wait for the mysql server to be ready (at controller startup)

controller/controller.py

@@ -1541,6 +1541,26 @@ class DockerController:
 
         self.check_db()
 
+    @asyncio.coroutine
+    def db_startup(self):
+        log.info("wait until the db server is ready")
+
+        ses = self.session
+        while True:
+            with contextlib.suppress(sqlalchemy.exc.OperationalError):
+                log.debug("db ping")
+                with ses.begin():
+                    ses.execute("SELECT 1")
+                break
+
+            with contextlib.suppress(asyncio.TimeoutError):
+                yield from asyncio.wait_for(asyncio.shield(self._shutdown_requested), 10)
+                return
+        
+        log.info("db server ready")
+
+        self.check_db(startup=True)
+
     def check_db(self, *, startup=False):
         log.debug("check_db(startup=%r)", startup)
         try:
@@ -1592,7 +1612,7 @@ class DockerController:
             loop.add_signal_handler(signal.SIGINT,  self.shutdown)
             loop.add_reader(self.sock, self._sock_callback)
 
-            self.check_db(startup=True)
+            yield from self.db_startup()
             try:
                 yield from self._shutdown_requested
             finally: