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## Appendix I. Migrating from Cowboy 2.8 to 2.9

Cowboy 2.9 implements graceful shutdown of connection processes for both HTTP/1.1 and HTTP/2 connections.

Cowboy 2.9 is the first release to support the much awaited Erlang/OTP 24 out of the box. While users that were using Ranch 2.0 already were ready for OTP 24, the Ranch version used by Cowboy out of the box was not compatible and had to be updated.

Cowboy 2.9 also contains a small number of tweaks and bug fixes.

Cowboy 2.9 requires Erlang/OTP 22.0 or greater.

## I.1. Features added

- Cowboy will now gracefully shutdown HTTP/1.1 and HTTP/2 connections when the supervisor asks the connection process to exit, or when `sys:terminate/2,3` is used. Two new configuration options were added for HTTP/2 to determine the timeouts for the graceful shutdown steps.
- REST handler `AcceptCallback` can now return `{created, URI}` or `{see_other, URI}` to determine what response status code should be sent (typically to differentiate between a new resource and an update). The return value `{true, URI}` is now deprecated.
- Update Ranch to 1.8.0.
- Update Cowlib to 2.11.0.

## I.2. Bugs fixed

- Fix concurrent body streaming getting stuck with HTTP/2. The alarm could get into blocking state indefinitely when two or more request processes were streaming bodies.
- Fix HTTP/2 rate limiting using the wrong default values in some cases.
- Don’t produce an error report when the request process exited normally (`normal` or `shutdown` exit reasons).
- Fix `cowboy_tracer_h` to support trace messages without timestamps.

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