datastore-pubsub

provides an implementation of an api for pubsub to be used as a datastore with TieredDatastore

Lead Maintainer

Vasco Santos.

Table of Contents

• datastore-pubsub
  • Lead Maintainer
  • Table of Contents
    • Install
  • Usage
  • API
    • Setup
    • Get
    • Put
    • Unsubscribe
  • Contribute
  • License

Install

npm install datastore-pubsub

Usage

const DatastorePubsub = require('datastore-pubsub')

const dsPubsub = new DatastorePubsub(pubsub, datastore, peerId, validator)

API

Setup

new DatastorePubsub(pubsub, datastore, peerId, validator, subscriptionKeyFn)

Creates a DatastorePubsub instance.

Arguments:

• pubsub (Object): implementation of a pubsub (must have publish and subscribe functions), such as libp2p/pubsub.
• datastore (Object): datastore compliant with interface-datastore, such as datastore-fs.
• peerId (PeerId Instance): peer identifier object.
• validator (Object): containing validate function and select function.
• subscriptionKeyFn (function): function to manipulate the key topic received according to the needs, as well as to block the message received to be published.
• keyEncoders (Object) - optional object to aid in encoding and decoding keys, with the following properties
• keyEncoders.keyToTopic (function) - convert a key to a topic
• keyEncoders.topicToKey (function) - convert a topic to a key
• keyEncoders.keyToStoreKey (function) - convert a key to a datastore key

Note: validator object must be composed by two functions, validate (data, key, callback) and select (receivedRecord, currentRecord, callback). validate aims to verify if a new record received by pubsub is valid to be stored locally by the node. If it is valid and the node already has a local record stored, select is the function provided to be responsible for deciding which record is the best (newer) between the already stored and the received through pubsub. A validator example can be found at: TODO (js-ipns)

const dsPubsub = new DatastorePubsub(pubsub, datastore, peerId, validator)

Get

dsPubsub.get(key, callback)

Try to subscribe a topic with Pubsub and receive the current local value if available.

Arguments:

• key (Buffer): a key representing a unique identifier of the object to subscribe.
• callback (function): operation result.

callback must follow function (err, data) {} signature, where err is an error if the operation was not successful. If no err is received, a data is received containing the most recent known record stored (Buffer).

Put

dsPubsub.put(key, val, callback)

Publishes a value through pubsub.

Arguments:

• key (Buffer): a key representing a unique identifier of the object to publish.
• val (Buffer): value to be propagated.
• callback (function): operation result.

callback must follow function (err) {} signature, where err is an error if the operation was not successful.

Unsubscribe

dsPubsub.unsubscribe(key, callback)

Unsubscribe a previously subscribe value.

Arguments:

• key (Buffer): a key representing a unique identifier of the object to publish.

Contribute

Feel free to join in. All welcome. Open an issue!

This repository falls under the IPFS Code of Conduct.

License

Copyright (c) Protocol Labs, Inc. under the MIT License. See LICENSE file for details.