aedes-cached-persistence

aedes-cached-persistence

Abstract class to write an Aedes persistence with in-process caching of subscriptions. It implements the API defined by aedes-persistence.

• aedes-cached-persistence
  • Install
  • Provided methods
  • Implement another persistence
    • Inheritance
    • Tests
  • License

Install

To install aedes-cached-persistence, simply use npm:

npm install aedes-cached-persistence --save

Provided methods

• CachedPersistence()
• instance.subscriptionsByTopic()
• instance.cleanSubscriptions()
• instance.destroy()

Implement another persistence

Inheritance

In order to reuse aedes-cached-persistence, you need to:

const CachedPersistence = require('aedes-cached-persistence')

// if you need http://npm.im/aedes-packet, it is available
// from this module as well
// const { Packet } = CachedPersistence

class MyPersistence extends CachedPersistence {
    constructor(opts) {
       super(opts)
    }
    addSubscriptions(client, subs, cb) {
        // ..persistence specific implementation..
        // call super._addedSubscriptions when you are done
        super._addedSubscriptions(client, subs.map(mapSub), cb)
    }
    removeSubscriptions(client, subs, cb) {
        // ..persistence specific implementation..
        // call super._removedSubscriptions when you are done
        super._removedSubscriptions(client, subs.map(mapSub), cb)
    }
}

function mapSub (sub) {
  return { topic: sub.topic }
}

Tests

A persistence needs to pass all tests defined in ./abstract.js. You can import and use that test suite in the following manner:

const test = require('node:test')
const myperst = require('./')
const abs = require('aedes-cached-persistence/abstract')

abs({
  test: test,
  persistence: myperst
})

If you require some async stuff before returning, a callback is also supported:

const test = require('node:test')
const myperst = require('./')
const abs = require('aedes-persistence/abstract')
const clean = require('./clean') // invented module

abs({
  test: test,
  buildEmitter: require('mymqemitter'), // optional
  persistence: function build (cb) {
    clean(function (err) {
      cb(err, myperst())
    })
  }
})

License

MIT