amqp.go

// This: https://www.rabbitmq.com/tutorials/tutorial-one-go.html
// But without all the copied code between send and receive :)

package main

import (
  "os"
  "log"
  "strings"
  "github.com/streadway/amqp"
)

type rabbfunc func(*amqp.Connection, *amqp.Channel, amqp.Queue)

func FailOnError(err error, msg string) {
  if err != nil {
    log.Fatalf("%s: %s", msg, err)
  }
}

func WithRabbit(operation rabbfunc) {
  conn, err := amqp.Dial("amqp://guest:guest@localhost:5672/")
  FailOnError(err, "Failed to connect to RabbitMQ")
  defer conn.Close()

  ch, err := conn.Channel()
  FailOnError(err, "Failed to open a channel")
  defer ch.Close()

  q, err := ch.QueueDeclare(
    "hello", // name
    false,   // durable
    false,   // delete when unused
    false,   // exclusive
    false,   // no-wait
    nil,     // arguments
  )
  FailOnError(err, "Failed to declare a queue")

  operation(conn, ch, q)
}

func buildSend(body string) (rabbfunc) {
  return func(conn *amqp.Connection, ch *amqp.Channel, q amqp.Queue) {
    err := ch.Publish(
      "",     // exchange
      q.Name, // routing key
      false,  // mandatory
      false,  // immediate
      amqp.Publishing {
        ContentType: "text/plain",
        Body:        []byte(body),
      })
    FailOnError(err, "Failed to publish a message")
  }
}

func buildReceive() (rabbfunc) {
  return func(conn *amqp.Connection, ch *amqp.Channel, q amqp.Queue) {
    msgs, err := ch.Consume(
      q.Name, // queue
      "",     // consumer
      true,   // auto-ack
      false,  // exclusive
      false,  // no-local
      false,  // no-wait
      nil,    // args
    )
    FailOnError(err, "Failed to register a consumer")

    forever := make(chan bool)

    go func() {
      for d := range msgs {
        log.Printf("Received a message: %s", d.Body)
      }
    }()

    log.Printf(" [*] Waiting for messages. To exit press CTRL+C")

    <-forever
  }
}

func usage() {
  panic("Usage: msg [ send <messaage> | receive ]")
}

func main() {
  if len(os.Args) < 2 {
    usage()
  }
  switch os.Args[1] {
  case "send":
    message := strings.Join(os.Args[2:], " ")
    WithRabbit(buildSend(message))
  case "receive":
    WithRabbit(buildReceive())
  default:
    usage()
  }
}