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https://issues.apache.org/jira/browse/AIRFLOW-62?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15277493#comment-15277493
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Alex Papanicolaou commented on AIRFLOW-62:
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I think you're right that it's celery. Just ran it with a local executor and
it worked fine.
> XCom push not working reliably
> ------------------------------
>
> Key: AIRFLOW-62
> URL: https://issues.apache.org/jira/browse/AIRFLOW-62
> Project: Apache Airflow
> Issue Type: Bug
> Components: db, operators
> Affects Versions: Airflow 1.7.0
> Environment: Postgres backed Airflow running with Celery inside of
> the puckel Docker setup.
> Reporter: Alex Papanicolaou
> Assignee: Jeremiah Lowin
>
> I have a DAG that polls for activity in various data streams from a database
> and then uploads the activity statuses to a table. Each of the polling tasks
> are python operators that once they get the polling result, return a dict as
> an XCom push. The dict contains two entries which are strings, one which is
> a bool, and one which is a datetime object. There is a final task that pulls
> all the results and uploads the collective statuses to a table. I chose this
> pattern since I figured it might be better to do one collective write
> operation on all the results.
> Before I moved ahead to the github master branch I was using 1.7.0 from PyPI
> and this worked fine. Now that I am on the github master branch, I find that
> the XCom pushing is unreliable. The returned values in the logs show up
> correctly but when doing the XCom pull, I get None for some of the returned
> values. Investigating the XCom result in the Webserver also shows nothing
> there. But if I rerun a task where the XCom failed, the push works and the
> XCom result is as it should be.
> Nothing appears to have changed in the codebase so I am at a loss. Perhaps
> it really wasn't working before? How would the backing postgres handle these
> simultaneous writes? I can't imagine that would be a problem.
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