Petit chat

Requirements

• send notifications to users

• chat with 2 or more users

• use an sso to connect

• messages can have

  • text OK
  • attachments OK
  • reactions OK

• scylladb as db

Notifications

Use external notification gateway -> talk to it using a queue system // topic by userId -> can have many workers

Push notifications SSE when app is opened -> requires internal notification system to handle distributed app -> Queue / reactive messaging

SSO

-> use keycloak

Messages / Signal (to support more use cases)

-> use cassandra udt / collections to store the infos ? -> handle the query get all files in chat -> use S3 to store attachments -> seaweedfs -> dedupe using hashing ?

Queries

db: scylladb

• find user by username -> ok but not paged
• find all my chats paged -> ok but not paged
• get messages from chat at offset -> ok
• find in chat by message content -> need text indexer
  • should implem meili search first for basic use -> OK
  • implem elastic or more powerful with sharding later

For each message -> handle reactions -> ok not paged for now -> handle views (wich users saw the message) / can handle the deliver state as well -> ok, not paged for now

Optimizations ?

store the count of reactions on the signal directly -> use atomic increment / decrement

Signal types

• msg
• joined / leaved
• calls

TODO

• add signal types

  • joined / leaved -> WIP, need test / support for jitsi for audio / video ?
  • calls

• add support for current status

• add support for share point api for status (microsoft integration)

• add support for a way to add plugings (slack like)

  • add support for webhook

• check websocket infrastructure for user handling (WIP)

• add support for E2E encryption

  • add support for asymetric encryption

• add image pipeline when sending a file into the chat, check if it is an image, if it's an image, then transform it and then upload it to file service and add extension to it

• add support for settings for images

  • auto load
  • low quality to save bandwidth

Architecture

client <-> network-provider.gateway
network-provider.gateway <->  api.controller
network-provider.gateway -> seaweed.volume
network-provider.gateway -> sso.controller

api -> sso.controller
api.service <-> queue
api.service -> seaweed.master
api.service -> seaweed.volume
api.service -> text-indexer
api.repository -> db-cluster.db

network-provider {
  gateway
}

seaweed {
  volume
  master
  master -> volume
}

api {
  controller
  service
  repository
  controller -> service
  service -> repository
}

sso {
  controller
  postgres
  controller -> postgres
}

db-cluster {
  db
  manager
  manager -> db
}

# d2-vscode can syntax highlight nested markdown correctly.
y: |`md
  
`|

api
client
api -> notification-service: grpc link

notification-service {
  notification-worker
}

websocket-plexer {

}

# we do this to avoid opening multiple connexions
# will help with sticky connections in the future
client -> websocket-plexer -> api
client -> websocket-plewer -> notification-service

Microservice to handle notifications

shape: sequence_diagram
title: Notification {
  shape: text
}

api
client2 {
  shape: person
}

client2 -> api: send message with client1 in it

client1 {
  shape: person
}
queue_sse_ws
queue_push
worker_push
api -> queue_sse_ws
api -> queue_push: With 10 delay

if fetched {
  queue_sse_ws -> client1
  client1 -> api: Tell message was fetched
  api -> queue_push: cancel push notification
}

if not fetched {
  queue_push -> worker_push: after the delay
  worker_push -> client1: on message
}

to cancel a message: https://gist.github.com/tabdulazim/0a5b27802c6ce779bf95d131923402b3