jedcunningham commented on a change in pull request #18068:
URL: https://github.com/apache/airflow/pull/18068#discussion_r706247473
##########
File path: Dockerfile
##########
@@ -479,6 +479,7 @@ LABEL org.apache.airflow.distro="debian" \
org.opencontainers.image.title="Production Airflow Image" \
org.opencontainers.image.description="Reference, production-ready Apache
Airflow image"
+ENV DUMB_INIT_SETSID="1"
Review comment:
Since its the default, do we really care to set it?
##########
File path: chart/templates/workers/worker-deployment.yaml
##########
@@ -180,6 +180,10 @@ spec:
envFrom:
{{- include "custom_airflow_environment_from" . | default "\n []" |
indent 10 }}
env:
+ # For images before Airflow 2.1.4 setting DUMB_INIT_SESSID to 0
fixes signal propagation
+ # to make Warm Shutdown works properly for Celery Workers
Review comment:
```suggestion
# Only signal the main process, not the process group, to make
Warm Shutdown work properly
```
##########
File path: docs/docker-stack/entrypoint.rst
##########
@@ -161,6 +161,34 @@ If there are any other arguments - they are simply passed
to the "airflow" comma
> docker run -it apache/airflow:2.1.2-python3.6 version
2.1.2
+Signal propagation
+------------------
+
+Airflow uses ``dumb-init`` to run as "init" in the entrypoint. This is in
order to propagate
+signals and reap child processes properly. This means that the process that
you run, does not have
Review comment:
```suggestion
signals and reap child processes properly. This means that the process that
you run does not have
```
##########
File path: docs/docker-stack/entrypoint.rst
##########
@@ -161,6 +161,34 @@ If there are any other arguments - they are simply passed
to the "airflow" comma
> docker run -it apache/airflow:2.1.2-python3.6 version
2.1.2
+Signal propagation
+------------------
+
+Airflow uses ``dumb-init`` to run as "init" in the entrypoint. This is in
order to propagate
+signals and reap child processes properly. This means that the process that
you run, does not have
+to install signal handlers to work properly and be killed when the container
is gracefully terminated.
+The behaviour of signal propagation is configured by ``DUMB_INIT_SETSID``
variable which is set to
+``1`` by default - meaning that the signals will be propagated to the whole
process group, but you can
+set it to ``0`` to enable ``single-child`` behaviour of ``dumb-init`` which
only propagates the
+signals to only single child process.
+
+
++------------------+-----------------------------------------------------------------------------------------------+
+| DUMB_INIT_SETSID | Use case
|
++------------------+-----------------------------------------------------------------------------------------------+
+| 1 (default) | If you run your processes as ``["bash", "-c"]`` command,
and bash spawn some new processes, |
Review comment:
I think this should be refactored to have "propagate signals to all
processes in the process group" come before the `bash` example, as the bash bit
really is just one example not core to this setting.
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