A bus-like facade over AMQP for simple messaging patterns. Makes using RabbitMQ for idomatic messaging dead simple.
The interface and routing topology are opinionated, and based loosely on ideas from the MassTransit project and various best-practice articles.
The library provides a Bus class, which as has seven functions:
- start
- stop
- publish
- subscribe
- unsubscribe
- call
- bind
Bus is also an EventEmitter, and raises 'started' and 'stopped' events, as well as log info events: 'debug', 'info', and 'error'.
Bus
A bus object manages the connections, channels, reconnection/disconnection logic. The creating and deleting of exchanges and queues is also handled automatically.
const Bus = require('amqp-bus');
// Create a bus instance.
// By default connection will be to guest:guest@localhost.
// See docs for options (host, vhost, credentials, etc.)
const bus = new Bus();
// start the bus. This creates the connection, among other things.
bus.start();
// When bus is started, you can use it.
bus.on('started', ()=> {
//do stuff with the bus...
});As a subscriber:
Subscribe to a named message type that could be published, such as 'user.created', supplying a handler function to process the received messages.
const subscriptionOptions = {
messageType: 'user.created'
};
bus.subscribe(subscriptionOptions, (message) => {
// message is the JSON object that was published.
// do something with message...
});As a message type publisher:
Broadcast a message to any/all subscribers.
const userCreatedEvent = {
id: 42
name 'john'
};
const publishOptions = {
messageType: 'user.created'
};
bus.publish(publishOptions, userCreatedEvent);As a topic publisher:
Publish using a known exchange and routing key, to route message to specific consumer(s).
const publishOptions = {
exchangeName: 'user.notifications',
routingKey: 'notifications.user.42'
};
const message = {
notification : 'something cool happend'
};
bus.publish(publishOptions, message);As a topic subscriber:
Subscribe to messages from a known exchange with a specific routing key, or key pattern.
const subscriptionOptions = {
exchangeName: 'user.notifications',
routingKey: 'notifications.user.42'
};
const handler = (message) => {
// do something with received messages.
};
let subscription;
bus.subscribe(subscriptionOptions, handler)
.then((result) => {
subscription = result
});
//later, you can unsubscribe to stop receiving messages and clean up.
bus.unsubscribe(subscription);Note: the unsubscribe can also be used with the messageType subscriptions, but may not be as useful.
As an RPC callee:
Bind a handler function to a message type. The return value of the handler will be sent back to caller as the reply.
const handleRequest = (message) => {
return {
id: 42,
name: 'john'
};
// You may also return a promise, and the resolved value will be sent as the reply.
};
bus.bind('user.query.by-id', handler);As an RPC caller:
Call with a message type and receive the reply in a promise.
const message = {
id: 42
};
bus.call('user.query.by-id', message)
.then((reply) => {
// do something with the reply...
});
Stopping the bus:
// later, to clean up and disconnect:
bus.stop();coming soon
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