Add retry logic for Django and Psycopg2 InterfaceErrors #290
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auvipy
requested changes
Feb 25, 2022
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I want to add this to next release, can you please address the review comment? |
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@auvipy Yes, I am working on this today since I had other tasks to finish Friday. |
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ok |
auvipy
approved these changes
Mar 1, 2022
intgr
reviewed
Mar 1, 2022
| from kombu.exceptions import DecodeError | ||
| from psycopg2 import InterfaceError as Psycopg2InterfaceError |
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This adds a hard dependency on psycopg2, but django-celery-results can be used with other databases as well.
I have opened PR #292 to fix this.
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This PR implements #119 in a slightly different way. It adds retry logic only for django.db.utils.InterfaceError and psycopg2.InterfaceError, which can be errors like "connection already closed".
It does not retry any DatabaseError, which can be errors like "numeric value out of range" or "foreign key check failed". See https://www.psycopg.org/docs/module.html#exceptions for more info.
exception_safe_to_retry() is overridden from the parent class: https://docs.celeryproject.org/en/stable/_modules/celery/backends/base.html#BaseBackend
This method is called when an exception is raised in _store_result() and always_retry / result_backend_always_retry is set to True. If the exception is an InterfaceError, the connection is closed as a side effect of calling exception_safe_to_retry().
Then the retry logic implemented in the parent class continues, and Django will automatically open a new connection for the next attempt to store the task result or get the task metadata.