HearbeatFuture: Use correct timeout in error message

The timeout argument in `wait` tells how much we need to wait taking
into consideration that we already waited for some other futures.
The total wait time that this future had available to complete is
different: it includes time we spent waiting for other futures.
This created confusing hearbeat messages, that could even show negative
wait times.
I fixed it by putting both timeouts in the error message. The `timeout`
parameter of `OperationTimedOut` I changed to the original timeout
because I think it is more useful and relevant here.

Author: Lorak-mmk

cassandra/connection.py

@@ -1821,15 +1821,15 @@ def __init__(self, connection, owner):
                 self._exception = Exception("Failed to send heartbeat because connection 'in_flight' exceeds threshold")
                 self._event.set()
 
-    def wait(self, timeout):
+    def wait(self, timeout, original_timeout):
         self._event.wait(timeout)
         if self._event.is_set():
             if self._exception:
                 raise self._exception
         else:
-            raise OperationTimedOut("Connection heartbeat timeout after %s seconds" % (timeout,),
+            raise OperationTimedOut("Connection heartbeat timeout (total wait=%s seconds, this wait call=%s seconds)" % (original_timeout, timeout),
                                     self.connection.endpoint,
-                                    timeout=timeout,
+                                    timeout=original_timeout,
                                     in_flight=self.connection.in_flight)
 
     def _options_callback(self, response):
@@ -1894,7 +1894,7 @@ def run(self):
                     self._raise_if_stopped()
                     connection = f.connection
                     try:
-                        f.wait(timeout_left)
+                        f.wait(timeout_left, self._timeout)
                         # TODO: move this, along with connection locks in pool, down into Connection
                         with connection.lock:
                             connection.in_flight -= 1

tests/unit/test_connection.py

@@ -518,7 +518,7 @@ def send_msg(msg, req_id, msg_callback):
         connection.defunct.assert_has_calls([call(ANY)] * get_holders.call_count)
         exc = connection.defunct.call_args_list[0][0][0]
         assert isinstance(exc, OperationTimedOut)
-        assert exc.errors == 'Connection heartbeat timeout after 0.05 seconds'
+        assert exc.errors == 'Connection heartbeat timeout (total wait=0.05 seconds, this wait call=0.05 seconds)'
         assert exc.last_host == DefaultEndPoint('localhost')
         assert exc.timeout == 0.05
         assert isinstance(exc.in_flight, int)