Merge lp:~rlucio/nova/lp690314 into lp:~hudson-openstack/nova/trunk

[Ryan Lucio]

Adds the pool_recycle option to the sql engine startup call. This enables connection auto-timeout so that connection pooling will work properly. The recommended setting (per sqlalchemy FAQ page) has been hardcoded. What this means is that if a db connection sits idle for an hour, the engine will automatically close the connection and return it to the available thread pool. See Bug #690314 for info.

WRT hardcoding the timeout, there is no indication (based on what I read) that there is any reason to use a different value. It was suggested by another dev that we should hard code 1800 but I am not aware of any advantage in that value.

The fix was tested and verified on multi-node deployments of Austin and Bexar with MySQL, and it was also verified that the change does not affect sqlite users (dev environment testing only).

[Thierry Carrez (ttx)]

3600 sounds like a sane default given most databases idle connection timeout... but I don't think we should hardcode it. Adding a flag to change that default value would allow us to cover all corner cases ?

[Ryan Lucio (rlucio)]

If you think it is necessary that is fine. How about a new flag, sql_idle_timeout that defaults to 3600?

[Devin Carlen (devcamcar)]

sql_idle_timeout flag is a reasonable addition

[lp:~rlucio/nova/lp690314]

505. By Ryan Lucio on 2010-12-31

Converted the pool_recycle setting to be a flag with a default of 3600 seconds

506. By Ryan Lucio on 2011-01-03

removed extra whitespace chars at the end of the changed lines

Unmerged revisions

=== modified file 'nova/db/sqlalchemy/session.py'
--- nova/db/sqlalchemy/session.py	2010-10-21 23:15:26 +0000
+++ nova/db/sqlalchemy/session.py	2010-12-31 00:24:09 +0000
@@ -36,7 +36,9 @@
     global _MAKER
     if not _MAKER:
         if not _ENGINE:
-            _ENGINE = create_engine(FLAGS.sql_connection, echo=False)
+            _ENGINE = create_engine(FLAGS.sql_connection, 
+                                    pool_recycle=FLAGS.sql_idle_timeout, 
+                                    echo=False)
         _MAKER = (sessionmaker(bind=_ENGINE,
                                 autocommit=autocommit,
                                 expire_on_commit=expire_on_commit))

=== modified file 'nova/flags.py'
--- nova/flags.py	2010-12-27 19:45:57 +0000
+++ nova/flags.py	2010-12-31 00:24:09 +0000
@@ -263,6 +263,9 @@
 DEFINE_string('sql_connection',
               'sqlite:///$state_path/nova.sqlite',
               'connection string for sql database')
+DEFINE_string('sql_idle_timeout',
+              '3600',
+              'timeout for idle sql database connections')
 
 DEFINE_string('compute_manager', 'nova.compute.manager.ComputeManager',
               'Manager for compute')