oslo_messaging中的heartbeat_check

最近在作OpenStack控制節點高可用（三控）的測試，當關掉其中一個控制節點的時候，nova service-list 看到全部nova服務都是down的。 nova-compute的log中有大量這種錯誤信息：

2016-11-08 03:46:23.887 127895 INFO oslo.messaging._drivers.impl_rabbit [-] A recoverable connection/channel error occurred, trying to reconnect: [Errno 32] Broken pipe
2016-11-08 03:46:27.275 127895 INFO oslo.messaging._drivers.impl_rabbit [-] A recoverable connection/channel error occurred, trying to reconnect: [Errno 32] Broken pipe
2016-11-08 03:46:27.276 127895 INFO oslo.messaging._drivers.impl_rabbit [-] A recoverable connection/channel error occurred, trying to reconnect: [Errno 32] Broken pipe
2016-11-08 03:46:27.276 127895 INFO oslo.messaging._drivers.impl_rabbit [-] A recoverable connection/channel error occurred, trying to reconnect: [Errno 32] Broken pipe
2016-11-08 03:46:27.277 127895 INFO oslo.messaging._drivers.impl_rabbit [-] A recoverable connection/channel error occurred, trying to reconnect: [Errno 32] Broken pipe
2016-11-08 03:46:27.277 127895 INFO oslo.messaging._drivers.impl_rabbit [-] A recoverable connection/channel error occurred, trying to reconnect: [Errno 32] Broken pipe
2016-11-08 03:46:27.278 127895 INFO oslo.messaging._drivers.impl_rabbit [-] A recoverable connection/channel error occurred, trying to reconnect: [Errno 32] Broken pipe
2016-11-08 03:46:27.278 127895 INFO oslo.messaging._drivers.impl_rabbit [-] A recoverable connection/channel error occurred, trying to reconnect: [Errno 32] Broken pipe

上述拋出的異常在oslo_messaging/_drivers/impl_rabbit.py中定位出來了：

 def _heartbeat_thread_job(self):
        """Thread that maintains inactive connections
        """
        while not self._heartbeat_exit_event.is_set():
            with self._connection_lock.for_heartbeat():
                recoverable_errors = (
                    self.connection.recoverable_channel_errors +
                    self.connection.recoverable_connection_errors)
                try:
                    try:
                        self._heartbeat_check()
                        # NOTE(sileht): We need to drain event to receive
                        # heartbeat from the broker but don't hold the
                        # connection too much times. In amqpdriver a connection
                        # is used exclusivly for read or for write, so we have
                        # to do this for connection used for write drain_events
                        # already do that for other connection
                        try:
                            self.connection.drain_events(timeout=0.001)
                        except socket.timeout:
                            pass
                    except recoverable_errors as exc:
                        LOG.info(_LI("A recoverable connection/channel error "
                                     "occurred, trying to reconnect: %s"), exc)
                        self.ensure_connection()
                        
                except Exception:
                    LOG.warning(_LW("Unexpected error during heartbeart "
                                    "thread processing, retrying..."))
                    LOG.debug('Exception', exc_info=True)
            self._heartbeat_exit_event.wait(
                timeout=self._heartbeat_wait_timeout)
        self._heartbeat_exit_event.clear()

本來heartbeat check就是來檢測組件服務和rabbitmq server之間的鏈接是不是活着的，oslo_messaging中的heartbeat_check任務在服務啓動的時候就跑在後臺了，當關閉一個控制節點時，實際上也關閉了一個rabbitmq server節點。只不過這裏會一直處於循環之中，一直拋出recoverable_errors捕獲到的異常，只有當self._heartbeat_exit_event.is_set()纔會退出while循環。按理說應該加個超時的東西，這樣就就不會一直處於循環之中，過好幾分鐘後才恢復。

今天我在虛擬機中安裝了三控高可用，在nova.conf中加了以下參數：

[oslo_messaging_rabbit]

rabbit_max_retries = 2    # 重連最大次數

heartbeat_timeout_threshold = 0    # 禁止heartbeat check

測試，nova_compute 並不會一直拋出recoverable_errors捕獲到的異常，nova service-list並不會出現全部服務down的狀況。

後續有待在物理機上測試。。。。。。