feathers-amqp-client
v0.0.10
Published
A simple AMQP client for feathers.js applications
Downloads
3
Readme
Feathers AMQP Client
Introduction
This library allows a feathers.js app to receive messages from an AMQP 0.8 broker (e.g. RabbitMQ). A service function can be associated with a queue, so that messages pushed on the queue will be passed to this feathers service.
Its main use case is a 'job-queue' model, where one or many event producers publish events, and multiple consumers consume these events, but each event must go to only one consumer.
This is different to feathers sync, which sends all events to all clients, so that they can synchronise their internal state.
How to use
receiver.service.js
const { bindStream } = require('feathers-amqp-client');
const createService = require('feathers-memory');
module.exports = function (app) {
app.use('/posts', createService({}));
const service = app.service('posts');
bindStream(service.create.bind(service), {
server: {name: 'amqp://user:pass@host:port'},
exchange: { name: 'my-exchange'},
queue: { name: 'my-task-queue' }
});
}
The above example creates a simple in-memory resource, 'posts', and connects it to the task queue, 'my-task-queue'. The task queue will be configured to draw messages from the 'my-exchange' exchange. Neither the queue, nor the exchange, need exist beforehand.
service.create.bind(service)
is necessary, as feathers services require access to
the this
context.
Message Format and Manipulation
feathers-amqp-client expects messages in the following form:
{ data: {...}}
In other words, an object with a data
property. This data property will be passed
directly into bound service function. To manipulate the data before passing it to the
service, you can do something like this:
bindStream(data => {
const dataForService = /* do something to the data */
return service.create(dataForService)
}), {
exchange: { name: 'my-exchange'},
queue: { name: 'my-task-queue' }
});
Handling failure
feathers-amqp-client automatically reconnects on unexpected errors or server-triggered disconnects. This means it can recover after the AMQP broker crashes. However,any messages sent between the broker restart and the re-established connection will be lost, unless the queue is set up to persist them.
The client will wait 5 seconds after a disconnect before reconnecting. To change this,
set reconnectDelay
in the config parameter to bindStream.
Development and Testing
To run the tests locally:
npm install
npm test
Note - for the integration tests you must have docker installed. The tests assume the docker
socket is available at /var/run/docker.sock
To override this (e.g. on Windows) set the DOCKER_SOCKET_PATH
environment variable.