gNats Server

Features

• The following commands are supported
  • CONNECT
  • PING
  • SUB
  • PUB
  • UNSUB

Run the application

• First clone the project
  • https://github.com/melsonic/gNats-Server.git && cd gNats-Server
• Run the project
  • make
• If you have Docker installed, you can also run it as a Docker container.
  • docker compose up
• After the Application is up and running, it's time to test the application
  • Run telnet localhost 4222 to connect a client to the server

Output

• Scenerio: Two clients subscribed to the same subject
  
  
  

• Here is the output of nats bench tool publishing 1 Million messages of size 16 byte each.
  
  
  

Learnings & Notes

• conn.Read() returns io.EOF when client signals graceful end of input i.e no more reading. Not closing the connection on io.EOF will result into infinite loop(infinite zero byte reading from the pipe)
• INFO{} should send payload, else by default it sends 0 & results in maximum payload exceeded error.
• zero allocation byte parser parsing method
  • It can be used to optimize storage. Normally, storage is required to store the parsed tokens. But in this method the parser changes state and based on current state and next byte, it takes relevant actions.
• nats bench sends CONNECT {"verbose":false,...}, so the application needs to parse this verbose arg in order to determine weather to send +OK response or not. If the application sends +OK with nats bench, it will result into the following error Expected PONG, got +OK.
• While dockerizing the application, I faced an error $GOPATH/go.mod exist but should not, which was due to the fact that in golang image, the default workdir($HOME/go) is same as $GO_PATH($HOME/go). So, it is required to change the WORKDIR in the first place while building the image.
  • read-more.

TODO

• Write Tests
• Support string subjectId (currently supports only integer subject id)
• Optimize Unsub Handler (change []chan string to map[chan] in subSubscribers map[int][]chan string for easier removal)