exception handling of callback failures doesn't take into account retriable errors

[Kevin Benton]

Subscribers to callback events can perform DB operations that may encounter deadlocks or other DB errors that should be retried after restarting the entire transaction. However, in the cases where we catch exceptions.CallbackFailure and then raise a different exception, the DB retry wrapper cannot recognize that it is retriable failure and will make it fatal for the request. This can lead to a user getting a SubnetInUse or something similar because of something completely unrelated to the actual validation.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/326928

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/326928
Committed: https://git.openstack.org/cgit/openstack/neutron/commit/?id=143b19c8d5e6805c4ce0abe78748c0add42a2072
Submitter: Jenkins
Branch: master

commit 143b19c8d5e6805c4ce0abe78748c0add42a2072
Author: Kevin Benton <email address hidden>
Date: Tue Jun 7 15:27:48 2016 -0700

    Separate exception class for retriables in callbacks

    There are various places where we emit a callback to allow
    subscribers to do validation or additional bookkeeping during
    the various life-cycle events of objects. However, a subscriber
    can encounter a DB Deadlock, StaleDataError or other retriable
    error that just needs the transaction to be restarted. In the
    rest of the Neutron code these exceptions bubble up to the API
    layer where the whole request is restarted. However, the exception
    catching for the callbacks in various places was preventing these
    errors from being retried because they were lost in conversion.

    This patch has the callback manager convert retriable exceptions
    into RetryRequest exceptions that will not be caught by handlers
    of CallbackError so by default it will bubble up to the API layer
    and be retried. 'notify' callers can avoid this behavior by
    additionally catching RetryRequest.

    Closes-Bug: #1590316
    Change-Id: I6732c60f89de4318b5f56327c5bc966bd250baae

[Doug Hellmann (doug-hellmann)]

This issue was fixed in the openstack/neutron 9.0.0.0b2 development milestone.