mapcatcom/mongo-leader

Leader election backed by MongoDB

mongo-leader

Leader election backed by MongoDB, inspired by the redis-leader. Class Leader extends the Node.js EventEmmiter class.

Install

npm install mongo-leader

Example

const { Leader } = require("mongo-leader");
const { MongoClient } = require("mongodb");

const url = "mongodb://localhost:27017";

MongoClient.connect(url, { useNewUrlParser: true }, function (err, client) {
  const db = client.db("test");
  const leader = new Leader(db, { ttl: 5000, wait: 1000 });
  setInterval(() => {
    leader.isLeader().then((leader) => console.log(`Am I leader? : ${leader}`));
  }, 100);
});

API

new Leader(db, options)

Create a new Leader class

db is a MongoClient object

options.ttl Lock time to live in milliseconds.
Will be automatically released after that time.
Default and minimum values are 1000.

options.wait Time between tries getting elected in milliseconds.
Default and minimum values are 100.

options.key Unique identifier for the group of instances trying to be elected as leader.
Default value is 'default'

isLeader()

The function determines whether the instance is a leader.

Returns promise that resolved to true if the instance is a leader; otherwise, false.

Events

elected The event fired when the instance become a leader.

revoked The event fired when the instance revoked from it's leadership.

License

This project is licensed under the MIT License.