<h1 dir="auto">Checklist</h1>

<ul class="contains-task-list">
<li class="task-list-item"><input type="checkbox" id="" disabled="" class="task-list-item-checkbox" checked=""> I have read the relevant section in the<br>
<a href="http://docs.celeryproject.org/en/latest/contributing.html#other-bugs" rel="nofollow">contribution guide</a><br>
on reporting bugs.</li>
<li class="task-list-item"><input type="checkbox" id="" disabled="" class="task-list-item-checkbox" checked=""> I have checked the <a href="https://github.com/celery/celery/issues?q=is%3Aissue+label%3A%22Issue+Type%3A+Bug+Report%22+-label%3A%22Category%3A+Documentation%22">issues list</a><br>
for similar or identical bug reports.</li>
<li class="task-list-item"><input type="checkbox" id="" disabled="" class="task-list-item-checkbox" checked=""> I have checked the <a href="https://github.com/celery/celery/pulls?q=is%3Apr+label%3A%22PR+Type%3A+Bugfix%22+-label%3A%22Category%3A+Documentation%22">pull requests list</a><br>
for existing proposed fixes.</li>
<li class="task-list-item"><input type="checkbox" id="" disabled="" class="task-list-item-checkbox" checked=""> I have checked the <a href="https://github.com/celery/celery/commits/master">commit log</a><br>
to find out if the bug was already fixed in the master branch.</li>
<li class="task-list-item"><input type="checkbox" id="" disabled="" class="task-list-item-checkbox" checked=""> I have included all related issues and possible duplicate issues<br>
in this issue (If there are none, check this box anyway).</li>
</ul>
<h2 dir="auto">Mandatory Debugging Information</h2>
<ul class="contains-task-list">
<li class="task-list-item"><input type="checkbox" id="" disabled="" class="task-list-item-checkbox" checked=""> I have included the output of <code class="notranslate">celery -A proj report</code> in the issue.<br>
(if you are not able to do this, then at least specify the Celery<br>
version affected).</li>
<li class="task-list-item"><input type="checkbox" id="" disabled="" class="task-list-item-checkbox"> I have verified that the issue exists against the <code class="notranslate">master</code> branch of Celery.</li>
<li class="task-list-item"><input type="checkbox" id="" disabled="" class="task-list-item-checkbox" checked=""> I have included the contents of <code class="notranslate">pip freeze</code> in the issue.</li>
<li class="task-list-item"><input type="checkbox" id="" disabled="" class="task-list-item-checkbox" checked=""> I have included all the versions of all the external dependencies required<br>
to reproduce this bug.</li>
</ul>
<h2 dir="auto">Optional Debugging Information</h2>

<ul class="contains-task-list">
<li class="task-list-item"><input type="checkbox" id="" disabled="" class="task-list-item-checkbox"> I have tried reproducing the issue on more than one Python version<br>
and/or implementation.</li>
<li class="task-list-item"><input type="checkbox" id="" disabled="" class="task-list-item-checkbox"> I have tried reproducing the issue on more than one message broker and/or<br>
result backend.</li>
<li class="task-list-item"><input type="checkbox" id="" disabled="" class="task-list-item-checkbox" checked=""> I have tried reproducing the issue on more than one version of the message<br>
broker and/or result backend.</li>
<li class="task-list-item"><input type="checkbox" id="" disabled="" class="task-list-item-checkbox"> I have tried reproducing the issue on more than one operating system.</li>
<li class="task-list-item"><input type="checkbox" id="" disabled="" class="task-list-item-checkbox"> I have tried reproducing the issue on more than one workers pool.</li>
<li class="task-list-item"><input type="checkbox" id="" disabled="" class="task-list-item-checkbox"> I have tried reproducing the issue with autoscaling, retries,<br>
ETA/Countdown &amp; rate limits disabled.</li>
<li class="task-list-item"><input type="checkbox" id="" disabled="" class="task-list-item-checkbox"> I have tried reproducing the issue after downgrading<br>
and/or upgrading Celery and its dependencies.</li>
</ul>
<h2 dir="auto">Related Issues and Possible Duplicates</h2>

<h4 dir="auto">Related Issues</h4>
<ul dir="auto">
<li>None</li>
</ul>
<h4 dir="auto">Possible Duplicates</h4>
<ul dir="auto">
<li>None</li>
</ul>
<h2 dir="auto">Environment &amp; Settings</h2>

<p dir="auto"><strong>Celery version</strong>:</p>

<details>
<summary><b><code class="notranslate">celery report</code> Output:</b></summary>
<p dir="auto">
</p><div class="snippet-clipboard-content notranslate position-relative overflow-auto" data-snippet-clipboard-copy-content="software -&gt; celery:4.3.0 (rhubarb) kombu:4.6.0 py:3.6.8
            billiard:3.6.0.0 redis:3.2.0
platform -&gt; system:Linux arch:64bit
            kernel version:4.15.0-50-generic imp:CPython
loader   -&gt; celery.loaders.app.AppLoader
settings -&gt; transport:redis results:django-db"><pre class="notranslate"><code class="notranslate">software -&gt; celery:4.3.0 (rhubarb) kombu:4.6.0 py:3.6.8
            billiard:3.6.0.0 redis:3.2.0
platform -&gt; system:Linux arch:64bit
            kernel version:4.15.0-50-generic imp:CPython
loader   -&gt; celery.loaders.app.AppLoader
settings -&gt; transport:redis results:django-db
</code></pre></div>
<p dir="auto"></p>
</details>
<h1 dir="auto">Steps to Reproduce</h1>
<p dir="auto">Run a celery worker with a MySQL backend (possibly through Django).<br>
After the worker is up, shut down the MySQL service.<br>
Try running a task.</p>
<h2 dir="auto">Required Dependencies</h2>

<ul dir="auto">
<li><strong>Minimal Python Version</strong>: N/A or Unknown</li>
<li><strong>Minimal Celery Version</strong>: 4.2.0</li>
<li><strong>Minimal Kombu Version</strong>: N/A or Unknown</li>
<li><strong>Minimal Broker Version</strong>: N/A or Unknown</li>
<li><strong>Minimal Result Backend Version</strong>: N/A or Unknown</li>
<li><strong>Minimal OS and/or Kernel Version</strong>: N/A or Unknown</li>
<li><strong>Minimal Broker Client Version</strong>: N/A or Unknown</li>
<li><strong>Minimal Result Backend Client Version</strong>: N/A or Unknown</li>
</ul>
<h3 dir="auto">Python Packages</h3>

<details>
<summary><b><code class="notranslate">pip freeze</code> Output:</b></summary>
<p dir="auto">
</p><div class="snippet-clipboard-content notranslate position-relative overflow-auto" data-snippet-clipboard-copy-content="celery==4.3.0
Django==2.2.1
mysqlclient==1.4.2"><pre class="notranslate"><code class="notranslate">celery==4.3.0
Django==2.2.1
mysqlclient==1.4.2
</code></pre></div>
<p dir="auto">(only relevant packages)</p>
<p dir="auto"></p>
</details>
<h3 dir="auto">Other Dependencies</h3>

<details>
<p dir="auto">
N/A
</p>
</details>
<h2 dir="auto">Minimally Reproducible Test Case</h2>

<details>
<p dir="auto">
</p><div class="highlight highlight-source-python notranslate position-relative overflow-auto" dir="auto" data-snippet-clipboard-copy-content=""><pre class="notranslate"></pre></div>
<p dir="auto"></p>
</details>
<h1 dir="auto">Expected Behavior</h1>

<p dir="auto">This is a non-recoverable error. The worker process should terminate, which would be treated as an error by a monitoring tool that will restart it.</p>
<h1 dir="auto">Actual Behavior</h1>
<p dir="auto">An exception is printed to stderr. The worker itself keeps running, receiving tasks, but never running them.<br>
An exception is printed after each "Task accepted" log message.</p>
<details>
<p dir="auto">
</p><div class="snippet-clipboard-content notranslate position-relative overflow-auto" data-snippet-clipboard-copy-content="[ERROR/MainProcess] Pool callback raised exception: OperationalError(2002, &quot;Can't connect to local MySQL server through socket '/var/run/mysqld/mysqld.sock' (2)&quot;)
Traceback (most recent call last):
  File &quot;[REDACTED]/lib/python3.6/site-packages/django/db/backends/base/base.py&quot;, line 217, in ensure_connection
    self.connect()
  File &quot;[REDACTED]/lib/python3.6/site-packages/django/db/backends/base/base.py&quot;, line 195, in connect
    self.connection = self.get_new_connection(conn_params)
  File &quot;[REDACTED]/lib/python3.6/site-packages/django/db/backends/mysql/base.py&quot;, line 227, in get_new_connection
    return Database.connect(**conn_params)
  File &quot;[REDACTED]/lib/python3.6/site-packages/MySQLdb/__init__.py&quot;, line 84, in Connect
    return Connection(*args, **kwargs)
  File &quot;[REDACTED]/lib/python3.6/site-packages/MySQLdb/connections.py&quot;, line 164, in __init__
    super(Connection, self).__init__(*args, **kwargs2)
MySQLdb._exceptions.OperationalError: (2002, &quot;Can't connect to local MySQL server through socket '/var/run/mysqld/mysqld.sock' (2)&quot;)

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File &quot;[REDACTED]/lib/python3.6/site-packages/billiard/pool.py&quot;, line 1750, in safe_apply_callback
    fun(*args, **kwargs)
  File &quot;[REDACTED]/lib/python3.6/site-packages/celery/worker/request.py&quot;, line 371, in on_failure
    store_result=self.store_errors,
  File &quot;[REDACTED]/lib/python3.6/site-packages/celery/backends/base.py&quot;, line 160, in mark_as_failure
    traceback=traceback, request=request)
  File &quot;[REDACTED]/lib/python3.6/site-packages/celery/backends/base.py&quot;, line 342, in store_result
    request=request, **kwargs)
  File &quot;[REDACTED]/lib/python3.6/site-packages/django_celery_results/backends/database.py&quot;, line 35, in _store_result
    task_kwargs=task_kwargs,
  File &quot;[REDACTED]/lib/python3.6/site-packages/django_celery_results/managers.py&quot;, line 50, in _inner
    return fun(*args, **kwargs)
  File &quot;[REDACTED]/lib/python3.6/site-packages/django_celery_results/managers.py&quot;, line 126, in store_result
    obj, created = self.get_or_create(task_id=task_id, defaults=fields)
  File &quot;[REDACTED]/lib/python3.6/site-packages/django/db/models/manager.py&quot;, line 82, in manager_method
    return getattr(self.get_queryset(), name)(*args, **kwargs)
  File &quot;[REDACTED]/lib/python3.6/site-packages/django/db/models/query.py&quot;, line 538, in get_or_create
    return self.get(**kwargs), False
  File &quot;[REDACTED]/lib/python3.6/site-packages/django/db/models/query.py&quot;, line 402, in get
    num = len(clone)
  File &quot;[REDACTED]/lib/python3.6/site-packages/django/db/models/query.py&quot;, line 256, in __len__
    self._fetch_all()
  File &quot;[REDACTED]/lib/python3.6/site-packages/django/db/models/query.py&quot;, line 1242, in _fetch_all
    self._result_cache = list(self._iterable_class(self))
  File &quot;[REDACTED]/lib/python3.6/site-packages/django/db/models/query.py&quot;, line 55, in __iter__
    results = compiler.execute_sql(chunked_fetch=self.chunked_fetch, chunk_size=self.chunk_size)
  File &quot;[REDACTED]/lib/python3.6/site-packages/django/db/models/sql/compiler.py&quot;, line 1098, in execute_sql
    cursor = self.connection.cursor()
  File &quot;[REDACTED]/lib/python3.6/site-packages/django/db/backends/base/base.py&quot;, line 256, in cursor
    return self._cursor()
  File &quot;[REDACTED]/lib/python3.6/site-packages/django/db/backends/base/base.py&quot;, line 233, in _cursor
    self.ensure_connection()
  File &quot;[REDACTED]/lib/python3.6/site-packages/django/db/backends/base/base.py&quot;, line 217, in ensure_connection
    self.connect()
  File &quot;[REDACTED]/lib/python3.6/site-packages/django/db/utils.py&quot;, line 89, in __exit__
    raise dj_exc_value.with_traceback(traceback) from exc_value
  File &quot;[REDACTED]/lib/python3.6/site-packages/django/db/backends/base/base.py&quot;, line 217, in ensure_connection
    self.connect()
  File &quot;[REDACTED]/lib/python3.6/site-packages/django/db/backends/base/base.py&quot;, line 195, in connect
    self.connection = self.get_new_connection(conn_params)
  File &quot;[REDACTED]/lib/python3.6/site-packages/django/db/backends/mysql/base.py&quot;, line 227, in get_new_connection
    return Database.connect(**conn_params)
  File &quot;[REDACTED]/lib/python3.6/site-packages/MySQLdb/__init__.py&quot;, line 84, in Connect
    return Connection(*args, **kwargs)
  File &quot;[REDACTED]/lib/python3.6/site-packages/MySQLdb/connections.py&quot;, line 164, in __init__
    super(Connection, self).__init__(*args, **kwargs2)
django.db.utils.OperationalError: (2002, &quot;Can't connect to local MySQL server through socket '/var/run/mysqld/mysqld.sock' (2)&quot;)"><pre class="notranslate"><code class="notranslate">[ERROR/MainProcess] Pool callback raised exception: OperationalError(2002, "Can't connect to local MySQL server through socket '/var/run/mysqld/mysqld.sock' (2)")
Traceback (most recent call last):
  File "[REDACTED]/lib/python3.6/site-packages/django/db/backends/base/base.py", line 217, in ensure_connection
    self.connect()
  File "[REDACTED]/lib/python3.6/site-packages/django/db/backends/base/base.py", line 195, in connect
    self.connection = self.get_new_connection(conn_params)
  File "[REDACTED]/lib/python3.6/site-packages/django/db/backends/mysql/base.py", line 227, in get_new_connection
    return Database.connect(**conn_params)
  File "[REDACTED]/lib/python3.6/site-packages/MySQLdb/__init__.py", line 84, in Connect
    return Connection(*args, **kwargs)
  File "[REDACTED]/lib/python3.6/site-packages/MySQLdb/connections.py", line 164, in __init__
    super(Connection, self).__init__(*args, **kwargs2)
MySQLdb._exceptions.OperationalError: (2002, "Can't connect to local MySQL server through socket '/var/run/mysqld/mysqld.sock' (2)")

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "[REDACTED]/lib/python3.6/site-packages/billiard/pool.py", line 1750, in safe_apply_callback
    fun(*args, **kwargs)
  File "[REDACTED]/lib/python3.6/site-packages/celery/worker/request.py", line 371, in on_failure
    store_result=self.store_errors,
  File "[REDACTED]/lib/python3.6/site-packages/celery/backends/base.py", line 160, in mark_as_failure
    traceback=traceback, request=request)
  File "[REDACTED]/lib/python3.6/site-packages/celery/backends/base.py", line 342, in store_result
    request=request, **kwargs)
  File "[REDACTED]/lib/python3.6/site-packages/django_celery_results/backends/database.py", line 35, in _store_result
    task_kwargs=task_kwargs,
  File "[REDACTED]/lib/python3.6/site-packages/django_celery_results/managers.py", line 50, in _inner
    return fun(*args, **kwargs)
  File "[REDACTED]/lib/python3.6/site-packages/django_celery_results/managers.py", line 126, in store_result
    obj, created = self.get_or_create(task_id=task_id, defaults=fields)
  File "[REDACTED]/lib/python3.6/site-packages/django/db/models/manager.py", line 82, in manager_method
    return getattr(self.get_queryset(), name)(*args, **kwargs)
  File "[REDACTED]/lib/python3.6/site-packages/django/db/models/query.py", line 538, in get_or_create
    return self.get(**kwargs), False
  File "[REDACTED]/lib/python3.6/site-packages/django/db/models/query.py", line 402, in get
    num = len(clone)
  File "[REDACTED]/lib/python3.6/site-packages/django/db/models/query.py", line 256, in __len__
    self._fetch_all()
  File "[REDACTED]/lib/python3.6/site-packages/django/db/models/query.py", line 1242, in _fetch_all
    self._result_cache = list(self._iterable_class(self))
  File "[REDACTED]/lib/python3.6/site-packages/django/db/models/query.py", line 55, in __iter__
    results = compiler.execute_sql(chunked_fetch=self.chunked_fetch, chunk_size=self.chunk_size)
  File "[REDACTED]/lib/python3.6/site-packages/django/db/models/sql/compiler.py", line 1098, in execute_sql
    cursor = self.connection.cursor()
  File "[REDACTED]/lib/python3.6/site-packages/django/db/backends/base/base.py", line 256, in cursor
    return self._cursor()
  File "[REDACTED]/lib/python3.6/site-packages/django/db/backends/base/base.py", line 233, in _cursor
    self.ensure_connection()
  File "[REDACTED]/lib/python3.6/site-packages/django/db/backends/base/base.py", line 217, in ensure_connection
    self.connect()
  File "[REDACTED]/lib/python3.6/site-packages/django/db/utils.py", line 89, in __exit__
    raise dj_exc_value.with_traceback(traceback) from exc_value
  File "[REDACTED]/lib/python3.6/site-packages/django/db/backends/base/base.py", line 217, in ensure_connection
    self.connect()
  File "[REDACTED]/lib/python3.6/site-packages/django/db/backends/base/base.py", line 195, in connect
    self.connection = self.get_new_connection(conn_params)
  File "[REDACTED]/lib/python3.6/site-packages/django/db/backends/mysql/base.py", line 227, in get_new_connection
    return Database.connect(**conn_params)
  File "[REDACTED]/lib/python3.6/site-packages/MySQLdb/__init__.py", line 84, in Connect
    return Connection(*args, **kwargs)
  File "[REDACTED]/lib/python3.6/site-packages/MySQLdb/connections.py", line 164, in __init__
    super(Connection, self).__init__(*args, **kwargs2)
django.db.utils.OperationalError: (2002, "Can't connect to local MySQL server through socket '/var/run/mysqld/mysqld.sock' (2)")
</code></pre></div>
<p dir="auto"></p>
</details>
<p dir="auto">This is unhelpful. Without looking at the logs you wouldn't know anything was wrong.</p>
<p dir="auto">In the production setting, the exception is only printed as many times as there are concurrent workers, which makes it even harder to identify. I was not able to reproduce this particular behavior locally, and get an exception each time.</p>
<h1 dir="auto">Checklist</h1>

<ul class="contains-task-list">
<li class="task-list-item"><input type="checkbox" id="" disabled="" class="task-list-item-checkbox" checked=""> I have verified that the issue exists against the <code class="notranslate">master</code> branch of Celery.</li>
<li class="task-list-item"><input type="checkbox" id="" disabled="" class="task-list-item-checkbox"> This has already been asked to the <a href="https://groups.google.com/forum/#!forum/celery-users" rel="nofollow">discussion group</a> first.</li>
<li class="task-list-item"><input type="checkbox" id="" disabled="" class="task-list-item-checkbox" checked=""> I have read the relevant section in the<br>
<a href="http://docs.celeryproject.org/en/latest/contributing.html#other-bugs" rel="nofollow">contribution guide</a><br>
on reporting bugs.</li>
<li class="task-list-item"><input type="checkbox" id="" disabled="" class="task-list-item-checkbox" checked=""> I have checked the <a href="https://github.com/celery/celery/issues?q=is%3Aissue+label%3A%22Issue+Type%3A+Bug+Report%22+-label%3A%22Category%3A+Documentation%22">issues list</a><br>
for similar or identical bug reports.</li>
<li class="task-list-item"><input type="checkbox" id="" disabled="" class="task-list-item-checkbox" checked=""> I have checked the <a href="https://github.com/celery/celery/pulls?q=is%3Apr+label%3A%22PR+Type%3A+Bugfix%22+-label%3A%22Category%3A+Documentation%22">pull requests list</a><br>
for existing proposed fixes.</li>
<li class="task-list-item"><input type="checkbox" id="" disabled="" class="task-list-item-checkbox" checked=""> I have checked the <a href="https://github.com/celery/celery/commits/master">commit log</a><br>
to find out if the bug was already fixed in the master branch.</li>
<li class="task-list-item"><input type="checkbox" id="" disabled="" class="task-list-item-checkbox" checked=""> I have included all related issues and possible duplicate issues<br>
in this issue (If there are none, check this box anyway).</li>
</ul>
<h2 dir="auto">Mandatory Debugging Information</h2>
<ul class="contains-task-list">
<li class="task-list-item"><input type="checkbox" id="" disabled="" class="task-list-item-checkbox" checked=""> I have included the output of <code class="notranslate">celery -A proj report</code> in the issue.<br>
(if you are not able to do this, then at least specify the Celery<br>
version affected).</li>
<li class="task-list-item"><input type="checkbox" id="" disabled="" class="task-list-item-checkbox" checked=""> I have verified that the issue exists against the <code class="notranslate">master</code> branch of Celery.</li>
<li class="task-list-item"><input type="checkbox" id="" disabled="" class="task-list-item-checkbox" checked=""> I have included the contents of <code class="notranslate">pip freeze</code> in the issue.</li>
<li class="task-list-item"><input type="checkbox" id="" disabled="" class="task-list-item-checkbox" checked=""> I have included all the versions of all the external dependencies required<br>
to reproduce this bug.</li>
</ul>
<h2 dir="auto">Optional Debugging Information</h2>

<ul class="contains-task-list">
<li class="task-list-item"><input type="checkbox" id="" disabled="" class="task-list-item-checkbox"> I have tried reproducing the issue on more than one Python version<br>
and/or implementation.</li>
<li class="task-list-item"><input type="checkbox" id="" disabled="" class="task-list-item-checkbox"> I have tried reproducing the issue on more than one message broker and/or<br>
result backend.</li>
<li class="task-list-item"><input type="checkbox" id="" disabled="" class="task-list-item-checkbox"> I have tried reproducing the issue on more than one version of the message<br>
broker and/or result backend.</li>
<li class="task-list-item"><input type="checkbox" id="" disabled="" class="task-list-item-checkbox"> I have tried reproducing the issue on more than one operating system.</li>
<li class="task-list-item"><input type="checkbox" id="" disabled="" class="task-list-item-checkbox"> I have tried reproducing the issue on more than one workers pool.</li>
<li class="task-list-item"><input type="checkbox" id="" disabled="" class="task-list-item-checkbox"> I have tried reproducing the issue with autoscaling, retries,<br>
ETA/Countdown &amp; rate limits disabled.</li>
<li class="task-list-item"><input type="checkbox" id="" disabled="" class="task-list-item-checkbox"> I have tried reproducing the issue after downgrading<br>
and/or upgrading Celery and its dependencies.</li>
</ul>
<h2 dir="auto">Related Issues and Possible Duplicates</h2>

<h4 dir="auto">Related Issues</h4>
<ul dir="auto">
<li>None</li>
</ul>
<h4 dir="auto">Possible Duplicates</h4>
<ul dir="auto">
<li>None</li>
</ul>
<h2 dir="auto">Environment &amp; Settings</h2>

<p dir="auto"><strong>Celery version</strong>:</p>

<details>
<summary><b><code class="notranslate">celery report</code> Output:</b></summary>
<p dir="auto">
</p><div class="snippet-clipboard-content notranslate position-relative overflow-auto" data-snippet-clipboard-copy-content="software -&gt; celery:5.0.0 (singularity) kombu:5.0.2 py:3.8.5
            billiard:3.6.3.0 py-amqp:5.0.1
platform -&gt; system:Darwin arch:64bit
            kernel version:18.7.0 imp:CPython
loader   -&gt; celery.loaders.app.AppLoader
settings -&gt; transport:amqp results:disabled

deprecated_settings: None
"><pre class="notranslate"><code class="notranslate">software -&gt; celery:5.0.0 (singularity) kombu:5.0.2 py:3.8.5
            billiard:3.6.3.0 py-amqp:5.0.1
platform -&gt; system:Darwin arch:64bit
            kernel version:18.7.0 imp:CPython
loader   -&gt; celery.loaders.app.AppLoader
settings -&gt; transport:amqp results:disabled

deprecated_settings: None

</code></pre></div>
<p dir="auto"></p>
</details>
<h1 dir="auto">Steps to Reproduce</h1>
<h2 dir="auto">Required Dependencies</h2>

<ul dir="auto">
<li><strong>Minimal Python Version</strong>: N/A or Unknown</li>
<li><strong>Minimal Celery Version</strong>: 5.0.0</li>
<li><strong>Minimal Kombu Version</strong>: 5.0.2</li>
<li><strong>Minimal Broker Version</strong>: N/A or Unknown</li>
<li><strong>Minimal Result Backend Version</strong>: N/A or Unknown</li>
<li><strong>Minimal OS and/or Kernel Version</strong>: N/A or Unknown</li>
<li><strong>Minimal Broker Client Version</strong>: N/A or Unknown</li>
<li><strong>Minimal Result Backend Client Version</strong>: N/A or Unknown</li>
</ul>
<h3 dir="auto">Python Packages</h3>

<details>
<summary><b><code class="notranslate">pip freeze</code> Output:</b></summary>
<p dir="auto">
</p><div class="snippet-clipboard-content notranslate position-relative overflow-auto" data-snippet-clipboard-copy-content="amqp==5.0.1
appdirs==1.4.4
appnope==0.1.0
asgiref==3.2.10
astor==0.8.1
attrs==20.2.0
backcall==0.2.0
bandit==1.6.2
bcrypt==3.2.0
billiard==3.6.3.0
blinker==1.4
celery==5.0.0
certifi==2020.6.20
cffi==1.14.3
chardet==3.0.4
click==7.1.2
click-default-group==1.2.2
click-didyoumean==0.0.3
click-repl==0.1.6
colorama==0.4.3
coreapi==2.3.3
coreschema==0.0.4
coverage==5.3
darglint==1.5.4
decorator==4.4.2
dennis==0.9
Django==3.0.10
django-admin-tools==0.9.0
django-autocomplete-light==3.5.0
django-coverage-plugin==1.8.0
django-csp==3.7
django-debug-toolbar==2.2
django-extensions==3.0.9
django-feature-policy==3.4.0
django-filter==2.4.0
django-health-check==3.14.1
django-http-referrer-policy==1.0.1
django-lifecycle==0.7.7
django-migration-linter==2.4.0
django-querycount==0.7.0
django-split-settings==1.0.1
django-stubs==1.5.0
django-test-migrations==1.0.0
djangorestframework==3.11.1
docutils==0.16
dotenv-linter==0.1.3
dparse==0.5.1
drf-yasg==1.17.1
eradicate==1.0
Faker==4.1.3
flake8==3.8.3
flake8-bandit==2.1.2
flake8-broken-line==0.2.1
flake8-bugbear==19.8.0
flake8-commas==2.0.0
flake8-comprehensions==3.2.3
flake8-debugger==3.2.1
flake8-django==1.1.1
flake8-docstrings==1.5.0
flake8-eradicate==0.3.0
flake8-isort==3.0.1
flake8-logging-format==0.6.0
flake8-plugin-utils==1.3.1
flake8-polyfill==1.0.2
flake8-pytest-style==1.3.0
flake8-quotes==2.1.2
flake8-rst-docstrings==0.0.12
flake8-string-format==0.2.3
flower==0.9.5
gitdb==4.0.5
GitPython==3.1.8
gunicorn==20.0.4
humanize==2.6.0
hypothesis==5.36.0
idna==2.10
importlib-metadata==1.1.3
inflection==0.5.1
iniconfig==1.0.1
ipython==7.18.1
ipython-genutils==0.2.0
isort==4.3.21
itypes==1.2.0
jedi==0.17.2
Jinja2==2.11.2
kombu==5.0.2
MarkupSafe==1.1.1
mccabe==0.6.1
more-itertools==8.5.0
mypy==0.770
mypy-extensions==0.4.3
nplusone==1.0.0
orjson==3.3.1
packaging==20.4
parso==0.7.1
pbr==5.5.0
pep8-naming==0.9.1
pexpect==4.8.0
pickleshare==0.7.5
pluggy==0.13.1
ply==3.11
polib==1.1.0
prometheus-client==0.8.0
prompt-toolkit==3.0.7
psycopg2==2.8.6
ptyprocess==0.6.0
py==1.9.0
pycodestyle==2.6.0
pycparser==2.20
pydantic==1.6.1
pydocstyle==5.1.1
pyflakes==2.2.0
Pygments==2.7.1
PyJWT==1.7.1
pyparsing==2.4.7
pytest==6.0.2
pytest-cov==2.10.1
pytest-deadfixtures==2.2.1
pytest-django==3.10.0
pytest-randomly==3.4.1
pytest-testmon==1.0.3
pytest-timeout==1.4.2
python-dateutil==2.8.1
python-decouple==3.3
pytz==2020.1
PyYAML==5.3.1
requests==2.24.0
restructuredtext-lint==1.3.1
ruamel.yaml==0.16.12
ruamel.yaml.clib==0.2.2
safety==1.9.0
sentry-sdk==0.17.8
six==1.15.0
smmap==3.0.4
snowballstemmer==2.0.0
sortedcontainers==2.2.2
sqlparse==0.3.1
stevedore==3.2.2
structlog==20.1.0
testfixtures==6.14.2
text-unidecode==1.3
toml==0.10.1
tornado==6.0.4
traitlets==5.0.4
typed-ast==1.4.1
typing-extensions==3.7.4.3
uritemplate==3.0.1
urllib3==1.25.10
urlman==1.3.0
vine==5.0.0
wcwidth==0.2.5
wemake-python-styleguide==0.14.1
wrapt==1.12.1
zipp==3.2.0"><pre class="notranslate"><code class="notranslate">amqp==5.0.1
appdirs==1.4.4
appnope==0.1.0
asgiref==3.2.10
astor==0.8.1
attrs==20.2.0
backcall==0.2.0
bandit==1.6.2
bcrypt==3.2.0
billiard==3.6.3.0
blinker==1.4
celery==5.0.0
certifi==2020.6.20
cffi==1.14.3
chardet==3.0.4
click==7.1.2
click-default-group==1.2.2
click-didyoumean==0.0.3
click-repl==0.1.6
colorama==0.4.3
coreapi==2.3.3
coreschema==0.0.4
coverage==5.3
darglint==1.5.4
decorator==4.4.2
dennis==0.9
Django==3.0.10
django-admin-tools==0.9.0
django-autocomplete-light==3.5.0
django-coverage-plugin==1.8.0
django-csp==3.7
django-debug-toolbar==2.2
django-extensions==3.0.9
django-feature-policy==3.4.0
django-filter==2.4.0
django-health-check==3.14.1
django-http-referrer-policy==1.0.1
django-lifecycle==0.7.7
django-migration-linter==2.4.0
django-querycount==0.7.0
django-split-settings==1.0.1
django-stubs==1.5.0
django-test-migrations==1.0.0
djangorestframework==3.11.1
docutils==0.16
dotenv-linter==0.1.3
dparse==0.5.1
drf-yasg==1.17.1
eradicate==1.0
Faker==4.1.3
flake8==3.8.3
flake8-bandit==2.1.2
flake8-broken-line==0.2.1
flake8-bugbear==19.8.0
flake8-commas==2.0.0
flake8-comprehensions==3.2.3
flake8-debugger==3.2.1
flake8-django==1.1.1
flake8-docstrings==1.5.0
flake8-eradicate==0.3.0
flake8-isort==3.0.1
flake8-logging-format==0.6.0
flake8-plugin-utils==1.3.1
flake8-polyfill==1.0.2
flake8-pytest-style==1.3.0
flake8-quotes==2.1.2
flake8-rst-docstrings==0.0.12
flake8-string-format==0.2.3
flower==0.9.5
gitdb==4.0.5
GitPython==3.1.8
gunicorn==20.0.4
humanize==2.6.0
hypothesis==5.36.0
idna==2.10
importlib-metadata==1.1.3
inflection==0.5.1
iniconfig==1.0.1
ipython==7.18.1
ipython-genutils==0.2.0
isort==4.3.21
itypes==1.2.0
jedi==0.17.2
Jinja2==2.11.2
kombu==5.0.2
MarkupSafe==1.1.1
mccabe==0.6.1
more-itertools==8.5.0
mypy==0.770
mypy-extensions==0.4.3
nplusone==1.0.0
orjson==3.3.1
packaging==20.4
parso==0.7.1
pbr==5.5.0
pep8-naming==0.9.1
pexpect==4.8.0
pickleshare==0.7.5
pluggy==0.13.1
ply==3.11
polib==1.1.0
prometheus-client==0.8.0
prompt-toolkit==3.0.7
psycopg2==2.8.6
ptyprocess==0.6.0
py==1.9.0
pycodestyle==2.6.0
pycparser==2.20
pydantic==1.6.1
pydocstyle==5.1.1
pyflakes==2.2.0
Pygments==2.7.1
PyJWT==1.7.1
pyparsing==2.4.7
pytest==6.0.2
pytest-cov==2.10.1
pytest-deadfixtures==2.2.1
pytest-django==3.10.0
pytest-randomly==3.4.1
pytest-testmon==1.0.3
pytest-timeout==1.4.2
python-dateutil==2.8.1
python-decouple==3.3
pytz==2020.1
PyYAML==5.3.1
requests==2.24.0
restructuredtext-lint==1.3.1
ruamel.yaml==0.16.12
ruamel.yaml.clib==0.2.2
safety==1.9.0
sentry-sdk==0.17.8
six==1.15.0
smmap==3.0.4
snowballstemmer==2.0.0
sortedcontainers==2.2.2
sqlparse==0.3.1
stevedore==3.2.2
structlog==20.1.0
testfixtures==6.14.2
text-unidecode==1.3
toml==0.10.1
tornado==6.0.4
traitlets==5.0.4
typed-ast==1.4.1
typing-extensions==3.7.4.3
uritemplate==3.0.1
urllib3==1.25.10
urlman==1.3.0
vine==5.0.0
wcwidth==0.2.5
wemake-python-styleguide==0.14.1
wrapt==1.12.1
zipp==3.2.0
</code></pre></div>
<p dir="auto"></p>
</details>
<h3 dir="auto">Other Dependencies</h3>

<details>
<p dir="auto">
N/A
</p>
</details>
<h2 dir="auto">Minimally Reproducible Test Case</h2>

<details>
<p dir="auto">
</p><div class="highlight highlight-source-shell notranslate position-relative overflow-auto" dir="auto" data-snippet-clipboard-copy-content="celery -A proj inspect ping -d celery@$HOSTNAME"><pre class="notranslate">celery -A proj inspect ping -d celery@<span class="pl-smi">$HOSTNAME</span></pre></div>
<p dir="auto"></p>
</details>
<h1 dir="auto">Expected Behavior</h1>

<div class="snippet-clipboard-content notranslate position-relative overflow-auto" data-snippet-clipboard-copy-content="-&gt;  celery@$HOSTNAME: OK
        pong"><pre class="notranslate"><code class="notranslate">-&gt;  celery@$HOSTNAME: OK
        pong
</code></pre></div>
<h1 dir="auto">Actual Behavior</h1>

<div class="snippet-clipboard-content notranslate position-relative overflow-auto" data-snippet-clipboard-copy-content="Traceback (most recent call last):
  File &quot;/Users/aszubarev/Library/Caches/pypoetry/virtualenvs/service-notification-py-xHAuYcng-py3.8/bin/celery&quot;, line 8, in &lt;module&gt;
    sys.exit(main())
  File &quot;/Users/aszubarev/Library/Caches/pypoetry/virtualenvs/service-notification-py-xHAuYcng-py3.8/lib/python3.8/site-packages/celery/__main__.py&quot;, line 15, in main
    sys.exit(_main())
  File &quot;/Users/aszubarev/Library/Caches/pypoetry/virtualenvs/service-notification-py-xHAuYcng-py3.8/lib/python3.8/site-packages/celery/bin/celery.py&quot;, line 150, in main
    return celery(auto_envvar_prefix=&quot;CELERY&quot;)
  File &quot;/Users/aszubarev/Library/Caches/pypoetry/virtualenvs/service-notification-py-xHAuYcng-py3.8/lib/python3.8/site-packages/click/core.py&quot;, line 829, in __call__
    return self.main(*args, **kwargs)
  File &quot;/Users/aszubarev/Library/Caches/pypoetry/virtualenvs/service-notification-py-xHAuYcng-py3.8/lib/python3.8/site-packages/click/core.py&quot;, line 782, in main
    rv = self.invoke(ctx)
  File &quot;/Users/aszubarev/Library/Caches/pypoetry/virtualenvs/service-notification-py-xHAuYcng-py3.8/lib/python3.8/site-packages/click/core.py&quot;, line 1259, in invoke
    return _process_result(sub_ctx.command.invoke(sub_ctx))
  File &quot;/Users/aszubarev/Library/Caches/pypoetry/virtualenvs/service-notification-py-xHAuYcng-py3.8/lib/python3.8/site-packages/click/core.py&quot;, line 1066, in invoke
    return ctx.invoke(self.callback, **ctx.params)
  File &quot;/Users/aszubarev/Library/Caches/pypoetry/virtualenvs/service-notification-py-xHAuYcng-py3.8/lib/python3.8/site-packages/click/core.py&quot;, line 610, in invoke
    return callback(*args, **kwargs)
  File &quot;/Users/aszubarev/Library/Caches/pypoetry/virtualenvs/service-notification-py-xHAuYcng-py3.8/lib/python3.8/site-packages/click/decorators.py&quot;, line 21, in new_func
    return f(get_current_context(), *args, **kwargs)
  File &quot;/Users/aszubarev/Library/Caches/pypoetry/virtualenvs/service-notification-py-xHAuYcng-py3.8/lib/python3.8/site-packages/celery/bin/control.py&quot;, line 125, in inspect
    replies = ctx.obj.app.control.inspect(timeout=timeout,
  File &quot;/Users/aszubarev/Library/Caches/pypoetry/virtualenvs/service-notification-py-xHAuYcng-py3.8/lib/python3.8/site-packages/celery/app/control.py&quot;, line 97, in _request
    return self._prepare(self.app.control.broadcast(
  File &quot;/Users/aszubarev/Library/Caches/pypoetry/virtualenvs/service-notification-py-xHAuYcng-py3.8/lib/python3.8/site-packages/celery/app/control.py&quot;, line 477, in broadcast
    return self.mailbox(conn)._broadcast(
  File &quot;/Users/aszubarev/Library/Caches/pypoetry/virtualenvs/service-notification-py-xHAuYcng-py3.8/lib/python3.8/site-packages/kombu/pidbox.py&quot;, line 319, in _broadcast
    raise ValueError(
ValueError: destination must be a list/tuple not &lt;class 'set'&gt;
Sentry is attempting to send 0 pending error messages
Waiting up to 2 seconds
Press Ctrl-C to quit"><pre class="notranslate"><code class="notranslate">Traceback (most recent call last):
  File "/Users/aszubarev/Library/Caches/pypoetry/virtualenvs/service-notification-py-xHAuYcng-py3.8/bin/celery", line 8, in &lt;module&gt;
    sys.exit(main())
  File "/Users/aszubarev/Library/Caches/pypoetry/virtualenvs/service-notification-py-xHAuYcng-py3.8/lib/python3.8/site-packages/celery/__main__.py", line 15, in main
    sys.exit(_main())
  File "/Users/aszubarev/Library/Caches/pypoetry/virtualenvs/service-notification-py-xHAuYcng-py3.8/lib/python3.8/site-packages/celery/bin/celery.py", line 150, in main
    return celery(auto_envvar_prefix="CELERY")
  File "/Users/aszubarev/Library/Caches/pypoetry/virtualenvs/service-notification-py-xHAuYcng-py3.8/lib/python3.8/site-packages/click/core.py", line 829, in __call__
    return self.main(*args, **kwargs)
  File "/Users/aszubarev/Library/Caches/pypoetry/virtualenvs/service-notification-py-xHAuYcng-py3.8/lib/python3.8/site-packages/click/core.py", line 782, in main
    rv = self.invoke(ctx)
  File "/Users/aszubarev/Library/Caches/pypoetry/virtualenvs/service-notification-py-xHAuYcng-py3.8/lib/python3.8/site-packages/click/core.py", line 1259, in invoke
    return _process_result(sub_ctx.command.invoke(sub_ctx))
  File "/Users/aszubarev/Library/Caches/pypoetry/virtualenvs/service-notification-py-xHAuYcng-py3.8/lib/python3.8/site-packages/click/core.py", line 1066, in invoke
    return ctx.invoke(self.callback, **ctx.params)
  File "/Users/aszubarev/Library/Caches/pypoetry/virtualenvs/service-notification-py-xHAuYcng-py3.8/lib/python3.8/site-packages/click/core.py", line 610, in invoke
    return callback(*args, **kwargs)
  File "/Users/aszubarev/Library/Caches/pypoetry/virtualenvs/service-notification-py-xHAuYcng-py3.8/lib/python3.8/site-packages/click/decorators.py", line 21, in new_func
    return f(get_current_context(), *args, **kwargs)
  File "/Users/aszubarev/Library/Caches/pypoetry/virtualenvs/service-notification-py-xHAuYcng-py3.8/lib/python3.8/site-packages/celery/bin/control.py", line 125, in inspect
    replies = ctx.obj.app.control.inspect(timeout=timeout,
  File "/Users/aszubarev/Library/Caches/pypoetry/virtualenvs/service-notification-py-xHAuYcng-py3.8/lib/python3.8/site-packages/celery/app/control.py", line 97, in _request
    return self._prepare(self.app.control.broadcast(
  File "/Users/aszubarev/Library/Caches/pypoetry/virtualenvs/service-notification-py-xHAuYcng-py3.8/lib/python3.8/site-packages/celery/app/control.py", line 477, in broadcast
    return self.mailbox(conn)._broadcast(
  File "/Users/aszubarev/Library/Caches/pypoetry/virtualenvs/service-notification-py-xHAuYcng-py3.8/lib/python3.8/site-packages/kombu/pidbox.py", line 319, in _broadcast
    raise ValueError(
ValueError: destination must be a list/tuple not &lt;class 'set'&gt;
Sentry is attempting to send 0 pending error messages
Waiting up to 2 seconds
Press Ctrl-C to quit
</code></pre></div>