros(1)_control?
1. Implement RobotHW (hardware abstraction layer)
a. init(), read(), write()
b. JointStateInterface and [Position|Velocity|Effort]JointInterface
2. Implement a control node
a. Load URDF (“/robot_description” parameter) - usually needed
b. Initialize RobotHW
c. Initialize ControllerManager
d. Start main loop `while(ros::ok())`
i. read()
ii. update() — controllers
iii. write()
Standard controllers
● joint_state_broadcaster
● diff_drive_controller
● joint_trajectory_controller
● gripper_controllers
● Forwarding controllers for groups of joints
○ position_controllers
○ velocity_controllers
○ effort_controllers
Image from ros_control paper
What is a bit tricky in ros(1)_control?
● Joint interfaces limited to: “position”, “velocity”, and “effort
● Complex code-base — lots of templating and inheritance
● “Control node” has to be implemented for each hardware
● Unclear semantic — everything is a RobotHW
● Hardware composition possible, but not straightforward
Improvements in ros2_control
● Joint interfaces limited to: “position”, “velocity”, and “effort
○ Interface types are “strings” — fully flexible
● Complex code-base — lots of templating and inheritance
○ Cleaner code-base, modern C++
● “Control node” has to be implemented for each hardware
○ Default “ros2_control_node”, no need for boilerplates
● Unclear semantic — everything is a RobotHW
○ Actuator, Sensor, and System hardware types
● Hardware composition possible, but not straightforward


#  Run the demo


##  0.14.3 (2021-05-10)


    $ ros2 lifecycle get /lc_talker
    unconfigured [1]


It returns a list of all possible states this node can be.


The ` lifecycle_service_client ` application is a fixed order script for demo
purposes only. It explains the use and the API calls made for this lifecycle
implementation, but may be inconvenient to use otherwise. For this reason we
implemented a command line tool which lets you dynamically change states or
various nodes.


---

[
API Docs ](http://docs.ros.org/en/eloquent/p/lifecycle "View API documentation
on docs.ros.org") [
Browse Code ](https://github.com/ros2/demos/tree/eloquent/lifecycle "View
source code on repository")


  * Remove unnecessary dependency on ros2run ( [ #413 ](https://github.com/ros2/demos/issues/413) )
  * Contributors: Michel Hidalgo


>
>     if (hardware_interface::[Actuator|Sensor|System]Interface::on_init(info)
> != CallbackReturn::SUCCESS)
>     {
>       return CallbackReturn::ERROR;
>     }
>


  * Use default on_activate()/on_deactivate() implemenetation of Node ( [ #552 ](https://github.com/ros2/demos/issues/552) )
  * Contributors: Ivan Santiago Paunovic


####  Additional Links


Please note that the index of the published message is already at 11. The
purpose of this demo is to show that even though we call ` publish ` at every
state of the lifecycle talker, only when the state in active, the messages are
actually published. As for the beta1, all other messages are getting ignored.
This behavior may change in future versions in order to provide better error
handling.


_No additional links._


_No plugins found._


  * lifecycle_talker
  * lifecycle_listener
  * lifecycle_service_client


CHANGELOG


* Publisher ` <node_name>__transition_event ` : publishes in case a transition is happening.


_No launch files found_


  * Fix use of future in lifecycle demo ( [ #534 ](https://github.com/ros2/demos/issues/534) )
  * Fixing deprecated subscriber callback warnings ( [ #532 ](https://github.com/ros2/demos/issues/532) )
  * Contributors: Abrar Rahman Protyasha, Christophe Bedard


  * Python lifecycle nodes
  * Lifecycle manager: A global node, handling and dispatching trigger requests for multiple nodes.
  * LifeyclceSubscriber/LifecycleWalltimer/... add more lifecycle controlled entities.


  * Cleaned up lifecycle demo ( [ #283 ](https://github.com/ros2/demos/issues/283) )
  * Updated for refactoring in rclcpp ( [ #276 ](https://github.com/ros2/demos/issues/276) )
  * Added semicolons to all RCLCPP and RCUTILS macros. ( [ #278 ](https://github.com/ros2/demos/issues/278) )
  * Fixed typo in comment ( [ #270 ](https://github.com/ros2/demos/issues/270) )
  * Contributors: Chris Lalancette, Karsten Knese, Yutaka Kondo


For a more verbose explanation on the applied state machine, we refer to the
design page which provides an in-detail explanation about each state and
transition.


####  Maintainers


#  Run the demo


##  0.28.0 (2023-04-27)


---

[
API Docs ](http://docs.ros.org/en/crystal/p/lifecycle "View API documentation
on docs.ros.org") [
Browse Code ](https://github.com/ros2/demos/tree/crystal/lifecycle "View
source code on repository")


Failed to get question list, you can ticket an issue [ here
](https://github.com/ros-infrastructure/rosindex/issues/new)


**Checkout URI** |  [ https://github.com/ros2/demos.git
](https://github.com/ros2/demos.git)
---|---
**VCS Type** |  git
**VCS Version** |  ardent
**Last Updated**

2017-12-09  |  **Dev Status** |  DEVELOPED
**CI status** |  No Continuous Integration
**Released** |  RELEASED
**Tags** |  _No category tags._
**Contributing** |  [ Help Wanted (  0  ) ](/r/demos/#ardent-contribute-lists-
help-wanted)
[ Good First Issues (  0  ) ](/r/demos/#ardent-contribute-lists-good-first-
issue)
[ Pull Requests to Review (  0  ) ](/r/demos/#ardent-contribute-lists-pull-
requests)

###  Package Description


The principle is implemented in this demo as the typical talker/listener demo.
However, imaging a real scenario with attached hardware which may have a
rather long booting phase, i.e. a laser or camera. One could image bringing up
the device driver in the configuring state, start and stop only the publishing
of the device\'s data and only in the cleanup/shutdown phase actually shutdown
the device.


    $ ros2 lifecycle list lc_talker -a
    - configure [1]
      Start: unconfigured
      Goal: configuring
    - transition_success [10]
      Start: configuring
      Goal: inactive
    - transition_failure [11]
      Start: configuring
      Goal: unconfigured
    - transition_error [12]
      Start: configuring
      Goal: errorprocessing

    [...]

    - transition_error [62]
      Start: errorprocessing
      Goal: finalized


](https://policy.medium.com/medium-privacy-
policy-f03bf92035c9?source=post_page-----
5fafa2738700--------------------------------)


  * Updated for NodeOptions Node constructor. ( [ #308 ](https://github.com/ros2/demos/issues/308) )
  * Contributors: Michael Carroll


##  Triggering transition 2 (activate)


Return either a primary or transition state.


The difference to the transition event before is that our listener now also
receives the actual published data.


` $ ros2 run lifecycle lifecycle_talker ` ` $ ros2 run lifecycle
lifecycle_listener ` ` $ ros2 run lifecycle lifecycle_service_client ` [
![asciicast](https://asciinema.org/a/249049.png)
](https://asciinema.org/a/249049) [
![asciicast](https://asciinema.org/a/249050.png)
](https://asciinema.org/a/249050) [
![asciicast](https://asciinema.org/a/249051.png)
](https://asciinema.org/a/249051)


9. Change return type of ` on_activate  ` and ` on_deactivate  ` to ` CallbackReturn  `


  * change ParameterEventHandler to take events as const ref instead of shared pointer ( [ #494 ](https://github.com/ros2/demos/issues/494) )
  * Contributors: William Woodall


##  0.7.5 (2019-05-29)


  * Added readme.rst ( [ #300 ](https://github.com/ros2/demos/issues/300) )
  * Contributors: Karsten Knese


    $ ros2 lifecycle list lc_talker
    - configure [1]
      Start: unconfigured
      Goal: configuring
    - shutdown [5]
      Start: unconfigured
      Goal: shuttingdown


      auto lc_client = std::make_shared<LifecycleServiceClient>("lc_client");
      lc_client->init();

      rclcpp::executors::SingleThreadedExecutor exe;
      exe.add_node(lc_client);

      std::shared_future<void> script = std::async(
        std::launch::async,
        std::bind(callee_script, lc_client));
      exe.spin_until_future_complete(script);

      rclcpp::shutdown();

      return 0;
    }


  * Overview
  * 0  Assets
  * 8  Dependencies
  * 0  Tutorials
  * 0  Q & A


  * configuring
  * activating
  * deactivating
  * cleaningup
  * shuttingdown


#  Outlook


lifecycle_talker lifecycle_listener lifecycle_service_client


humble  iron  rolling  noetic


Lets Update the CMakeLists.txt and compile,


##  0.16.0 (2021-08-11)


_See[ ROS Wiki Tutorials ](http://wiki.ros.org/lifecycle/Tutorials) for more
details. _


* Service ` <node_name>__change_state ` : triggers a transition for the current node.


` $ ros2 run lifecycle lifecycle_talker ` ` $ ros2 run lifecycle
lifecycle_listener ` ` $ ros2 run lifecycle lifecycle_service_client ` [
![asciicast](https://asciinema.org/a/e0f11qvpberltp8r1w04wzw9t.png)
](https://asciinema.org/a/e0f11qvpberltp8r1w04wzw9t) [
![asciicast](https://asciinema.org/a/442pjcu729t3vsld7n225orl7.png)
](https://asciinema.org/a/442pjcu729t3vsld7n225orl7) [
![asciicast](https://asciinema.org/a/6o20wbnhx6tk3y2hr5dk8fwm5.png)
](https://asciinema.org/a/6o20wbnhx6tk3y2hr5dk8fwm5)


No version for distro **noetic** . Known supported distros are highlighted in
the buttons above.


Built with [ Sphinx ](https://www.sphinx-doc.org/) using a [ theme
](https://github.com/readthedocs/sphinx_rtd_theme) provided by [ Read the Docs
](https://readthedocs.org) .


The demo is split into 3 separate applications:


[ API Docs ](http://docs.ros.org/en/foxy/p/lifecycle "View API documentation
on docs.ros.org") [ Browse Code
](https://github.com/ros2/demos/tree/foxy/lifecycle "View source code on
repository")


##  Triggering transition 2 (activate)


The ` lifecycle_listener ` is a simple listener which shows the
characteristics of the lifecycle talker. The talker enables message publishing
only in the active state and thus the listener only receives messages when the
talker is in an active state.


##  0.6.2 (2019-01-15)


  * Converted launch files to the new launch style. ( [ #262 ](https://github.com/ros2/demos/issues/262) )
  * Updated to support remapping arguments to python nodes by passing unused arguments to rclpy from argparse. ( [ #252 ](https://github.com/ros2/demos/issues/252) )
  * Updated to handle change in signature to ` get_service_name ` . ( [ #245 ](https://github.com/ros2/demos/issues/245) )
  * Updated launch files to account for the \"old launch\" getting renamespaced as ` launch ` -> ` launch.legacy ` . ( [ #239 ](https://github.com/ros2/demos/issues/239) )
  * Updated service client demos to handle multiple requests. ( [ #228 ](https://github.com/ros2/demos/issues/228) )
  * Contributors: Geoffrey Biggs, Kevin Allen, Shane Loretz, William Woodall, dhood


    $ ros2 service call /lc_talker/change_state lifecycle_msgs/ChangeState "{transition: {id: 2}}"
    requester: making request: lifecycle_msgs.srv.ChangeState_Request(transition=lifecycle_msgs.msg.Transition(id=2, label=''))

    response:
    lifecycle_msgs.srv.ChangeState_Response(success=True)


###  Source Tutorials


The ` lifecycle_listener ` is a simple listener which shows the
characteristics of the lifecycle talker. The talker enables the message
publishing only in the active state and thus making the listener receiving
only messages when the talker is in an active state.


This service call takes a transition id. Only in the case, that this
transition ID is a valid transition of the current state, the transition is
fulfilled. All other cases are getting ignored.


##  0.9.0 (2020-04-30)


    [lc_listener] data_callback: Lifecycle HelloWorld #11
    [lc_listener] data_callback: Lifecycle HelloWorld #12
    ...


##  Guidelines and Best Practices  


In the following we assume that we are inside the namespace `
rclcpp_lifecycle::node_interfaces::LifecycleNodeInterface ` to shorten the
name of the return type. All these callbacks have a positive default return
value ( ` return CallbackReturn::SUCCESS ` ). This allows a lifecycle node to
change its state even though no explicit callback function was overwritten.
There is one other callback function for error handling. Whenever a state
transition throws an uncaught exception, we call ` on_error ` .


  * lifecycle_talker
  * lifecycle_listener
  * lifecycle_service_client


Primary States (steady states):


If we look at the output of the ` lifecycle_talker ` , we notice that nothing
seems to happen. And this does make sense, since every node starts as `
unconfigured ` . The lifecycle_talker is not configured yet and in our
example, no publishers and timers are created yet. The same behavior can be
seen for the ` lifecycle_listener ` , which is less surprising given that no
publishers are available at this moment. The interesting part starts with the
third terminal. In there we launch our ` lifecycle_service_client ` which is
responsible for changing the states of the ` lifecycle_talker ` .


CHANGELOG


###  Wiki Tutorials


####  Authors


All these callbacks have a positive default return value ( ` return
RCL_LIFECYCLE_RET_OK ` ). This allows a lifecycle node to change its state
even though no explicit callback function was overwritten. There is one other
callback function for error handling. Whenever a state transition throws an
uncaught exception, we call ` on_error ` .


##  0.24.1 (2023-02-24)


The above description points to the current state of the development as for
beta1. The future todo list for this topic comprises:


###  Recent questions tagged ` lifecycle ` at **[ Robotics Stack Exchange
](https://robotics.stackexchange.com/) **


README


  * Cleaned up lifecycle demo ( [ #283 ](https://github.com/ros2/demos/issues/283) )
  * Updated for refactoring in rclcpp ( [ #276 ](https://github.com/ros2/demos/issues/276) )
  * Added semicolons to all RCLCPP and RCUTILS macros. ( [ #278 ](https://github.com/ros2/demos/issues/278) )
  * Fixed typo in comment ( [ #270 ](https://github.com/ros2/demos/issues/270) )
  * Contributors: Chris Lalancette, Karsten Knese, Yutaka Kondo


#  The demo code


    [lc_client] Transition 2 successfully triggered.
    [lc_client] Node lc_talker has current state active.


    $ ros2 lifecycle set /lc_talker configure
    Transitioning successful


        RCUTILS_LOG_INFO_NAMED(
          get_name(),
          "on shutdown is called from state %s.",
          state.label().c_str());
        return rclcpp_lifecycle::node_interfaces::LifecycleNodeInterface::CallbackReturn::SUCCESS;
      }
    private:
      std::shared_ptr<rclcpp_lifecycle::LifecyclePublisher<sensor_msgs::msg::Image>> publisher_;
      std::shared_ptr<rclcpp::TimerBase> timer_;
      cv::VideoCapture cap_;
    };

    int main(int argc, char * argv[])
    {
      setvbuf(stdout, NULL, _IONBF, BUFSIZ);

      rclcpp::init(argc, argv);

      rclcpp::executors::SingleThreadedExecutor exe;

      std::shared_ptr<CameraNode> camera_node =
        std::make_shared<CameraNode>("camera_node");

      exe.add_node(camera_node->get_node_base_interface());

      exe.spin();

      rclcpp::shutdown();

      return 0;
    }


##  0.12.1 (2021-03-18)


#  The demo


The possible transitions to invoke are:


* [ github-ros2-demos ](/p/lifecycle/github-ros2-demos)


**Tags** |  _No category tags._
---|---
**Version** |  0.4.0
**License** |  Apache License 2.0
**Build type** |  AMENT_CMAKE
**Use** |  RECOMMENDED

###  Repository Summary


[ Robotics Automation  ](/tag/robotics-automation?source=post_page-----
5fafa2738700---------------robotics_automation-----------------)


Failed to get question list, you can ticket an issue [ here
](https://github.com/ros-infrastructure/rosindex/issues/new)


![](/assets/package.png) |


##  What\'s happening


[ Artificial Intelligence  ](/tag/artificial-intelligence?source=post_page
-----5fafa2738700---------------artificial_intelligence-----------------)


_See[ ROS Wiki Tutorials ](http://wiki.ros.org/lifecycle/Tutorials) for more
details. _


Every child of LifecycleNodes have a set of callbacks provided. These
callbacks go along with the applied state machine attached to it. These
callbacks are:


##  0.9.2 (2020-05-26)


  * Use default on_activate()/on_deactivate() implemenetation of Node ( [ #552 ](https://github.com/ros2/demos/issues/552) )
  * Contributors: Ivan Santiago Paunovic


The ` lifecycle_talker ` represents a managed node and publishes according to
which state the node is in. We split the tasks of the talker node into
separate pieces and execute them as follows:


All right, let’s kick things off with a basic camera_node package.


_No direct system dependencies._


###  Services


_Not currently indexed._


##  0.6.1 (2018-12-13)


This service call takes a transition id. The transition is fulfilled only in
the case that this transition ID is a valid transition from the current state.
All other cases are ignored.


#  Changelog for package lifecycle


In the following we assume that we are inside the namespace `
rclcpp_lifecycle::node_interfaces::LifecycleNodeInterface ` to shorten the
name of the return type. All these callbacks have a positive default return
value ( ` return CallbackReturn::SUCCESS ` ). This allows a lifecycle node to
change its state even though no explicit callback function was overridden.
There is one other callback function for error handling. Whenever a state
transition throws an uncaught exception, we call ` on_error ` :


Deps  |  |  Name  |  [ ](/p/lifecycle_msgs#iron-deps) |  [ 1
](/packages/lifecycle_msgs) |  [ lifecycle_msgs ](/p/lifecycle_msgs#iron)
---|---|---
[ ](/p/rclcpp_lifecycle#iron-deps) |  [ 1 ](/packages/rclcpp_lifecycle) |  [
rclcpp_lifecycle ](/p/rclcpp_lifecycle#iron)
[ ](/p/std_msgs#iron-deps) |  [ 2 ](/packages/std_msgs) |  [ std_msgs
](/p/std_msgs#iron)
[ ](/p/ament_cmake#iron-deps) |  [ 1 ](/packages/ament_cmake) |  [ ament_cmake
](/p/ament_cmake#iron)
[ ](/p/ament_lint_auto#iron-deps) |  [ 1 ](/packages/ament_lint_auto) |  [
ament_lint_auto ](/p/ament_lint_auto#iron)
[ ](/p/ament_lint_common#iron-deps) |  [ 1 ](/packages/ament_lint_common) |  [
ament_lint_common ](/p/ament_lint_common#iron)
[ ](/p/ros_testing#iron-deps) |  [ 1 ](/packages/ros_testing) |  [ ros_testing
](/p/ros_testing#iron)

###  System Dependencies


_No launch files found_


Our implementation differentiates between ` Primary States ` and ` Transition
States ` . Primary States are supposed to be steady states in which any node
can do the respected task. On the other hand, Transition States are meant as
temporary intermediate states attached to a transition. The result of these
intermediate states are used to indicate whether a transition between two
primary states is considered successful or not. Thus, any managed node can be
in one of the following states:


##  0.22.0 (2022-09-13)


  * Mabel Zhang
  * Michael Jeronimo


It returns a list of all possible transitions this node can execute.


_No additional links._


11. If you have any ` return_type::ERROR  ` in ` on_init  ` , ` on_activate  ` , or ` in_deactivate  ` change to ` CallbackReturn::ERROR  `


---

[
API Docs ](http://docs.ros.org/en/rolling/p/lifecycle "View API documentation
on docs.ros.org") [
Browse Code ](https://github.com/ros2/demos/tree/rolling/lifecycle "View
source code on repository")


At the same time, every lifecycle node has by default 5 different
communication interfaces.


ROS2 introduces the concept of managed nodes, also called ` LifecycleNode ` s.
In the following tutorial, we explain the purpose of these nodes, what makes
them different from regular nodes and how they comply to a lifecycle
management. Managed nodes are scoped within a state machine of a finite amount
of states. These states can be changed by invoking a transition id which
indicates the succeeding consecutive state. The state machine is implemented
as described at the [ ROS2 design page
](http://design.ros2.org/articles/node_lifecycle.html) .


At the same time the lifecycle listener receives a notification as it listens
to every state change notification of the lifecycle talker. In fact, the
listener receives two consecutive notifications. One for changing from the
primary state \"unconfigured\" to \"configuring\", and a second notification
changing the state from \"configuring\" to \"inactive\" (since the configuring
step was successful in the talker).


The principle is implemented in this demo as the typical talker/listener demo.
However, imaging a real scenario with attached hardware which may have a
rather long booting phase, i.e. a laser or camera. One could image bringing up
the device driver in the configuring state, start and stop only the publishing
of the device\'s data and only in the cleanup/shutdown phase actually shutdown
the device.


* ` rcl_lifecycle_ret_t on_error(const rclcpp_lifecycle::State & previous_state) `


#  Introduction


If we have a look at the code, there is one significant change for the
lifecycle talker compared to a regular talker. Our node does not inherit from
the regular ` rclcpp::node::Node ` but from ` rclcpp_lifecycle::LifecycleNode
` .


For the rest of the demo, you will see similar output as we deactivate and
activate the lifecycle talker and finally shut it down.


###  Plugins


####  Additional Links


* Service ` <node_name>__change_state ` : triggers a transition for the current node.


_No service files found_


The possible transitions to invoke are:


  * Add lifecycle rostest ( [ #336 ](https://github.com/ros2/demos/issues/336) )
  * Contributors: Michel Hidalgo


###  Recent questions tagged ` lifecycle ` at **[ Robotics Stack Exchange
](https://robotics.stackexchange.com/) **


      Error: OR] [1703729558.642715534] [mock_generic_system]: Got multiple (2) starting interfaces for joint 'joint2' - this is not supported!
      Error: OR] [1703729558.642726604] [resource_manager]: Component 'HardwareSystem2dofStandardInterfacesWithDifferentControlModes' did not accept new command resource combination:
      7:  Start interfaces:
      7: [
      7:   flange_vacuum/vacuum
      7:   joint1/position
      7:   joint1/velocity
      7:   joint2/acceleration
      7:   joint2/velocity
      7: ]
      7: Stop interfaces:
      7: [
      7: ]

I saw a couple of this, when running the following test ` 7: Test command:
/usr/bin/python3.10 "-u"
"/opt/ros/rolling/share/ament_cmake_test/cmake/run_test.py"
"/home/runner/work/ros2_control/ros2_control/.work/target_ws/build/hardware_interface/test_results/hardware_interface/test_generic_system.gtest.xml"
"--package-name" "hardware_interface" "--output-file"
"/home/runner/work/ros2_control/ros2_control/.work/target_ws/build/hardware_interface/ament_cmake_gmock/test_generic_system.txt"
"--command"
"/home/runner/work/ros2_control/ros2_control/.work/target_ws/build/hardware_interface/test_generic_system"
"--
gtest_output=xml:/home/runner/work/ros2_control/ros2_control/.work/target_ws/build/hardware_interface/test_results/hardware_interface/test_generic_system.gtest.xml"
`

---

All reactions
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Contributor  Author
###
**[ christophfroehlich ](/christophfroehlich) ** commented  Dec 29, 2023
Oh sorry, the link to the specific line did not work. The ` TestSystemHardware
` is in unconfigured state, but the rm complains repeatedly


Alternatively, these three programs can be run together in the same terminal
using the launch file (as of ROS 2 Bouncy):


###  Source Tutorials


##  0.31.1 (2023-09-07)


Sign up


#  Run the demo


Other Versions  v: iron


* [ github-ros2-demos ](/p/lifecycle/github-ros2-demos)


##  0.26.0 (2023-04-11)


####  Maintainers


In order to run this demo, we open three terminals and source our ROS2
environment variables either from the binary distributions or the workspace we
compiled from source.


This demo shows a typical talker/listener pair of nodes. However, imagine a
real scenario with attached hardware which may have a rather long booting
phase, i.e. a laser or camera. One could imagine bringing up the device driver
in the configuring state, start and stop only the publishing of the device\'s
data in active/deactive state, and only in the cleanup/shutdown state actually
shutdown the device.


    [lc_listener] data_callback: Lifecycle HelloWorld #11
    [lc_listener] data_callback: Lifecycle HelloWorld #12
    ...


The ` lifecycle_talker ` represents a managed node and publishes according to
which state the node is in. We split the tasks of the talker node into
separate pieces and execute them as followed.


_No message files found._


_No service files found_


No questions yet, you can ask one [ here
](https://robotics.stackexchange.com/questions/tagged/lifecycle+eloquent) .


Feb 26, 2023


###  Package Dependencies


  * unconfigured
  * inactive
  * active
  * shutdown


  * Cleaned up lifecycle demo ( [ #283 ](https://github.com/ros2/demos/issues/283) )
  * Updated for refactoring in rclcpp ( [ #276 ](https://github.com/ros2/demos/issues/276) )
  * Added semicolons to all RCLCPP and RCUTILS macros. ( [ #278 ](https://github.com/ros2/demos/issues/278) )
  * Fixed typo in comment ( [ #270 ](https://github.com/ros2/demos/issues/270) )
  * Contributors: Chris Lalancette, Karsten Knese, Yutaka Kondo


ROS2 introduces the concept of managed nodes, also called ` LifecycleNode ` s.
In the following tutorial, we explain the purpose of these nodes, what makes
them different from regular nodes and how they comply to a lifecycle
management. Managed nodes are scoped within a state machine of a finite amount
of states. These states can be changed by invoking a transition id which
indicates the succeeding consecutive state. The state machine is implemented
as described at the [ ROS2 design page
](http://design.ros2.org/articles/node_lifecycle.html) .


##  0.8.0 (2019-09-26)


##  0.8.1 (2019-10-23)


##  0.17.0 (2021-10-18)


Hardware components represent abstraction of physical hardware in ros2_control
framework. There are three types of hardware Actuator, Sensor and System. For
details on each type check [ Hardware Components
](../../../getting_started/getting_started.html#overview-hardware-components)
description.


  * configuring
  * activating
  * deactivating
  * cleaningup
  * shuttingdown


---

[
API Docs ](http://docs.ros.org/en/dashing/p/lifecycle "View API documentation
on docs.ros.org") [
Browse Code ](https://github.com/ros2/demos/tree/dashing/lifecycle "View
source code on repository")


* Karsten Knese


##  0.33.1 (2024-02-07)


    $ ros2 service call /lc_talker/change_state lifecycle_msgs/ChangeState "{transition: {id: 2}}"
    requester: making request: lifecycle_msgs.srv.ChangeState_Request(transition=lifecycle_msgs.msg.Transition(id=2, label=''))

    response:
    lifecycle_msgs.srv.ChangeState_Response(success=True)


  * Added readme.rst ( [ #300 ](https://github.com/ros2/demos/issues/300) )
  * Contributors: Karsten Knese


If we look at the output of the ` lifecycle_talker ` , we notice that nothing
seems to happen. And this does make sense, since every node starts as `
unconfigured ` . The lifecycle_talker is not configured yet and in our
example, no publishers and timers are created yet. The same behavior can be
seen for the ` lifecycle_listener ` , which is less surprising given that no
publishers are available at this moment. The interesting part starts with the
third terminal. In there we launch our ` lifecycle_service_client ` which is
responsible for changing the states of the ` lifecycle_talker ` .


    $ ros2 service call /lc_talker/change_state lifecycle_msgs/ChangeState "{node_name: lc_talker, transition: {id: 2}}"
    requester: making request: lifecycle_msgs.srv.ChangeState_Request(node_name='lc_talker', transition=lifecycle_msgs.msg.Transition(id=2, label=''))

    response:
    lifecycle_msgs.srv.ChangeState_Response(success=True)


Failed to get question list, you can ticket an issue [ here
](https://github.com/ros-infrastructure/rosindex/issues/new)


Our implementation differentiates between ` Primary States ` and ` Transition
States ` . Primary States are supposed to be steady states in which any node
can do the respected task. On the other hand, Transition States are meant as
temporary intermediate states attached to a transition. The result of these
intermediate states are used to indicate whether a transition between two
primary states is considered successful or not. Thus, any managed node can be
in one of the following states:


#  Introduction


            get_logger(), "Lifecycle publisher is active. Publishing:");
        }

        sensor_msgs::msg::Image::UniquePtr msg(new sensor_msgs::msg::Image());

        // Pack the OpenCV image into the ROS image.
        msg->header.frame_id = "camera_frame";
        msg->height = frame_.rows;
        msg->width = frame_.cols;
        msg->encoding = mat_type2encoding(frame_.type());
        msg->is_bigendian = false;
        msg->step = static_cast<sensor_msgs::msg::Image::_step_type>(frame_.step);
        msg->data.assign(frame_.datastart, frame_.dataend);
        publisher_->publish(std::move(msg));
      }

      /* The on_configure function is called when the node is in the Configuring state of the lifecycle.
       * In this function, the camera is opened and checked if it is successfully opened.
       * Then, a publisher is created for publishing the camera image with a queue size of 10. Additionally,
       * a timer is created to trigger the publish function of the CameraNode class every 1 second.
       * Finally, an informational message is printed to indicate that the node has been configured
       * and the callback returns rclcpp_lifecycle::node_interfaces::LifecycleNodeInterface::CallbackReturn::SUCCESS.
       * If there is an error opening the camera, an error message is printed and the callback returns
       * rclcpp_lifecycle::node_interfaces::LifecycleNodeInterface::CallbackReturn::FAILURE,
       * indicating that the node failed to configure.
      */
      rclcpp_lifecycle::node_interfaces::LifecycleNodeInterface::CallbackReturn
      on_configure(const rclcpp_lifecycle::State &)
      {
        // Open the camera.
        cap_.open(0);
        if (!cap_.isOpened()) {
          RCLCPP_ERROR(get_logger(), "Failed to open camera.");
          return rclcpp_lifecycle::node_interfaces::LifecycleNodeInterface::CallbackReturn::FAILURE;
        }

        publisher_ = this->create_publisher<sensor_msgs::msg::Image>("camera_image", 10);

        timer_ = this->create_wall_timer(
          1s, std::bind(&CameraNode::publish, this));


Reference Link: [ LifecycleNode
](https://docs.ros2.org/latest/api/rclcpp_lifecycle/classrclcpp__lifecycle_1_1LifecycleNode.html#a9c845ec37c12f3100e2b7f6107802746)


##  0.6.0 (2018-12-07)


For the rest of the demo, you will see similar output as we deactivate and
activate the lifecycle talker and finally shut it down.


* [ github-ros2-demos ](/p/lifecycle/github-ros2-demos)


This service call takes a transition id. The transition is fulfilled only in
the case that this transition ID is a valid transition from the current state.
All other cases are ignored.


* Service ` <node_name>__get_available_transitions ` : Same as above, meant to an introspection tool.


##  Triggering transition 1 (configure)


All reactions
[
![@christophfroehlich](https://avatars.githubusercontent.com/u/3367244?s=40&u=98db36351213b952b1c6ce663c1fde4108272539&v=4)
](/christophfroehlich) [ christophfroehlich ](/christophfroehlich) added the [
bug ](/ros-controls/ros2_control/labels/bug) label  Aug 22, 2023
[
![@christophfroehlich](https://avatars.githubusercontent.com/u/3367244?s=40&u=98db36351213b952b1c6ce663c1fde4108272539&v=4)
](/christophfroehlich) [ christophfroehlich ](/christophfroehlich) mentioned
this issue  Dec 25, 2023
[ [Example 13] Multi-robot system with lifecycle management  ros-
controls/ros2_control_demos#417  ](/ros-controls/ros2_control_demos/pull/417)
Open
[
![@christophfroehlich](https://avatars.githubusercontent.com/u/3367244?s=80&u=98db36351213b952b1c6ce663c1fde4108272539&v=4)
](/christophfroehlich)
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Contributor  Author
###
**[ christophfroehlich ](/christophfroehlich) ** commented  Dec 28, 2023
We recently also get these error messages with the tests here: [
https://github.com/ros-
controls/ros2_control/actions/runs/7343670255/job/19994517445#step:6:13108
](https://github.com/ros-
controls/ros2_control/actions/runs/7343670255/job/19994517445#step:6:13108)
👀 [ @saikishor ](https://github.com/saikishor)

---

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](/saikishor)
Copy link
Member
###
**[ saikishor ](/saikishor) ** commented  Dec 29, 2023
[ @christophfroehlich ](https://github.com/christophfroehlich) Thanks for
reporting it. You are referring to the below output right?


No questions yet, you can ask one [ here
](https://robotics.stackexchange.com/questions/tagged/lifecycle+galactic) .


$ ros2 run lifecycle lifecycle_service_client_py.py change_state --change-state-args configure lc_talker


##  0.28.1 (2023-05-11)


####  Authors


    [lc_client] Transition 1 successfully triggered.
    [lc_client] Node lc_talker has current state inactive.


    cd camera_node && touch src/lc_service_client.cpp

    #include <chrono>
    #include <memory>
    #include <string>
    #include <thread>

    #include "lifecycle_msgs/msg/state.hpp"
    #include "lifecycle_msgs/msg/transition.hpp"
    #include "lifecycle_msgs/srv/change_state.hpp"
    #include "lifecycle_msgs/srv/get_state.hpp"

    #include "rclcpp/rclcpp.hpp"

    #include "rcutils/logging_macros.h"

    using namespace std::chrono_literals;

    static constexpr char const * lifecycle_node = "camera_node";
    static constexpr char const * node_get_state_topic = "camera_node/get_state";
    static constexpr char const * node_change_state_topic = "camera_node/change_state";

    template<typename FutureT, typename WaitTimeT>
    std::future_status
    wait_for_result(
      FutureT & future,
      WaitTimeT time_to_wait)
    {
      auto end = std::chrono::steady_clock::now() + time_to_wait;
      std::chrono::milliseconds wait_period(100);
      std::future_status status = std::future_status::timeout;
      do {
        auto now = std::chrono::steady_clock::now();
        auto time_left = end - now;
        if (time_left <= std::chrono::seconds(0)) {break;}
        status = future.wait_for((time_left < wait_period) ? time_left : wait_period);
      } while (rclcpp::ok() && status != std::future_status::ready);


    $ ros2 service call /lc_talker/get_state lifecycle_msgs/GetState
    requester: making request: lifecycle_msgs.srv.GetState_Request()

    response:
    lifecycle_msgs.srv.GetState_Response(current_state=lifecycle_msgs.msg.State(id=1, label='unconfigured'))


* Publisher ` <node_name>__transition_event ` : publishes in case a transition is happening.


    [lc_listener] data_callback: Lifecycle HelloWorld #11
    [lc_listener] data_callback: Lifecycle HelloWorld #12
    ...


_No service files found_


####  Additional Links


Please note that the index of the published message is already at 11. The
purpose of this demo is to show that even though we call ` publish ` at every
state of the lifecycle talker, the messages are only actually published when
the state in active.


$ ros2 interface show lifecycle_msgs/msg/Transition


---

[
API Docs ](http://docs.ros.org/en/humble/p/lifecycle "View API documentation
on docs.ros.org") [
Browse Code ](https://github.com/ros2/demos/tree/humble/lifecycle "View source
code on repository")


    $ ros2 lifecycle list lc_talker
    - configure [1]
      Start: unconfigured
      Goal: configuring
    - shutdown [5]
      Start: unconfigured
      Goal: shuttingdown


Name  |  Repo  |  Deps  |  [ lifecycle_py ](/p/lifecycle_py/github-
ros2-demos#humble) |  [ github-ros2-demos ](/r/demos/github-ros2-demos) |  [
](/p/lifecycle_py/github-ros2-demos#humble-deps)
---|---|---
[ test_launch_ros ](/p/test_launch_ros/github-ros2-launch_ros#humble) |  [
github-ros2-launch_ros ](/r/launch_ros/github-ros2-launch_ros) |  [
](/p/test_launch_ros/github-ros2-launch_ros#humble-deps)
[ desktop ](/p/desktop/github-ros2-variants#humble) |  [ github-ros2-variants
](/r/variants/github-ros2-variants) |  [ ](/p/desktop/github-
ros2-variants#humble-deps)

###  Launch files


If we have a look at the code, there is one significant change for the
lifecycle talker compared to a regular talker. Our node does not inherit from
the regular ` rclcpp::node::Node ` but from ` rclcpp_lifecycle::LifecycleNode
` .


##  0.7.1 (2019-04-26)


    [lc_talker] on_activate() is called.
    [lc_talker] Lifecycle publisher is active. Publishing: [Lifecycle HelloWorld #11]
    [lc_talker] Lifecycle publisher is active. Publishing: [Lifecycle HelloWorld #12]
    ...


* Service ` <node_name>__get_available_states ` : This is meant to be an introspection tool.


](https://speechify.com/medium?source=post_page-----
5fafa2738700--------------------------------)


` $ ros2 run lifecycle lifecycle_talker ` ` $ ros2 run lifecycle
lifecycle_listener ` ` $ ros2 run lifecycle lifecycle_service_client ` [
![asciicast](https://asciinema.org/a/249049.png)
](https://asciinema.org/a/249049) [
![asciicast](https://asciinema.org/a/249050.png)
](https://asciinema.org/a/249050) [
![asciicast](https://asciinema.org/a/249051.png)
](https://asciinema.org/a/249051)


 using ControllerCommandMsg = control_msgs::msg::JointJog;
 …
};
Messages and modifying a controller
controller_interface::return_type RRBotController::update()
{
 auto current_command = input_command_.readFromRT();
 for (size_t i = 0; i < command_interfaces_.size(); ++i) {
 if (!std::isnan((*current_command)->displacements[i])) {
 command_interfaces_[i].set_value((*current_command)->displacements[i]);
 }
 }
...
 return controller_interface::return_type::OK;
}
Messages and modifying a controller
ros2 launch rrbot_bringup rrbot_with_rrbot_controller.launch.py
ros2 control list_controllers
ros2 control list_hardware_interfaces
ros2 topic echo /rrbot_controller/state
ros2 topic echo /joint_states ros2 topic pub /rrbot_controller/commands
control_msgs/msg/JointJog "joint_names:
- joint1
- joint2
displacements:
- 0.5
- 0.5"


Sign up


  * Fix typo ( [ #445 ](https://github.com/ros2/demos/issues/445) )
  * Replace ` ros2 msg ` command in lifecycle README ( [ #446 ](https://github.com/ros2/demos/issues/446) )
  * Contributors: Audrow Nash, Shota Aoki


##  lifecycle_talker, lifecycle_listener and lifecycle_service_client


##  0.23.0 (2022-11-02)


##  0.8.3 (2019-11-11)


    [lc_talker] on_configure() is called.
    Lifecycle publisher is currently inactive. Messages are not published.
    ...


Please note that the index of the published message is already at 11. The
purpose of this demo is to show that even though we call ` publish ` at every
state of the lifecycle talker, only when the state in active, the messages are
actually published. As for the beta1, all other messages are getting ignored.
This behavior may change in future versions in order to provide better error
handling.


makes the lifecycle talker change its state to active. Active means that all
publishers and timers are now activated. Therefore the messages are now
getting published.


#  The demo code


  * ` rcl_lifecycle_ret_t on_configure(const rclcpp_lifecycle::State & previous_state) `
  * ` rcl_lifecycle_ret_t on_activate(const rclcpp_lifecycle::State & previous_state) `
  * ` rcl_lifecycle_ret_t on_deactivate(const rclcpp_lifecycle::State & previous_state) `
  * ` rcl_lifecycle_ret_t on_cleanup(const rclcpp_lifecycle::State & previous_state) `
  * ` rcl_lifecycle_ret_t on_shutdown(const rclcpp_lifecycle::State & previous_state) `


###  Package Dependencies


##  0.14.2 (2021-04-26)


The ` lifecycle_listener ` is a simple listener which shows the
characteristics of the lifecycle talker. The talker enables the message
publishing only in the active state and thus making the listener receiving
only messages when the talker is in an active state.


The demo is split into 3 different separate applications.


For the rest of the demo, you will see similar output as we deactivate and
activate the lifecycle talker and finally shut it down.


    $ ros2 service call /lc_talker/change_state lifecycle_msgs/ChangeState "{transition: {id: 2}}"
    requester: making request: lifecycle_msgs.srv.ChangeState_Request(transition=lifecycle_msgs.msg.Transition(id=2, label=''))

    response:
    lifecycle_msgs.srv.ChangeState_Response(success=True)


In order to trigger a transition, we call the ` change_state ` service


ros2 launch lifecycle lifecycle_demo.launch.py


ROS 2 introduces the concept of managed nodes, also called ` LifecycleNode `
s. In the following tutorial, we explain the purpose of these nodes, what
makes them different from regular nodes and how they comply to a lifecycle
management. Managed nodes contain a state machine with a set of predefined
states. These states can be changed by invoking a transition id which
indicates the succeeding consecutive state. The state machine is implemented
as described at the [ ROS 2 design page
](http://design.ros2.org/articles/node_lifecycle.html) .


####  Maintainers


` $ ros2 run lifecycle lifecycle_talker ` ` $ ros2 run lifecycle
lifecycle_listener ` ` $ ros2 run lifecycle lifecycle_service_client ` [
![asciicast](https://asciinema.org/a/e0f11qvpberltp8r1w04wzw9t.png)
](https://asciinema.org/a/e0f11qvpberltp8r1w04wzw9t) [
![asciicast](https://asciinema.org/a/442pjcu729t3vsld7n225orl7.png)
](https://asciinema.org/a/442pjcu729t3vsld7n225orl7) [
![asciicast](https://asciinema.org/a/6o20wbnhx6tk3y2hr5dk8fwm5.png)
](https://asciinema.org/a/6o20wbnhx6tk3y2hr5dk8fwm5)


Talks about #robotics, #computervision, and #embeddedsystems


* Service ` <node_name>__get_state ` : query about the current state of the node.


###  Plugins


###  Dependant Packages


ros2 launch lifecycle lifecycle_demo_launch.py


Every child of LifecycleNodes have a set of callbacks provided. These
callbacks go along with the applied state machine attached to it. These
callbacks are:


The ` lifecycle_service_client ` is a script calling different transitions on
the ` lifecycle_talker ` . This is meant as the external user controlling the
lifecycle of nodes.


  * [ Hardware Interface Types ](hardware_interface_types_userdoc.html)
  * [ Writing a Hardware Component ](writing_new_hardware_component.html)
  * [ Different Update Rates ](different_update_rates_userdoc.html)


This gives room for executing custom error handling. Only (!) in the case that
this function returns ` CallbackReturn::SUCCESS ` , the state machine
transitions to the state ` unconfigured ` . By default, the ` on_error `
returns ` CallbackReturn::FAILURE ` and the state machine transitions into `
finalized ` .


It returns a list of all possible states this node can be.


The ` lifecycle_listener ` is a simple listener which shows the
characteristics of the lifecycle talker. The talker enables message publishing
only in the active state and thus the listener only receives messages when the
talker is in an active state.


  * lifecycle_talker
  * lifecycle_listener
  * lifecycle_service_client


##  0.7.0 (2019-04-14)


##  0.6.2 (2019-01-15)


* Service ` <node_name>__change_state ` : triggers a transition for the current node.


---

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###
**[ christophfroehlich ](/christophfroehlich) ** commented  Jan 7, 2024
Thanks, I'll check again if the two PRs got merged!

---

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](/christophfroehlich) [ christophfroehlich ](/christophfroehlich) mentioned
this issue  Jan 8, 2024
[ Fix multiple calls of cleanup when system is unconfigured  #1279  ](/ros-
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pull request  Jan 9, 2024  that will  close  this issue
[ Fix multiple calls of cleanup when system is unconfigured  #1279  ](/ros-
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](/destogl) [ destogl ](/destogl) closed this as [ completed ](/ros-
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in [ #1279 ](/ros-controls/ros2_control/pull/1279) Jan 12, 2024
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Name  |  Repo  |  Deps  |  [ test_launch_ros ](/p/test_launch_ros/github-
ros2-launch_ros#galactic) |  [ github-ros2-launch_ros ](/r/launch_ros/github-
ros2-launch_ros) |  [ ](/p/test_launch_ros/github-ros2-launch_ros#galactic-
deps)
---|---|---
[ desktop ](/p/desktop/github-ros2-variants#galactic) |  [ github-
ros2-variants ](/r/variants/github-ros2-variants) |  [ ](/p/desktop/github-
ros2-variants#galactic-deps)

###  Launch files


Makes the lifecycle talker change its state to active. That means all
publishers and timers are now activated and therefore the messages are now
getting published.


The ` lifecycle_talker ` represents a managed node and publishes according to
which state the node is in. We split the tasks of the talker node into
separate pieces and execute them as followed.


---

[
API Docs ](http://docs.ros.org/en/galactic/p/lifecycle "View API documentation
on docs.ros.org") [
Browse Code ](https://github.com/ros2/demos/tree/galactic/lifecycle "View
source code on repository")


    [lc_listener] notify callback: Transition from state unconfigured to configuring
    [lc_listener] notify callback: Transition from state configuring to inactive


  * Karsten Knese
  * Mabel Zhang


##  0.14.0 (2021-04-06)


##  0.9.4 (2022-07-25)


##  0.14.1 (2021-04-19)


lifecycle_talker lifecycle_listener lifecycle_service_client


* [ github-ros2-demos ](/p/lifecycle/github-ros2-demos)


The lifecycle listener on the same time receives a notification as it listens
to every state change notification of the lifecycle talker. In fact, the
listener receives two consecutive notifications. One for changing from the
primary state \"unconfigured\" to \"configuring\". Because the configuring
step was successful within the lifecycle talker, a second notification from
\"configuring\" to \"inactive\".


  * Fix use of future in lifecycle demo ( [ #534 ](https://github.com/ros2/demos/issues/534) )
  * Fixing deprecated subscriber callback warnings ( [ #532 ](https://github.com/ros2/demos/issues/532) )
  * Contributors: Abrar Rahman Protyasha, Christophe Bedard


* Service ` <node_name>__get_available_states ` : This is meant to be an introspection tool.


1. Rename ` configure  ` to ` on_init  ` and change return type to ` CallbackReturn  `


  * Added readme.rst ( [ #300 ](https://github.com/ros2/demos/issues/300) )
  * Contributors: Karsten Knese


    [lc_talker] on_configure() is called.
    Lifecycle publisher is currently inactive. Messages are not published.
    ...


    [lc_listener] data_callback: Lifecycle HelloWorld #11
    [lc_listener] data_callback: Lifecycle HelloWorld #12
    ...


_No launch files found_


  * Updated for NodeOptions Node constructor. ( [ #308 ](https://github.com/ros2/demos/issues/308) )
  * Contributors: Michael Carroll


All of the above commands are nothing more than calling the lifecycle node\'s
services. With that being said, we can also call these services directly with
the ros2 command line interface:


###  Handling of errors that happen during read() and write() calls  


  * Add missing required parameter in LifecycleNode launch action ( [ #456 ](https://github.com/ros2/demos/issues/456) )
  * Contributors: Ivan Santiago Paunovic


The above description points to the current state of the development as for
beta1. The future todo list for this topic comprises:


    rclcpp_lifecycle::node_interfaces::LifecycleNodeInterface::CallbackReturn
    on_configure(const rclcpp_lifecycle::State & previous_state)

    rclcpp_lifecycle::node_interfaces::LifecycleNodeInterface::CallbackReturn
    on_activate(const rclcpp_lifecycle::State & previous_state)

    rclcpp_lifecycle::node_interfaces::LifecycleNodeInterface::CallbackReturn
    on_deactivate(const rclcpp_lifecycle::State & previous_state)

    rclcpp_lifecycle::node_interfaces::LifecycleNodeInterface::CallbackReturn
    on_cleanup(const rclcpp_lifecycle::State & previous_state)

    rclcpp_lifecycle::node_interfaces::LifecycleNodeInterface::CallbackReturn
    on_shutdown(const rclcpp_lifecycle::State & previous_state)


    [lc_listener]: notify callback: Transition from state inactive to activating
    [lc_listener]: notify callback: Transition from state activating to active


_No direct system dependencies._


$ ros2 msg show lifecycle_msgs/Transition


##  0.5.0 (2018-06-27)


  * Update asciinema recordings ( [ #360 ](https://github.com/ros2/demos/issues/360) )
  * Use rate instead of thread::sleep to react to Ctrl-C ( [ #348 ](https://github.com/ros2/demos/issues/348) )
  * Contributors: Dirk Thomas, Karsten Knese


  * Fix typo ( [ #445 ](https://github.com/ros2/demos/issues/445) )
  * Replace ` ros2 msg ` command in lifecycle README ( [ #446 ](https://github.com/ros2/demos/issues/446) )
  * Contributors: Audrow Nash, Shota Aoki


The ` lifecycle_listener ` is a simple listener which shows the
characteristics of the lifecycle talker. The talker enables the message
publishing only in the active state and thus making the listener receiving
only messages when the talker is in an active state.


* Karsten Knese


    [lc_client] Transition 2 successfully triggered.
    [lc_client] Node lc_talker has current state active.


Alternatively, these three programs can be run together in the same terminal
using the launch file:


Compile and Run,


##  Triggering transition 2 (activate)


    add_executable(display_node
      src/display_node.cpp)
      target_link_libraries(display_node
      ${rclcpp_lifecycle_LIBRARIES}
      ${lifecycle_msgs_LIBRARIES}
      ${sensor_msgs_LIBRARIES}
      ${OpenCV_LIBRARIES})

    install(TARGETS
      camera_node
      display_node
      DESTINATION lib/${PROJECT_NAME})


##  0.25.0 (2023-03-01)


○ Hardware interfaces are always plugins with lifecycle
○ A robot-cell can now be created via plug-and-play
Architecture of ros2_control
“Everything is an interface ”
● ∞ number of interface types → control_msgs/DynamicJointState
○ Type-names are freely choosable
○ Standard names: “position”, “velocity”, “acceleration”, and “effort”
● This enables:
○ Semantic clarity of interface-types (use as clear type-name as possible)
○ Out-of-the-box support for digital and analog inputs and outputs
○ Use of multiple sensors for the same “value”
○ “Interface-type” == string → no need for templating and complex inheritance
URDF extension with <ros2_control>-tag
● Defines hardware type and name
● <hardware>
○ plugin and its parameters
● <joint>
○ Describes 1 DoF
○ Name, interfaces, and parameters
● <sensor>
○ Sensing component that is not related to a joint
○ name, state interfaces, and parameters
● <gpio>
○ Everything else
○ Size, data type, name, interfaces, and parameters
All interfaces has internally type double!
URDF extension with
<ros2_control>-tag
Lifecycle for controllers and hardware
● Managed nodes - interface
https://design.ros2.org/articles/node_lifecycle.html
How to use ros2_control
● Write <ros2_control> tag for your robot
○ Tip: write as xacro macro
● Implement hardware interface
○ Actuator - for 1 DoF actuators, e.g., motors
○ Sensor - for sensors
○ System - for multi DoF actuators, e.g., robots
● Configure controllers / controller manager
○ Do not forget to configure used interfaces


ROS2 introduces the concept of managed nodes, also called ` LifecycleNode ` s.
In the following tutorial, we explain the purpose of these nodes, what makes
them different from regular nodes and how they comply to a lifecycle
management. Managed nodes are scoped within a state machine of a finite amount
of states. These states can be changed by invoking a transition id which
indicates the succeeding consecutive state. The state machine is implemented
as described at the [ ROS2 design page
](http://design.ros2.org/articles/node_lifecycle.html) .


](https://help.medium.com/hc/en-us?source=post_page-----
5fafa2738700--------------------------------)


##  0.9.1 (2020-05-12)


  * Python lifecycle nodes
  * Lifecycle manager: A global node, handling and dispatching trigger requests for multiple nodes.
  * LifeyclceSubscriber/LifecycleWalltimer/... add more lifecycle controlled entities.


###  Dependant Packages


  * Cleanup the README.rst for the lifecycle demo. ( [ #508 ](https://github.com/ros2/demos/issues/508) )
  * Contributors: Chris Lalancette


* Service ` <node_name>__get_state ` : query about the current state of the node.


##  0.18.0 (2021-12-17)


  * lifecycle_talker
  * lifecycle_listener
  * lifecycle_service_client


##  0.6.0 (2018-12-07)


](/jobs-at-medium/work-at-medium-959d1a85284e?source=post_page-----
5fafa2738700--------------------------------)


Follow


##  lifecycle_talker, lifecycle_listener and lifecycle_service_client


All of the above commands are nothing else than calling the lifecycle node\'s
services. With that being said, we can also call these services directly with
the ros2 command line interface:


####  Additional Links


It is slightly less convenient, because you have to know the IDs which
correspond to each transition. You can find them though in the lifecycle_msgs
package.


###  Wiki Tutorials


Primary States (steady states):


_No service files found_


* Service ` <node_name>__get_available_states ` : This is meant to be an introspection tool.


#  Outlook


##  What\'s happening


##  0.7.0 (2019-04-14)


  * Cleaned up lifecycle demo ( [ #283 ](https://github.com/ros2/demos/issues/283) )
  * Updated for refactoring in rclcpp ( [ #276 ](https://github.com/ros2/demos/issues/276) )
  * Added semicolons to all RCLCPP and RCUTILS macros. ( [ #278 ](https://github.com/ros2/demos/issues/278) )
  * Fixed typo in comment ( [ #270 ](https://github.com/ros2/demos/issues/270) )
  * Contributors: Chris Lalancette, Karsten Knese, Yutaka Kondo


##  0.21.0 (2022-04-29)


[ ![Logo](../../../../_static/logo_ros-controls.png) ](../../../../index.html)


---

[
API Docs ](http://docs.ros.org/en/bouncy/p/lifecycle "View API documentation
on docs.ros.org") [
Browse Code ](https://github.com/ros2/demos/tree/bouncy/lifecycle "View source
code on repository")


#  Changelog for package lifecycle


##  0.5.0 (2018-06-27)


The ` lifecycle_service_client ` application is a fixed order script for this
demo purpose only. It explains the use and the API calls made for this
lifecycle implementation, but may be inconvenient to use otherwise. For this
reason we implemented a command line tool which lets you dynamically change
states or various nodes.


It returns a list of all possible transitions this node can execute.


* [ github-ros2-demos ](/p/lifecycle/github-ros2-demos)


    $ ros2 service call /lc_talker/get_state lifecycle_msgs/GetState
    requester: making request: lifecycle_msgs.srv.GetState_Request()

    response:
    lifecycle_msgs.srv.GetState_Response(current_state=lifecycle_msgs.msg.State(id=1, label='unconfigured'))


  * Fix lifecycle_service_client namespace ( [ #369 ](https://github.com/ros2/demos/issues/369) )
  * Contributors: Cameron Evans


#  Introduction


  * configuring
  * activating
  * deactivating
  * cleaningup
  * shuttingdown


  * Replace deprecated launch_ros usage ( [ #437 ](https://github.com/ros2/demos/issues/437) )
  * Update launch_ros action usage ( [ #431 ](https://github.com/ros2/demos/issues/431) )
  * code style only: wrap after open parenthesis if not in one line ( [ #429 ](https://github.com/ros2/demos/issues/429) )
  * Contributors: Dirk Thomas, Jacob Perron


If we have a look at the code, there is one significant change for the
lifecycle talker compared to a regular talker. Our node does not inherit from
the regular ` rclcpp::node::Node ` but from ` rclcpp_lifecycle::LifecycleNode
` .


[ Master ](../../../../../master/doc/ros2_control/hardware_interface/doc/hardware_components_userdoc.html)


Transition States (intermediate states):


makes the lifecycle talker change its state to active. That means all
publishers and timers are now activated and herefore the messages are now
getting published.


##  0.7.2 (2019-05-08)


All of the above commands are nothing else than calling the lifecycle node\'s
services. With that being said, we can also call these services directly with
the ros2 command line interface:


_Not currently indexed._


Our implementation differentiates between ` Primary States ` and ` Transition
States ` . Primary States are supposed to be steady states in which any node
can do the respected task. On the other hand, Transition States are meant as
temporary intermediate states attached to a transition. The result of these
intermediate states are used to indicate whether a transition between two
primary states is considered successful or not. Thus, any managed node can be
in one of the following states:


    [lc_talker] on_configure() is called.
    Lifecycle publisher is currently inactive. Messages are not published.
    ...


* Service ` <node_name>__get_state ` : query about the current state of the node. Return either a primary or transition state.


##  0.8.0 (2019-09-26)


For the rest of the demo, you will see similar output as we deactivate and
activate the lifecycle talker and finally shut it down.


In order to see what states are currently available:


##  0.31.0 (2023-08-21)


Primary States (steady states):


##  0.14.2 (2021-04-26)


##  0.7.6 (2019-05-30)


#  Outlook


Name  |  Repo  |  Deps  |  [ test_launch_ros ](/p/test_launch_ros/github-
ros2-launch_ros#foxy) |  [ github-ros2-launch_ros ](/r/launch_ros/github-
ros2-launch_ros) |  [ ](/p/test_launch_ros/github-ros2-launch_ros#foxy-deps)
---|---|---
[ desktop ](/p/desktop/github-ros2-variants#foxy) |  [ github-ros2-variants
](/r/variants/github-ros2-variants) |  [ ](/p/desktop/github-
ros2-variants#foxy-deps)

###  Launch files


` $ ros2 run lifecycle lifecycle_talker ` ` $ ros2 run lifecycle
lifecycle_listener ` ` $ ros2 run lifecycle lifecycle_service_client ` [
![asciicast](https://asciinema.org/a/249049.png)
](https://asciinema.org/a/249049) [
![asciicast](https://asciinema.org/a/249050.png)
](https://asciinema.org/a/249050) [
![asciicast](https://asciinema.org/a/249051.png)
](https://asciinema.org/a/249051)


###  Messages


###  [ lifecycle ](/p/lifecycle) package from [ demos ](/r/demos/github-
ros2-demos) repo


    [lc_talker] on_activate() is called.
    [lc_talker] Lifecycle publisher is active. Publishing: [Lifecycle HelloWorld #11]
    [lc_talker] Lifecycle publisher is active. Publishing: [Lifecycle HelloWorld #12]
    ...


    $ ros2 lifecycle list lc_talker -a
    - configure [1]
      Start: unconfigured
      Goal: configuring
    - transition_success [10]
      Start: configuring
      Goal: inactive
    - transition_failure [11]
      Start: configuring
      Goal: unconfigured
    - transition_error [12]
      Start: configuring
      Goal: errorprocessing

    [...]

    - transition_error [62]
      Start: errorprocessing
      Goal: finalized


Makes the lifecycle talker change its state to inactive. Inactive means that
all publishers and timers are created and configured. However, the node is
still not active. Therefore no messages are getting published.


It returns a list of all possible states this node can be.


##  0.9.1 (2020-05-12)


In order to trigger a transition, we call the ` change_state ` service


###  Wiki Tutorials


  1. configuring: We initialize our publisher and timer
  2. activate: We activate the publisher and timer in order to enable a publishing
  3. deactivate: We stop the publisher and timer
  4. cleanup: We destroy the publisher and timer


####  Authors


    $ ros2 service call /lc_talker/get_state lifecycle_msgs/GetState
    requester: making request: lifecycle_msgs.srv.GetState_Request()

    response:
    lifecycle_msgs.srv.GetState_Response(current_state=lifecycle_msgs.msg.State(id=1, label='unconfigured'))


##  What\'s happening


##  0.7.2 (2019-05-08)


[ Open in app
](https://rsci.app.link/?%24canonical_url=https%3A%2F%2Fmedium.com%2Fp%2F5fafa2738700&%7Efeature=LoOpenInAppButton&%7Echannel=ShowPostUnderUser&source=---two_column_layout_nav----------------------------------)


Name  |  Repo  |  Deps  |  [ desktop ](/p/desktop/github-ros2-variants#bouncy)
|  [ github-ros2-variants ](/r/variants/github-ros2-variants) |  [
](/p/desktop/github-ros2-variants#bouncy-deps)
---|---|---

###  Launch files


###  Recent questions tagged ` lifecycle ` at **[ Robotics Stack Exchange
](https://robotics.stackexchange.com/) **


  * Update the package.xml files with the latest Open Robotics maintainers ( [ #466 ](https://github.com/ros2/demos/issues/466) )
  * Contributors: Michael Jeronimo


  * Converted launch files to the new launch style. ( [ #262 ](https://github.com/ros2/demos/issues/262) )
  * Updated to support remapping arguments to python nodes by passing unused arguments to rclpy from argparse. ( [ #252 ](https://github.com/ros2/demos/issues/252) )
  * Updated to handle change in signature to ` get_service_name ` . ( [ #245 ](https://github.com/ros2/demos/issues/245) )
  * Updated launch files to account for the \"old launch\" getting renamespaced as ` launch ` -> ` launch.legacy ` . ( [ #239 ](https://github.com/ros2/demos/issues/239) )
  * Updated service client demos to handle multiple requests. ( [ #228 ](https://github.com/ros2/demos/issues/228) )
  * Contributors: Geoffrey Biggs, Kevin Allen, Shane Loretz, William Woodall, dhood


The lifecycle listener on the same time receives a notification as it listens
to every state change notification of the lifecycle talker. In fact, the
listener receives two consecutive notifications. One for changing from the
primary state \"unconfigured\" to \"configuring\". Because the configuring
step was successful within the lifecycle talker, a second notification from
\"configuring\" to \"inactive\".


* ` CallbackReturn on_error(const rclcpp_lifecycle::State & previous_state) `


* [ github-ros2-demos ](/p/lifecycle/github-ros2-demos)


    $ ros2 run lifecycle lifecycle_service_client_py.py
    usage: lifecycle_service_client_py.py [-h]
                                          [--change-state-args {configure,cleanup,shutdown,activate,deactivate}]
                                          {change_state,get_state,get_available_states,get_available_transitions}
                                          node


**Tags** |  _No category tags._
---|---
**Version** |  0.14.4
**License** |  Apache License 2.0
**Build type** |  AMENT_CMAKE
**Use** |  RECOMMENDED

###  Repository Summary


  * Fix typo ( [ #445 ](https://github.com/ros2/demos/issues/445) )
  * Replace ` ros2 msg ` command in lifecycle README ( [ #446 ](https://github.com/ros2/demos/issues/446) )
  * Contributors: Audrow Nash, Shota Aoki


![](/assets/package.png) |


Deps  |  |  Name  |  [ ](/p/ament_cmake#rolling-deps) |  [ 1
](/packages/ament_cmake) |  [ ament_cmake ](/p/ament_cmake#rolling)
---|---|---
[ ](/p/ament_lint_auto#rolling-deps) |  [ 1 ](/packages/ament_lint_auto) |  [
ament_lint_auto ](/p/ament_lint_auto#rolling)
[ ](/p/ament_lint_common#rolling-deps) |  [ 1 ](/packages/ament_lint_common) |
[ ament_lint_common ](/p/ament_lint_common#rolling)
[ ](/p/ros_testing#rolling-deps) |  [ 1 ](/packages/ros_testing) |  [
ros_testing ](/p/ros_testing#rolling)
[ ](/p/lifecycle_msgs#rolling-deps) |  [ 1 ](/packages/lifecycle_msgs) |  [
lifecycle_msgs ](/p/lifecycle_msgs#rolling)
[ ](/p/rclcpp#rolling-deps) |  [ 1 ](/packages/rclcpp) |  [ rclcpp
](/p/rclcpp#rolling)
[ ](/p/rclcpp_lifecycle#rolling-deps) |  [ 1 ](/packages/rclcpp_lifecycle) |
[ rclcpp_lifecycle ](/p/rclcpp_lifecycle#rolling)
[ ](/p/std_msgs#rolling-deps) |  [ 2 ](/packages/std_msgs) |  [ std_msgs
](/p/std_msgs#rolling)

###  System Dependencies


  * Added readme.rst ( [ #300 ](https://github.com/ros2/demos/issues/300) )
  * Contributors: Karsten Knese


_No direct system dependencies._


In this post, we discussed ROS2 Lifecycle interface. The Lifecycle interface
makes it easier to manage the lifecycle of different software components, such
as nodes.


    [lc_talker] on_activate() is called.
    [lc_talker] Lifecycle publisher is active. Publishing: [Lifecycle HelloWorld #11]
    [lc_talker] Lifecycle publisher is active. Publishing: [Lifecycle HelloWorld #12]
    ...


Between Foxy and Galactic we made substantial changes to the interface of
hardware components to enable management of their lifecycle. The following
list shows a set of quick changes to port existing hardware components to
Galactic:


makes the lifecycle talker change its state to inactive. Inactive means that
all publishers and timers are created and configured. However, the node is
still not active. Therefore no messages are getting published.


#  Introduction


* Service ` <node_name>__get_available_transitions ` : Same as above, meant to an introspection tool.


##  0.7.4 (2019-05-20)


Releases


  * Add lifecycle rostest ( [ #336 ](https://github.com/ros2/demos/issues/336) )
  * Contributors: Michel Hidalgo


ROS 2 introduces the concept of managed nodes, also called ` LifecycleNode `
s. In the following tutorial, we explain the purpose of these nodes, what
makes them different from regular nodes and how they comply to a lifecycle
management. Managed nodes contain a state machine with a set of predefined
states. These states can be changed by invoking a transition id which
indicates the succeeding consecutive state. The state machine is implemented
as described at the [ ROS 2 design page
](http://design.ros2.org/articles/node_lifecycle.html) .


In order to trigger a transition, we call the ` change_state ` service


  * Cleaned up lifecycle demo ( [ #283 ](https://github.com/ros2/demos/issues/283) )
  * Updated for refactoring in rclcpp ( [ #276 ](https://github.com/ros2/demos/issues/276) )
  * Added semicolons to all RCLCPP and RCUTILS macros. ( [ #278 ](https://github.com/ros2/demos/issues/278) )
  * Fixed typo in comment ( [ #270 ](https://github.com/ros2/demos/issues/270) )
  * Contributors: Chris Lalancette, Karsten Knese, Yutaka Kondo


The next step would be to execute a state change:


The demo is split into 3 different separate applications.


The lifecycle listener receives the same set of notifications as before.
Lifecycle talker changed its state from inactive to active.


    [lc_listener]: notify callback: Transition from state inactive to activating
    [lc_listener]: notify callback: Transition from state activating to active


  * ardent
  * bouncy
  * crystal
  * eloquent
  * dashing
  * galactic
  * foxy
  * lunar
  * jade
  * indigo
  * hydro
  * kinetic
  * melodic


#  Hardware Components  


##  Triggering transition 2 (activate)


* Publisher ` <node_name>__transition_event ` : publishes in case a transition is happening.


class LifecycleTalker : public rclcpp_lifecycle::LifecycleNode


In the world of robotics, _managing the lifecycle of different software
components can be a challenging task_ . Each component may have its own
_dependencies_ , _configuration parameters_ , and _runtime events_ to handle.
This can lead to complex launch files and scripts that make it difficult to
manage and update the system. And, the state machine design is important in
robotics systems because they provide a structured and predictable way to
manage the behaviour and functionality of robotic software components. _ROS1
doesn’t have an inbuilt interface for managing the lifecycle of software
components_ , which can make it challenging to ensure that different nodes in
a system are operating correctly and communicating with each other
effectively. This is where **_ROS2’s Lifecycle Nodes come in — they provide a
standardized interface for managing the state of a software component, from
its creation and initialization to its shutdown and cleanup._ **


##  0.21.0 (2022-04-29)


In order to see what states are currently available:


If we have a look at the code, there is one significant change for the
lifecycle talker compared to a regular talker. Our node does not inherit from
the regular ` rclcpp::node::Node ` but from ` rclcpp_lifecycle::LifecycleNode
` .


###  Package Dependencies


##  0.19.0 (2022-01-14)


In the case you want to get the current state of the ` lc_talker ` node, you
would call:


The ` lifecycle_listener ` is a simple listener which shows the
characteristics of the lifecycle talker. The talker enables message publishing
only in the active state and thus the listener only receives messages when the
talker is in an active state.


  * Added readme.rst ( [ #300 ](https://github.com/ros2/demos/issues/300) )
  * Contributors: Karsten Knese


The ` lifecycle_talker ` represents a managed node and publishes according to
which state the node is in. We split the tasks of the talker node into
separate pieces and execute them as followed.


It is slightly less convenient, because you have to know the IDs which
correspond to each transition. You can find them though in the lifecycle_msgs
package.


  * Update asciinema recordings ( [ #360 ](https://github.com/ros2/demos/issues/360) )
  * Use rate instead of thread::sleep to react to Ctrl-C ( [ #348 ](https://github.com/ros2/demos/issues/348) )
  * Contributors: Dirk Thomas, Karsten Knese


ros2 launch lifecycle lifecycle_demo.launch.py


The difference from the earlier transition event is that our listener now also
receives the actual published data.


We have another command to see the full state machine of the camera_node.


##  0.7.3 (2019-05-10)


    $ ros2 lifecycle get /lc_talker
    unconfigured [1]


This gives room for executing custom error handling. Only (!) in the case that
this function returns ` CallbackReturn::SUCCESS ` , the state machine
transitions to the state ` unconfigured ` . By default, the ` on_error `
returns ` CallbackReturn::FAILURE ` and the state machine transitions into `
finalized ` .


  * Replace ready_fn with ReadyToTest action ( [ #404 ](https://github.com/ros2/demos/issues/404) )
  * Contributors: Peter Baughman


In this case we see that currently, the available transitions are ` configure
` and ` shutdown ` . The complete state machine can be viewed with the
following command, which can be helpful for debugging or visualization
purposes:


####  Package Summary


**Checkout URI** |  [ https://github.com/ros2/demos.git
](https://github.com/ros2/demos.git)
---|---
**VCS Type** |  git
**VCS Version** |  bouncy
**Last Updated**

2018-10-30  |  **Dev Status** |  DEVELOPED
**CI status** |  No Continuous Integration
**Released** |  RELEASED
**Tags** |  _No category tags._
**Contributing** |  [ Help Wanted (  0  ) ](/r/demos/#bouncy-contribute-lists-
help-wanted)
[ Good First Issues (  0  ) ](/r/demos/#bouncy-contribute-lists-good-first-
issue)
[ Pull Requests to Review (  0  ) ](/r/demos/#bouncy-contribute-lists-pull-
requests)

###  Package Description


##  0.24.0 (2023-02-14)


###  Package Dependencies


No questions yet, you can ask one [ here
](https://robotics.stackexchange.com/questions/tagged/lifecycle+crystal) .


#  Introduction


For a more verbose explanation on the applied state machine, we refer to the
design page which provides an in-detail explanation about each state and
transition.


##  0.9.3 (2020-06-01)


  * Cleanup the README.rst for the lifecycle demo. ( [ #508 ](https://github.com/ros2/demos/issues/508) )
  * Contributors: Chris Lalancette


##  0.8.2 (2019-11-08)


The lifecycle listener receives the same set of notifications as before.
Lifecycle talker changed its state from inactive to active.


##  0.14.0 (2021-04-06)


At the same time, every lifecycle node has by default 5 different
communication interfaces.


The demo is split into 3 different separate applications.


It returns a list of all possible states this node can be.


![](/assets/package.png) |


The ` lifecycle_service_client ` is a script calling different transitions on
the ` lifecycle_talker ` . This is meant as the external user controlling the
lifecycle of nodes.


  * Overview
  * 0  Assets
  * 7  Dependencies
  * 0  Tutorials
  * 0  Q & A


 </joint>
 <joint name="joint2">
 <command_interface name="position">
 <param name="min">-1</param>
 <param name="max">1</param>
 </command_interface>
 <state_interface name="position"/>
 </joint>
</ros2_control>
ros2 launch rrbot_bringup rrbot.launch.py
Implementing a forwarding controller
class RRBotControllerArray : public controller_interface::ControllerInterface
{
public:
 controller_interface::return_type init(const std::string & controller_name) override;
 controller_interface::InterfaceConfiguration command_interface_configuration() const override;
 controller_interface::InterfaceConfiguration state_interface_configuration() const override;
 CallbackReturn on_configure(const rclcpp_lifecycle::State & previous_state) override;
 CallbackReturn on_activate(const rclcpp_lifecycle::State & previous_state) override;
 CallbackReturn on_deactivate(const rclcpp_lifecycle::State & previous_state) override;
 controller_interface::return_type update() override;
...
};
Implementing a forwarding controller
class RRBotControllerArray : public controller_interface::ControllerInterface
{
...
protected:
 std::vector<std::string> joint_names_;
 std::string interface_name_;
 using ControllerCommandMsg = example_interfaces::msg::Float64MultiArray;
 rclcpp::Subscription<ControllerCommandMsg>::SharedPtr command_subscriber_ = nullptr;
 realtime_tools::RealtimeBuffer<std::shared_ptr<ControllerCommandMsg>> input_command_;
 using ControllerStateMsg = control_msgs::msg::JointControllerState;
 using ControllerStatePublisher = realtime_tools::RealtimePublisher<ControllerStateMsg>;
 rclcpp::Publisher<ControllerStateMsg>::SharedPtr s_publisher_;
 std::unique_ptr<ControllerStatePublisher> state_publisher_;
};
Implementing a forwarding controller
controller_interface::return_type RRBotControllerArray::update()


makes the lifecycle talker change its state to inactive. Inactive means that
all publishers and timers are created and configured. However, the node is
still not active. Therefore no messages are getting published.


The above description points to the current state of the development as for
beta1. The future todo list for this topic comprises:


This demo shows a typical talker/listener pair of nodes. However, imagine a
real scenario with attached hardware which may have a rather long booting
phase, i.e. a laser or camera. One could imagine bringing up the device driver
in the configuring state, start and stop only the publishing of the device\'s
data in active/deactive state, and only in the cleanup/shutdown state actually
shutdown the device.


##  lifecycle_talker, lifecycle_listener and lifecycle_service_client


 if (configure_default(info) != hardware_interface::return_type::OK) {
 return hardware_interface::return_type::ERROR;
 }
 hw_states_.resize(info_.joints.size(), std::numeric_limits<double>::quiet_NaN());
 hw_commands_.resize(info_.joints.size(), std::numeric_limits<double>::quiet_NaN());
 status_ = hardware_interface::status::CONFIGURED;
 return hardware_interface::return_type::OK;
}
Implementing a system component
hardware_interface::return_type RRBotHardwareInterface::read()
{
 // read robot states from hardware, in this example print only
 RCLCPP_INFO(rclcpp::get_logger("RRBotHardwareInterface"), "Reading...");
 // write command to hardware, in this example do mirror command to states
 for (size_t i = 0; i < hw_states_.size(); ++i){
 RCLCPP_INFO(
 rclcpp::get_logger("RRBotHardwareInterface"),
 "Got state %.2f for joint %d!", hw_states_[i], i);
 }
 return hardware_interface::return_type::OK;
}
hardware_interface::return_type RRBotHardwareInterface::write()
{
 // write command to hardware, in this example do mirror command to states
 for (size_t i = 0; i < hw_commands_.size(); ++i){
 hw_states_[i] = hw_states_[i] + (hw_commands_[i] - hw_states_[i]) / 100.0;
 }
 return hardware_interface::return_type::OK;
}
Implementing a system component
<ros2_control name="${name}" type="system">
 <hardware>
 <plugin>rrbot_hardware_interface/RRBotHardwareInterface</plugin>
 </hardware>
 <joint name="joint1">
 <command_interface name="position">
 <param name="min">-1</param>
 <param name="max">1</param>
 </command_interface>
 <state_interface name="position"/>


10. Change last return of ` on_activate  ` and ` on_deactivate  ` to ` return  CallbackReturn::SUCCESS;  `


_No message files found._


* Karsten Knese


####  Package Summary


About


* Publisher ` <node_name>__transition_event ` : publishes in case a transition is happening.


###  Messages


##  0.5.0 (2018-06-27)


_No launch files found_


In order to see what states are currently available:


###  [ lifecycle ](/p/lifecycle) package from [ demos ](/r/demos/github-
ros2-demos) repo


* Service ` <node_name>__get_available_states ` : This is meant to be an introspection tool.


##  0.11.0 (2020-12-10)


    $ ros2 lifecycle list lc_talker
    - configure [1]
      Start: unconfigured
      Goal: configuring
    - shutdown [5]
      Start: unconfigured
      Goal: shuttingdown


_No plugins found._


Package containing demos for lifecycle implementation


##  0.6.0 (2018-12-07)


[ lifecycle/README.rst
](https://github.com/ros2/demos/tree/bouncy/lifecycle/README.rst "Open in git
repository")


###  Recent questions tagged ` lifecycle ` at **[ Robotics Stack Exchange
](https://robotics.stackexchange.com/) **


##  0.9.3 (2020-06-01)


##  Written by  Jegathesan Shanmugam


##  0.7.4 (2019-05-20)


In order to run this demo, we open three terminals and source our ROS 2
environment variables either from the binary distributions or the workspace we
compiled from source.


ros2 launch lifecycle lifecycle_demo_launch.py


  * configure
  * activate
  * deactivate
  * cleanup
  * shutdown


  * Mabel Zhang
  * Michael Jeronimo


###  Messages


  * Make lifecycle demo automatically exit when done ( [ #558 ](https://github.com/ros2/demos/issues/558) )
  * Contributors: Shane Loretz


The demo is split into 3 separate applications:


###  Services


  1. configuring: We initialize our publisher and timer
  2. activate: We activate the publisher and timer in order to enable a publishing
  3. deactivate: We stop the publisher and timer
  4. cleanup: We destroy the publisher and timer


##  Triggering transition 2 (activate)


###  Source Tutorials


##  What\'s happening


    $ ros2 lifecycle set /lc_talker configure
    Transitioning successful


##  ros2 lifecycle command line interface


    $ ros2 lifecycle get /lc_talker
    unconfigured [1]


>
>
> hardware_interface::BaseInterface<hardware_interface::[Actuator|Sensor|System]Interface>
>
>
> to
>
>
>     hardware_interface::[Actuator|Sensor|System]Interface
>


##  0.8.1 (2019-10-23)


  * Replace ready_fn with ReadyToTest action ( [ #404 ](https://github.com/ros2/demos/issues/404) )
  * Contributors: Peter Baughman


##  0.7.5 (2019-05-29)


##  0.8.3 (2019-11-11)


lifecycle_talker lifecycle_listener lifecycle_service_client


Our implementation differentiates between ` Primary States ` and ` Transition
States ` . Primary States are supposed to be steady states in which any node
can do the respected task. On the other hand, Transition States are meant as
temporary intermediate states attached to a transition. The result of these
intermediate states are used to indicate whether a transition between two
primary states is considered successful or not. Thus, any managed node can be
in one of the following states:


#  ROS2 from the Ground Up: Part 8- Simplify Robotic Software Components
Management with ROS2 Lifecycle Nodes


    $ ros2 service call /lc_talker/change_state lifecycle_msgs/ChangeState "{transition: {id: 2}}"
    requester: making request: lifecycle_msgs.srv.ChangeState_Request(transition=lifecycle_msgs.msg.Transition(id=2, label=''))

    response:
    lifecycle_msgs.srv.ChangeState_Response(success=True)


In the case you want to get the current state of the ` lc_talker ` node,
you\'d call:


###  Services


    [lc_listener] data_callback: Lifecycle HelloWorld #11
    [lc_listener] data_callback: Lifecycle HelloWorld #12
    ...


##  0.7.6 (2019-05-30)


ROS2 introduces the concept of managed nodes, also called ` LifecycleNode ` s.
In the following tutorial, we explain the purpose of these nodes, what makes
them different from regular nodes and how they comply to a lifecycle
management. Managed nodes are scoped within a state machine of a finite amount
of states. These states can be changed by invoking a transition id which
indicates the succeeding consecutive state. The state machine is implemented
as described at the [ ROS2 design page
](http://design.ros2.org/articles/node_lifecycle.html) .


` $ ros2 run lifecycle lifecycle_talker ` ` $ ros2 run lifecycle
lifecycle_listener ` ` $ ros2 run lifecycle lifecycle_service_client ` [
![asciicast](https://asciinema.org/a/249049.png)
](https://asciinema.org/a/249049) [
![asciicast](https://asciinema.org/a/249050.png)
](https://asciinema.org/a/249050) [
![asciicast](https://asciinema.org/a/249051.png)
](https://asciinema.org/a/249051)


URDF and ros2_control
<ros2_control name="${name}" type="system">
 <hardware>
 <plugin>fake_components/GenericSystem</plugin>
 </hardware>
 <joint name="joint1">
 <command_interface name="position">
 <param name="min">-1</param>
 <param name="max">1</param>
 </command_interface>
 <state_interface name="position"/>
 </joint>
 <joint name="joint2">
 <command_interface name="position">
 <param name="min">-1</param>
 <param name="max">1</param>
 </command_interface>
 <state_interface name="position"/>
 </joint>
</ros2_control>
Implementing a system component
class RRBotHardwareInterface
 : public hardware_interface::BaseInterface<hardware_interface::SystemInterface>
{
public:
 hardware_interface::return_type configure(const hardware_interface::HardwareInfo & info) override;
 std::vector<hardware_interface::StateInterface> export_state_interfaces() override;
 std::vector<hardware_interface::CommandInterface> export_command_interfaces() override;
 hardware_interface::return_type start() override;
 hardware_interface::return_type stop() override;
 hardware_interface::return_type read() override;
 hardware_interface::return_type write() override;
private:
 std::vector<double> hw_commands_;
 std::vector<double> hw_states_;
};
Implementing a system component
hardware_interface::return_type RRBotHardwareInterface::configure(
 const hardware_interface::HardwareInfo & info)
{


Return either a primary or transition state.


##  0.32.0 (2023-11-06)


##  0.5.1 (2018-06-28)


###  Source Tutorials


    rclcpp_lifecycle::node_interfaces::LifecycleNodeInterface::CallbackReturn
    on_configure(const rclcpp_lifecycle::State & previous_state)

    rclcpp_lifecycle::node_interfaces::LifecycleNodeInterface::CallbackReturn
    on_activate(const rclcpp_lifecycle::State & previous_state)

    rclcpp_lifecycle::node_interfaces::LifecycleNodeInterface::CallbackReturn
    on_deactivate(const rclcpp_lifecycle::State & previous_state)

    rclcpp_lifecycle::node_interfaces::LifecycleNodeInterface::CallbackReturn
    on_cleanup(const rclcpp_lifecycle::State & previous_state)

    rclcpp_lifecycle::node_interfaces::LifecycleNodeInterface::CallbackReturn
    on_shutdown(const rclcpp_lifecycle::State & previous_state)


##  0.7.0 (2019-04-14)


](https://blog.medium.com/?source=post_page-----
5fafa2738700--------------------------------)


Deps  |  |  Name  |  [ ](/p/lifecycle_msgs#dashing-deps) |  [ 1
](/packages/lifecycle_msgs) |  [ lifecycle_msgs ](/p/lifecycle_msgs#dashing)
---|---|---
[ ](/p/rclcpp_lifecycle#dashing-deps) |  [ 1 ](/packages/rclcpp_lifecycle) |
[ rclcpp_lifecycle ](/p/rclcpp_lifecycle#dashing)
[ ](/p/std_msgs#dashing-deps) |  [ 2 ](/packages/std_msgs) |  [ std_msgs
](/p/std_msgs#dashing)
[ ](/p/ament_cmake#dashing-deps) |  [ 1 ](/packages/ament_cmake) |  [
ament_cmake ](/p/ament_cmake#dashing)
[ ](/p/ros2run#dashing-deps) |  [ 1 ](/packages/ros2run) |  [ ros2run
](/p/ros2run#dashing)
[ ](/p/ament_lint_auto#dashing-deps) |  [ 1 ](/packages/ament_lint_auto) |  [
ament_lint_auto ](/p/ament_lint_auto#dashing)
[ ](/p/ament_lint_common#dashing-deps) |  [ 1 ](/packages/ament_lint_common) |
[ ament_lint_common ](/p/ament_lint_common#dashing)
[ ](/p/ros_testing#dashing-deps) |  [ 1 ](/packages/ros_testing) |  [
ros_testing ](/p/ros_testing#dashing)

###  System Dependencies


ros2 launch lifecycle lifecycle_demo.launch.py


#  The demo code


#  Run the demo


##  Triggering transition 2 (activate)


##  0.8.3 (2019-11-11)


This service call takes a transition id. The transition is fulfilled only in
the case that this transition ID is a valid transition from the current state.
All other cases are ignored.


####  Package Summary


##  0.6.1 (2018-12-13)


##  0.12.0 (2021-01-25)


* [ github-ros2-demos ](/p/lifecycle/github-ros2-demos)


##  0.8.2 (2019-11-08)


  * Converted launch files to the new launch style. ( [ #262 ](https://github.com/ros2/demos/issues/262) )
  * Updated to support remapping arguments to python nodes by passing unused arguments to rclpy from argparse. ( [ #252 ](https://github.com/ros2/demos/issues/252) )
  * Updated to handle change in signature to ` get_service_name ` . ( [ #245 ](https://github.com/ros2/demos/issues/245) )
  * Updated launch files to account for the \"old launch\" getting renamespaced as ` launch ` -> ` launch.legacy ` . ( [ #239 ](https://github.com/ros2/demos/issues/239) )
  * Updated service client demos to handle multiple requests. ( [ #228 ](https://github.com/ros2/demos/issues/228) )
  * Contributors: Geoffrey Biggs, Kevin Allen, Shane Loretz, William Woodall, dhood


Please note that the index of the published message is already at 11. The
purpose of this demo is to show that even though we call ` publish ` at every
state of the lifecycle talker, the messages are only actually published when
the state in active.


_No plugins found._


    [lc_listener] notify callback: Transition from state unconfigured to configuring
    [lc_listener] notify callback: Transition from state configuring to inactive


_No additional links._


* Service ` <node_name>__get_available_transitions ` : Same as above, meant to an introspection tool.


##  Triggering transition 1 (configure)


##  0.8.4 (2019-11-19)


[ ![Jegathesan
Shanmugam](https://miro.medium.com/v2/resize:fill:88:88/2*h3PRzfT7jps1zKlfhvGp6Q.jpeg)
](/@nullbyte.in?source=post_page-----
5fafa2738700--------------------------------)


###  Wiki Tutorials


The demo is split into 3 separate applications:


    $ ros2 run lifecycle lifecycle_service_client_py.py get_state lc_talker
    lc_talker is in state unconfigured(1)


  * Replace deprecated launch_ros usage ( [ #437 ](https://github.com/ros2/demos/issues/437) )
  * Update launch_ros action usage ( [ #431 ](https://github.com/ros2/demos/issues/431) )
  * code style only: wrap after open parenthesis if not in one line ( [ #429 ](https://github.com/ros2/demos/issues/429) )
  * Contributors: Dirk Thomas, Jacob Perron


Transition States (intermediate states):


In the following we assume that we are inside the namespace `
rclcpp_lifecycle::node_interfaces::LifecycleNodeInterface ` to shorten the
name of the return type. All these callbacks have a positive default return
value ( ` return CallbackReturn::SUCCESS ` ). This allows a lifecycle node to
change its state even though no explicit callback function was overwritten.
There is one other callback function for error handling. Whenever a state
transition throws an uncaught exception, we call ` on_error ` .


The possible transitions to invoke are:


##  0.7.2 (2019-05-08)