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297 lines
12 KiB
Markdown
297 lines
12 KiB
Markdown
<p align="center">
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<img src="https://puma.io/images/logos/puma-logo-large.png">
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</p>
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# Puma: A Ruby Web Server Built For Concurrency
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[](https://gitter.im/puma/puma?utm\_source=badge&utm\_medium=badge&utm\_campaign=pr-badge)
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[](https://github.com/puma/puma/actions)
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[](https://travis-ci.org/puma/puma)
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[](https://codeclimate.com/github/puma/puma)
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[](https://dependabot.com/compatibility-score.html?dependency-name=puma&package-manager=bundler&version-scheme=semver)
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Puma is a **simple, fast, multi-threaded, and highly concurrent HTTP 1.1 server for Ruby/Rack applications**.
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## Built For Speed & Concurrency
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Puma processes requests using a C-optimized Ragel extension (inherited from Mongrel) that provides fast, accurate HTTP 1.1 protocol parsing in a portable way. Puma then serves the request using a thread pool. Each request is served in a separate thread, so truly concurrent Ruby implementations (JRuby, Rubinius) will use all available CPU cores.
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Puma was designed to be the go-to server for [Rubinius](https://rubinius.com), but also works well with JRuby and MRI.
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On MRI, there is a Global VM Lock (GVL) that ensures only one thread can run Ruby code at a time. But if you're doing a lot of blocking IO (such as HTTP calls to external APIs like Twitter), Puma still improves MRI's throughput by allowing IO waiting to be done in parallel.
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## Quick Start
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```
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$ gem install puma
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$ puma
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```
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Without arguments, puma will look for a rackup (.ru) file in the current working directory called `config.ru`.
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## Frameworks
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### Rails
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Puma is the default server for Rails, included in the generated Gemfile.
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Start your server with the `rails` command:
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```
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$ rails server
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```
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Many configuration options and Puma features are not available when using `rails server`. It is recommended that you use Puma's executable instead:
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```
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$ bundle exec puma
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```
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### Sinatra
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You can run your Sinatra application with Puma from the command line like this:
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```
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$ ruby app.rb -s Puma
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```
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Or you can configure your Sinatra application to always use Puma:
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```ruby
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require 'sinatra'
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configure { set :server, :puma }
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```
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## Configuration
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Puma provides numerous options. Consult `puma -h` (or `puma --help`) for a full list of CLI options, or see [dsl.rb](https://github.com/puma/puma/blob/master/lib/puma/dsl.rb).
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You can also find several configuration examples as part of the
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[test](https://github.com/puma/puma/tree/master/test/config) suite.
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### Thread Pool
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Puma uses a thread pool. You can set the minimum and maximum number of threads that are available in the pool with the `-t` (or `--threads`) flag:
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```
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$ puma -t 8:32
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```
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Puma will automatically scale the number of threads, from the minimum until it caps out at the maximum, based on how much traffic is present. The current default is `0:16`. Feel free to experiment, but be careful not to set the number of maximum threads to a large number, as you may exhaust resources on the system (or cause contention for the Global VM Lock, when using MRI).
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Be aware that additionally Puma creates threads on its own for internal purposes (e.g. handling slow clients). So, even if you specify -t 1:1, expect around 7 threads created in your application.
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### Clustered mode
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Puma also offers "clustered mode". Clustered mode `fork`s workers from a master process. Each child process still has its own thread pool. You can tune the number of workers with the `-w` (or `--workers`) flag:
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```
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$ puma -t 8:32 -w 3
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```
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Note that threads are still used in clustered mode, and the `-t` thread flag setting is per worker, so `-w 2 -t 16:16` will spawn 32 threads in total, with 16 in each worker process.
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In clustered mode, Puma can "preload" your application. This loads all the application code *prior* to forking. Preloading reduces total memory usage of your application via an operating system feature called [copy-on-write](https://en.wikipedia.org/wiki/Copy-on-write) (Ruby 2.0+ only). Use the `--preload` flag from the command line:
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```
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$ puma -w 3 --preload
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```
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If you're using a configuration file, use the `preload_app!` method:
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```ruby
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# config/puma.rb
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workers 3
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preload_app!
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```
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Additionally, you can specify a block in your configuration file that will be run on boot of each worker:
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```ruby
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# config/puma.rb
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on_worker_boot do
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# configuration here
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end
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```
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This code can be used to setup the process before booting the application, allowing
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you to do some Puma-specific things that you don't want to embed in your application.
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For instance, you could fire a log notification that a worker booted or send something to statsd. This can be called multiple times.
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`before_fork` specifies a block to be run before workers are forked:
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```ruby
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# config/puma.rb
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before_fork do
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# configuration here
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end
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```
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Preloading can’t be used with phased restart, since phased restart kills and restarts workers one-by-one, and preload_app copies the code of master into the workers.
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### Error handling
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If puma encounters an error outside of the context of your application, it will respond with a 500 and a simple
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textual error message (see `lowlevel_error` in [this file](https://github.com/puma/puma/blob/master/lib/puma/server.rb)).
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You can specify custom behavior for this scenario. For example, you can report the error to your third-party
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error-tracking service (in this example, [rollbar](http://rollbar.com)):
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```ruby
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lowlevel_error_handler do |e|
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Rollbar.critical(e)
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[500, {}, ["An error has occurred, and engineers have been informed. Please reload the page. If you continue to have problems, contact support@example.com\n"]]
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end
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```
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### Binding TCP / Sockets
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Bind Puma to a socket with the `-b` (or `--bind`) flag:
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```
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$ puma -b tcp://127.0.0.1:9292
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```
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To use a UNIX Socket instead of TCP:
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```
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$ puma -b unix:///var/run/puma.sock
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```
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If you need to change the permissions of the UNIX socket, just add a umask parameter:
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```
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$ puma -b 'unix:///var/run/puma.sock?umask=0111'
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```
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Need a bit of security? Use SSL sockets:
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```
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$ puma -b 'ssl://127.0.0.1:9292?key=path_to_key&cert=path_to_cert'
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```
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#### Controlling SSL Cipher Suites
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To use or avoid specific SSL cipher suites, use `ssl_cipher_filter` or `ssl_cipher_list` options.
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##### Ruby:
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```
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$ puma -b 'ssl://127.0.0.1:9292?key=path_to_key&cert=path_to_cert&ssl_cipher_filter=!aNULL:AES+SHA'
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```
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##### JRuby:
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```
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$ puma -b 'ssl://127.0.0.1:9292?keystore=path_to_keystore&keystore-pass=keystore_password&ssl_cipher_list=TLS_RSA_WITH_AES_128_CBC_SHA,TLS_RSA_WITH_AES_256_CBC_SHA'
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```
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See https://www.openssl.org/docs/man1.0.2/apps/ciphers.html for cipher filter format and full list of cipher suites.
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Disable TLS v1 with the `no_tlsv1` option:
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```
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$ puma -b 'ssl://127.0.0.1:9292?key=path_to_key&cert=path_to_cert&no_tlsv1=true'
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```
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### Control/Status Server
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Puma has a built-in status and control app that can be used to query and control Puma.
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```
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$ puma --control-url tcp://127.0.0.1:9293 --control-token foo
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```
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Puma will start the control server on localhost port 9293. All requests to the control server will need to include control token (in this case, `token=foo`) as a query parameter. This allows for simple authentication. Check out [status.rb](https://github.com/puma/puma/blob/master/lib/puma/app/status.rb) to see what the status app has available.
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You can also interact with the control server via `pumactl`. This command will restart Puma:
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```
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$ pumactl --control-url 'tcp://127.0.0.1:9293' --control-token foo restart
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```
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To see a list of `pumactl` options, use `pumactl --help`.
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### Configuration File
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You can also provide a configuration file with the `-C` (or `--config`) flag:
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```
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$ puma -C /path/to/config
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```
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If no configuration file is specified, Puma will look for a configuration file at `config/puma.rb`. If an environment is specified, either via the `-e` and `--environment` flags, or through the `RACK_ENV` or the `RAILS_ENV` environment variables, Puma looks for configuration at `config/puma/<environment_name>.rb`.
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If you want to prevent Puma from looking for a configuration file in those locations, provide a dash as the argument to the `-C` (or `--config`) flag:
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```
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$ puma -C "-"
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```
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The other side-effects of setting the environment are whether to show stack traces (in `development` or `test`), and setting RACK_ENV may potentially affect middleware looking for this value to change their behavior. The default puma RACK_ENV value is `development`. You can see all config default values [here](https://github.com/puma/puma/blob/12d1706ddc71b89ed2ee26275e31c788e94ff541/lib/puma/configuration.rb#L170).
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Check out [dsl.rb](https://github.com/puma/puma/blob/master/lib/puma/dsl.rb) to see all available options.
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## Restart
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Puma includes the ability to restart itself. When available (MRI, Rubinius, JRuby), Puma performs a "hot restart". This is the same functionality available in *Unicorn* and *NGINX* which keep the server sockets open between restarts. This makes sure that no pending requests are dropped while the restart is taking place.
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For more, see the [restart documentation](https://github.com/puma/puma/blob/master/docs/restart.md).
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## Signals
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Puma responds to several signals. A detailed guide to using UNIX signals with Puma can be found in the [signals documentation](https://github.com/puma/puma/blob/master/docs/signals.md).
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## Platform Constraints
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Some platforms do not support all Puma features.
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* **JRuby**, **Windows**: server sockets are not seamless on restart, they must be closed and reopened. These platforms have no way to pass descriptors into a new process that is exposed to Ruby. Also, cluster mode is not supported due to a lack of fork(2).
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* **Windows**: Cluster mode is not supported due to a lack of fork(2).
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## Known Bugs
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For MRI versions 2.2.7, 2.2.8, 2.2.9, 2.2.10 2.3.4 and 2.4.1, you may see ```stream closed in another thread (IOError)```. It may be caused by a [Ruby bug](https://bugs.ruby-lang.org/issues/13632). It can be fixed with the gem https://rubygems.org/gems/stopgap_13632:
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```ruby
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if %w(2.2.7 2.2.8 2.2.9 2.2.10 2.3.4 2.4.1).include? RUBY_VERSION
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begin
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require 'stopgap_13632'
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rescue LoadError
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end
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end
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```
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## Deployment
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Puma has support for Capistrano with an [external gem](https://github.com/seuros/capistrano-puma).
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It is common to use process monitors with Puma. Modern process monitors like systemd or upstart
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provide continuous monitoring and restarts for increased
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reliability in production environments:
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* [tools/jungle](https://github.com/puma/puma/tree/master/tools/jungle) for sysvinit (init.d) and upstart
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* [docs/systemd](https://github.com/puma/puma/blob/master/docs/systemd.md)
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## Community Extensions
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### Plugins
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* [puma-heroku](https://github.com/puma/puma-heroku) — default Puma configuration for running on Heroku
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* [puma-metrics](https://github.com/harmjanblok/puma-metrics) — export Puma metrics to Prometheus
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* [puma-plugin-statsd](https://github.com/yob/puma-plugin-statsd) — send Puma metrics to statsd
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* [puma-plugin-systemd](https://github.com/sj26/puma-plugin-systemd) — deeper integration with systemd for notify, status and watchdog
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### Monitoring
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* [puma-status](https://github.com/ylecuyer/puma-status) — Monitor CPU/Mem/Load of running puma instances from the CLI
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## Contributing
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Find details for contributing in the [contribution guide].
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[contribution guide]: https://github.com/puma/puma/blob/master/CONTRIBUTING.md
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## License
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Puma is copyright Evan Phoenix and contributors, licensed under the BSD 3-Clause license. See the included LICENSE file for details.
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