ChatSystem

Chat system

Problem Statement

It’s required to build a chat system. The system should allow creating new applications where each application will have a token(generated by the system) and a name(provided by the client). The token is the identifier that devices use to send chats to that application. Each application can have many chats. a chat should have a number. Numbering of chats in each application starts from 1 and no 2 chats in the same application may have the same number. The number of the chat should be returned in the chat creation request. A chat contains messages and messages have numbers that start from 1 for each chat. The number of the message should also be returned in the message creation request. The client should never see the ID of any of the entities. The client identifies the application by its token and the chat by its number along with the application token. Add an endpoint for searching through messages of a specific chat. It should be able to partially match messages’ bodies. You must use ElasticSearch for this. The applications table should contain a column called chats_count that contains the number of chats for this application. Similarly, the chats table should contain a column called messages_count that contains the number of messages in this chat. These columns don’t have to be live. However, they shouldn’t be lagging more than 1 hour. Assume that the system is to receive many requests. It might be running on multiple servers in parallel and thus multiple requests may be processed concurrently. Make sure to handle race conditions. Try to minimize the queries and avoid writing directly to MySQL while serving the requests(especially for the chats and messages creation endpoints). You can use a queuing system to achieve that. It is allowed for chats and messages to take time to be persisted. You should optimize your tables by adding appropriate indices.

Stack

High level diagram

System Curl

1. Create Application

curl --location --request POST 'localhost:8080/api/v1/apps' \
--header 'Content-Type: application/json' \
--data-raw '{
    "name":"instaBug"
}'

1. Update application

curl --location --request PUT 'localhost:8080/api/v1/apps/evtrozx' \
--header 'Content-Type: application/json' \
--data-raw '{
    "name":"instabug"
}'

1. Get Application by token

curl --location --request GET 'localhost:8080/api/v1/apps/evtrozx'
}'

1. create Chat

curl --location --request POST 'localhost:8080/api/v1/apps/evtrozx/chats'

1. Get Chat by chat number

curl --location --request GET 'localhost:8080/api/v1/apps/evtrozx/chats/1'

1. Create Message

curl --location --request POST 'localhost:8080/api/v1/apps/evtrozx/chats/1/messages' \
--header 'Content-Type: application/json' \
--data-raw '{
    "content":"wassup!!!!"
}'

1. Get Message by its number

curl --location --request GET 'localhost:8080/api/v1/apps/evtrozx/chats/1/messages/3'

1. Message autocomplete

curl --location --request GET 'localhost:8080/api/v1/apps/evtrozx/chats/1/messages/autocomplete?limit=3&page=1&keyword=hello'```

Cronjobs

running every 30 mins to update the chat and messages count

Run The system

$ go mod tidy
$ go mod vendor
$ docker-compose up [runinng mysql,elasticsearch,redis and rabbit mq containers]
$ go run services/api/main.go [api]
$ go run services/consumer/main.go [worker]