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Class: Puma::Rack::Builder

Relationships & Source Files
Inherits: Object
Defined in: lib/puma/rack/builder.rb

Overview

Builder implements a small ::Puma::DSL to iteratively construct ::Puma::Rack applications.

Example:

require 'rack/lobster'
app = {Rack::Builder.new} do
  use Rack::CommonLogger
  use Rack::ShowExceptions
  map "/lobster" do
    use Rack::Lint
    run Rack::Lobster.new
  end
end

run app

Or

app = {Rack::Builder.app} do
  use Rack::CommonLogger
  run lambda { |env| [200, {'Content-Type' => 'text/plain'}, ['OK']] }
end

run app

#use adds middleware to the stack, #run dispatches to an application. You can use #map to construct a URLMap in a convenient way.

Class Method Summary

Instance Method Summary

Constructor Details

.new(default_app = nil, &block) ⇒ Builder

[ GitHub ]

  
# File 'lib/puma/rack/builder.rb', line 178

def initialize(default_app = nil,&block)
  @use, @map, @run, @warmup = [], nil, default_app, nil

  # Conditionally load rack now, so that any rack middlewares,
  # etc are available.
  begin
    require 'rack'
  rescue LoadError
  end

  instance_eval(&block) if block_given?
end

Class Method Details

.app(default_app = nil, &block)

[ GitHub ]

  
# File 'lib/puma/rack/builder.rb', line 191

def self.app(default_app = nil, &block)
  self.new(default_app, &block).to_app
end

.new_from_string(builder_script, file = "(rackup)")

[ GitHub ]

  
# File 'lib/puma/rack/builder.rb', line 173

def self.new_from_string(builder_script, file="(rackup)")
  eval "Puma::Rack::Builder.new {\n" + builder_script + "\n}.to_app",
    TOPLEVEL_BINDING, file, 0
end

.parse_file(config, opts = Options.new)

[ GitHub ]

  
# File 'lib/puma/rack/builder.rb', line 157

def self.parse_file(config, opts = Options.new)
  options = {}
  if config =~ /\.ru$/
    cfgfile = ::File.read(config)
    if cfgfile[/^#\\(.*)/] && opts
      options = opts.parse! $1.split(/\s+/)
    end
    cfgfile.sub!(/^__END__\n.*\Z/m, '')
    app = new_from_string cfgfile, config
  else
    require config
    app = Object.const_get(::File.basename(config, '.rb').capitalize)
  end
  return app, options
end

Instance Method Details

#call(env)

[ GitHub ]

  
# File 'lib/puma/rack/builder.rb', line 285

def call(env)
  to_app.call(env)
end

#generate_map(default_app, mapping) (private)

[ GitHub ]

  
# File 'lib/puma/rack/builder.rb', line 291

def generate_map(default_app, mapping)
  require 'puma/rack/urlmap'

  mapped = default_app ? {'/' => default_app} : {}
  mapping.each { |r,b| mapped[r] = self.class.new(default_app, &b).to_app }
  URLMap.new(mapped)
end

#map(path, &block)

Creates a route within the application.

Rack::Builder.app do
  map '/' do
    run Heartbeat
  end
end

The #use method can also be used here to specify middleware to run under a specific path:

Rack::Builder.app do
  map '/' do
    use Middleware
    run Heartbeat
  end
end

This example includes a piece of middleware which will run before requests hit Heartbeat.

[ GitHub ]

  
# File 'lib/puma/rack/builder.rb', line 272

def map(path, &block)
  @map ||= {}
  @map[path] = block
end

#run(app)

Takes an argument that is an object that responds to #call and returns a ::Puma::Rack response. The simplest form of this is a lambda object:

run lambda { |env| [200, { "Content-Type" => "text/plain" }, ["OK"]] }

However this could also be a class:

class Heartbeat
  def self.call(env)
   [200, { "Content-Type" => "text/plain" }, ["OK"]]
 end
end

run Heartbeat
[ GitHub ]

  
# File 'lib/puma/rack/builder.rb', line 236

def run(app)
  @run = app
end

#to_app

[ GitHub ]

  
# File 'lib/puma/rack/builder.rb', line 277

def to_app
  app = @map ? generate_map(@run, @map) : @run
  fail "missing run or map statement" unless app
  app = @use.reverse.inject(app) { |a,e| e[a] }
  @warmup.call(app) if @warmup
  app
end

#use(middleware, *args, &block)

Specifies middleware to use in a stack.

class Middleware
  def initialize(app)
    @app = app
  end

  def call(env)
    env["rack.some_header"] = "setting an example"
    @app.call(env)
  end
end

use Middleware
run lambda { |env| [200, { "Content-Type" => "text/plain" }, ["OK"]] }

All requests through to this application will first be processed by the middleware class. The #call method in this example sets an additional environment key which then can be referenced in the application if required.

[ GitHub ]

  
# File 'lib/puma/rack/builder.rb', line 214

def use(middleware, *args, &block)
  if @map
    mapping, @map = @map, nil
    @use << proc { |app| generate_map app, mapping }
  end
  @use << proc { |app| middleware.new(app, *args, &block) }
end

#warmup(prc = nil, &block)

Takes a lambda or block that is used to warm-up the application.

warmup do |app|
  client = Rack::MockRequest.new(app)
  client.get('/')
end

use SomeMiddleware
run MyApp
[ GitHub ]

  
# File 'lib/puma/rack/builder.rb', line 249

def warmup(prc=nil, &block)
  @warmup = prc || block
end