ZmanEmet - realtime communication between MySQL & Socket.io client

A node.js package for Real-Time update between your MySQL server and the user interface. The package listens to event on an MySQL database and updates the user in real time.

This package is based on the original ZongJi and the original mysql-events modules.

Written by Niv Apo

Install

npm install zmanemet

Quick Start

const mysql = require('mysql');
const ZmanEmet = require('zmanemet');
const { Server } = require("socket.io");

const program = async () => {
    
    // Create a connection to your DB
    const connection = mysql.createConnection({
        host: 'localhost',
        user: 'root',
        password: 'root',
    });
    
    // Create a socket.IO server
    const io = new Server(3000);
    
    // Create a ZmanEmet instance and pass your db & socket.io connections
    const instance = new ZmanEmet(connection,io);
    
    // Start your instance
    await instance.start();
    
    // Create a trigger for an event
    let trigger = {
        name: 'TEST',
        expression: 'MY_SCHEMA.users.name',
        statement: "UPDATE", // see MySQLEvents.STATEMENTS.ALL for full list of options
        onEvent: (event) => {
            // Process the event and return the data to send to the client
            let {before,after} = event.affectedRows[0];

            let user_id = after.id;
            let room_id = `user_${user_id}`; // The socket room to send the update
            let event_name = "user.update"; // The event name in the sockets on the client side

            // The data that will be sent to the socket
            let data = {
                user_id:user_id,
                new_name:after.name
            }
            
            // Optional - send an update to the client via socket.io server
            return [room_id,event_name,data];
        },
    };
    zman.addTrigger(trigger);
  
    // Add a listener for connection issues
    instance.on(MySQLEvents.EVENTS.CONNECTION_ERROR, console.error);
};

program()
  .then(() => console.log('Waiting for database events...'))
  .catch(console.error);

Usage

#constructor(dbConnection, socketsConnection)

• Instantiate and create a database connection using a preexisting connection

  const connection = mysql.createConnection({
    host: 'localhost',
    user: 'username',
    password: 'password',
  });
  
  const myInstance = new ZmanEmet(connection,io);

#start()

• start function ensures that MySQL is connected before resolving its promise

  myInstance.start()
    .then(() => console.log('I\'m running!'))
    .catch(err => console.error('Something bad happened', err));

#stop()

• stop function terminates MySQL connection and stops ZongJi before resolving its promise

  myInstance.stop()
    .then(() => console.log('I\'m stopped!'))
    .catch(err => console.error('Something bad happened', err));

#pause()

• pause function pauses MySQL connection until #resume() is called, this it useful when you're receiving more data than you can handle at the time

  myInstance.pause();

#resume()

• resume function resumes a paused MySQL connection, so it starts to generate binlog events again

  myInstance.resume();

#addTrigger({ name, expression, statement, onEvent })

• Adds a trigger for the given expression/statement and calls the onEvent function when the event happens

  instance.addTrigger({
    name: 'MY_TRIGGER',
    expression: 'MY_SCHEMA.MY_TABLE.MY_COLUMN',
    statement: MySQLEvents.STATEMENTS.INSERT,
    onEvent: async (event) => {
      // Here you will get the events for the given expression/statement.
      // This function executes after a trigger has fired from the DB and before the data was sent to the sockets.
      // You can process the data and send just what you want to the socket.io
          
      let socket_room = "";
      let event_name = "";
      let event_data = "";
      
      return [socket_room,event_name,event_data];
    },
  });

• The name argument must be unique for each expression/statement, it will be user later if you want to remove a trigger

  instance.addTrigger({
    name: 'MY_TRIGGER',
    expression: 'MY_SCHEMA.*',
    statement: MySQLEvents.STATEMENTS.ALL,
    ...
  });
  
  instance.removeTrigger({
    name: 'MY_TRIGGER',
    expression: 'MY_SCHEMA.*',
    statement: MySQLEvents.STATEMENTS.ALL,
  });

• The expression argument is very dynamic, you can replace any step by * to make it wait for any schema, table or column events

  instance.addTrigger({
    name: 'Name updates from table USERS at SCHEMA2',
    expression: 'SCHEMA2.USERS.name',
    ...
  });

  instance.addTrigger({
    name: 'All database events',
    expression: '*',
    ...
  });

  instance.addTrigger({
    name: 'All events from SCHEMA2',
    expression: 'SCHEMA2.*',
    ...
  });

  instance.addTrigger({
    name: 'All database events for table USERS',
    expression: '*.USERS',
    ...
  });

  instance.addTrigger({
    name: 'All database events for table USERS',
    expression: '*.USERS',
    ...
  });

• The statement argument indicates in which database operation an event should be triggered

  instance.addTrigger({
    ...
    statement: MySQLEvents.STATEMENTS.ALL,
    ...
  });

  Allowed statements
• The onEvent argument is a function where the trigger events should be threated

  instance.addTrigger({
    ...
    onEvent: (event) => {
      console.log(event); // { type, schema, table, affectedRows: [], affectedColumns: [], timestamp, }
    },
    ...
  });

#removeTrigger({ name, expression, statement })

• Removes a trigger from the current instance

  instance.removeTrigger({
    name: 'My previous created trigger',
    expression: '',
    statement: MySQLEvents.STATEMENTS.INSERT,
  });

Tigger event object

It has the following structure:

{
  type: 'INSERT | UPDATE | DELETE',
  schema: 'SCHEMA_NAME',
  table: 'TABLE_NAME',
  affectedRows: [{
    before: {
      column1: 'A',
      column2: 'B',
      column3: 'C',
      ...
    },
    after: {
      column1: 'D',
      column2: 'E',
      column3: 'F',
      ...
    },
  }],
  affectedColumns: [
    'column1',
    'column2',
    'column3',
  ],
  timestamp: 1530645380029,
  nextPosition: 1343,
  binlogName: 'bin.001',
}

Make sure the database user has the privilege to read the binlog on database that you want to watch on.

LICENSE

MIT © Niv Apo