Hemera-rabbitmq

This is a plugin to use RabbitMQ with Hemera.

RabbitMQ is a messaging broker - an intermediary for messaging. It gives your applications a common platform to send and receive messages, and your messages a safe place to live until received. It is complementary to the primary NATS transport system.

The client use JSON to transfer data.

Start RabbitMQ instance

Start a rabbitmq instance via docker-compose

docker-compose up

Administration

Visit http://127.0.0.1:15672 and log in with

Username: user
Password: user

Example

const Hemera = require('nats-hemera')
const nats = require('nats').connect()
const hemera = new Hemera(nats, {
  logLevel: 'info'
})
hemera.use(require('hemera-joi'))
// Topology & configuration via JSON look at https://github.com/arobson/rabbot
hemera.use(require('hemera-rabbitmq', { rabbot: options }))

Plugin dependencies

• hemera-joi

Interface

• RabbitMQ API

  • Publish
  • Request
  • Create pub/sub subscriber
  • Create request/reply subscriber
  • Consume events

---

publish

The pattern is:

• topic: is the service name to publish to rabbitmq
• cmd: is the command to execute publish
• exchange: the name of the exachange string
• options: rabbot transport options object
• data: the data to transfer object

Example:

hemera.act(
  {
    topic: 'rabbitmq',
    cmd: 'publish',
    exchange: 'pubsub',
    options: {
      type: 'MyMessage'
    },
    data: {
      name: 'peter',
      amount: 50
    }
  },
  function() {}
)

---

request

The pattern is:

• topic: is the service name to publish to rabbitmq
• cmd: is the command to execute publish
• exchange: the name of the exachange string
• options: rabbot transport options object
• data: the data to transfer object

Example:

hemera.act(
  {
    topic: 'rabbitmq',
    cmd: 'request',
    exchange: 'request',
    options: {
      type: 'MyRequest'
    },
    data: {
      name: 'peter',
      amount: 50
    }
  },
  function() {}
)

---

Create pub/sub subscriber

Create a new rabbitmq subscriber which handles the interest on this subject and forward all messages with pub/sub semantic to the hemera service. You can define a pattern which represent the destination hemera service.

The interface is:

• pattern: the pattern which arrive hemera
• type: the type string

Example:

hemera.rabbitmq.addPubSubProxy(
  {
    type: 'MyMessage'
    pattern: {}
  }
)

---

Create request/reply subscriber

Create a new rabbitmq subscriber which handles the interest on this subject and forward all messages with request/reply semantic to the hemera service. You can define a pattern which represent the destination hemera service.

The interface is:

• pattern: the pattern which arrive hemera
• type: the type string

Example:

hemera.rabbitmq.addRequestProxy(
  {
    type: 'MyMessage'
    pattern: {}
  }
)

---

Consume events

The pattern is:

• topic: is a combination of the service name and the type rabbitmq.<type>

Example:

hemera.add(
  {
    topic: 'rabbitmq.MyMessage'
  },
  function(req, reply) {
    // In case of pub / sub you can't reply
    // In case of request / reply you can reply only with valid json
    // In case of error or crash the message is redelivered
  }
)