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.


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


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


##  0.7.3 (2019-05-10)


  * changes to avoid deprecated API\'s ( [ #332 ](https://github.com/ros2/demos/issues/332) )
  * Corrected publish calls with shared_ptr signature ( [ #327 ](https://github.com/ros2/demos/issues/327) )
  * Contributors: William Woodall, ivanpauno


  * unconfigured
  * inactive
  * active
  * shutdown


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


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


#  The demo


###  Package Dependencies


##  0.9.1 (2020-05-12)


* Publisher ` <node_name>__transition_event ` : publishes in case a transition is happening. This allows users to get notified of transition events within the network.


[ 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")


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


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


**Tags** |  _No category tags._
---|---
**Version** |  0.9.4
**License** |  Apache License 2.0
**Build type** |  AMENT_CMAKE
**Use** |  RECOMMENDED

###  Repository Summary


#  The demo code


Another example, the ROS Navigation Stack,


_No message files found._


Transition States (intermediate states):


##  0.11.0 (2020-12-10)


CHANGELOG


##  0.18.0 (2021-12-17)


  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


    $ ros2 lifecycle set /lc_talker configure
    Transitioning successful


_No direct system dependencies._


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


###  Services


There are 4 primary states:
1\. **Unconfigured**
2\. **Inactive**
3\. **Active**
4\. **Finalized**


8. Rename ` start()  ` to ` on_activate(const  rclcpp_lifecycle::State  & previous_state)  ` and ` stop()  ` to ` on_deactivate(const  rclcpp_lifecycle::State  & previous_state)  `


####  Maintainers


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:


[ action_tutorials ](/p/action_tutorials/github-ros2-demos) [ composition
](/p/composition/github-ros2-demos) [ demo_nodes_cpp
](/p/demo_nodes_cpp/github-ros2-demos) [ demo_nodes_cpp_native
](/p/demo_nodes_cpp_native/github-ros2-demos) [ demo_nodes_py
](/p/demo_nodes_py/github-ros2-demos) [ dummy_map_server
](/p/dummy_map_server/github-ros2-demos) [ dummy_robot_bringup
](/p/dummy_robot_bringup/github-ros2-demos) [ dummy_sensors
](/p/dummy_sensors/github-ros2-demos) [ image_tools ](/p/image_tools/github-
ros2-demos) [ intra_process_demo ](/p/intra_process_demo/github-ros2-demos)
lifecycle  [ logging_demo ](/p/logging_demo/github-ros2-demos) [
pendulum_control ](/p/pendulum_control/github-ros2-demos) [ pendulum_msgs
](/p/pendulum_msgs/github-ros2-demos) [ quality_of_service_demo_cpp
](/p/quality_of_service_demo_cpp/github-ros2-demos) [
quality_of_service_demo_py ](/p/quality_of_service_demo_py/github-ros2-demos)
[ topic_monitor ](/p/topic_monitor/github-ros2-demos)
---|---

github-ros2-demos


I hope this information was helpful and that you found it useful. If you have
any questions or comments, please don’t hesitate to let me know. I appreciate
your feedback and are happy to help answer any questions you may have. Thank
you for taking the time to read this.


If we look at the output of the ` lifecycle_talker ` , we notice that nothing
seems to happen. This makes 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 ` .


class LifecycleTalker : public rclcpp_lifecycle::LifecycleNode


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


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


##  0.6.0 (2018-12-07)


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.


  * A few uncrustify fixes for 0.78. ( [ #667 ](https://github.com/ros2/demos/issues/667) )
  * Update maintainer list in package.xml files ( [ #665 ](https://github.com/ros2/demos/issues/665) )
  * Contributors: Chris Lalancette, Michael Jeronimo


##  0.7.0 (2019-04-14)


##  0.14.2 (2021-04-26)


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


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

###  Launch files


_No direct system dependencies._


##  0.7.3 (2019-05-10)


  * configuring
  * activating
  * deactivating
  * cleaningup
  * shuttingdown


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


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


###  Plugins


    $ 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)


CHANGELOG


[ 245 Followers ](/@nullbyte.in/followers?source=post_page-----
5fafa2738700--------------------------------)


In order to see what states are currently available:


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:


Package containing demos for lifecycle implementation


##  What\'s happening


    ros2 lifecycle list camera_node -a

    # Output
    - 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
    - cleanup [2]
     Start: inactive
     Goal: cleaningup
    - transition_success [20]
     Start: cleaningup
     Goal: unconfigured
    - transition_failure [21]
     Start: cleaningup
     Goal: inactive
    - transition_error [22]
     Start: cleaningup
     Goal: errorprocessing
    - activate [3]
     Start: inactive
     Goal: activating
    - transition_success [30]
     Start: activating
     Goal: active
    - transition_failure [31]
     Start: activating
     Goal: inactive
    - transition_error [32]
     Start: activating


Assignees
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Successfully merging a pull request may close this issue.
[ Fix multiple calls of cleanup when system is unconfigured ](/ros-
controls/ros2_control/pull/1279) [ ros-controls/ros2_control ](/ros-
controls/ros2_control)
2 participants
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![@christophfroehlich](https://avatars.githubusercontent.com/u/3367244?s=52&v=4)
](/christophfroehlich) [
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` $ 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)


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


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:


##  0.29.0 (2023-06-07)


The next step would be to execute a state change:


    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)


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


_No message files found._


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


##  0.14.1 (2021-04-19)


  * 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


####  Additional Links


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


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


**Tags** |  _No category tags._
---|---
**Version** |  0.7.9
**License** |  Apache License 2.0
**Build type** |  AMENT_CMAKE
**Use** |  RECOMMENDED

###  Repository Summary


##  0.18.0 (2021-12-17)


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:


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


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


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


CHANGELOG


#  Introduction


##  ros2 lifecycle command line interface


#  Changelog for package lifecycle


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


##  0.8.3 (2019-11-11)


` $ 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)


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


_Not currently indexed._


##  0.5.0 (2018-06-27)


##  lifecycle_talker, lifecycle_listener and lifecycle_service_client


####  Authors


##  0.5.1 (2018-06-28)


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


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.


ros2 launch lifecycle lifecycle_demo.launch.py


##  0.7.2 (2019-05-08)


    $ ros2 lifecycle get /lc_talker
    unconfigured [1]


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.


$ ros2 msg show lifecycle_msgs/Transition


    * [ Collections ](/collections)
  * [ Pricing ](/pricing)
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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 ` .


##  0.20.1 (2022-04-08)


##  0.7.0 (2019-04-14)


    $ 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'))


Karsten Knese, Victor Lopez,
Jordan Palacios, Olivier
Stasse, Mathias Arbo, Jaron
Lundwall, Colin MacKenzie,
Matthew Reynolds, Andy
Zelenak, Lovro Ivanov, Jafar
Abdi, Tyler Weaver, Anas Abou
Allaban, Yutaka Kondo, Mateus
Amarante, Auguste Bourgois
and many more!
Thank you!


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


a community-maintained index of robotics software | [ privacy ](/privacy.txt)


---

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


##  0.6.1 (2018-12-13)


#  The demo


    $ 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


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


###  Dependant Packages


[ bug  ](/ros-controls/ros2_control/labels/bug)
##  Comments
[
![@christophfroehlich](https://avatars.githubusercontent.com/u/3367244?s=80&u=98db36351213b952b1c6ce663c1fde4108272539&v=4)
](/christophfroehlich)
Copy link
Contributor
###
**[ christophfroehlich ](/christophfroehlich) ** commented  Aug 22, 2023
**Describe the bug**
After changing the lifecycle of a hardware component, no matter if via
controller-manager service or from the component's write method returning `
hardware_interface::return_type::ERROR ` , the controller manager spams the
console with something like

    [ros2_control_node-1] [WARN] [1691260478.510570255] [resource_manager]: (hardware 'RRBotSystemPositionOnly'): 'rrbot_joint1/position' command interface not in available list. This should not happen (hint: multiple cleanup calls).
    [ros2_control_node-1] [WARN] [1691260478.510572441] [resource_manager]: (hardware 'RRBotSystemPositionOnly'): 'rrbot_joint2/position' command interface not in available list. This should not happen (hint: multiple cleanup calls).
    [ros2_control_node-1] [WARN] [1691260478.510574080] [resource_manager]: (hardware 'RRBotSystemPositionOnly'): 'rrbot_joint1/position' state interface not in available list. This should not happen (hint: multiple cleanup calls).
    [ros2_control_node-1] [WARN] [1691260478.510575651] [resource_manager]: (hardware 'RRBotSystemPositionOnly'): 'rrbot_joint2/position' state interface not in available list. This should not happen (hint: multiple cleanup calls).

And the component can't be activated again. If this is a result of overflow of
the logger, or some failed state of the ressource manager?
**To Reproduce**
Steps to reproduce the behavior:
Follow the instructions of [ this demo example
](https://github.com/StoglRobotics-forks/ros2_control_demos/pull/7) .
**Expected behavior**
A clean deactivation or shutdown of the hw component, being able to reactivate
it again.
**Screenshots**
**Environment (please complete the following information):**
  * OS: ubuntu 22.04
  * ros2_control rolling from source

---

The text was updated successfully, but these errors were encountered:


  * 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 next step would be to execute a state change:


##  0.7.4 (2019-05-20)


[ action_tutorials_cpp ](/p/action_tutorials_cpp/github-ros2-demos) [
action_tutorials_interfaces ](/p/action_tutorials_interfaces/github-
ros2-demos) [ action_tutorials_py ](/p/action_tutorials_py/github-ros2-demos)
[ composition ](/p/composition/github-ros2-demos) [ demo_nodes_cpp
](/p/demo_nodes_cpp/github-ros2-demos) [ demo_nodes_cpp_native
](/p/demo_nodes_cpp_native/github-ros2-demos) [ demo_nodes_py
](/p/demo_nodes_py/github-ros2-demos) [ dummy_map_server
](/p/dummy_map_server/github-ros2-demos) [ dummy_robot_bringup
](/p/dummy_robot_bringup/github-ros2-demos) [ dummy_sensors
](/p/dummy_sensors/github-ros2-demos) [ image_tools ](/p/image_tools/github-
ros2-demos) [ intra_process_demo ](/p/intra_process_demo/github-ros2-demos)
lifecycle  [ lifecycle_py ](/p/lifecycle_py/github-ros2-demos) [ logging_demo
](/p/logging_demo/github-ros2-demos) [ pendulum_control
](/p/pendulum_control/github-ros2-demos) [ pendulum_msgs
](/p/pendulum_msgs/github-ros2-demos) [ quality_of_service_demo_cpp
](/p/quality_of_service_demo_cpp/github-ros2-demos) [
quality_of_service_demo_py ](/p/quality_of_service_demo_py/github-ros2-demos)
[ topic_monitor ](/p/topic_monitor/github-ros2-demos) [ topic_statistics_demo
](/p/topic_statistics_demo/github-ros2-demos)
---|---

github-ros2-demos


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.


##  0.20.0 (2022-03-01)


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.


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

###  Launch files


Package containing demos for lifecycle implementation


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


  * changes to avoid deprecated API\'s ( [ #332 ](https://github.com/ros2/demos/issues/332) )
  * Corrected publish calls with shared_ptr signature ( [ #327 ](https://github.com/ros2/demos/issues/327) )
  * Contributors: William Woodall, ivanpauno


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


  * Mabel Zhang
  * Michael Jeronimo


[ composition ](/p/composition/github-ros2-demos) [ demo_nodes_cpp
](/p/demo_nodes_cpp/github-ros2-demos) [ demo_nodes_cpp_native
](/p/demo_nodes_cpp_native/github-ros2-demos) [ demo_nodes_py
](/p/demo_nodes_py/github-ros2-demos) [ dummy_map_server
](/p/dummy_map_server/github-ros2-demos) [ dummy_robot_bringup
](/p/dummy_robot_bringup/github-ros2-demos) [ dummy_sensors
](/p/dummy_sensors/github-ros2-demos) [ image_tools ](/p/image_tools/github-
ros2-demos) [ intra_process_demo ](/p/intra_process_demo/github-ros2-demos)
lifecycle  [ logging_demo ](/p/logging_demo/github-ros2-demos) [
pendulum_control ](/p/pendulum_control/github-ros2-demos) [ pendulum_msgs
](/p/pendulum_msgs/github-ros2-demos) [ topic_monitor
](/p/topic_monitor/github-ros2-demos)
---|---

github-ros2-demos


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


  * 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


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:


#  The demo


###  Messages


##  0.14.0 (2021-04-06)


[ 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")


Transition States (intermediate states):


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


##  0.6.1 (2018-12-13)


  * Karsten Knese
  * Mabel Zhang


  * Update maintainers to Audrow Nash and Michael Jeronimo ( [ #543 ](https://github.com/ros2/demos/issues/543) )
  * Contributors: Audrow Nash


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


In order to see what states are currently available:


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


The next step would be to execute a state change:


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


##  0.9.3 (2020-06-01)


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

2020-10-28  |  **Dev Status** |  DEVELOPED
**CI status** |  No Continuous Integration
**Released** |  RELEASED
**Tags** |  _No category tags._
**Contributing** |  [ Help Wanted (  0  ) ](/r/demos/#dashing-contribute-
lists-help-wanted)
[ Good First Issues (  0  ) ](/r/demos/#dashing-contribute-lists-good-first-
issue)
[ Pull Requests to Review (  0  ) ](/r/demos/#dashing-contribute-lists-pull-
requests)

###  Package Description


##  0.7.4 (2019-05-20)


    cd camera_node && touch src/display_node.cpp

    // display_node.cpp
    #include <memory>
    #include <string>

    #include "lifecycle_msgs/msg/transition_event.hpp"
    #include "rclcpp/rclcpp.hpp"
    #include "rcutils/logging_macros.h"
    #include "sensor_msgs/msg/image.hpp"

    #include "utils.cpp"

    class DisplayNode : public rclcpp::Node
    {
    public:
      explicit DisplayNode(const std::string & node_name)
      : Node(node_name)
      {
        subscriber_ = this->create_subscription<sensor_msgs::msg::Image>(
          "camera_image", 10,
          std::bind(&DisplayNode::data_callback, this, std::placeholders::_1));

        sub_notification_ = this->create_subscription<lifecycle_msgs::msg::TransitionEvent>(
          "/camera_image/transition_event",
          10,
          std::bind(&DisplayNode::notification_callback, this, std::placeholders::_1));
      }

      void data_callback(const sensor_msgs::msg::Image::UniquePtr msg)
      {
        cv::Mat frame(
              msg->height, msg->width,
              encoding2mat_type(msg->encoding),
              msg->data.data());
        cv::imshow("window", frame);
        cv::waitKey(1);


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


##  0.11.0 (2020-12-10)


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

###  System Dependencies


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


  * 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


##  0.8.4 (2019-11-19)


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


     Goal: errorprocessing
    - deactivate [4]
     Start: active
     Goal: deactivating
    - transition_success [40]
     Start: deactivating
     Goal: inactive
    - transition_failure [41]
     Start: deactivating
     Goal: active
    - transition_error [42]
     Start: deactivating
     Goal: errorprocessing
    - shutdown [5]
     Start: unconfigured
     Goal: shuttingdown
    - shutdown [6]
     Start: inactive
     Goal: shuttingdown
    - shutdown [7]
     Start: active
     Goal: shuttingdown
    - transition_success [50]
     Start: shuttingdown
     Goal: finalized
    - transition_failure [51]
     Start: shuttingdown
     Goal: finalized
    - transition_error [52]
     Start: shuttingdown
     Goal: errorprocessing
    - transition_success [60]
     Start: errorprocessing
     Goal: unconfigured
    - transition_failure [61]
     Start: errorprocessing
     Goal: finalized
    - transition_error [62]
     Start: errorprocessing
     Goal: finalized


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


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


###  Source Tutorials


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


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


##  0.8.3 (2019-11-11)


If we look at the output of the ` lifecycle_talker ` , we notice that nothing
seems to happen. This makes 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 ` .


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


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


##  0.7.5 (2019-05-29)


Welcome to the eighth part of my series on ROS2. For those who may be new to
the series, I have covered a range of topics including an [ introduction to
ROS2 ](/@nullbyte.in/ros2-from-the-ground-up-part-1-an-introduction-to-the-
robot-operating-system-4c2065c5e032) , how to create [ publishers and
subscribers ](/@nullbyte.in/ros2-from-the-ground-up-part-2-publishers-and-
subscribers-8deda54927c7) , [ custom message and service creation
](/@nullbyte.in/ros2-from-the-ground-up-part-3-a-hands-on-guide-to-creating-
custom-messages-and-turtlebot3-service-96a68df2e670) , [ composition
](/@nullbyte.in/ros2-from-the-ground-up-part-4-building-robust-robotics-
systems-with-ros2-composition-209ed023d8e5) and [ executor
](/@nullbyte.in/ros2-from-the-ground-up-part-5-concurrency-executors-and-
callback-groups-c45900973fd2) , and [ DDS ](/@nullbyte.in/ros2-from-the-
ground-up-part-6-dds-in-ros2-for-reliable-robotics-communication-c9f16c3b4cc6)
and [ QoS configuration ](/@nullbyte.in/ros2-from-the-ground-up-
part-7-achieving-reliable-communication-in-ros-2-with-qos-
configurations-83c534c3aff5) . If you haven’t had a chance to check out the
previous posts, be sure to take a look! In this post, we will be exploring
another important aspect of ROS2: **Lifecycle Nodes**


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.


Help


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


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


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


      }

      void notification_callback(const lifecycle_msgs::msg::TransitionEvent::SharedPtr msg)
      {
        RCLCPP_INFO(
          get_logger(), "notify callback: Transition from state %s to %s",
          msg->start_state.label.c_str(), msg->goal_state.label.c_str());
      }

    private:
      std::shared_ptr<rclcpp::Subscription<sensor_msgs::msg::Image>> subscriber_;
      std::shared_ptr<rclcpp::Subscription<lifecycle_msgs::msg::TransitionEvent>>
      sub_notification_;
      cv::Mat frame_;
    };

    int main(int argc, char ** argv)
    {

      setvbuf(stdout, NULL, _IONBF, BUFSIZ);

      rclcpp::init(argc, argv);

      auto display_node = std::make_shared<DisplayNode>("display_node");
      rclcpp::spin(display_node);

      rclcpp::shutdown();

      return 0;
    }


    $ ros2 lifecycle get /lc_talker
    unconfigured [1]


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.


  * Update maintainers to Audrow Nash and Michael Jeronimo ( [ #543 ](https://github.com/ros2/demos/issues/543) )
  * Contributors: Audrow Nash


_No service files found_


####  Package Summary


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


##  ros2 lifecycle command line interface


_No message files found._


During the transition states, specific logic is executed to determine if the
transition is successful. Success or failure is then communicated to the
lifecycle management software through the lifecycle management interface.


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


__ [ ROS2_Control: Iron ](../../../../index.html)


##  0.8.0 (2019-09-26)


####  Authors


###  Dependant Packages


  * 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


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


Reference: [ ROS2 Design
](https://design.ros2.org/articles/node_lifecycle.html)


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.


##  0.5.0 (2018-06-27)


  * Aditya Pande
  * Audrow Nash
  * Michael Jeronimo


    $ ros2 service call /lc_talker/get_state lifecycle_msgs/GetState "{node_name: lc_talker}"
    requester: making request: lifecycle_msgs.srv.GetState_Request(node_name='lc_talker')

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


_No README found._ _No README in repository either._


 uint32 size
 uint32 stride
 uint32 data_offset
float64[] data
std_msgs/Header header
string[] joint_names
float64[] displacements
float64[] velocities
float64 duration
example_msgs/Float64MultiArray control_msgs/JointJog
Messages and modifying a controller
class RRBotController : public controller_interface::ControllerInterface
{
public:
 ...
protected:
 ...


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


#  Introduction


[ action_tutorials_cpp ](/p/action_tutorials_cpp/github-ros2-demos) [
action_tutorials_interfaces ](/p/action_tutorials_interfaces/github-
ros2-demos) [ action_tutorials_py ](/p/action_tutorials_py/github-ros2-demos)
[ composition ](/p/composition/github-ros2-demos) [ demo_nodes_cpp
](/p/demo_nodes_cpp/github-ros2-demos) [ demo_nodes_cpp_native
](/p/demo_nodes_cpp_native/github-ros2-demos) [ demo_nodes_py
](/p/demo_nodes_py/github-ros2-demos) [ dummy_map_server
](/p/dummy_map_server/github-ros2-demos) [ dummy_robot_bringup
](/p/dummy_robot_bringup/github-ros2-demos) [ dummy_sensors
](/p/dummy_sensors/github-ros2-demos) [ image_tools ](/p/image_tools/github-
ros2-demos) [ intra_process_demo ](/p/intra_process_demo/github-ros2-demos)
lifecycle  [ lifecycle_py ](/p/lifecycle_py/github-ros2-demos) [ logging_demo
](/p/logging_demo/github-ros2-demos) [ pendulum_control
](/p/pendulum_control/github-ros2-demos) [ pendulum_msgs
](/p/pendulum_msgs/github-ros2-demos) [ quality_of_service_demo_cpp
](/p/quality_of_service_demo_cpp/github-ros2-demos) [
quality_of_service_demo_py ](/p/quality_of_service_demo_py/github-ros2-demos)
[ topic_monitor ](/p/topic_monitor/github-ros2-demos) [ topic_statistics_demo
](/p/topic_statistics_demo/github-ros2-demos)
---|---

github-ros2-demos


    $ 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)


##  0.5.1 (2018-06-28)


    $ ros2 lifecycle set /lc_talker configure
    Transitioning successful


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


_No direct system dependencies._


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


_No additional authors._


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


##  0.7.0 (2019-04-14)


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


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.


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.


##  Triggering transition 1 (configure)


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:


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) .


3. Remove include of headers ` base_interface.hpp  ` and ` hardware_interface_status_values.hpp  `


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


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


The possible transitions to invoke are:


##  0.30.0 (2023-06-12)


##  0.13.0 (2021-03-25)


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


##  0.6.2 (2019-01-15)


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:


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:


##  0.19.0 (2022-01-14)


    # Build
    colcon build --packages-select camera_node

    # Run camera node - Terminal 1
    ros2 run camera_node camera_node

    # Run display node - Terminal 2
    ros2 run camera_node display_node

    # Run service_client - Terminal 3
    ros2 run camera_node lc_service_client


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


$ ros2 interface show lifecycle_msgs/msg/Transition


        }
        if (!lc_client->get_state()) {
          return;
        }
      }

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

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

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

      rclcpp::init(argc, argv);


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


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


###  Dependant Packages


##  lifecycle_talker, lifecycle_listener and lifecycle_service_client


    $ ros2 lifecycle get /lc_talker
    unconfigured [1]


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.


#  Run the demo


####  Package Summary


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

###  System Dependencies


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


##  0.7.6 (2019-05-30)


    $ 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


###  Package Dependencies


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

###  System Dependencies


_No launch files found_


Reference Link: [ node
](https://docs.ros2.org/foxy/api/rclcpp/classrclcpp_1_1Node.html#abaa409bd2dc2cc2437fd9e47378cc5af)


##  0.5.1 (2018-06-28)


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.


I always share interesting articles and updates on [ LinkedIn
](https://www.linkedin.com/in/nullbyte91/) , so if you want to stay informed,
feel free to follow me on the platform.


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:


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


##  0.10.0 (2020-06-17)


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:


[ action_tutorials_cpp ](/p/action_tutorials_cpp/github-ros2-demos) [
action_tutorials_interfaces ](/p/action_tutorials_interfaces/github-
ros2-demos) [ action_tutorials_py ](/p/action_tutorials_py/github-ros2-demos)
[ composition ](/p/composition/github-ros2-demos) [ demo_nodes_cpp
](/p/demo_nodes_cpp/github-ros2-demos) [ demo_nodes_cpp_native
](/p/demo_nodes_cpp_native/github-ros2-demos) [ demo_nodes_py
](/p/demo_nodes_py/github-ros2-demos) [ dummy_map_server
](/p/dummy_map_server/github-ros2-demos) [ dummy_robot_bringup
](/p/dummy_robot_bringup/github-ros2-demos) [ dummy_sensors
](/p/dummy_sensors/github-ros2-demos) [ image_tools ](/p/image_tools/github-
ros2-demos) [ intra_process_demo ](/p/intra_process_demo/github-ros2-demos)
lifecycle  [ logging_demo ](/p/logging_demo/github-ros2-demos) [
pendulum_control ](/p/pendulum_control/github-ros2-demos) [ pendulum_msgs
](/p/pendulum_msgs/github-ros2-demos) [ quality_of_service_demo_cpp
](/p/quality_of_service_demo_cpp/github-ros2-demos) [
quality_of_service_demo_py ](/p/quality_of_service_demo_py/github-ros2-demos)
[ topic_monitor ](/p/topic_monitor/github-ros2-demos) [ topic_statistics_demo
](/p/topic_statistics_demo/github-ros2-demos)
---|---

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'))


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.


[ ](/?source=---two_column_layout_nav----------------------------------)


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


Primary States (steady states):


](/about?autoplay=1&source=post_page-----
5fafa2738700--------------------------------)


* Karsten Knese


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


  * 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


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:


####  Additional Links


ros2_control - a robot-agnostic
control framework for ROS2
WR Meetup #13 – 7 Oct. 2021
Outline
● Why do we need a control framework in ROS/ROS2?
● History & basic concepts
● How to use ros(1)_control?
● What is a bit tricky in ros(1)_control?
● Architecture of ros2_control
● “Everything is an interface ”
● URDF extension with <ros2_control>-tag
● Examples from users
Buckle up, this will be an adventure :)
$whoarewe
Bence Magyar
● PhD in Robotics
● Lead Software Engineer at FiveAI
● ros_control and ros2_control maintainer
Denis Štogl
● Control Engineer and Roboticist (PhD soon official)
● Robotics Consultant at Stogl Robotics Consulting
● ros2_control maintainer
Why do we need a control framework in ROS?
1. “Control” is tricky — everybody needs it (to run a physical robot)
2. “Stop reinventing the wheel when controlling hardware”
● Provide standardized interfaces for “high-level”/task control “nodes”
○ MoveIt, Navigation, <your_sexy_cool_application>, …
● Establish standard set of controllers:
○ “Implement control-method once and use it on various hardware”
● To implement access management each time is annoying
● Optimize controllers and management-functions for real-time performance
● Standardization of hardware-abstraction layer
What & where
pr2_controller_manager
(pr2_mechanism)
2009
ros_control
2012/2013
ros2_control
2017/2021


##  0.5.1 (2018-06-28)


  * 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


##  0.10.0 (2020-06-17)


_No additional links._


##  0.8.2 (2019-11-08)


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.


    $ 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


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


  * 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


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


Transition States (intermediate states):


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


##  0.8.3 (2019-11-11)


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


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


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


Text to speech


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


##  0.16.0 (2021-08-11)


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


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.


##  0.6.1 (2018-12-13)


##  0.22.0 (2022-09-13)


##  0.7.5 (2019-05-29)


          return;
        }
      }

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

      // activate it again
      {
        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()) {
          return;
        }
      }

      // and deactivate it again
      {
        time_between_state_changes.sleep();
        if (!rclcpp::ok()) {
          return;
        }
        if (!lc_client->change_state(lifecycle_msgs::msg::Transition::TRANSITION_DEACTIVATE)) {
          return;


##  What\'s happening


  * [ ](../../../../index.html)
  * [ ros2_control ](../../doc/index.html)
  * Hardware Components
  * [ Edit on GitHub ](https://github.com/ros-controls/ros2_control/blob/iron/hardware_interface/doc/hardware_components_userdoc.rst)


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.


##  lifecycle_talker, lifecycle_listener and lifecycle_service_client


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


  * 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


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:


    [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]
    ...


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:


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


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


##  0.9.0 (2020-04-30)


  * configure
  * activate
  * deactivate
  * cleanup
  * shutdown


[ Sign in
](/m/signin?operation=login&redirect=https%3A%2F%2Fmedium.com%2F%40nullbyte.in%2Fros2-from-
the-ground-up-part-8-simplify-robotic-software-components-management-with-
ros2-5fafa2738700&source=post_page---two_column_layout_nav
-----------------------global_nav-----------)


_No additional links._


##  0.8.1 (2019-10-23)


  * changes to avoid deprecated API\'s ( [ #332 ](https://github.com/ros2/demos/issues/332) )
  * Corrected publish calls with shared_ptr signature ( [ #327 ](https://github.com/ros2/demos/issues/327) )
  * Contributors: William Woodall, ivanpauno


##  0.6.2 (2019-01-15)


###  Plugins


###  Package Dependencies


##  0.7.0 (2019-04-14)


    # First lets get the service list
    ros2 service list

    # output
    /camera_node/change_state
    /camera_node/describe_parameters
    /camera_node/get_available_states
    /camera_node/get_available_transitions
    /camera_node/get_parameter_types
    /camera_node/get_parameters
    /camera_node/get_state
    /camera_node/get_transition_graph
    /camera_node/list_parameters
    /camera_node/set_parameters
    /camera_node/set_parameters_atomically

    # This is a list of services that the camera node created.
    # Now lets get the current state of the camera_node
    ros2 service call /camera_node/get_state lifecycle_msgs/srv/GetState {}

    # Output
    ros2 service call /camera_node/get_state lifecycle_msgs/srv/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'))

    # So the camera node in unconfigured state

    # Change the camera_node from unconfigured to configured state
    ros2 lifecycle set /camera_node configure

    # Now you could see the camera node changes to configured state


In addition to managing the startup and shutdown of each component, **ROS2
Lifecycle Nodes can also be used to handle runtime events** , such as
reconfiguration of the Navigation stack or changes to the environment. _For
example, if the robot encounters a new obstacle while navigating, the costmap
generator may need to be reconfigured to account for the new obstacle_ . Using
the ROS2 Lifecycle Node API, you can define a state transition that handles
this reconfiguration while the other components continue to run.


    add_executable(lc_service_client
      src/lc_service_client.cpp)
      target_link_libraries(lc_service_client
      ${rclcpp_lifecycle_LIBRARIES}
      ${std_msgs_LIBRARIES})

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


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.


##  0.8.4 (2019-11-19)


Reference: [ link ](https://www.researchgate.net/figure/Standard-ROS-
Navigation-Stack-7_fig2_312018119)


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


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


##  0.7.3 (2019-05-10)


5. replace first three lines in ` on_init  ` to


_No plugins found._


####  Authors


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

2024-03-28  |  **Dev Status** |  DEVELOPED
**CI status** |  No Continuous Integration
**Released** |  RELEASED
**Tags** |  _No category tags._
**Contributing** |  [ Help Wanted (  0  ) ](/r/demos/#rolling-contribute-
lists-help-wanted)
[ Good First Issues (  0  ) ](/r/demos/#rolling-contribute-lists-good-first-
issue)
[ Pull Requests to Review (  0  ) ](/r/demos/#rolling-contribute-lists-pull-
requests)

###  Package Description


[ Jegathesan Shanmugam ](/@nullbyte.in?source=post_page-----
5fafa2738700--------------------------------)


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


##  ros2 lifecycle command line interface


_No service files found_


##  0.5.1 (2018-06-28)


Package containing demos for lifecycle implementation


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


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

###  System Dependencies


##  0.8.4 (2019-11-19)


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

2022-12-07  |  **Dev Status** |  DEVELOPED
**CI status** |  No Continuous Integration
**Released** |  RELEASED
**Tags** |  _No category tags._
**Contributing** |  [ Help Wanted (  0  ) ](/r/demos/#galactic-contribute-
lists-help-wanted)
[ Good First Issues (  0  ) ](/r/demos/#galactic-contribute-lists-good-first-
issue)
[ Pull Requests to Review (  0  ) ](/r/demos/#galactic-contribute-lists-pull-
requests)

###  Package Description


##  0.7.1 (2019-04-26)


So far, we have changed the node state from the command line. Now, we will do
it programmatically. We will demonstrates how to use the ROS 2 lifecycle
service API to change the state of a node.


##  0.5.0 (2018-06-27)


[ Previous ](../../controller_manager/doc/controller_chaining.html "Controller
Chaining / Cascade Control") [ Next  ](hardware_interface_types_userdoc.html
"ros2_control hardware interface types")


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


Display output after changing camera node state to configure


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


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

2019-01-15  |  **Dev Status** |  DEVELOPED
**CI status** |  No Continuous Integration
**Released** |  RELEASED
**Tags** |  _No category tags._
**Contributing** |  [ Help Wanted (  0  ) ](/r/demos/#crystal-contribute-
lists-help-wanted)
[ Good First Issues (  0  ) ](/r/demos/#crystal-contribute-lists-good-first-
issue)
[ Pull Requests to Review (  0  ) ](/r/demos/#crystal-contribute-lists-pull-
requests)

###  Package Description


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


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


Privacy


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


##  0.10.1 (2020-09-21)


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


  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


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


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.


##  0.5.1 (2018-06-28)


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


The next step would be to execute a state change:


Transition States (intermediate states):


####  Authors


####  Package Summary


##  0.8.2 (2019-11-08)


#  The demo


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


     [ Iron (latest) ](hardware_components_userdoc.html)

     [ Humble ](../../../../../humble/doc/ros2_control/hardware_interface/doc/hardware_components_userdoc.html)

     [ Galactic (EOL) ](../../../../../galactic/doc/ros2_control/hardware_interface/doc/hardware_components_userdoc.html)

     [ Foxy (EOL) ](../../../../../foxy/index.html)


_No direct system dependencies._


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


##  Triggering transition 1 (configure)


####  Additional Links


##  0.24.1 (2023-02-24)


ROS Resources: [ Documentation ](http://docs.ros.org/) | [ Support
](http://wiki.ros.org/Support) | [ Discussion Forum
](http://discourse.ros.org/) | [ Service Status ](http://status.ros.org/) | [
ros @ Robotics Stack Exchange
](https://robotics.stackexchange.com/questions/tagged/ros)
---

[ ROS Index ](/)


---

[
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")


lifecycle_talker lifecycle_listener lifecycle_service_client


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


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

###  Launch files


##  0.10.0 (2020-06-17)


###  Wiki Tutorials


  * 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


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


#  The demo code


##  0.27.0 (2023-04-13)


##  0.14.4 (2022-12-06)


_No launch files found_


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


###  Messages


##  0.12.1 (2021-03-18)


##  0.27.1 (2023-05-11)


##  0.9.1 (2020-05-12)


  * configure
  * activate
  * deactivate
  * cleanup
  * shutdown


_Not currently indexed._


##  0.15.0 (2021-05-14)


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


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


  * lifecycle_talker
  * lifecycle_listener
  * lifecycle_service_client


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.


The demo is split into 3 different separate applications.


**Tags** |  _No category tags._
---|---
**Version** |  0.5.1
**License** |  Apache License 2.0
**Build type** |  AMENT_CMAKE
**Use** |  RECOMMENDED

###  Repository Summary


Teams


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


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


###  Package Dependencies


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

###  System Dependencies


  * configuring
  * activating
  * deactivating
  * cleaningup
  * shuttingdown


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:


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

2022-07-25  |  **Dev Status** |  DEVELOPED
**CI status** |  No Continuous Integration
**Released** |  RELEASED
**Tags** |  _No category tags._
**Contributing** |  [ Help Wanted (  0  ) ](/r/demos/#foxy-contribute-lists-
help-wanted)
[ Good First Issues (  0  ) ](/r/demos/#foxy-contribute-lists-good-first-
issue)
[ Pull Requests to Review (  0  ) ](/r/demos/#foxy-contribute-lists-pull-
requests)

###  Package Description


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


#  Changelog for package lifecycle


](/@nullbyte.in?source=post_page-----
5fafa2738700--------------------------------)


The possible transitions to invoke are:


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


##  0.9.2 (2020-05-26)


If we look at the output of the ` lifecycle_talker ` , we notice that nothing
seems to happen. This makes 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 ` .


_No plugins found._


CHANGELOG


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.


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


##  Triggering transition 2 (activate)


Return either a primary or transition state.


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


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


Older


[ 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")


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


###  Wiki Tutorials


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.


_No launch files found_


##  0.24.0 (2023-02-14)


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.


[ Computer Vision  ](/tag/computer-vision?source=post_page-----5fafa2738700
---------------computer_vision-----------------)


Transition States (intermediate states):


_Not currently indexed._


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


    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)


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


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


    [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]
    ...


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

###  Launch files


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:


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


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


##  0.27.0 (2023-04-13)


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


[ 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")


lifecycle_talker lifecycle_listener lifecycle_service_client


Error handling follows the [ node lifecycle
](https://design.ros2.org/articles/node_lifecycle.html) . If successful `
CallbackReturn::SUCCESS  ` is returned and hardware is again in ` UNCONFIGURED
` state, if any ` ERROR  ` or ` FAILURE  ` happens the hardware ends in `
FINALIZED  ` state and can not be recovered. The only option is to reload the
complete plugin, but there is currently no service for this in the Controller
Manager.


The possible transitions to invoke are:


    $ 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)


    $ 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


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


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


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


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 ` :


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.


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:


##  0.11.0 (2020-12-10)


  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


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


##  0.7.6 (2019-05-30)


Blog


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
` .


$ ros2 interface show lifecycle_msgs/msg/Transition


##  0.7.1 (2019-04-26)


CHANGELOG


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.


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


_Not currently indexed._


  * unconfigured
  * inactive
  * active
  * shutdown


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


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 questions yet, you can ask one [ here
](https://robotics.stackexchange.com/questions/tagged/lifecycle+iron) .


###  Dependant Packages


**Tags** |  _No category tags._
---|---
**Version** |  0.6.2
**License** |  Apache License 2.0
**Build type** |  AMENT_CMAKE
**Use** |  RECOMMENDED

###  Repository Summary


* Karsten Knese


#  Changelog for package lifecycle


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


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


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 demo code


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 ` :


##  0.10.0 (2020-06-17)


Package containing demos for lifecycle implementation


###  Plugins


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


Primary States (steady states):


##  0.7.2 (2019-05-08)


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.


Follow


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


##  0.33.0 (2024-01-24)


    $ 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'))


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


[ 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")


##  0.9.3 (2020-06-01)


##  0.9.2 (2020-05-26)


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.


[ ](/search?source=---two_column_layout_nav----------------------------------)


        return rclcpp_lifecycle::node_interfaces::LifecycleNodeInterface::CallbackReturn::SUCCESS;
      }

      /* The on_cleanup function is a callback function that is executed when the node is being
       * cleaned up or shutdown. In this function, the timer_ and publisher_ are reset,
       * which means they are destroyed and any resources they were holding are released.
       * Then an information message is logged to indicate that the cleanup has been completed.

       * The return type of this function is rclcpp_lifecycle::node_interfaces::LifecycleNodeInterface::CallbackReturn,
       * which is an enumeration that indicates whether the callback function was successful or not.
       * In this case, it always returns SUCCESS, which means that the cleanup was completed successfully.
       */
      rclcpp_lifecycle::node_interfaces::LifecycleNodeInterface::CallbackReturn
      on_cleanup(const rclcpp_lifecycle::State &)
      {
        timer_.reset();
        publisher_.reset();

        RCUTILS_LOG_INFO_NAMED(get_name(), "CameraNode cleanup.");

        return rclcpp_lifecycle::node_interfaces::LifecycleNodeInterface::CallbackReturn::SUCCESS;
      }

      /* This is the on_shutdown callback function for the CameraNode class,
       * which is called when the node is being shut down.
       * The function takes in a state argument of type rclcpp_lifecycle::State, which represents the current state
       * of the node when it is being shut down.

       * The function first resets the timer_ and publisher_ objects, and then logs an information message
       * indicating that the on_shutdown function is being called and prints the label of the state that the node is in.

       * Finally, the function returns rclcpp_lifecycle::node_interfaces::LifecycleNodeInterface::CallbackReturn::SUCCESS
       * to indicate that the shutdown procedure has completed successfully.
       */
      rclcpp_lifecycle::node_interfaces::LifecycleNodeInterface::CallbackReturn
      on_shutdown(const rclcpp_lifecycle::State & state)
      {
        timer_.reset();
        publisher_.reset();


##  lifecycle_service_client_py.py


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


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


[ ros-infrastructure/rosindex  ](https://github.com/ros-
infrastructure/rosindex "Find rosindex in Github") | _generated on 2024-04-03_


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


In addition to the four primary states, there are six transition states in the
lifecycle of a node, which are intermediate states during a requested
transition. These transition states are:
1\. **Configuring** : The node is being configured, which typically involves
setting up the parameters and connections necessary for the node to operate.
2\. **CleaningUp** : The node is being shut down and its resources are being
cleaned up.
3\. **ShuttingDown** : The node is shutting down, typically in response to a
request to do so.
4\. **Activating** : The node is in the process of becoming active, such as by
initializing its hardware or connecting to other nodes.
5\. **Deactivating** : The node is in the process of becoming inactive, such
as by disconnecting from other nodes or shutting down its hardware.
6\. **ErrorProcessing** : An error has occurred during a transition, and the
node is in the process of handling the error.


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:


##  0.6.1 (2018-12-13)


##  Triggering transition 2 (activate)


[ action_tutorials_cpp ](/p/action_tutorials_cpp/github-ros2-demos) [
action_tutorials_interfaces ](/p/action_tutorials_interfaces/github-
ros2-demos) [ action_tutorials_py ](/p/action_tutorials_py/github-ros2-demos)
[ composition ](/p/composition/github-ros2-demos) [ demo_nodes_cpp
](/p/demo_nodes_cpp/github-ros2-demos) [ demo_nodes_cpp_native
](/p/demo_nodes_cpp_native/github-ros2-demos) [ demo_nodes_py
](/p/demo_nodes_py/github-ros2-demos) [ dummy_map_server
](/p/dummy_map_server/github-ros2-demos) [ dummy_robot_bringup
](/p/dummy_robot_bringup/github-ros2-demos) [ dummy_sensors
](/p/dummy_sensors/github-ros2-demos) [ image_tools ](/p/image_tools/github-
ros2-demos) [ intra_process_demo ](/p/intra_process_demo/github-ros2-demos)
lifecycle  [ lifecycle_py ](/p/lifecycle_py/github-ros2-demos) [ logging_demo
](/p/logging_demo/github-ros2-demos) [ pendulum_control
](/p/pendulum_control/github-ros2-demos) [ pendulum_msgs
](/p/pendulum_msgs/github-ros2-demos) [ quality_of_service_demo_cpp
](/p/quality_of_service_demo_cpp/github-ros2-demos) [
quality_of_service_demo_py ](/p/quality_of_service_demo_py/github-ros2-demos)
[ topic_monitor ](/p/topic_monitor/github-ros2-demos) [ topic_statistics_demo
](/p/topic_statistics_demo/github-ros2-demos)
---|---

github-ros2-demos


](https://medium.statuspage.io/?source=post_page-----
5fafa2738700--------------------------------)


  * 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


14 min read


  * configure
  * activate
  * deactivate
  * cleanup
  * shutdown


_No additional authors._


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.


#  Introduction


##  0.26.0 (2023-04-11)


##  0.20.1 (2022-04-08)


##  0.15.0 (2021-05-14)


##  0.7.6 (2019-05-30)


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).


Package containing demos for lifecycle implementation


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


##  0.6.2 (2019-01-15)


##  Triggering transition 1 (configure)


_No plugins found._


###  Source Tutorials


  * lifecycle_talker
  * lifecycle_listener
  * lifecycle_service_client


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


In order to see what states are currently available:


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


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 ` .


Terms


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


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


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.


##  0.9.0 (2020-04-30)


[ composition ](/p/composition/github-ros2-demos) [ demo_nodes_cpp
](/p/demo_nodes_cpp/github-ros2-demos) [ demo_nodes_cpp_native
](/p/demo_nodes_cpp_native/github-ros2-demos) [ demo_nodes_py
](/p/demo_nodes_py/github-ros2-demos) [ dummy_map_server
](/p/dummy_map_server/github-ros2-demos) [ dummy_robot_bringup
](/p/dummy_robot_bringup/github-ros2-demos) [ dummy_sensors
](/p/dummy_sensors/github-ros2-demos) [ image_tools ](/p/image_tools/github-
ros2-demos) [ intra_process_demo ](/p/intra_process_demo/github-ros2-demos)
lifecycle  [ logging_demo ](/p/logging_demo/github-ros2-demos) [
pendulum_control ](/p/pendulum_control/github-ros2-demos) [ pendulum_msgs
](/p/pendulum_msgs/github-ros2-demos) [ topic_monitor
](/p/topic_monitor/github-ros2-demos)
---|---

github-ros2-demos


    [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]
    ...


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.


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


###  Plugins


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


##  0.6.2 (2019-01-15)


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.


  * Audrow Nash
  * Michael Jeronimo


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


    $ ros2 lifecycle set /lc_talker configure
    Transitioning successful


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 ` .


###  Messages


_Not currently indexed._


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


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


$ ros2 msg show lifecycle_msgs/Transition