A documented Cowboy Stream Handler reference implementation

weaver · November 3, 2023, 8:42pm

Hi everyone!

I had to write a cowboy stream handler for work this week, and in the process, I put together this little reference module with comments to use as a jumping off point for when I have to write these in the future. Someone pointed out that I should share it online, so here it is! Figured others might find a use for it.

gist.github.com

https://gist.github.com/weaversam8/c77fe1df5749d6eaa459d9e1b6f61d9d

README.md

Cowboy, the popular Erlang web server, has deprecated [middleware][0] and replaced
the concept with [stream handlers][1], a more flexible, but more complicated API.
This page contains a documented reference implementation of a stream handler, to
help others when developing their stream handlers in the future.

[0]: https://ninenines.eu/docs/en/cowboy/2.8/guide/middlewares/
[1]: https://ninenines.eu/docs/en/cowboy/2.8/manual/cowboy_stream/

reference_stream_h.erl

-module(reference_stream_h).
-behavior(cowboy_stream).

-export([init/3]).
-export([data/4]).
-export([info/3]).
-export([terminate/3]).
-export([early_error/5]).

-record(state, {next}).

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eproxus · November 4, 2023, 8:13am

Brilliant! I did something similar a while ago too, but not as diligently commented as yours:

mmzeeman · November 4, 2023, 12:29pm

This is excellent. Does someone know if something similar exists for ranch protocol handlers?

bnjm · November 5, 2023, 12:00am

Awesome, thanks to both of you guys. Been looking for something like this lately in the cowboy examples. Maybe this would be worth a PR?

Maria-12648430 · November 7, 2023, 1:15pm

There are two example implementations of ranch_protocol shipping with ranch. The tcp_echo one is very simplicistic, tcp_reverse is more advanced and implemented as a gen_statem.