Where to find the airflow-scheduler.pid

[yogyang]

Hi, I run the airflow using docker-compose.yaml from this https://airflow.apache.org/docs/apache-airflow/stable/start/docker.html, and I can not find the airflow-scheduler.pid, but I do see the airflow-webserver.pid, anyone know where should I get for the airflow-scheduler.pid ?

docker exec -it f8f4fec10253 ls
airflow-webserver.pid dags plugins unittests.cfg
airflow.cfg logs requirements.txt webserver_config.py

docker exec -it 70cfd14977cf ls
airflow.cfg logs requirements.txt webserver_config.py
dags plugins unittests.cfg

Thanks

[yogyang]

em. I found in local docker I need to use airflow scheduler -D, then it will generate the airflow-scheduler.pid.

[yogyang]

Faile on K8s, I changed the line https://github.com/apache/airflow/blob/master/chart/templates/scheduler/scheduler-deployment.yaml#L113 to args: ["bash", "-c", "exec airflow scheduler -D"], the k8s container would failed with error:

Traceback (most recent call last):
  File "/home/airflow/.local/lib/python3.7/site-packages/sqlalchemy/engine/base.py", line 771, in _commit_impl
    self.engine.dialect.do_commit(self.connection)
  File "/home/airflow/.local/lib/python3.7/site-packages/sqlalchemy/engine/default.py", line 561, in do_commit
    dbapi_connection.commit()
psycopg2.errors.ProtocolViolation: invalid frontend message type 97
server closed the connection unexpectedly
        This probably means the server terminated abnormally
        before or while processing the request.


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

Traceback (most recent call last):
  File "/home/airflow/.local/lib/python3.7/site-packages/airflow/jobs/scheduler_job.py", line 1280, in _execute
    self._run_scheduler_loop()
  File "/home/airflow/.local/lib/python3.7/site-packages/airflow/jobs/scheduler_job.py", line 1354, in _run_scheduler_loop
    self.adopt_or_reset_orphaned_tasks()
  File "/home/airflow/.local/lib/python3.7/site-packages/airflow/utils/session.py", line 65, in wrapper
    return func(*args, session=session, **kwargs)
  File "/usr/local/lib/python3.7/contextlib.py", line 119, in __exit__
    next(self.gen)
  File "/home/airflow/.local/lib/python3.7/site-packages/airflow/utils/session.py", line 32, in create_session
    session.commit()
  File "/home/airflow/.local/lib/python3.7/site-packages/sqlalchemy/orm/session.py", line 1046, in commit
    self.transaction.commit()
  File "/home/airflow/.local/lib/python3.7/site-packages/sqlalchemy/orm/session.py", line 508, in commit
    t[1].commit()
  File "/home/airflow/.local/lib/python3.7/site-packages/sqlalchemy/engine/base.py", line 1762, in commit
    self._do_commit()
  File "/home/airflow/.local/lib/python3.7/site-packages/sqlalchemy/engine/base.py", line 1793, in _do_commit
    self.connection._commit_impl()
  File "/home/airflow/.local/lib/python3.7/site-packages/sqlalchemy/engine/base.py", line 773, in _commit_impl
    self._handle_dbapi_exception(e, None, None, None, None)
  File "/home/airflow/.local/lib/python3.7/site-packages/sqlalchemy/engine/base.py", line 1511, in _handle_dbapi_exception
    sqlalchemy_exception, with_traceback=exc_info[2], from_=e
  File "/home/airflow/.local/lib/python3.7/site-packages/sqlalchemy/util/compat.py", line 182, in raise_
    raise exception
  File "/home/airflow/.local/lib/python3.7/site-packages/sqlalchemy/engine/base.py", line 771, in _commit_impl
    self.engine.dialect.do_commit(self.connection)
  File "/home/airflow/.local/lib/python3.7/site-packages/sqlalchemy/engine/default.py", line 561, in do_commit
    dbapi_connection.commit()
sqlalchemy.exc.DatabaseError: (psycopg2.errors.ProtocolViolation) invalid frontend message type 97
server closed the connection unexpectedly
        This probably means the server terminated abnormally
        before or while processing the request.

[XD-DENG]

When you apply -D, the actual process you intend to run will run as a separate process, and your main process exits. Just like what you do in terminal, but in K8S the pod will terminate if the main process terminates. This seems like why to me.

I assume you just want to know the PID for whatever reason? In this case, try to get the PID of your scheduler with command pgrep scheduler, instead of relying on the PID file.

Hope this helps.

[yogyang]

really thank you for your reply, actually what I want to do is

in my airflow image, I have a file named requirements.txt, as the user can add new PyPI dependencies to that requirements.txt. in the entrypoint of the image, I add pip install -r requriments.txt to get extra dependencies installed.

In my k8s deployment, I use the git-sync sidecar to get the latest dags codes, what I want is when the git-sync found codes updated, I can trigger the scheduler container to restart to get the newly added dependencies installed.

so I plan to get scheduler PID, and run kill -9 {PID} in the git_sync sidecar.

em if I could not get the PID from static file, I guess I need to build another git_sync image with pgrep installed.

[XD-DENG]

A few points for your reference:

• If you simply want to get the scheduler PID, the command pgrep scheduler I shared above should do the trick.
• For Docker/K8S pod context, you are encouraged to run a single process in a container/pod. To restart a container/pod, possibly it makes more sense to me if you manage it from Docker/K8S level, rather than "process" level.

[yogyang]

yeah, you are right, I think I should make it work in more K8s way. Thanks~