A toy message queueing server in Go

Over a few hours in the last week, I wrote MQ Go as a toy message-queue-over-HTTP.

The server accepts and sends all messages as JSON objects in the body of HTTP requests.

Once an MQ Go server is started, clients can request to join as a receiver or sender. Clients provide a mode specification and a URL endpoint for messages from the server.

When a client POSTs a message to the server’s /send/ URL, that message is added to the backing queue. A scheduler pops messages off of this queue as they become available and as worker threads become available. Once a worker is available, that message is sent to all clients registered as receivers.

One pattern that really helps reason about my code is the struct type for message passing. Using a struct to wrap the values that need to be passed between goroutines helps to decouple logic between parts of the program for me.

To make this work, I had to learn a little bit more about concurrency in Go. I hadn’t ever written any concurrent software before. Go’s channels provide intuitive concurrency support for many use cases. Traditional primitives like mutexes fill in in circumstances where channels might be cumbersome–like maintaining thread-safety on shared global state.

I think I will add a couple of features to MQ Go – maybe the ability to create more than one queue, or the ability to require an acknowledgement of receipt. Otherwise I may also try to put together an implementation of STOMP or some subset of that protocol in Go.

Tags: golang