Attach SQLAlchemy listeners to objects, not classes

Otherwse listeners get duplicated when running tests.

Fixes #2267.

master/buildbot/db/enginestrategy.py

@@ -27,7 +27,7 @@
 import sqlalchemy as sa
 from twisted.python import log
 from sqlalchemy.engine import strategies, url
-from sqlalchemy.pool import NullPool, Pool
+from sqlalchemy.pool import NullPool
 from buildbot.util import sautils
 
 # from http://www.mail-archive.com/sqlalchemy@googlegroups.com/msg15079.html
@@ -91,7 +91,7 @@ class CheckpointFullfsyncDisabler(object):
                 disabler.connect = connect_listener
                 engine.pool.add_listener(disabler)
             else:
-                sa.event.listen(Pool, 'connect', connect_listener)
+                sa.event.listen(engine.pool, 'connect', connect_listener)
 
             log.msg("setting database journal mode to 'wal'")
             try:
@@ -127,6 +127,10 @@ def special_case_mysql(self, u, kwargs):
         else:
             u.query['charset'] = 'utf8'
 
+        return u, kwargs, None
+
+    def set_up_mysql_engine(self, u, engine):
+        """Special setup for mysql engines"""
         # add the reconnecting PoolListener that will detect a
         # disconnected connection and automatically start a new
         # one.  This provides a measure of additional safety over
@@ -149,11 +153,9 @@ class ReconnectingListener(object):
                 pass
             rcl = ReconnectingListener()
             rcl.checkout = checkout_listener
-            kwargs['listeners'] = [ rcl ]
+            engine.pool.add_listener(rcl)
         else:
-            sa.event.listen(Pool, 'checkout', checkout_listener)
-
-        return u, kwargs, None
+            sa.event.listen(engine.pool, 'checkout', checkout_listener)
 
     def create(self, name_or_url, **kwargs):
         if 'basedir' not in kwargs:
@@ -188,6 +190,8 @@ def create(self, name_or_url, **kwargs):
 
         if u.drivername.startswith('sqlite'):
             self.set_up_sqlite_engine(u, engine)
+        elif u.drivername.startswith('mysql'):
+            self.set_up_mysql_engine(u, engine)
 
         return engine
 

master/buildbot/test/unit/test_db_enginestrategy.py

@@ -17,7 +17,6 @@
 from twisted.python import runtime
 from sqlalchemy.engine import url
 from sqlalchemy.pool import NullPool
-import sqlalchemy as sa
 from buildbot.db import enginestrategy
 
 class BuildbotEngineStrategy_special_cases(unittest.TestCase):
@@ -27,8 +26,6 @@ class BuildbotEngineStrategy_special_cases(unittest.TestCase):
     mysql_kwargs = dict(basedir='my-base-dir',
             connect_args=dict(init_command='SET storage_engine=MyISAM'),
             pool_recycle=3600)
-    if hasattr(sa, '__version__') and sa.__version__.startswith('0.6'):
-        mysql_kwargs['listeners'] = [ 'ReconnectingListener' ]
     sqlite_kwargs = dict(basedir='/my-base-dir', poolclass=NullPool)
 
     def setUp(self):