Falcon is a multi-process, multi-fiber Rack HTTP server built on top of async, async-io and async-http. Each request is run within a light weight fiber and can block on up-stream requests without stalling the entire server process. Supports HTTP/1 and HTTP/2 natively.

Installation

Add this line to your application’s Gemfile:

gem 'falcon'

And then execute:

$ bundle

Or install it yourself as:

$ gem install falcon

Usage

You can run falcon serve directly, and it will load the config.ru and start serving on port 9292.

WebSockets

Falcon supports rack.hijack for HTTP/1.x connections. You can thus use async-websocket in any controller layer to serve WebSocket connections.

ActionCable

The rack.hijack functionality is compatible with ActionCable. If you use the async adapter, you should run falcon in threaded mode, or in forked mode with --concurrency 1. Otherwise, your messaging system will be distributed over several processes with no IPC mechanism.

Integration with Guard

Falcon can restart very quickly and is ideal for use with guard. See guard-falcon for more details.

Integration with Capybara

It is a very fast and light-weight implementation for Capybara:

Using with Rackup

You can invoke Falcon via rackup:

rackup –server falcon

This will run a single-threaded instance of Falcon.

Performance

Falcon is uses an asynchronous event-driven reactor to provide non-blocking IO. It can handle an arbitrary number of in-flight requests with minimal overhead per request.

It uses one Fiber per request, which yields in the presence of blocking IO.

Memory Usage

Falcon uses a pre-fork model which loads the entire rack application before forking. This reduces per-process memory usage.

Throughput

Contributing

1. Fork it
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Add some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create new Pull Request

License

Released under the MIT license.

Copyright, 2017, by Samuel G. D. Williams.

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the “Software”), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.