MongoDB Live Data Server

This project is essentially a MongoDB live data driver (based either on polling or on Oplog tailing) combined with a DDP server, extracted out of Meteor, with Fibers and underscore dependencies removed and code converted to Typescript.

Live data is one of the root concepts of Meteor. Data is served via WebSockets via the DDP protocol and updated automatically whenever something changes in the database. Also, calling server methods via WebSocket is supported.

Using Meteor locks you into the Meteor ecosystem, which has some problems (mostly for historical reasons). Using live data as a separate npm package might be preferable in many scenarios. Also, people who are trying to migrate from Meteor, might find this package useful as an intermediate step.

Installation

npm i mongodb-livedata-server

Usage

As a most common example, this is how you can use livedata with Express.js:

const { DDPServer, LiveCursor, LiveMongoConnection } = require('mongodb-livedata-server')
const express = require('express')
const app = express()
const port = 3000

app.get('/', (req, res) => {
  res.send('Hello World!')
})

const httpServer = app.listen(port, () => {
  console.log(`Example app listening on port ${port}`)
})

const liveMongoConnection = new LiveMongoConnection(process.env.MONGO_URL, {
    oplogUrl: process.env.MONGO_OPLOG_URL
});
const liveDataServer = new DDPServer({}, httpServer);

liveDataServer.methods({
    "test-method": async (msg) => {
        console.log("Test msg: ", msg);
        return "hello! Current timestamp is: " + Date.now()
    }
})

liveDataServer.publish({
    "test-subscription": async () => {
        return new LiveCursor(liveMongoConnection, "test-collection", { category: "apples" });
    }
})

liveDataServer.methods and liveDataServer.publish have exactly same interface as Meteor.methods and Meteor.publish respectively, notice however that when publishing subscriptions, you must use LiveCursor rather than a normal MongoDB cursor.

Important notes

• The project is in alpha. Use at your own risk.
• Neither method context nor subscription context have the unblock method anymore (because this package doesn't use Fibers)
• Meteor syntax for MongoDB queries is not supported. Please always use MongoDB Node.js driver syntax. For example, instead of

  const doc = myCollection.findOne(id);

  use

  const doc = await myCollection.findOne({ _id: id });

• Neither MongoDB.ObjectId nor it's Meteor.js alternative is supported at the moment. String ids only.

DDP Extension

• Starting from 0.1.0, this library extends DDP with init message, which is used to avoid initial spam of added messages.
• Starting from 0.1.1, init message will only be sent if version 1a of DDP protocol is specified. Additionally, when version 1a is specified, server will not send removes for all documents when stopping a subscription, and rely on the client for the cleanup instead.