6. 消息发送重试

当连接失败，Celery会自动重试发送消息，我们可以对重试行为进行设置，譬如说多久重试一次、最大重试次数或者干脆不重试！

当然这只是官方文档说的，我在Windows上进行测试，故意设置了局域网中没有使用的ip地址作为broker的地址，本来以为会像文档中讲的那样，在重试3次后返回并提示错误，结果死活不返回；查看配置文档，找了各种配置项进行修改，都是这样，后来在Linux下面运行就正常了！感觉Celery在Windows下运行真的好多坑啊！

from celery import Celery


app = Celery('tasks',
             backend='amqp://agent:agent@*.*.*.*:5672',
             broker='amqp://agent:agent@*.*.*.*:5672')

app.conf.update(broker_connection_timeout=4.0, broker_connection_max_retries=3)


@app.task
def add(x, y):
    return x + y

  
if __name__ == '__main__':
    add.apply_async((2, 3), retry=True, retry_policy={
        'max_retries': 3,
        'interval_start': 0,
        'interval_step': 0.2,
        'interval_max': 0.2,
    })

通过快捷键退出程序后，可以看到如下输出，明显是阻塞在和broker的tcp连接上了，而且超时时间肯定巨长或者是无限等待

    callback)
  File "E:\Python34\lib\site-packages\kombu\utils\functional.py", line 333, in
etry_over_time
    return fun(*args, **kwargs)
  File "E:\Python34\lib\site-packages\kombu\connection.py", line 261, in connec

    return self.connection
  File "E:\Python34\lib\site-packages\kombu\connection.py", line 802, in connec
ion
    self._connection = self._establish_connection()
  File "E:\Python34\lib\site-packages\kombu\connection.py", line 757, in _estab
ish_connection
    conn = self.transport.establish_connection()
  File "E:\Python34\lib\site-packages\kombu\transport\pyamqp.py", line 130, in
stablish_connection
    conn.connect()
  File "E:\Python34\lib\site-packages\amqp\connection.py", line 282, in connect
    self.transport.connect()
  File "E:\Python34\lib\site-packages\amqp\transport.py", line 109, in connect
    self._connect(self.host, self.port, self.connect_timeout)
  File "E:\Python34\lib\site-packages\amqp\transport.py", line 150, in _connect
    self.sock.connect(sa)
KeyboardInterrupt