Reviewed: https://review.openstack.org/610034
Committed:
https://git.openstack.org/cgit/openstack/nova/commit/?id=00d08a3288f61268f8a823991fadf0d83c36c04d
Submitter: Zuul
Branch: master
commit 00d08a3288f61268f8a823991fadf0d83c36c04d
Author: Sean Mooney <w...@seanmooney.info>
Date: Fri Oct 12 14:26:14 2018 +0100
Harden placement init under wsgi
- This change tries to address an edge case discovered
when running placement under mod_wsgi where
if the placement wsgi application is re-initialize the db_api
configure method attempts to reconfigure a started transaction
factory.
- This since oslo.db transaction factories do not support
reconfiguration at runtime this result in an exception being
raised preventing reloading of the Placement API without
restarting apache to force mod_wsgi to recreate the
python interpreter.
- This change introduces a run once decorator to allow annotating
functions that should only be executed once for the lifetime fo
an interpreter.
- This change applies the run_once decorator to the db_api configure
method, to suppress the attempt to reconfigure the current
TransactionFactory on application reload.
Co-Authored-By: Balazs Gibizer <balazs.gibi...@ericsson.com>
Closes-Bug: #1799246
Related-Bug: #1784155
Change-Id: I704196711d30c1124e713ac31111a8ea6fa2f1ba
** Changed in: nova
Status: In Progress => Fix Released
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https://bugs.launchpad.net/bugs/1799246
Title:
module level init of db transation contexts cause failure under
mod_wsgi on module reload
Status in OpenStack Compute (nova):
Fix Released
Bug description:
Description
===========
This is related to a downstream bug first reported
here:https://bugzilla.redhat.com/show_bug.cgi?id=1630069 where in it was
discovers that due to how
triplo currently deploys the placemetn api under mod_wsgi
when deployed under mod_wsgi if the wsgi application exits with an error it
is reloaded
back into the same python interperter instance. As a result of this behavior
module level
variable have a longer lifetime then the lifetime of the application. when
run under uwsgi
when the application is reloaded it is reloaded in a new python interperter
meaning
the lifetime of the module level variables is scoped to the life time of the
application.
As a result of the life time semantics of mod_wsgi the placment api and
nova-api
must assume that the wsgi applications init can be invoked multiple times on
failure.
The current use of the sqlalcamey enginefacade transaction_context is not
reentrant
resulting in a type error being raised on subsequet calls to configure when
the wsgi
application is reloaded.
Expected result
===============
it should be possible to reload the nova and placement api wsgi application
under mod_wsgi on failure
Actual result
=============
46087 [Wed Oct 10 15:10:49.433284 2018] [:error] [pid 14] [remote
172.25.0.10:208] mod_wsgi (pid=14): Target WSGI script
'/var/www/cgi-bin/nova/nova-placement-api' cannot be loaded as Python module.
46088 [Wed Oct 10 15:10:49.433305 2018] [:error] [pid 14] [remote
172.25.0.10:208] mod_wsgi (pid=14): Exception occurred processing WSGI script
'/var/www/cgi-bin/nova/nova-placement-api'.
46089 [Wed Oct 10 15:10:49.433320 2018] [:error] [pid 14] [remote
172.25.0.10:208] Traceback (most recent call last):
46090 [Wed Oct 10 15:10:49.433333 2018] [:error] [pid 14] [remote
172.25.0.10:208] File "/var/www/cgi-bin/nova/nova-placement-api", line 54, in
<module>
46091 [Wed Oct 10 15:10:49.433354 2018] [:error] [pid 14] [remote
172.25.0.10:208] application = init_application()
46092 [Wed Oct 10 15:10:49.433361 2018] [:error] [pid 14] [remote
172.25.0.10:208] File
"/usr/lib/python2.7/site-packages/nova/api/openstack/placement/wsgi.py", line
108, in init_application
46093 [Wed Oct 10 15:10:49.433386 2018] [:error] [pid 14] [remote
172.25.0.10:208] db_api.configure(conf.CONF)
46094 [Wed Oct 10 15:10:49.433392 2018] [:error] [pid 14] [remote
172.25.0.10:208] File
"/usr/lib/python2.7/site-packages/nova/api/openstack/placement/db_api.py", line
35, in configure
46095 [Wed Oct 10 15:10:49.433403 2018] [:error] [pid 14] [remote
172.25.0.10:208] **_get_db_conf(conf.placement_database))
46096 [Wed Oct 10 15:10:49.433408 2018] [:error] [pid 14] [remote
172.25.0.10:208] File
"/usr/lib/python2.7/site-packages/oslo_db/sqlalchemy/enginefacade.py", line
788, in configure
46097 [Wed Oct 10 15:10:49.433420 2018] [:error] [pid 14] [remote
172.25.0.10:208] self._factory.configure(**kw)
46098 [Wed Oct 10 15:10:49.433425 2018] [:error] [pid 14] [remote
172.25.0.10:208] File
"/usr/lib/python2.7/site-packages/debtcollector/renames.py", line 43, in
decorator
46099 [Wed Oct 10 15:10:49.433435 2018] [:error] [pid 14] [remote
172.25.0.10:208] return wrapped(*args, **kwargs)
46100 [Wed Oct 10 15:10:49.433440 2018] [:error] [pid 14] [remote
172.25.0.10:208] File
"/usr/lib/python2.7/site-packages/oslo_db/sqlalchemy/enginefacade.py", line
312, in configure
46101 [Wed Oct 10 15:10:49.433449 2018] [:error] [pid 14] [remote
172.25.0.10:208] self._configure(False, kw)
46102 [Wed Oct 10 15:10:49.433453 2018] [:error] [pid 14] [remote
172.25.0.10:208] File
"/usr/lib/python2.7/site-packages/oslo_db/sqlalchemy/enginefacade.py", line
317, in _configure
46103 [Wed Oct 10 15:10:49.433462 2018] [:error] [pid 14] [remote
172.25.0.10:208] raise TypeError("this TransactionFactory is already
started")
46104 [Wed Oct 10 15:10:49.433473 2018] [:error] [pid 14] [remote
172.25.0.10:208] TypeError: this TransactionFactory is already started
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