Re-land https://codereview.chromium.org/2101993002/

third_party/buildbot_8_4p1/buildbot/db/pool.py

 # This file is part of Buildbot.  Buildbot is free software: you can
 # redistribute it and/or modify it under the terms of the GNU General Public
 # License as published by the Free Software Foundation, version 2.
 #
 # This program is distributed in the hope that it will be useful, but WITHOUT
 # ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
 # FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more
 # details.
 #
 # You should have received a copy of the GNU General Public License along with
@@ skipping 51 matching lines @@
     def __init__(self, engine):
         pool_size = 5
         if hasattr(engine, 'optimal_thread_pool_size'):
             pool_size = engine.optimal_thread_pool_size
         threadpool.ThreadPool.__init__(self,
                         minthreads=1,
                         maxthreads=pool_size,
                         name='DBThreadPool')
         self.engine = engine
         if engine.dialect.name == 'sqlite':
-            log.msg("applying SQLite workaround from Buildbot bug #1810")
-            self.__broken_sqlite = self.detect_bug1810()
+            vers = self.get_sqlite_version()
+            log.msg("Using SQLite Version %s" % (vers,))
+            if vers < (3,3,17):
+                log.msg("NOTE: this old version of SQLite does not support "
+                        "multiple simultaneous accesses to the database; "
+                        "add the 'pool_size=1' argument to your db url")
+            brkn = self.__broken_sqlite = self.detect_bug1810()
+            if brkn:
+                log.msg("Applying SQLite workaround from Buildbot bug #1810")
         self._start_evt = reactor.callWhenRunning(self._start)
 
     def _start(self):
         self._start_evt = None
         if not self.running:
             self.start()
             self._stop_evt = reactor.addSystemEventTrigger(
                     'during', 'shutdown', self._stop)
             self.running = True
 
@@ skipping 124 matching lines @@
 
         try:
             test()
         except sqlite.OperationalError:
             # this is the expected error indicating it's broken
             return True
 
         # but this version should not fail..
         test(select_from_sqlite_master=True)
         return False # not broken - no workaround required
+
+    def get_sqlite_version(self):
+        engine = sa.create_engine('sqlite://')
+        conn = engine.contextual_connect()
+
+        try:
+            r = conn.execute("SELECT sqlite_version()")
+            vers_row = r.fetchone()
+            r.close()
+        except:
+            return (0,)
+
+        if vers_row:
+            try:
+                return tuple(map(int, vers_row[0].split('.')))
+            except (TypeError, ValueError):
+                return (0,)
+        else:
+            return (0,)