Invalidate on failed connect handler

Fixed bug in connection pool where a connection could be present in the
pool without all of its "connect" event handlers called, if a previous
"connect" handler threw an exception; note that the dialects themselves
have connect handlers that emit SQL, such as those which set transaction
isolation, which can fail if the database is in a non-available state, but
still allows a connection.  The connection is now invalidated first if any
of the connect handlers fail.

Change-Id: I61d6f4827a98ab8455f1c3e1c55d046eeccec09a
Fixes: #4225

1 files changed, 29 insertions, 0 deletions

diff --git a/test/engine/test_pool.py b/test/engine/test_pool.py
index e3f34dfa7..b699afbc6 100644
--- a/test/engine/test_pool.py
+++ b/test/engine/test_pool.py
@@ -730,6 +730,35 @@ class PoolEventsTest(PoolTestBase):
         p2.connect()
         eq_(canary, ["listen_one", "listen_two", "listen_one", "listen_three"])
 
+    def test_connect_event_fails_invalidates(self):
+        fail = False
+
+        def listen_one(conn, rec):
+            if fail:
+                raise Exception("it failed")
+
+        def listen_two(conn, rec):
+            rec.info['important_flag'] = True
+
+        p1 = pool.QueuePool(
+            creator=MockDBAPI().connect, pool_size=1, max_overflow=0)
+        event.listen(p1, 'connect', listen_one)
+        event.listen(p1, 'connect', listen_two)
+
+        conn = p1.connect()
+        eq_(conn.info['important_flag'], True)
+        conn.invalidate()
+        conn.close()
+
+        fail = True
+        assert_raises(Exception, p1.connect)
+
+        fail = False
+
+        conn = p1.connect()
+        eq_(conn.info['important_flag'], True)
+        conn.close()
+
     def teardown(self):
         # TODO: need to get remove() functionality
         # going