Merge pull request #100 from yahoo/race_condition_fix

Deal with the server being busy when it is starting up.

redislite/client.py

@@ -126,7 +126,7 @@ def _connection_count(self):
         for client in self.client_list():
             flags = client.get('flags', '')
             flags = flags.upper()
-            if 'U' in flags or 'N' in flags:
+            if 'U' in flags or 'N' in flags:  # pragma: no cover
                 active_connections += 1
         return active_connections
 
@@ -200,9 +200,33 @@ def _start_redis(self):
             raise RedisLiteException(
                 'Redis socket file %s is not present' % self.socket_file
             )
+
         self._save_setting_registry()
         self.running = True
 
+    def _wait_for_server_start(self):
+        """
+        Wait until the server is not busy when receiving a request
+
+        Raises
+        ------
+        RedisLiteServerStartError - Server start timed out
+        """
+        timeout = True
+        for i in range(0, self.start_timeout * 10):
+            try:
+                self.ping()
+                timeout = False
+                break
+            except redis.BusyLoadingError:
+                pass
+            time.sleep(.1)
+        if timeout:  # pragma: no cover
+            raise RedisLiteServerStartError(
+                'The redis-server process failed to start; unreachable after '
+                '{0} seconds'.format(self.start_timeout)
+            )
+
     def _is_redis_running(self):
         """
         Determine if there is a config setting for a currently running redis
@@ -367,7 +391,7 @@ def __init__(self, *args, **kwargs):
         super(RedisMixin, self).__init__(*args, **kwargs)  # pragma: no cover
 
         logger.debug("Pinging the server to ensure we're connected")
-        self.ping()
+        self._wait_for_server_start()
 
     def __del__(self):
         self._cleanup()  # pragma: no cover

tests/test_client.py

@@ -279,6 +279,23 @@ def test_connection_fallthrough(self):
         with self.assertRaises(ConnectionError):
             redislite.Redis(port=1).keys()
 
+    def test_shutdown_race_condition(self):
+        """
+        Test that there is no race condition when a shutdown is run after
+        a large data operation.
+        """
+        if os.path.exists('bug.redis'):
+            os.remove('bug.redis')
+        db = redislite.StrictRedis('bug.redis')
+        for key in range(10000):
+            db.hset("h1", os.urandom(32), " " * 65536)
+        db.save()
+        db._cleanup()
+        del db
+        db = redislite.StrictRedis('bug.redis')
+        if os.path.exists('bug.redis'):
+            os.remove('bug.redis')
+
 
 if __name__ == '__main__':
     logging.basicConfig(level=logging.DEBUG)