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aedes-persistence

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The spec for an Aedes persistence, with abstract tests and a fast in-memory implementation.

Install

To install aedes-persistence, simply use npm:

npm install aedes-persistence --save

API

persistence([opts])

Creates a new instance of a persistence, that is already ready to operate. The default implementation is in-memory only.

instance.storeRetained(packet, callback(err))

Store a retained message, calls the callback when it was saved.

instance.createRetainedStream(pattern)

Return a stream that will load all retained messages matching the given pattern (according to the MQTT spec) asynchronously. Deprecated.

instance.createRetainedStreamCombi(patterns)

Return a stream that will load all retained messages matching given patterns (according to the MQTT spec) asynchronously.

instance.addSubscriptions(client, subscriptions, callback(err, client))

Add the given offline subscriptions for the given Client. The client must have connected with clean: false, as this is not checked here. This is called when a client issue a SUBSCRIBE packet.

subscriptions is in the same format of the subscribe property in the SUBSCRIBE packet:

[{
  topic: 'hello/world',
  qos: 1,
}, {
  topic: 'hello/#',
  qos: 2,
}]

instance.removeSubscriptions(client, subscriptions, callback(err, client))

The inverse of addSubscriptions but subscriptions is an array of topic names.

instance.subscriptionsByClient(client, callback(err, subscriptions, client))

Returns all the offline subscriptions for the given client. Called when a client with clean: false connects to restore its subscriptions.

subscriptions is in the same format of the subscribe property in the SUBSCRIBE packet:

[{
  topic: 'hello/world',
  qos: 1,
}, {
  topic: 'hello/#',
  qos: 2,
}]

instance.countOffline(cb(err, numOfSubscriptions, numOfClients))

Returns the number of offline subscriptions and the number of offline clients.

instance.subscriptionsByTopic(pattern, callback(err, subscriptions))

Returns all the offline subscriptions matching the given pattern. Called when a PUBLISH with qos: 1 or qos: 2 is received.

The subscriptions are in the format:

{
  clientId: client.id,
  topic: sub.topic,
  qos: sub.qos
}

instance.cleanSubscriptions(client, callback(err, client))

Removes all offline subscriptions for a given client.

instance.outgoingEnqueue(subscription, packet, callback(err))

Enqueue a potentially offline delivery. subscription is one of the objects returned by subscriptionsByTopic. Deprecated.

instance.outgoingEnqueueCombi(subscriptions, packet, callback(err))

Enqueue a potentially offline delivery. subscriptions is the whole subscriptions objects returned by subscriptionsByTopic.

instance.outgoingUpdate(client, packet, callback(err))

Called before a (potentially) offline packet is delivered, the caller should update the packet.messageId before updating.

instance.outgoingClearMessageId(client, packet, callback(err, packet))

Removes a packet with the given messageId (passing a PUBACK is ok) from the persistence. Passes back original packet to the callback.

instance.outgoingStream(client)

Return a stream that will load all offline messages for the given client asynchronously.

instance.incomingStorePacket(client, packet, cb(err, packet))

Store an incoming packet for the given client. Used for QoS 2.

instance.incomingGetPacket(client, packet, cb(err, packet))

Retrieve an incoming packet with the same messageId for the given client. Used for QoS 2.

instance.incomingDelPacket(client, packet, cb(err, packet))

Deletes incoming packet with the same messageId for the given client. Used for QoS 2.

instance.putWill(client, packet, cb(err))

Stores the will of a client. Used to support multi-broker environments and to not lose wills in case of a crash.

instance.getWill(client, packet, cb(err))

Retrieves the will of a client. Used to support multi-broker environments and to not lose wills in case of a crash.

instance.delWill(client, packet, cb(err))

Removes the will of a client. Used to support multi-broker environments and to not lose wills in case of a crash.

instance.streamWill(brokers)

Streams all the wills for the given brokers. The brokers are in the format:

{
  mybroker: {
    brokerId: 'mybroker'
  }
}

instance.getClientList(topic)

Returns a stream which has all the clientIds subscribed to the specified topic

instance.destroy(cb(err))

Destroy current persistence. Use callback cb(err) to catch errors if any

Implement another persistence

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('tape').test
const myperst = require('./')
const abs = require('aedes-persistence/abstract')

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

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

const test = require('tape').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())
    })
  }
})

Collaborators

License

MIT