How to check is a connection ok?

[zhangzx7054]

I tried to use channel.is_open and connetcion.is_open to get the connection's and channel's status, but failed.
The return value is always True, even though I stopped rabbitmq server.
Here is my test code.

import pika 
import time

 credit = pika.PlainCredentials(username='cloud', password='cloud')
 connection = pika.BlockingConnection(pika.ConnectionParameters(host='10.32.1.12', credentials=credit))
 channel = connection.channel()

while True:
     connect_close = connection.is_closed
     connect_open = connection.is_open
     channel_close = channel.is_closed
     channel_open = channel.is_open
     print("connection is_closed ", connect_close)
     print("connection is_open ", connect_open)
     print("channel is_closed ", channel_close)
     print("channel is_open ", channel_open)
     print("")
     time.sleep(5)

Here is the print log. When rabbitmq server stops, the print log is still the same as below.

[lukebakken]

Hello @zhangzx7054 -

Since you are using a BlockingConnection, heartbeats will only be processed if you actually do something with the channel. You can see this behavior with the following code:

import logging
import pika 
import time

logging.basicConfig(level=logging.DEBUG)

creds = pika.PlainCredentials(username='guest', password='guest')
params = pika.ConnectionParameters(host='localhost', credentials=creds,
                                   heartbeat_interval=10, blocked_connection_timeout=10)
connection = pika.BlockingConnection(params)
channel = connection.channel()

while True:
     print(time.strftime('%c', time.localtime()))
     channel.basic_publish('', 'my-alphabet-queue', 'abc')
     connect_close = connection.is_closed
     connect_open = connection.is_open
     channel_close = channel.is_closed
     channel_open = channel.is_open
     print("connection is_closed ", connect_close)
     print("connection is_open ", connect_open)
     print("channel is_closed ", channel_close)
     print("channel is_open ", channel_open)
     print("")
     time.sleep(5)

If you use one of the asynchronous adapters for your client code, you will also see the heartbeat mechanism detect lost connections. Please refer to the example code.

[austinnichols101]

@lukebakken Is there a way to directly trigger a heartbeat send_and_check with a BlockingConnection?

My current workaround to "do something with the channel" is to check for the existence of an exchange, but I would prefer to simply force a heartbeat to show RMQ that my process is still alive.

self._channel.exchange_declare(exchange=self.EXCHANGE, passive=True)

More specifically, I would like to be able to manually send a heartbeat frame from a BlockingConnection.

self._connection._send_frame(self._new_heartbeat_frame())

[vitaly-krugl]

If you periodically call BlockingConnection.process_data_events or BlockingConnection.sleep() it will attempt to send a heartbeat when it's time, and should raise ConnectionClosed when it fails to send on a closed TCP/IP stream.

In practice, you have to be prepared any time for a dropped connection (RabbitMQ issue, network issue, etc.). Checking a connection just before sending something is not guarantee that connection won't be lost while your're sending, so you need to anticipate re-connection and retries. For example, see _RETRY_ON_AMQP_ERROR decorator and _ChannelManager wrapper of AMQP client