Cowboy 2.5

2018 03 Oct

Cowboy 2.5.0 has been released!

Cowboy 2.5 focused on making the test suites pass. It is now possible to get all the Cowboy tests to pass successfully, at least on Linux and on the more recent Erlang/OTP versions.

HTTP/1.1 has been improved with a fix for the TCP reset problem and the ability to stream a response body without using chunked transfer-encoding.

Two functions have been added: cowboy_req:stream_events/3 encodes and streams one or more text/event-stream events, and cowboy_req:read_and_match_urlencoded_body/2,3 reads, parses and matches application/x-www-form-urlencoded request bodies. I'm not a fan of the long name, or the fact it does so many things at the same time, but its usefulness is undeniable.

The more interesting new features are experimental.

A new interface has been added to Websocket handlers that allows for greater extensibility. It changes the return values from a number of different tuples to a list of commands (similar to stream handlers or to gen_statem). A new command has been introduced that tells Cowboy to stop/resume reading from the socket.

A logger option has been added to define which logger module shall be used. It defaults to error_logger but can be configured to Erlang/OTP 21's new logger module, the widely used lager or any module compatible with the logger module interface. In addition a log stream handler command has been added, allowing stream handlers to silence certain log messages if necessary.

Many bugs have also been fixed.

A complete list of changes can be found in the migration guide: Migrating from Cowboy 2.4 to 2.5.

You can donate to this project via GitHub Sponsors. These funds are used to pay for additional servers for testing.

As usual, feedback is appreciated, and issues or questions should be sent via Github tickets. Thanks!