Cherry-pick buildbot 95deef27d7c531ead19e0ac86a9aa1546d4ee7f9:

third_party/buildbot_8_4p1/buildbot/test/unit/test_db_pool.py

Index: third_party/buildbot_8_4p1/buildbot/test/unit/test_db_pool.py
diff --git a/third_party/buildbot_8_4p1/buildbot/test/unit/test_db_pool.py b/third_party/buildbot_8_4p1/buildbot/test/unit/test_db_pool.py
index 09d0e21d7a35180933b924c4a11cb73eb31d02cc..35d480223928e6bddd678aaf55df0087d37f0082 100644
--- a/third_party/buildbot_8_4p1/buildbot/test/unit/test_db_pool.py
+++ b/third_party/buildbot_8_4p1/buildbot/test/unit/test_db_pool.py
@@ -13,9 +13,11 @@
 #
 # Copyright Buildbot Team Members
 
+import os
+import time
 import sqlalchemy as sa
 from twisted.trial import unittest
-from twisted.internet import defer
+from twisted.internet import defer, reactor
 from buildbot.db import pool
 from buildbot.test.util import db
 
@@ -103,6 +105,49 @@ class Basic(unittest.TestCase):
         d.addCallback( lambda r : self.pool.do_with_engine(insert_into_table))
         return d
 
+
+class Stress(unittest.TestCase):
+
+    def setUp(self):
+        setup_engine = sa.create_engine('sqlite:///test.sqlite')
+        setup_engine.execute("pragma journal_mode = wal")
+        setup_engine.execute("CREATE TABLE test (a integer, b integer)")
+
+        self.engine = sa.create_engine('sqlite:///test.sqlite')
+        self.engine.optimal_thread_pool_size = 2
+        self.pool = pool.DBThreadPool(self.engine)
+
+    def tearDown(self):
+        self.pool.shutdown()
+        os.unlink("test.sqlite")
+
+    @defer.deferredGenerator
+    def test_inserts(self):
+        def write(conn):
+            trans = conn.begin()
+            conn.execute("INSERT INTO test VALUES (1, 1)")
+            time.sleep(31)
+            trans.commit()
+        d1 = self.pool.do(write)
+
+        def write2(conn):
+            trans = conn.begin()
+            conn.execute("INSERT INTO test VALUES (1, 1)")
+            trans.commit()
+        d2 = defer.Deferred()
+        d2.addCallback(lambda _ :
+            self.pool.do(write2))
+        reactor.callLater(0.1, d2.callback, None)
+
+        wfd = defer.waitForDeferred(
+            defer.DeferredList([ d1, d2 ]))
+        yield wfd
+        wfd.getResult()
+
+    # don't run this test, since it takes 30s
+    del test_inserts
+
+
 class Native(unittest.TestCase, db.RealDatabaseMixin):
 
     # similar tests, but using the BUILDBOT_TEST_DB_URL