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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

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.
        },
    ]
}