Simple chatrooms using PHP websockets and mongodb

Websocket server(server/Websocket.php and server/Client.php) is forked from https://github.com/heminei/php-websocket and modified according to the requirements.

Features

• Authentication using jwt cookie instead of php sessions.
• Supports multiple rooms.
• Display online users for each room on the client.
• Scroll positions between rooms will be preserved when switching between rooms(client side).
• Application works with sharding collection in mongodb.
• Deploy sharded clusters using docker containers.

Requirements

• Mongodb
• Composer (to download required php libraries)
• Mongodb extension for php
• Docker (optional for sharding)

Installation

1. Clone the repo.

   git clone https://github.com/AndeYashwanth/PHP-Websocket-Chatrooms
   cd PHP-Websocket-Chatrooms/
   

2. Install dependencies from composer.json

   composer install
   

Sharding(Optional)

Initialize shards

Folder Sharding/ is a submodule for this repo. Go through it's readme to create and configure docker instances of shards.(Its very simple)

Shard database

In order to shard a collection, first you need to shard a database.

1. Connect to query router(mongos)

   mongo --port 60000
   

2. Select chat database

   use chat
   

3. enable sharding for chat db

   sh.enableSharding("chat")
   

Create Indexes

db.messages.createIndex({"room_id":1, "from.user_id":1})

db.messages.createIndex({"room_id":1, "_id":1})

Shard messages collection

sh.shardCollection("chat.messages", {"room_id":1, "from.user_id":1})

Running

1. start server.php in server/server.php

   php server/server.php
   

2. open login.php in client/login.php and login/register. User will be created if he/she doesn't exist.
3. You will be redirected to client/client.php after successful login/sign-up.

Known Issues

• Pressing shift+enter to increase text-box size on the client will lag.
• Upon testing a single client can send upto 80 messages/sec. Not sure if it is true for single client at a time or multiple clients.
• In mongodb you a lookup cannot be done to another collection which is sharded from a collection which is unsharded/sharded. So seperate queries need to be made instead of using $lookup.
  Affected Collections:-
  • messages :
    • Problem: 'from' field stores json with 'user_name' and 'user_id' fields. So if a user changes his 'user_name' it should be updated in every message he sent till date.
    • Solution: Shard key for messages collection is used as (room_id, from.user_id).
  • rooms :
    • Problem: 'online_users' stores json similar to messages.from
    • Solution: When user updates username, update the online_users array for every room he has access to.
• Due to limitation of unsigned 64bit integer, message_ids are only 63 bits. Somewhat similar to twitter snowflake.
  • 42 bit timestamp in milli seconds
  • 12 bit server id
  • 9 bit increment (i.e., for each ms server can generate upto 2⁹ message ids)
• $server_id in server/MessageIdGenerator.php should be manually set between 0 and 2¹²-1 when used in distributed environment.
• Some features like displaying online users on client might break when not used with single app server.

Upcoming features.

• Add password authentication to mongo instances in docker containers.
• Edit message.(to be implemented on client side)
• Upload files(upload maybe handled and stored by another service, and just the url is stored in DB).
• Delivery report.
• No.of users seen report.
• Making application work with sharding in mongodb.
• Support application to deploy on multiple instances of web servers.
• Rate limit number of messages/sec for each room.
• Deploy sharded clusters using docker containers.

Database Schema

Database: chat

• users collection

  {
      "_id": String,
      "user_name": String,
      "rooms_access":["$rooms._id"] //to which chat room _ids user has access to.
  }
  

• rooms collection

  {
      "_id": int, //room_id
      "room_name": String,
      "banned_users":["$users._id"], //_id of users banned
      "rate_limit": int, // messages/sec similar to discord.
      "online_users":[{'user_id': "$users._id", 'user_name': "$users.user_name"}] //Users who are currently online.
  }
  

• messages collection

  {
      '_id': int, //63 bit integer
      'from':{'user_id': '$users._id', 'user_name': '$users.user_name'},
      'message': String, 
      'last_edited': int,
      'attachments':[String], //list of urls of files
      'stats':[ //user is added only after message is delivered to some user.
          {
              'user_id': "$users_id",
              'user_name': "$users.user_name",
              'delivered_on': int, //time of delivery
              'read_on': int //time of read.
          },
      ]
  }