db-mongo

Helper functions for mongodb and mongoose. Here some features:

• realtime queries (RealtimeQuery class)
• persistent variables as in key-value paradigm (DbVar class)

Prerequisites

Ensure you have a MongoDB database set up and the necessary MongoDB drivers installed in your project. This class is intended to be used in a TypeScript environment.

Installation

npm install @winkgroup/db-mongo

or

yarn add @winkgroup/db-mongo

RealtimeQuery

RealtimeQuery class is designed for managing real-time queries with MongoDB. This class uses MongoDB's Change Streams feature, which allows applications to access real-time data changes without the complexity and risk of tailing the oplog. Change streams are available for replica sets and sharded clusters.

Change Streams, and consequently the watch() function, require a replica set or sharded cluster configuration. This is because they rely on the oplog (operations log) for tracking changes, and a standalone MongoDB server (single-node instance) does not maintain an oplog by default.

It's worth noting that you can configure a single-node instance of MongoDB to run as a replica set, which enables the oplog and allows the use of change streams. This setup is sometimes used for development purposes. However, in a production environment, a replica set typically consists of multiple nodes for redundancy and failover capabilities.

Usage

Here an usage example:

import { MongoClient } from 'mongodb';
import { RealtimeQuery } from '@winkgroup/db-mongo';

async function main() {
    // Connection URL and database/collection names
    const url = 'your-mongodb-connection-string';
    const dbName = 'your-database-name';
    const collectionName = 'your-collection-name';

    // Create a new MongoClient
    const client = new MongoClient(url);

    try {
        // Connect the client to the server
        await client.connect();
        console.log("Connected successfully to server");

        // Get the database and collection
        const db = client.db(dbName);
        const collection = db.collection(collectionName);

        // Instantiate RealtimeQuery
        const realtimeQuery = new RealtimeQuery({
            db: db,
            collectionName: collectionName,
        });

        // Subscribe to real-time updates
        realtimeQuery.subscribe(
            {
                queryObj: {}, // Empty query object means 'all documents'
                limit: 50,
                skip: 0,
            },
            (list) => {
                console.info('Received new data:', list);
            }
        );

        // Start listening to changes
        realtimeQuery.start();
    }
}

main().catch(console.error);

Methods

• subscribe(queryParams: QueryParams, callback: QueryCallback): Subscribe to changes in the database. Triggers the callback when the query result changes. It returns a subscriberId.
• unsubscribe(subscriberId: string): Unsubscribe from changes. Stops receiving updates for the specified subscription.

where:

interface QueryParams {
    queryObj: object;
    limit: number;
    skip: number;
    sort?: object;
}

type QueryCallback<Doc> = (
    list: Doc[],
    changeDoc: ChangeStreamDocument,
    changeList: ChangeQueryDocumentList<Doc>
) => void;

and "Doc" represents a generic type parameter. It's a placeholder for the actual type of the documents that you'll be working with in your MongoDB collection.

Interactive Integration Test

Under playground folder some extra code is provided to make some interctive integration tests. This is a command line interface test realtime queries Here the steps to run this test:

1. copy playground/config.template.json to playground/config.json
2. edit playground/config.json setting the credetials of a real mega account
3. run npm run realtime or yarn realtime

DbVar Class

The DbVar class provides an abstraction over a MongoDB collection, allowing you to manage the variables stored in the collection easily. The main methods are:

• get(name: string): Retrieves the value of a variable by its name.
• set(name: string, value: any): Sets or updates the value of a variable.
• unset(name: string): Removes a variable from the collection.

When creating a new DbVar object, you can optionally specify the name of the collection you want to use. If not provided, the default "vars" collection name is used.

To use the DbVar class, you need an instance of MongoDB's Db class. Here's how you can utilize the DbVar methods:

import DbVar from './path-to-DbVar';
import { MongoClient } from 'mongodb';

// Connect to your MongoDB database
const client = new MongoClient('your-mongodb-connection-string');
await client.connect();
const db = client.db('your-database-name');

// Create an instance of DbVar
const customCollectionName = 'myCustomCollection'; // optional
const dbVar = new DbVar(db, customCollectionName);

// Set a variable
await dbVar.set('myVar', 'myValue');

// Get a variable
const value = await dbVar.get('myVar');
console.log(value);  // Output: 'myValue'

// Unset a variable
await dbVar.unset('myVar');

License

This project is licensed under the MIT License - see the LICENSE file for details.

Maintainers

• fairsayan