Lock wait of mysql blocks all eventlet thread

[Nachi Ueno]

I faced the problem with mysql transaction and eventlet.

Quantum using transaction support of sqlalchemy
Quantum also using eventlet for RPC

Let's say there are api request A and B.
Sql request of A will lock B's sql request.
so B's sql request will wait the A's transaction.

On the other hand, we are using evenetlet.
Since we are using mysql c client, the API request may block eventlet
thread.

so when B start wait sql lock, it blocks all eventlet thread including api request A until lock timeout.

This bp for nova looks like solve the quantum one also.
https://blueprints.launchpad.net/nova/+spec/non-blocking-db

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/17779

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/17779
Committed: http://github.com/openstack/quantum/commit/7b5f6fd6ae0722f49b563f2f3f293a34d8f632d9
Submitter: Jenkins
Branch: master

commit 7b5f6fd6ae0722f49b563f2f3f293a34d8f632d9
Author: Gary Kotton <email address hidden>
Date: Mon Dec 10 12:39:22 2012 +0000

    Add eventlet db_pool use for mysql

    This adds the use of eventlet's db_pool module so that we can make mysql
    calls without blocking the whole process.
    New config options are introduced:

    sql_dbpool_enable -- Enables the use of eventlet's db_pool
    sql_min_pool_size -- Set the minimum number of SQL connections
    sql_max_pool_size -- Set the maximum number of SQL connections
    sql_idle_timeout -- Timeout before idle sql connections are reaped

    The default for sql_dbpool_enable is False for now, so there is
    no forced behavior changes for those using mysql. sql_min_pool_size
    is defaulted to 1 to match behavior if not using db_pool.

    Fixes bug 1086173

    Change-Id: Ied0aae33211585743fe955028a75c4e192a15d2f