Make sure your connection to RabbitMQ stays active -- ninefinity

If, like me, you use Go and github.com/streadway/amqp to access RabbitMQ, you might wonder how to make sure your program reconnects to RabbitMQ after the connection was lost. Here’s how:

There’s a method called NotifyClose that belongs to amqp.Connection:

func NotifyClose(c chan *amqp.Error) (chan *amqp.Error)

This method registers a listener for close events caused by errors while the connection should be active. The listener can be used to re-establish the connection and to re-run the setup process.

Here’s one way to use the listener:

package main

import (
  "flag"
  "github.com/streadway/amqp"
  "log"
  "time"
)

var amqpUri = flag.String("r", "amqp://guest:[email protected]/", "RabbitMQ URI")

var (
  rabbitConn       *amqp.Connection
  rabbitCloseError chan *amqp.Error
)

// Try to connect to the RabbitMQ server as
// long as it takes to establish a connection
//
func connectToRabbitMQ(uri string) *amqp.Connection {
  for {
    conn, err := amqp.Dial(uri)

    if err == nil {
      return conn
    }   

    log.Println(err)
    log.Printf("Trying to reconnect to RabbitMQ at %s\n", uri)
    time.Sleep(500 * time.Millisecond)
  }
}

// re-establish the connection to RabbitMQ in case
// the connection has died
//
func rabbitConnector(uri string) {
  var rabbitErr *amqp.Error

  for {
    rabbitErr = <-rabbitCloseError
    if rabbitErr != nil {
      log.Printf("Connecting to %s\n", *amqpUri)

      rabbitConn = connectToRabbitMQ(uri)
      rabbitCloseError = make(chan *amqp.Error)
      rabbitConn.NotifyClose(rabbitCloseError)

      // run your setup process here
    }   
  }
}

func main() {
  flag.Parse()

  // create the rabbitmq error channel
  rabbitCloseError = make(chan *amqp.Error)

  // run the callback in a separate thread
  go rabbitConnector(*amqpUri)

  // establish the rabbitmq connection by sending
  // an error and thus calling the error callback
  rabbitCloseError <- amqp.ErrClosed

}

Photo Credits

Rabbit! / Kaninchen! by Robobobobo (cropped, colors mapped to monochrome range, vignetted, licensed under CC BY-SA 2.0).