API server should not create a new database handle on each request

[Doug Hellmann]

In the DBHook we call get_engine() for each request. We should only do that *one time* and save the result, then reuse that reference on other requests. Otherwise we're doing extra work to scan the plugins and create new database handles.

https://github.com/openstack/ceilometer/blob/master/ceilometer/api/hooks.py#L41

[xingzhou (xingzhou)]

@Doug, will the fix only keep one database Connection object? I'm glad to see if there is only one Connection object that API server is using, this will also help to fix https://bugs.launchpad.net/ceilometer/+bug/1188649

[Doug Hellmann (doug-hellmann)]

No, these bugs are not related as far as I can tell. The problem reported in this bug is that we scan the plugins for every web request. We really only need to do that on startup. We can also, I think, use the same database connection object for all requests, but we will need to test that part more carefully. The other bug has to do with the way the mongo driver connects, and having it support mongo clusters.

[xingzhou (xingzhou)]

To @jd__ and @Doug, for comment #2, will we cache the connection object in impl_mongodb.py in the patch of this defect? if not, I would like to open one new defect and upload a patch

[Julien Danjou (jdanjou)]

xingzhou: I already have a workaround for that in https://review.openstack.org/#/c/33290/ FWIW

[xingzhou (xingzhou)]

thanks @jd__, that patch solves my problem

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/36849

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/36849
Committed: http://github.com/openstack/ceilometer/commit/1c3c6a65142500b44e0c286887b2332de1994e8b
Submitter: Jenkins
Branch: master

commit 1c3c6a65142500b44e0c286887b2332de1994e8b
Author: Julien Danjou <email address hidden>
Date: Tue Jul 16 17:51:30 2013 +0200

    api: build the storage connection once and for all

    Fixes: bug#1178845

    Change-Id: Ic0c639224ba87c3e11f3e1eeba4915e3c8ba0e88