Amqp: d.Ack closes channel

Created on 22 Oct 2013 · 3Comments · Source: streadway/amqp

If I hit the consumer with enough messages at once (e.g. 10,000), using the code below the channel closes and will no longer take in new deliveries. However, if I remove d.Ack and just have the body of the delivery being printed, then there's no problem.

func main() {
    conn, _ := amqp.Dial(*uri)

    channel, _ := conn.Channel()

    deliveries, _ := channel.Consume(
        *queue, //queue
        "",
        false,
        false,
        false,
        false,
        nil)

    for d := range deliveries {
        go func(amqp.Delivery) {
            log.Printf("got %s", d.Body)
            d.Ack(false)
        }(d)
    }
}

Source

CodingAgainstChaos

Most helpful comment

Thanks so much for the help. @michaelklishin I was double-acking. I misunderstood Go anonymous functions. I got it working by breaking out a separate function and using that in the go routine. For anyone else that makes the same mistake, the error I got was Exception (406) Reason: "PRECONDITION_FAILED - unknown delivery tag 24782"

Here's the working code

func main() {
    conn, _ := amqp.Dial(*uri)

    channel, _ := conn.Channel()

    deliveries, _ := channel.Consume(
        *queue, //queue
        "",
        false,
        false,
        false,
        false,
        nil)

    for d := range deliveries {
        go doSomeWork(d)
    }
}
func doSomeWork(d amqp.Delivery){
     log.Printf("got %s", d.Body)
     d.Ack(false)
}

CodingAgainstChaos on 22 Oct 2013

👍3

All 3 comments

Your anonymous func is closing over d from the for statement. Try naming the param in scope of your func.

Also you can show asynchronous channel errors like:

go func() {
  log.Fatal(<-channel.NotifyClose(make(chan *amqp.Error)))
}()

streadway on 22 Oct 2013

@MattParker89 see RabbitMQ log, it will contain a channel exception. You are almost certainly double-acking deliveries.

michaelklishin on 22 Oct 2013

Here's the working code

func main() {
    conn, _ := amqp.Dial(*uri)

    channel, _ := conn.Channel()

    deliveries, _ := channel.Consume(
        *queue, //queue
        "",
        false,
        false,
        false,
        false,
        nil)

    for d := range deliveries {
        go doSomeWork(d)
    }
}
func doSomeWork(d amqp.Delivery){
     log.Printf("got %s", d.Body)
     d.Ack(false)
}

CodingAgainstChaos on 22 Oct 2013

👍3

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