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[Thierry Carrez <thierry.carrez+lp@xxxxxxxxx>]

** Also affects: oslo.db/juno
   Importance: High
     Assignee: Mike Bayer (zzzeek)
       Status: In Progress

** No longer affects: oslo.db/juno

** Also affects: oslo.db/juno
   Importance: Undecided
       Status: New

** Changed in: oslo.db/juno
    Milestone: None => 1.0.2

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https://bugs.launchpad.net/bugs/1374497

Title:
  change in oslo.db "ping" handling is causing issues in projects that
  are not using transactions

Status in OpenStack Identity (Keystone):
  Triaged
Status in Oslo Database library:
  Fix Committed
Status in oslo.db juno series:
  Triaged

Bug description:
  in https://review.openstack.org/#/c/106491/, the "ping" listener which
  emits "SELECT 1" at connection start was moved from being a connection
  pool "checkout" handler to a "transaction on begin" handler.
  Apparently Keystone and possibly others are using the Session in
  "autocommit" mode, despite that this is explicitly warned against in
  SQLAlchemy's docs (see
  http://docs.sqlalchemy.org/en/rel_0_9/orm/session.html#autocommit-
  mode), and for these projects they are seeing failed connections not
  transparently recovered (see
  https://bugs.launchpad.net/keystone/+bug/1361378).

  Alternatives include:

  1. move the ping listener back to being a "checkout" handler

  2. fix downstream projects to not use the session in autocommit mode

  In all likelihood, the fix here should involve both.   I have a longer
  term plan to fix EngineFacade once and for all so that the correct use
  patterns are explicit, but that still has to be blueprinted.

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