amqp-client

# amqp-client

An AMQP 0-9-1 client for Crystal.

## Installation

1. Add the dependency to your `shard.yml`:
```yaml
dependencies:
  amqp-client:
    github: cloudamqp/amqp-client.cr
```
2. Run `shards install`

## Usage

```crystal
require "amqp-client"

AMQP::Client.start("amqp://guest:guest@localhost") do |c|
  c.channel do |ch|
    # Always set a prefetch limit before consuming
    ch.prefetch(100)

    # Declare a temporary queue
    q = ch.queue("")

    # Declare a durable queue
    q = ch.queue("my-queue")

    # Subscribe to it, and manually acknowledge messages when processed
    q.subscribe(no_ack: false) do |msg|
      puts "Received: #{msg.body_io.to_s}"
      ch.basic_ack(msg.delivery_tag)
    end

    # publish directly to a queue without confirm (fire and forget)
    q.publish "msg"

    # publish directly to a queue and blocking while waiting for confirm
    q.publish_confirm "msg"

    # publish to any exchange/routing-key (fire and forget)
    ch.basic_publish "msg", exchange: "amq.topic", routing_key: "a"

    # publish to any exchange/routing-key and block while waiting for confirm
    ch.basic_publish_confirm "msg", exchange: "amq.topic", routing_key: "a"

    # When the Channel is in confirm mode a block can be given to the basic_publish
    # method and it will be executed when the message is confirmed by the server
    ch.confirm_select
    ch.basic_publish("msg", "amq.topic", "my.topic") do |ok|
      if ok
        puts "Message is confirmed by the server"
      else
        puts "Message was NOT confirmed by the server"
      end
    end

    # This statement will block until a message has arrived
    # The only way to "escape" the block is to unsubscribe
    q.subscribe(tag: "myconsumer", block: true) do |msg|
      q.unsubscribe("myconsumer")
    end

    # Consume and ack, nack or reject msgs
    ch.basic_consume("queue", tag: "consumer-tag", no_ack: false, exclusive: false, block: false) do |msg|
      case msg.body_io.to_s
      when "ack"
        ch.basic_ack(msg.delivery_tag)
      when "reject"
        ch.basic_reject(msg.delivery_tag, requeue: true)
      when "nack"
        ch.basic_nack(msg.delivery_tag, requeue: true, multiple: true)
      end
    end

    ch.prefetch(count: 1000) # alias for basic_qos

    name, message_count, consumer_count =
      ch.queue_declare(name: "myqueue", passive: false, durable: true,
                       exclusive: false, auto_delete: false)
    q = ch.queue # temporary queue that is deleted when the channel is closed
    ch.queue_purge("myqueue")
    ch.queue_bind("myqueue", "amq.topic", "routing-key")
    ch.queue_unbind("myqueue", "amq.topic", "routing-key")
    msg = ch.basic_get("myqueue", no_ack: true)
    ch.basic_ack(msg.delivery_tag)
    ch.queue_delete("myqueue")
    ch.exchange_declare("my-exchange", type: "topic")
    ch.exchange_delete("my-exchange")
  end
end
```

You can consume [stream queues](https://www.rabbitmq.com/streams.html) too: 

```crystal
require "amqp-client"

AMQP::Client.start do |c|
  c.channel do |ch|
    # prefetch required when consuming from stream queues
    ch.prefetch(10)
    # declare a stream queue using the x-queue-type argument
    q = ch.queue("stream1", args: AMQP::Client::Arguments.new({"x-queue-type": "stream"}))
    puts "Waiting for messages. To exit press CTRL+C"
    # Decide from where to subscribe using the x-stream-offset argument
    q.subscribe(block: true, no_ack: false, args: AMQP::Client::Arguments.new({"x-stream-offset": "first"})) do |msg|
      puts "Received: #{msg.body_io}"
      msg.ack
    end
  end
end
```

## Performance

1-byte messages, without properties/headers:

| Publish rate | Consume rate |
| ------------ | ------------ |
| 1.200.000 msgs/s | 1.000.000 msgs/s |

## Contributing

1. [Fork it](https://github.com/cloudamqp/amqp-client.cr/fork)
2. Create your feature branch (`git checkout -b my-new-feature`)
3. Commit your changes (`git commit -am 'Add some feature'`)
4. Push to the branch (`git push origin my-new-feature`)
5. Create a new Pull Request

## Contributors

- [Carl Hörberg](https://github.com/carlhoerberg) - creator and maintainer
- [Anders Bälter](https://github.com/baelter)