Does aknowledging the message kills handler thread? about amqp

[hreinhardt]

Hi,

I'm not sure I'm understanding your question. Do you mean something like this:

consumeMsgs chan "myQueue" Ack $ \(msg, env) -> do
    ackEnv env
    -- Could the handler-thread be killed right here, before the call to handleMsg?
    handleMsg msg

[p3rsik]

Yep, precisely

[hreinhardt]

In theory this could happen. For example, when you call closeConnection, all channel-threads will be killed, even if they might be in the middle of the consumeMsgs-callback. Similar behaviour exists for closeChannel.

In practice I think this scenario is unlikely and will probably only happen if you have a very high number of incoming messages; but if you absolutely need to avoid it, you may want to only call ackEnv after you've fully processed the message.

Alternatively, you could use the consumeMsgs-callback to put the message in some kind of queue, and then use a separate thread to read messages from the queue and handle them. Roughly like this:

import qualified Control.Concurrent.Chan as C

msgQueue <- C.newChan

consumeMsgs chan "myQueue" Ack $ \(msg, env) -> do
    C.writeChan msgQueue (msg, env)
    ackEnv env
    
-- in a different thread:
go = do
    (msg, env) <- C.readChan msgQueue
    -- TOOD: handle msg
    go

[p3rsik]

Thank you very much!