stompest客户端启动时不自动重连ActiveMQ

本是古典何须时尚 2022-08-24 01:57 248阅读 0赞

最近几个月来，每当迁移ActiveMQ的时候，就遇到worker进程重启的时候无法连接上ActiveMQ. 今天调试了下，终于发现了原因。

## 调试环境 ##

*  ActiveMQ 5.8，部署两个实例
 *  stompest 2.1.6

## 现象 ##

failover uri差不多是这样的：

failover:(tcp://10.153.75.143:61613,tcp://10.15.227.106:61613)?randomize=false

其中，10.153.75.143这个ActiveMQ实例处于未运行状态，10.15.227.106这个ActiveMQ实例处于正常运行状态。

当stompest客户端使用上面的failover配置连接ActiveMQ服务器的时候，出现如下异常：

Connecting to 10.153.75.143:61613 ...
    Could not connect to 10.153.75.143:61613 [Could not establish connection [[Errno 61] Connection refused]]
    Reconnect failed [Reconnect timeout: 0 attempts]
    Traceback (most recent call last):
      File "main.py", line 14, in <module>
        client = BaseMQClient.factory(config)
      File "/Users/liuxiong/src/maslino/test/mq_client.py", line 67, in factory
        return cls(mq_config)
      File "/Users/liuxiong/src/maslino/test/mq_client.py", line 81, in __init__
        self.connect()
      File "/Users/liuxiong/src/maslino/test/mq_client.py", line 88, in connect
        self.client.connect(heartBeats=(0, 10 * 1000), connectTimeout=60, connectedTimeout=60)
      File "/Users/liuxiong/virtualenvs/test/lib/python2.7/site-packages/stompest/sync/client.py", line 85, in connect
        for (broker, connectDelay) in self._failover:
      File "/Users/liuxiong/virtualenvs/test/lib/python2.7/site-packages/stompest/protocol/failover.py", line 50, in __iter__
        yield broker, self._delay()
      File "/Users/liuxiong/virtualenvs/test/lib/python2.7/site-packages/stompest/protocol/failover.py", line 85, in _delay
        raise StompConnectTimeout('Reconnect timeout: %d attempts' % self._maxReconnectAttempts)
    stompest.error.StompConnectTimeout: Reconnect timeout: 0 attempts

从上面的异常可以看出，stompest客户端尝试连接了服务器10.153.75.143，发现连接被拒绝，然后就抛出了个连接超时异常。

我们不是使用了failover配置吗？stompest客户端在发现服务器10.153.75.143连接不上的时候，怎么不去尝试连接服务器10.15.227.106？

## 解决办法 ##

经过一番搜索，终于发现了原因所在。

ActiveMQ的文档[http://activemq.apache.org/failover-transport-reference.html][http_activemq.apache.org_failover-transport-reference.html]对连接参数startupMaxReconnectAttempts这样解释道：

A value of **-1
    ** denotes that the number of connection attempts at startup should be unlimited.
    A value of  **>=0 
    **denotes the number of reconnect attempts at startup that will be made after which an error is sent back to the client when the client makes a subsequent reconnect attempt.

大致意思是，当startupMaxReconnectAttempts为-1时，不限制初始连接重试次数；当startupMaxReconnectAttempts为0时，不重试；当startupMaxReconnectAttempts大于0时，就重试startupMaxReconnectAttempts次。并且，ActiveMQ文档描述的默认值是-1.

然后，我们看看当failover uri中没有指定startupMaxReconnectAttempts参数的时候，stompest给的默认值是多少。在stompest的代码中，有这么一段：

_SUPPORTED_OPTIONS = {
        'initialReconnectDelay': _configurationOption(int, 10)
        , 'maxReconnectDelay': _configurationOption(int, 30000)
        , 'useExponentialBackOff': _configurationOption(_bool, True)
        , 'backOffMultiplier': _configurationOption(float, 2.0)
        , 'maxReconnectAttempts': _configurationOption(int, -1)
        , 'startupMaxReconnectAttempts': _configurationOption(int, 0)
        , 'reconnectDelayJitter': _configurationOption(int, 0)
        , 'randomize': _configurationOption(_bool, True)
        , 'priorityBackup': _configurationOption(_bool, False)
        #, 'backup': _configurationOption(_bool, False), # initialize and hold a second transport connection - to enable fast failover
        #, 'timeout': _configurationOption(int, -1), # enables timeout on send operations (in miliseconds) without interruption of reconnection process
        #, 'trackMessages': _configurationOption(_bool, False), # keep a cache of in-flight messages that will flushed to a broker on reconnect
        #, 'maxCacheSize': _configurationOption(int, 131072), # size in bytes for the cache, if trackMessages is enabled
        #, 'updateURIsSupported': _configurationOption(_bool, True), # determines whether the client should accept updates to its list of known URIs from the connected broker
    }

发现stompest给参数startupMaxReconnectAttempts设置的默认值是0，也就是说，当stompest刚开始连接ActiveMQ服务器时并不重试。

知道了原因，把failover uri修改成这样再试试：

failover:(tcp://10.153.75.143:61613,tcp://10.15.227.106:61613)?randomize=false,startupMaxReconnectAttempts=-1

连接日志如下：

Connecting to 10.153.75.143:61613 ...
    Could not connect to 10.153.75.143:61613 [Could not establish connection [[Errno 61] Connection refused]]
    Delaying connect attempt for 10 ms
    Connecting to 10.15.227.106:61613 ...
    Connection established
    Sending CONNECT frame [headers={u'passcode': 'transcode', u'login': 'vtc', u'heart-beat': '0,10000', u'host': '', u'accept-version': '1.0,1.1'}, version=1.0]
    Received CONNECTED frame [headers={u'session': u'ID:liuxiong-test-dev001-bjdxt9.qiyi.virtual-49666-1479094899264-2:3', u'heart-beat': u'10000,0', u'version': u'1.1', u'server': u'ActiveMQ/5.10.0'}, version=1.0]
    Connected to stomp broker [session=ID:liuxiong-test-dev001-bjdxt9.qiyi.virtual-49666-1479094899264-2:3, version=1.1]

可见，加上参数startupMaxReconnectAttempts=-1之后，stompest客户端在发现第一个ActiveMQ实例连接不上后会尝试连接第二个ActiveMQ实例。

[http_activemq.apache.org_failover-transport-reference.html]: https://link.jianshu.com?t=http://activemq.apache.org/failover-transport-reference.html