Class: Puma::DSL

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

Overview

The methods that are available for use inside the configuration file. These same methods are used in ::Puma cli and the rack handler internally.

Used manually (via CLI class):

config = Configuration.new({}) do |user_config|
  user_config.port 3001
end
config.load

puts config.options[:binds] # => "tcp://127.0.0.1:3001"

Used to load file:

$ cat puma_config.rb
port 3002

Resulting configuration:

config = Configuration.new(config_file: "puma_config.rb")
config.load

puts config.options[:binds] # => "tcp://127.0.0.1:3002"

You can also find many examples being used by the test suite in test/config.

::Puma v6 adds the option to specify a key name (String or Symbol) to the hooks that run inside the forked workers. All the hooks run inside the Cluster::Worker#run method.

Previously, the worker index and the LogWriter instance were passed to the hook blocks/procs. If a key name is specified, a hash is passed as the last parameter. This allows storage of data, typically objects that are created before the worker that need to be passed to the hook when the worker is shutdown.

The following hooks have been updated:

| DSL Method         |  Options Key            | Fork Block Location |
| on_worker_boot     | :before_worker_boot     | inside, before      |
| on_worker_shutdown | :before_worker_shutdown | inside, after       |
| on_refork          | :before_refork          | inside              |

Constant Summary

ON_WORKER_KEY =
# File 'lib/puma/dsl.rb', line 52
```
[String, Symbol].freeze
```

Class Method Summary

.new(options, config) ⇒ DSL constructor
.ssl_bind_str(host, port, opts)

convenience method so logic can be used in CI.

Instance Method Summary

#_load_from(path)
#_offer_plugins
#activate_control_app(url = "auto", opts = {})

Start the ::Puma control rack application on url.
#after_worker_boot(&block)

Alias for #after_worker_fork.
#after_worker_fork(&block) (also: #after_worker_boot)

Code to run in the master after a worker has been started.
#app(obj = nil, &block)

Use an object or block as the rack application.
#before_fork(&block)

Code to run immediately before master process forks workers (once on boot).
#bind(url)

Bind the server to url.
#bind_to_activated_sockets(bind = true)

Bind to (systemd) activated sockets, regardless of configured binds.
#clean_thread_locals(which = true)

Work around leaky apps that leave garbage in Thread locals across requests.
#clear_binds!
#custom_logger(custom_logger)

Pass in a custom logging class instance.
#debug

Show debugging info.
#default_host
#directory(dir)

The directory to operate out of.
#drain_on_shutdown(which = true)

When shutting down, drain the accept socket of pending connections and process them.
#early_hints(answer = true)
#environment(environment)

Set the environment in which the rack’s app will run.
#extra_runtime_dependencies(answer = [])

When using prune_bundler, if extra runtime dependencies need to be loaded to initialize your app, then this setting can be used.
#first_data_timeout(seconds)

Define how long the tcp socket stays open, if no data has been received.
#force_shutdown_after(val = :forever)

How long to wait for threads to stop when shutting them down.
#fork_worker(after_requests = 1000)

When enabled, workers will be forked from worker 0 instead of from the master process.
#get(key, default = nil)
#http_content_length_limit(limit)

The default value for http_content_length_limit is nil.
#idle_timeout(seconds)

If a new request is not received within this number of seconds, begin shutting down.
#inject(&blk)
#io_selector_backend(backend)

Specify the backend for the ::IO selector.
#load(file)

Load additional configuration from a file Files get loaded later via Configuration#load
#log_formatter(&block)
#log_requests(which = true)

Enable request logging.
#lowlevel_error_handler(obj = nil, &block)

Use obj or block as the low level error handler.
#max_fast_inline(num_of_requests)

The number of requests to attempt inline before sending a client back to the reactor to be subject to normal ordering.
#mutate_stdout_and_stderr_to_sync_on_write(enabled = true)
#on_booted(&block)

Code to run after puma is booted (works for both: single and clustered).
#on_refork(key = nil, &block)

When #fork_worker is enabled, code to run in Worker 0 before all other workers are re-forked from this process, after the server has temporarily stopped serving requests (once per complete refork cycle).
#on_restart(&block)

Code to run before doing a restart.
#on_thread_exit(&block)

Code to run immediately before a thread exits.
#on_thread_start(&block)

Code to run immediately before a thread starts.
#on_worker_boot(key = nil, &block)

Code to run in a worker when it boots to setup the process before booting the app.
#on_worker_fork(&block)

Code to run in the master right before a worker is started.
#on_worker_shutdown(key = nil, &block)

Code to run immediately before a worker shuts down (after it has finished processing HTTP requests).
#out_of_band(&block)

Code to run out-of-band when the worker is idle.
#persistent_timeout(seconds)

Define how long persistent connections can be idle before ::Puma closes them.
#pidfile(path)

Store the pid of the server in the file at “path”.
#plugin(name)

Load the named plugin for use by this configuration.
#port(port, host = nil)

Define the TCP port to bind to.
#preload_app!(answer = true)

Preload the application before starting the workers; this conflicts with phased restart feature.
#prune_bundler(answer = true)

This option is used to allow your app and its gems to be properly reloaded when not using preload.
#queue_requests(answer = true)

When set to true (the default), workers accept all requests and queue them before passing them to the handlers.
#quiet(which = true)

Disable request logging, if this isn’t used it’ll be enabled by default.
#rack_url_scheme(scheme = nil)

Allows setting env['rack.url_scheme'].
#rackup(path)

Load path as a rackup file.
#raise_exception_on_sigterm(answer = true)

By default, ::Puma will raise SignalException when SIGTERM is received.
#restart_command(cmd)

Command to use to restart ::Puma.
#set_default_host(host)
#set_remote_address(val = :socket)

Control how the remote address of the connection is set.
#shutdown_debug(val = true)

When a shutdown is requested, the backtraces of all the threads will be written to $stdout.
#silence_fork_callback_warning

Disable warning message when running single mode with callback hook defined.
#silence_single_worker_warning

Disable warning message when running in cluster mode with a single worker.
#ssl_bind(host, port, opts = {})

Instead of using #bind and manually constructing a URI like:
#state_path(path)

Use path as the file to store the server info state.
#state_permission(permission)

Use permission to restrict permissions for the state file.
#stdout_redirect(stdout = nil, stderr = nil, append = false)

Redirect STDOUT and STDERR to files specified.
#supported_http_methods(methods)

Supported http methods, which will replace Const::SUPPORTED_HTTP_METHODS.
#tag(string)

Additional text to display in process listing.
#threads(min, max)

Configure min to be the minimum number of threads to use to answer requests and max the maximum.
#wait_for_less_busy_worker(val = 0.005)

Attempts to route traffic to less-busy workers by causing them to delay listening on the socket, allowing workers which are not processing any requests to pick up new requests first.
#worker_boot_timeout(timeout)

Change the default worker timeout for booting.
#worker_check_interval(interval)

Change the default interval for checking workers.
#worker_culling_strategy(strategy)

Set the strategy for worker culling.
#worker_shutdown_timeout(timeout)

Set the timeout for worker shutdown.
#worker_timeout(timeout)

Verifies that all workers have checked in to the master process within the given timeout.
#workers(count)

How many worker processes to run.
#add_pem_values_to_options_store(opts) private

To avoid adding cert_pem and key_pem as URI params, we store them on the options from where ::Puma binder knows how to find and extract them.
#process_hook(options_key, key, block, meth) private
#warn_if_in_single_mode(hook_name) private

Constructor Details

.new(options, config) ⇒ `DSL`

[ GitHub ]

# File 'lib/puma/dsl.rb', line 123


def initialize(options, config)
  @config  = config
  @options = options

  @plugins = []
end

Class Method Details

.ssl_bind_str(host, port, opts)

convenience method so logic can be used in CI

See Also:

#ssl_bind

[ GitHub ]

# File 'lib/puma/dsl.rb', line 57


def self.ssl_bind_str(host, port, opts)
  verify = opts.fetch(:verify_mode, 'none').to_s

  tls_str =
    if opts[:no_tlsv1_1]  then '&no_tlsv1_1=true'
    elsif opts[:no_tlsv1] then '&no_tlsv1=true'
    else ''
    end

  ca_additions = "&ca=#{Puma::Util.escape(opts[:ca])}" if ['peer', 'force_peer'].include?(verify)

  low_latency_str = opts.key?(:low_latency) ? "&low_latency=#{opts[:low_latency]}" : ''
  backlog_str = opts[:backlog] ? "&backlog=#{Integer(opts[:backlog])}" : ''

  if defined?(JRUBY_VERSION)
    cipher_suites = opts[:ssl_cipher_list] ? "&ssl_cipher_list=#{opts[:ssl_cipher_list]}" : nil # old name
    cipher_suites = "#{cipher_suites}&cipher_suites=#{opts[:cipher_suites]}" if opts[:cipher_suites]
    protocols = opts[:protocols] ? "&protocols=#{opts[:protocols]}" : nil

    keystore_additions = "keystore=#{opts[:keystore]}&keystore-pass=#{opts[:keystore_pass]}"
    keystore_additions = "#{keystore_additions}&keystore-type=#{opts[:keystore_type]}" if opts[:keystore_type]
    if opts[:truststore]
      truststore_additions = "&truststore=#{opts[:truststore]}"
      truststore_additions = "#{truststore_additions}&truststore-pass=#{opts[:truststore_pass]}" if opts[:truststore_pass]
      truststore_additions = "#{truststore_additions}&truststore-type=#{opts[:truststore_type]}" if opts[:truststore_type]
    end

    "ssl://#{host}:#{port}?#{keystore_additions}#{truststore_additions}#{cipher_suites}#{protocols}" \
      "&verify_mode=#{verify}#{tls_str}#{ca_additions}#{backlog_str}"
  else
    ssl_cipher_filter = opts[:ssl_cipher_filter] ? "&ssl_cipher_filter=#{opts[:ssl_cipher_filter]}" : nil
    v_flags = (ary = opts[:verification_flags]) ? "&verification_flags=#{Array(ary).join ','}" : nil

    cert_flags = (cert = opts[:cert]) ? "cert=#{Puma::Util.escape(cert)}" : nil
    key_flags = (key = opts[:key]) ? "&key=#{Puma::Util.escape(key)}" : nil
    password_flags = (password_command = opts[:key_password_command]) ? "&key_password_command=#{Puma::Util.escape(password_command)}" : nil

    reuse_flag =
      if (reuse = opts[:reuse])
        if reuse == true
          '&reuse=dflt'
        elsif reuse.is_a?(Hash) && (reuse.key?(:size) || reuse.key?(:timeout))
          val = +''
          if (size = reuse[:size]) && Integer === size
            val << size.to_s
          end
          if (timeout = reuse[:timeout]) && Integer === timeout
            val << ",#{timeout}"
          end
          if val.empty?
            nil
          else
            "&reuse=#{val}"
          end
        else
          nil
        end
      else
        nil
      end

    "ssl://#{host}:#{port}?#{cert_flags}#{key_flags}#{password_flags}#{ssl_cipher_filter}" \
      "#{reuse_flag}&verify_mode=#{verify}#{tls_str}#{ca_additions}#{v_flags}#{backlog_str}#{low_latency_str}"
  end
end

Instance Method Details

#_load_from(path)

[ GitHub ]

# File 'lib/puma/dsl.rb', line 130


def _load_from(path)
  if path
    @path = path
    instance_eval(File.read(path), path, 1)
  end
ensure
  _offer_plugins
end

#_offer_plugins

[ GitHub ]

# File 'lib/puma/dsl.rb', line 139


def _offer_plugins
  @plugins.each do |o|
    if o.respond_to? :config
      @options.shift
      o.config self
    end
  end

  @plugins.clear
end

#activate_control_app(url = "auto", opts = {})

Start the ::Puma control rack application on url. This application can be communicated with to control the main server. Additionally, you can provide an authentication token, so all requests to the control server will need to include that token as a query parameter. This allows for simple authentication.

Check out App::Status to see what the app has available.

Examples:

activate_control_app 'unix:///var/run/pumactl.sock'

activate_control_app 'unix:///var/run/pumactl.sock', { auth_token: '12345' }

activate_control_app 'unix:///var/run/pumactl.sock', { no_token: true }

[ GitHub ]

# File 'lib/puma/dsl.rb', line 213


def activate_control_app(url="auto", opts={})
  if url == "auto"
    path = Configuration.temp_path
    @options[:control_url] = "unix://#{path}"
    @options[:control_url_temp] = path
  else
    @options[:control_url] = url
  end

  if opts[:no_token]
    # We need to use 'none' rather than :none because this value will be
    # passed on to an instance of OptionParser, which doesn't support
    # symbols as option values.
    #
    # See: https://github.com/puma/puma/issues/1193#issuecomment-305995488
    auth_token = 'none'
  else
    auth_token = opts[:auth_token]
    auth_token ||= Configuration.random_token
  end

  @options[:control_auth_token] = auth_token
  @options[:control_url_umask] = opts[:umask] if opts[:umask]
end

#add_pem_values_to_options_store(opts) (private)

To avoid adding cert_pem and key_pem as URI params, we store them on the options from where ::Puma binder knows how to find and extract them.

[ GitHub ]

# File 'lib/puma/dsl.rb', line 1153


def add_pem_values_to_options_store(opts)
  return if defined?(JRUBY_VERSION)

  @options[:store] ||= []

  # Store cert_pem and key_pem to options[:store] if present
  [:cert, :key].each do |v|
    opt_key = :"#{v}_pem"
    if opts[opt_key]
      index = @options[:store].length
      @options[:store] << opts[opt_key]
      opts[v] = "store:#{index}"
    end
  end
end

#after_worker_boot(&block)

Alias for #after_worker_fork.

[ GitHub ]

# File 'lib/puma/dsl.rb', line 698


alias_method :after_worker_boot, :after_worker_fork

#after_worker_fork(&block) Also known as: #after_worker_boot

Note:

Cluster mode only.

Code to run in the master after a worker has been started. The worker’s index is passed as an argument.

This is called everytime a worker is to be started.

Examples:

after_worker_fork do
  puts 'After worker fork...'
end

[ GitHub ]

# File 'lib/puma/dsl.rb', line 692


def after_worker_fork(&block)
  warn_if_in_single_mode('after_worker_fork')

  process_hook :after_worker_fork, nil, block, 'after_worker_fork'
end

#app(obj = nil, &block)

Use an object or block as the rack application. This allows the configuration file to be the application itself.

Examples:

app do |env|
  body = 'Hello, World!'

  [
    200,
    {
      'Content-Type' => 'text/plain',
      'Content-Length' => body.length.to_s
    },
    [body]
  ]
end

See Also:

Configuration#app

[ GitHub ]

# File 'lib/puma/dsl.rb', line 191


def app(obj=nil, &block)
  obj ||= block

  raise "Provide either a #call'able or a block" unless obj

  @options[:app] = obj
end

#before_fork(&block)

Note:

Cluster mode only.

Code to run immediately before master process forks workers (once on boot). These hooks can block if necessary to wait for background operations unknown to ::Puma to finish before the process terminates. This can be used to close any connections to remote servers (database, Redis, …) that were opened when preloading the code.

This can be called multiple times to add several hooks.

Examples:

before_fork do
  puts "Starting workers..."
end

[ GitHub ]

# File 'lib/puma/dsl.rb', line 625


def before_fork(&block)
  warn_if_in_single_mode('before_fork')

  @options[:before_fork] ||= []
  @options[:before_fork] << block
end

#bind(url)

Bind the server to url. “tcp://”, “unix://” and “ssl://” are the only accepted protocols. Multiple urls can be bound to, calling bind does not overwrite previous bindings.

The default is “tcp://0.0.0.0:9292”.

You can use query parameters within the url to specify options:

Set the socket backlog depth with backlog, default is 1024.
Set up an SSL certificate with key & cert.
Set up an SSL certificate for mTLS with key, cert, ca and verify_mode.
Set whether to optimize for low latency instead of throughput with low_latency, default is to not optimize for low latency. This is done via Socket::TCP_NODELAY.
Set socket permissions with umask.

Examples:

Backlog depth

bind 'unix:///var/run/puma.sock?backlog=512'

SSL cert

bind 'ssl://127.0.0.1:9292?key=key.key&cert=cert.pem'

SSL cert for mutual TLS (mTLS)

bind 'ssl://127.0.0.1:9292?key=key.key&cert=cert.pem&ca=ca.pem&verify_mode=force_peer'

Disable optimization for low latency

bind 'tcp://0.0.0.0:9292?low_latency=false'

Socket permissions

bind 'unix:///var/run/puma.sock?umask=0111'

See Also:

[ GitHub ]

# File 'lib/puma/dsl.rb', line 274


def bind(url)
  @options[:binds] ||= []
  @options[:binds] << url
end

#bind_to_activated_sockets(bind = true)

Bind to (systemd) activated sockets, regardless of configured binds.

Systemd can present sockets as file descriptors that are already opened. By default ::Puma will use these but only if it was explicitly told to bind to the socket. If not, it will close the activated sockets. This means all configuration is duplicated.

Binds can contain additional configuration, but only SSL config is really relevant since the unix and TCP socket options are ignored.

This means there is a lot of duplicated configuration for no additional value in most setups. This method tells the launcher to bind to all activated sockets, regardless of existing bind.

To clear configured binds, the value only can be passed. This will clear out any binds that may have been configured.

Examples:

Use any systemd activated sockets as well as configured binds

bind_to_activated_sockets

Only bind to systemd activated sockets, ignoring other binds

bind_to_activated_sockets 'only'

[ GitHub ]

# File 'lib/puma/dsl.rb', line 305


def bind_to_activated_sockets(bind=true)
  @options[:bind_to_activated_sockets] = bind
end

#clean_thread_locals(which = true)

Work around leaky apps that leave garbage in Thread locals across requests.

[ GitHub ]

# File 'lib/puma/dsl.rb', line 338


def clean_thread_locals(which=true)
  @options[:clean_thread_locals] = which
end

#clear_binds!

[ GitHub ]

# File 'lib/puma/dsl.rb', line 279


def clear_binds!
  @options[:binds] = []
end

#custom_logger(custom_logger)

Pass in a custom logging class instance

[ GitHub ]

# File 'lib/puma/dsl.rb', line 430


def custom_logger(custom_logger)
  @options[:custom_logger] = custom_logger
end

#debug

Show debugging info

[ GitHub ]

# File 'lib/puma/dsl.rb', line 436


def debug
  @options[:debug] = true
end

#default_host

[ GitHub ]

# File 'lib/puma/dsl.rb', line 154


def default_host
  @options[:default_host] || Configuration::DEFAULTS[:tcp_host]
end

#directory(dir)

The directory to operate out of.

The default is the current directory.

Examples:

directory '/u/apps/lolcat'

[ GitHub ]

# File 'lib/puma/dsl.rb', line 785


def directory(dir)
  @options[:directory] = dir.to_s
end

#drain_on_shutdown(which = true)

When shutting down, drain the accept socket of pending connections and process them. This loops over the accept socket until there are no more read events and then stops looking and waits for the requests to finish.

See Also:

Server#graceful_shutdown

[ GitHub ]

# File 'lib/puma/dsl.rb', line 347


def drain_on_shutdown(which=true)
  @options[:drain_on_shutdown] = which
end

#early_hints(answer = true)

[ GitHub ]

# File 'lib/puma/dsl.rb', line 457


def early_hints(answer=true)
  @options[:early_hints] = answer
end

#environment(environment)

Set the environment in which the rack’s app will run. The value must be a string.

The default is “development”.

Examples:

environment 'production'

[ GitHub ]

# File 'lib/puma/dsl.rb', line 358


def environment(environment)
  @options[:environment] = environment
end

#extra_runtime_dependencies(answer = [])

When using prune_bundler, if extra runtime dependencies need to be loaded to initialize your app, then this setting can be used. This includes any ::Puma plugins.

Before bundler is pruned, the gem names supplied will be looked up in the bundler context and then loaded again after bundler is pruned. Only applies if prune_bundler is used.

Examples:

extra_runtime_dependencies ['gem_name_1', 'gem_name_2']

extra_runtime_dependencies ['puma_worker_killer', 'puma-heroku']

See Also:

Puma::Launcher#extra_runtime_deps_directories

[ GitHub ]

# File 'lib/puma/dsl.rb', line 862


def extra_runtime_dependencies(answer = [])
  @options[:extra_runtime_dependencies] = Array(answer)
end

#first_data_timeout(seconds)

Define how long the tcp socket stays open, if no data has been received.

See Also:

Server.new

[ GitHub ]

# File 'lib/puma/dsl.rb', line 320


def first_data_timeout(seconds)
  @options[:first_data_timeout] = Integer(seconds)
end

#force_shutdown_after(val = :forever)

How long to wait for threads to stop when shutting them down. Defaults to :forever. Specifying :immediately will cause ::Puma to kill the threads immediately. Otherwise the value is the number of seconds to wait.

::Puma always waits a few seconds after killing a thread for it to try to finish up it’s work, even in :immediately mode.

See Also:

Server#graceful_shutdown

[ GitHub ]

# File 'lib/puma/dsl.rb', line 370


def force_shutdown_after(val=:forever)
  i = case val
      when :forever
        -1
      when :immediately
        0
      else
        Float(val)
      end

  @options[:force_shutdown_after] = i
end

#fork_worker(after_requests = 1000)

Note:

Cluster mode only.

When enabled, workers will be forked from worker 0 instead of from the master process. This option is similar to preload_app because the app is preloaded before forking, but it is compatible with phased restart.

This option also enables the refork command (SIGURG), which optimizes copy-on-write performance in a running app.

A refork will automatically trigger once after the specified number of requests (default 1000), or pass 0 to disable auto refork.

Version:

5.0.0

[ GitHub ]

# File 'lib/puma/dsl.rb', line 1070


def fork_worker(after_requests=1000)
  @options[:fork_worker] = Integer(after_requests)
end

#get(key, default = nil)

[ GitHub ]

# File 'lib/puma/dsl.rb', line 162


def get(key,default=nil)
  @options[key.to_sym] || default
end

#http_content_length_limit(limit)

The default value for http_content_length_limit is nil.

[ GitHub ]

# File 'lib/puma/dsl.rb', line 1113


def http_content_length_limit(limit)
  @options[:http_content_length_limit] = limit
end

#idle_timeout(seconds)

If a new request is not received within this number of seconds, begin shutting down.

See Also:

Server.new

[ GitHub ]

# File 'lib/puma/dsl.rb', line 332


def idle_timeout(seconds)
  @options[:idle_timeout] = Integer(seconds)
end

#inject(&blk)

[ GitHub ]

# File 'lib/puma/dsl.rb', line 158


def inject(&blk)
  instance_eval(&blk)
end

#io_selector_backend(backend)

Specify the backend for the ::IO selector.

Provided values will be passed directly to NIO::Selector.new, with the exception of :auto which will let nio4r choose the backend.

Check the documentation of NIO::Selector.backends for the list of valid options. Note that the available options on your system will depend on the operating system. If you want to use the pure Ruby backend (not recommended due to its comparatively low performance), set environment variable NIO4R_PURE to true.

The default is :auto.

See Also:

https://github.com/socketry/nio4r/blob/master/lib/nio/selector.rb

[ GitHub ]

# File 'lib/puma/dsl.rb', line 1096


def io_selector_backend(backend)
  @options[:io_selector_backend] = backend.to_sym
end

#load(file)

Load additional configuration from a file Files get loaded later via Configuration#load

[ GitHub ]

# File 'lib/puma/dsl.rb', line 240


def load(file)
  @options[:config_files] ||= []
  @options[:config_files] << file
end

#log_formatter(&block)

[ GitHub ]

# File 'lib/puma/dsl.rb', line 474


def log_formatter(&block)
  @options[:log_formatter] = block
end

#log_requests(which = true)

Enable request logging

[ GitHub ]

# File 'lib/puma/dsl.rb', line 425


def log_requests(which=true)
  @options[:log_requests] = which
end

#lowlevel_error_handler(obj = nil, &block)

Use obj or block as the low level error handler. This allows the configuration file to change the default error on the server.

Examples:

lowlevel_error_handler do |err|
  [200, {}, ["error page"]]
end

[ GitHub ]

# File 'lib/puma/dsl.rb', line 806


def lowlevel_error_handler(obj=nil, &block)
  obj ||= block
  raise "Provide either a #call'able or a block" unless obj
  @options[:lowlevel_error_handler] = obj
end

#max_fast_inline(num_of_requests)

The number of requests to attempt inline before sending a client back to the reactor to be subject to normal ordering.

[ GitHub ]

# File 'lib/puma/dsl.rb', line 1077


def max_fast_inline(num_of_requests)
  @options[:max_fast_inline] = Float(num_of_requests)
end

#mutate_stdout_and_stderr_to_sync_on_write(enabled = true)

[ GitHub ]

# File 'lib/puma/dsl.rb', line 1100


def mutate_stdout_and_stderr_to_sync_on_write(enabled=true)
  @options[:mutate_stdout_and_stderr_to_sync_on_write] = enabled
end

#on_booted(&block)

Code to run after puma is booted (works for both: single and clustered)

Examples:

on_booted do
  puts 'After booting...'
end

[ GitHub ]

# File 'lib/puma/dsl.rb', line 706


def on_booted(&block)
  @config.options[:events].on_booted(&block)
end

#on_refork(key = nil, &block)

Note:

Cluster mode with #fork_worker enabled only.

When #fork_worker is enabled, code to run in Worker 0 before all other workers are re-forked from this process, after the server has temporarily stopped serving requests (once per complete refork cycle).

This can be used to trigger extra garbage-collection to maximize copy-on-write efficiency, or close any connections to remote servers (database, Redis, …) that were opened while the server was running.

This can be called multiple times to add several hooks.

Examples:

on_refork do
  3.times {GC.start}
end

Version:

5.0.0

[ GitHub ]

# File 'lib/puma/dsl.rb', line 728


def on_refork(key = nil, &block)
  process_hook :before_refork, key, block, 'on_refork'
end

#on_restart(&block)

Code to run before doing a restart. This code should close log files, database connections, etc.

This can be called multiple times to add code each time.

Examples:

on_restart do
  puts 'On restart...'
end

[ GitHub ]

# File 'lib/puma/dsl.rb', line 392


def on_restart(&block)
  @options[:on_restart] ||= []
  @options[:on_restart] << block
end

#on_thread_exit(&block)

Code to run immediately before a thread exits. The worker does not accept new requests until this code finishes.

This hook is useful for cleaning up thread local resources when a thread is trimmed.

This can be called multiple times to add several hooks.

Examples:

on_thread_exit do
  puts 'On thread exit...'
end

[ GitHub ]

# File 'lib/puma/dsl.rb', line 761


def on_thread_exit(&block)
  @options[:before_thread_exit] ||= []
  @options[:before_thread_exit] << block
end

#on_thread_start(&block)

Code to run immediately before a thread starts. The worker does not start new threads until this code finishes.

This hook is useful for doing something when a thread starts.

This can be called multiple times to add several hooks.

Examples:

on_thread_start do
  puts 'On thread start...'
end

[ GitHub ]

# File 'lib/puma/dsl.rb', line 744


def on_thread_start(&block)
  @options[:before_thread_start] ||= []
  @options[:before_thread_start] << block
end

#on_worker_boot(key = nil, &block)

Note:

Cluster mode only.

Code to run in a worker when it boots to setup the process before booting the app.

This can be called multiple times to add several hooks.

Examples:

on_worker_boot do
  puts 'Before worker boot...'
end

[ GitHub ]

# File 'lib/puma/dsl.rb', line 642


def on_worker_boot(key = nil, &block)
  warn_if_in_single_mode('on_worker_boot')

  process_hook :before_worker_boot, key, block, 'on_worker_boot'
end

#on_worker_fork(&block)

Note:

Cluster mode only.

Code to run in the master right before a worker is started. The worker’s index is passed as an argument.

This can be called multiple times to add several hooks.

Examples:

on_worker_fork do
  puts 'Before worker fork...'
end

[ GitHub ]

# File 'lib/puma/dsl.rb', line 676


def on_worker_fork(&block)
  warn_if_in_single_mode('on_worker_fork')

  process_hook :before_worker_fork, nil, block, 'on_worker_fork'
end

#on_worker_shutdown(key = nil, &block)

Note:

Cluster mode only.

Code to run immediately before a worker shuts down (after it has finished processing HTTP requests). These hooks can block if necessary to wait for background operations unknown to ::Puma to finish before the process terminates.

This can be called multiple times to add several hooks.

Examples:

on_worker_shutdown do
  puts 'On worker shutdown...'
end

[ GitHub ]

# File 'lib/puma/dsl.rb', line 660


def on_worker_shutdown(key = nil, &block)
  warn_if_in_single_mode('on_worker_shutdown')

  process_hook :before_worker_shutdown, key, block, 'on_worker_shutdown'
end

#out_of_band(&block)

Code to run out-of-band when the worker is idle. These hooks run immediately after a request has finished processing and there are no busy threads on the worker. The worker doesn’t accept new requests until this code finishes.

This hook is useful for running out-of-band garbage collection or scheduling asynchronous tasks to execute after a response.

This can be called multiple times to add several hooks.

[ GitHub ]

# File 'lib/puma/dsl.rb', line 775


def out_of_band(&block)
  process_hook :out_of_band, nil, block, 'out_of_band'
end

#persistent_timeout(seconds)

Define how long persistent connections can be idle before ::Puma closes them.

See Also:

Server.new

[ GitHub ]

# File 'lib/puma/dsl.rb', line 326


def persistent_timeout(seconds)
  @options[:persistent_timeout] = Integer(seconds)
end

#pidfile(path)

Store the pid of the server in the file at “path”.

Examples:

pidfile '/u/apps/lolcat/tmp/pids/puma.pid'

[ GitHub ]

# File 'lib/puma/dsl.rb', line 411


def pidfile(path)
  @options[:pidfile] = path.to_s
end

#plugin(name)

Load the named plugin for use by this configuration

[ GitHub ]

# File 'lib/puma/dsl.rb', line 168


def plugin(name)
  @plugins << @config.load_plugin(name)
end

#port(port, host = nil)

Define the TCP port to bind to. Use #bind for more advanced options.

Examples:

port 9292

[ GitHub ]

# File 'lib/puma/dsl.rb', line 313


def port(port, host=nil)
  host ||= default_host
  bind URI::Generic.build(scheme: 'tcp', host: host, port: Integer(port)).to_s
end

#preload_app!(answer = true)

Note:

Cluster mode only.

Preload the application before starting the workers; this conflicts with phased restart feature. On by default if your app uses more than 1 worker.

Examples:

preload_app!

[ GitHub ]

# File 'lib/puma/dsl.rb', line 795


def preload_app!(answer=true)
  @options[:preload_app] = answer
end

#process_hook(options_key, key, block, meth) (private)

[ GitHub ]

# File 'lib/puma/dsl.rb', line 1169


def process_hook(options_key, key, block, meth)
  @options[options_key] ||= []
  if ON_WORKER_KEY.include? key.class
    @options[options_key] << [block, key.to_sym]
  elsif key.nil?
    @options[options_key] << block
  else
    raise "'#{meth}' key must be String or Symbol"
  end
end

#prune_bundler(answer = true)

Note:

This is incompatible with #preload_app!.

Note:

This is only supported for RubyGems 2.2+

This option is used to allow your app and its gems to be properly reloaded when not using preload.

When set, if ::Puma detects that it’s been invoked in the context of Bundler, it will cleanup the environment and re-run itself outside the Bundler environment, but directly using the files that Bundler has setup.

This means that ::Puma is now decoupled from your Bundler context and when each worker loads, it will be loading a new Bundler context and thus can float around as the release dictates.

See Also:

#extra_runtime_dependencies

[ GitHub ]

# File 'lib/puma/dsl.rb', line 829


def prune_bundler(answer=true)
  @options[:prune_bundler] = answer
end

#queue_requests(answer = true)

When set to true (the default), workers accept all requests and queue them before passing them to the handlers. When set to false, each worker process accepts exactly as many requests as it is configured to simultaneously handle.

Queueing requests generally improves performance. In some cases, such as a single threaded application, it may be better to ensure requests get balanced across workers.

Note that setting this to false disables HTTP keepalive and slow clients will occupy a handler thread while the request is being sent. A reverse proxy, such as nginx, can handle slow clients and queue requests before they reach ::Puma.

See Also:

Server

[ GitHub ]

# File 'lib/puma/dsl.rb', line 977


def queue_requests(answer=true)
  @options[:queue_requests] = answer
end

#quiet(which = true)

Disable request logging, if this isn’t used it’ll be enabled by default.

Examples:

quiet

[ GitHub ]

# File 'lib/puma/dsl.rb', line 419


def quiet(which=true)
  @options[:log_requests] = !which
end

#rack_url_scheme(scheme = nil)

Allows setting env['rack.url_scheme']. Only necessary if X-Forwarded-Proto is not being set by your proxy Normal values are ‘http’ or ‘https’.

[ GitHub ]

# File 'lib/puma/dsl.rb', line 453


def rack_url_scheme(scheme=nil)
  @options[:rack_url_scheme] = scheme
end

#rackup(path)

Load path as a rackup file.

The default is “config.ru”.

Examples:

rackup '/u/apps/lolcat/config.ru'

[ GitHub ]

# File 'lib/puma/dsl.rb', line 446


def rackup(path)
  @options[:rackup] ||= path.to_s
end

#raise_exception_on_sigterm(answer = true)

By default, ::Puma will raise SignalException when SIGTERM is received. In environments where SIGTERM is something expected, you can suppress these with this option.

This can be useful for example in Kubernetes, where rolling restart is guaranteed usually on infrastructure level.

Examples:

raise_exception_on_sigterm false

See Also:

[ GitHub ]

# File 'lib/puma/dsl.rb', line 845


def raise_exception_on_sigterm(answer=true)
  @options[:raise_exception_on_sigterm] = answer
end

#restart_command(cmd)

Command to use to restart ::Puma. This should be just how to load ::Puma itself (ie. ‘ruby -Ilib bin/puma’), not the arguments to ::Puma, as those are the same as the original process.

Examples:

restart_command '/u/app/lolcat/bin/restart_puma'

[ GitHub ]

# File 'lib/puma/dsl.rb', line 403


def restart_command(cmd)
  @options[:restart_cmd] = cmd.to_s
end

#set_default_host(host)

[ GitHub ]

# File 'lib/puma/dsl.rb', line 150


def set_default_host(host)
  @options[:default_host] = host
end

#set_remote_address(val = :socket)

Control how the remote address of the connection is set. This is configurable because to calculate the true socket peer address a kernel syscall is required which for very fast rack handlers slows down the handling significantly.

There are 5 possible values:

:socket (the default) - read the peername from the socket using the syscall. This is the normal behavior. If this fails for any reason (e.g., if the peer disconnects between the connection being accepted and the getpeername system call), Puma will return “0.0.0.0”
:localhost - set the remote address to “127.0.0.1”
**header: <http_header>**- set the remote address to the value of the provided http header. For instance: ‘set_remote_address header: “X-Real-IP”`. Only the first word (as separated by spaces or comma) is used, allowing headers such as X-Forwarded-For to be used as well. If this header is absent, Puma will fall back to the behavior of :socket
**proxy_protocol: :v1**- set the remote address to the value read from the HAproxy PROXY protocol, version 1. If the request does not have the PROXY protocol attached to it, will fall back to :socket
**<Any string>** - this allows you to hardcode remote address to any value you wish. Because Puma never uses this field anyway, it’s format is entirely in your hands.

[ GitHub ]

# File 'lib/puma/dsl.rb', line 1028


def set_remote_address(val=:socket)
  case val
  when :socket
    @options[:remote_address] = val
  when :localhost
    @options[:remote_address] = :value
    @options[:remote_address_value] = "127.0.0.1".freeze
  when String
    @options[:remote_address] = :value
    @options[:remote_address_value] = val
  when Hash
    if hdr = val[:header]
      @options[:remote_address] = :header
      @options[:remote_address_header] = "HTTP_" + hdr.upcase.tr("-", "_")
    elsif protocol_version = val[:proxy_protocol]
      @options[:remote_address] = :proxy_protocol
      protocol_version = protocol_version.downcase.to_sym
      unless [:v1].include?(protocol_version)
        raise "Invalid value for proxy_protocol - #{protocol_version.inspect}"
      end
      @options[:remote_address_proxy_protocol] = protocol_version
    else
      raise "Invalid value for set_remote_address - #{val.inspect}"
    end
  else
    raise "Invalid value for set_remote_address - #{val}"
  end
end

#shutdown_debug(val = true)

When a shutdown is requested, the backtraces of all the threads will be written to $stdout. This can help figure out why shutdown is hanging.

[ GitHub ]

# File 'lib/puma/dsl.rb', line 985


def shutdown_debug(val=true)
  @options[:shutdown_debug] = val
end

#silence_fork_callback_warning

Disable warning message when running single mode with callback hook defined.

[ GitHub ]

# File 'lib/puma/dsl.rb', line 607


def silence_fork_callback_warning
  @options[:silence_fork_callback_warning] = true
end

#silence_single_worker_warning

Note:

Cluster mode only.

Disable warning message when running in cluster mode with a single worker.

Cluster mode has some overhead of running an additional ‘control’ process in order to manage the cluster. If only running a single worker it is likely not worth paying that overhead vs running in single mode with additional threads instead.

There are some scenarios where running cluster mode with a single worker may still be warranted and valid under certain deployment scenarios, see github.com/puma/puma/issues/2534

Moving from workers = 1 to workers = 0 will save 10-30% of memory use.

[ GitHub ]

# File 'lib/puma/dsl.rb', line 602


def silence_single_worker_warning
  @options[:silence_single_worker_warning] = true
end

#ssl_bind(host, port, opts = {})

Instead of using #bind and manually constructing a URI like:

bind 'ssl://127.0.0.1:9292?key=key_path&cert=cert_path'

you can use the this method.

When binding on localhost you don’t need to specify cert and key, ::Puma will assume you are using the localhost gem and try to load the appropriate files.

When using the options hash parameter, the reuse: value is either true, which sets reuse ‘on’ with default values, or a hash, with :size and/or :timeout keys, each with integer values.

The cert: options hash parameter can be the path to a certificate file including all intermediate certificates in PEM format.

The cert_pem: options hash parameter can be String containing the cerificate and all intermediate certificates in PEM format.

Examples:

ssl_bind '127.0.0.1', '9292', {
  cert: path_to_cert,
  key: path_to_key,
  ssl_cipher_filter: cipher_filter, # optional
  verify_mode: verify_mode,         # default 'none'
  verification_flags: flags,        # optional, not supported by JRuby
  reuse: true                       # optional
}

Using self-signed certificate with the localhost gem:

ssl_bind '127.0.0.1', '9292'

Alternatively, you can provide cert_pem and key_pem:

ssl_bind '127.0.0.1', '9292', {
  cert_pem: File.read(path_to_cert),
  key_pem: File.read(path_to_key),
  reuse: {size: 2_000, timeout: 20} # optional
}

For JRuby, two keys are required: keystore & keystore_pass

ssl_bind '127.0.0.1', '9292', {
  keystore: path_to_keystore,
  keystore_pass: password,
  ssl_cipher_list: cipher_list,     # optional
  verify_mode: verify_mode          # default 'none'
}

[ GitHub ]

# File 'lib/puma/dsl.rb', line 552


def ssl_bind(host, port, opts = {})
  add_pem_values_to_options_store(opts)
  bind self.class.ssl_bind_str(host, port, opts)
end

#state_path(path)

Use path as the file to store the server info state. This is used by pumactl to query and control the server.

Examples:

state_path '/u/apps/lolcat/tmp/pids/puma.state'

[ GitHub ]

# File 'lib/puma/dsl.rb', line 562


def state_path(path)
  @options[:state] = path.to_s
end

#state_permission(permission)

Use permission to restrict permissions for the state file.

Examples:

state_permission 0600

Version:

5.0.0

[ GitHub ]

# File 'lib/puma/dsl.rb', line 572


def state_permission(permission)
  @options[:state_permission] = permission
end

#stdout_redirect(stdout = nil, stderr = nil, append = false)

Redirect STDOUT and STDERR to files specified. The append parameter specifies whether the output is appended, the default is false.

Examples:

stdout_redirect '/app/lolcat/log/stdout', '/app/lolcat/log/stderr'

stdout_redirect '/app/lolcat/log/stdout', '/app/lolcat/log/stderr', true

[ GitHub ]

# File 'lib/puma/dsl.rb', line 468


def stdout_redirect(stdout=nil, stderr=nil, append=false)
  @options[:redirect_stdout] = stdout
  @options[:redirect_stderr] = stderr
  @options[:redirect_append] = append
end

#supported_http_methods(methods)

Note:

If the methods value is :any, no method check with be performed, similar to ::Puma v5 and earlier.

Supported http methods, which will replace Const::SUPPORTED_HTTP_METHODS. The value of :any will allows all methods, otherwise, the value must be an array of strings. Note that methods are all uppercase.

Const::SUPPORTED_HTTP_METHODS is conservative, if you want a complete set of methods, the methods defined by the [IANA Method Registry](www.iana.org/assignments/http-methods/http-methods.xhtml) are pre-defined as the constant Const::IANA_HTTP_METHODS.

Examples:

Adds ‘PROPFIND’ to existing supported methods

supported_http_methods(Puma::Const::SUPPORTED_HTTP_METHODS + ['PROPFIND'])

Restricts methods to the array elements

supported_http_methods %w[HEAD GET POST PUT DELETE OPTIONS PROPFIND]

Restricts methods to the methods in the IANA Registry

supported_http_methods Puma::Const::IANA_HTTP_METHODS

Allows any method

supported_http_methods :any

[ GitHub ]

# File 'lib/puma/dsl.rb', line 1138


def supported_http_methods(methods)
  if methods == :any
    @options[:supported_http_methods] = :any
  elsif Array === methods && methods == (ary = methods.grep(String).uniq) &&
    !ary.empty?
    @options[:supported_http_methods] = ary
  else
    raise "supported_http_methods must be ':any' or a unique array of strings"
  end
end

#tag(string)

Additional text to display in process listing.

If you do not specify a tag, ::Puma will infer it. If you do not want ::Puma to add a tag, use an empty string.

Examples:

tag 'app name'

tag ''

[ GitHub ]

# File 'lib/puma/dsl.rb', line 875


def tag(string)
  @options[:tag] = string.to_s
end

#threads(min, max)

Configure min to be the minimum number of threads to use to answer requests and max the maximum.

The default is the environment variables PUMA_MIN_THREADS / PUMA_MAX_THREADS (or MIN_THREADS / MAX_THREADS if the PUMA_ variables aren’t set).

If these environment variables aren’t set, the default is “0, 5” in MRI or “0, 16” for other interpreters.

Examples:

threads 0, 16

threads 5, 5

[ GitHub ]

# File 'lib/puma/dsl.rb', line 490


def threads(min, max)
  min = Integer(min)
  max = Integer(max)
  if min > max
    raise "The minimum (#{min}) number of threads must be less than or equal to the max (#{max})"
  end

  if max < 1
    raise "The maximum number of threads (#{max}) must be greater than 0"
  end

  @options[:min_threads] = min
  @options[:max_threads] = max
end

#wait_for_less_busy_worker(val = 0.005)

Attempts to route traffic to less-busy workers by causing them to delay listening on the socket, allowing workers which are not processing any requests to pick up new requests first.

Only works on MRI. For all other interpreters, this setting does nothing.

See Also:

Version:

5.0.0

[ GitHub ]

# File 'lib/puma/dsl.rb', line 999


def wait_for_less_busy_worker(val=0.005)
  @options[:wait_for_less_busy_worker] = val.to_f
end

#warn_if_in_single_mode(hook_name) (private)

[ GitHub ]

# File 'lib/puma/dsl.rb', line 1180


def warn_if_in_single_mode(hook_name)
  return if @options[:silence_fork_callback_warning]

  if (@options[:workers] || 0) == 0
    log_string =
      "Warning: You specified code to run in a `#{hook_name}` block, " \
      "but Puma is not configured to run in cluster mode (worker count > 0 ), " \
      "so your `#{hook_name}` block did not run"

    LogWriter.stdio.log(log_string)
  end
end

#worker_boot_timeout(timeout)

Note:

Cluster mode only.

Change the default worker timeout for booting.

If unspecified, this defaults to the value of worker_timeout.

Examples:

worker_boot_timeout 60

See Also:

Puma::Cluster::Worker#ping_timeout

[ GitHub ]

# File 'lib/puma/dsl.rb', line 926


def worker_boot_timeout(timeout)
  @options[:worker_boot_timeout] = Integer(timeout)
end

#worker_check_interval(interval)

Note:

Cluster mode only.

Change the default interval for checking workers.

The default value is 5 seconds.

Examples:

worker_check_interval 5

See Also:

Cluster#check_workers

[ GitHub ]

# File 'lib/puma/dsl.rb', line 888


def worker_check_interval(interval)
  @options[:worker_check_interval] = Integer(interval)
end

#worker_culling_strategy(strategy)

Note:

Cluster mode only.

Set the strategy for worker culling.

There are two possible values:

:youngest - the youngest workers (i.e. the workers that were the most recently started) will be culled.
:oldest - the oldest workers (i.e. the workers that were started the longest time ago) will be culled.

Examples:

worker_culling_strategy :oldest

See Also:

Cluster#cull_workers

[ GitHub ]

# File 'lib/puma/dsl.rb', line 953


def worker_culling_strategy(strategy)
  stategy = strategy.to_sym

  if ![:youngest, :oldest].include?(strategy)
    raise "Invalid value for worker_culling_strategy - #{stategy}"
  end

  @options[:worker_culling_strategy] = strategy
end

#worker_shutdown_timeout(timeout)

Note:

Cluster mode only.

Set the timeout for worker shutdown.

See Also:

Puma::Cluster::Worker#term

[ GitHub ]

# File 'lib/puma/dsl.rb', line 935


def worker_shutdown_timeout(timeout)
  @options[:worker_shutdown_timeout] = Integer(timeout)
end

#worker_timeout(timeout)

Note:

Cluster mode only.

Verifies that all workers have checked in to the master process within the given timeout. If not the worker process will be restarted. This is not a request timeout, it is to protect against a hung or dead process. Setting this value will not protect against slow requests.

This value must be greater than worker_check_interval. The default value is 60 seconds.

Examples:

worker_timeout 60

See Also:

Puma::Cluster::Worker#ping_timeout

[ GitHub ]

# File 'lib/puma/dsl.rb', line 905


def worker_timeout(timeout)
  timeout = Integer(timeout)
  min = @options.fetch(:worker_check_interval, Configuration::DEFAULTS[:worker_check_interval])

  if timeout <= min
    raise "The minimum worker_timeout must be greater than the worker reporting interval (#{min})"
  end

  @options[:worker_timeout] = timeout
end

#workers(count)

Note:

Cluster mode only.

How many worker processes to run. Typically this is set to the number of available cores.

The default is the value of the environment variable WEB_CONCURRENCY if set, otherwise 0.

See Also:

Cluster

[ GitHub ]

# File 'lib/puma/dsl.rb', line 584


def workers(count)
  @options[:workers] = count.to_i
end

Class: Puma::DSL

Overview

Constant Summary

Class Method Summary

Instance Method Summary

Constructor Details

.new(options, config) ⇒ DSL

Class Method Details

.ssl_bind_str(host, port, opts)

Instance Method Details

#_load_from(path)

#_offer_plugins

#activate_control_app(url = "auto", opts = {})

#add_pem_values_to_options_store(opts) (private)

#after_worker_boot(&block)

#after_worker_fork(&block) Also known as: #after_worker_boot

#app(obj = nil, &block)

#before_fork(&block)

#bind(url)

#bind_to_activated_sockets(bind = true)

#clean_thread_locals(which = true)

#clear_binds!

#custom_logger(custom_logger)

#debug

#default_host

#directory(dir)

#drain_on_shutdown(which = true)

#early_hints(answer = true)

#environment(environment)

#extra_runtime_dependencies(answer = [])

#first_data_timeout(seconds)

#force_shutdown_after(val = :forever)

#fork_worker(after_requests = 1000)

#get(key, default = nil)

#http_content_length_limit(limit)

#idle_timeout(seconds)

#inject(&blk)

#io_selector_backend(backend)

#load(file)

#log_formatter(&block)

#log_requests(which = true)

#lowlevel_error_handler(obj = nil, &block)

#max_fast_inline(num_of_requests)

#mutate_stdout_and_stderr_to_sync_on_write(enabled = true)

#on_booted(&block)

#on_refork(key = nil, &block)

#on_restart(&block)

#on_thread_exit(&block)

#on_thread_start(&block)

#on_worker_boot(key = nil, &block)

#on_worker_fork(&block)

#on_worker_shutdown(key = nil, &block)

#out_of_band(&block)

#persistent_timeout(seconds)

#pidfile(path)

#plugin(name)

#port(port, host = nil)

#preload_app!(answer = true)

#process_hook(options_key, key, block, meth) (private)

#prune_bundler(answer = true)

#queue_requests(answer = true)

#quiet(which = true)

#rack_url_scheme(scheme = nil)

#rackup(path)

#raise_exception_on_sigterm(answer = true)

#restart_command(cmd)

#set_default_host(host)

#set_remote_address(val = :socket)

#shutdown_debug(val = true)

#silence_fork_callback_warning

#silence_single_worker_warning

#ssl_bind(host, port, opts = {})

#state_path(path)

#state_permission(permission)

#stdout_redirect(stdout = nil, stderr = nil, append = false)

#supported_http_methods(methods)

#tag(string)

#threads(min, max)

#wait_for_less_busy_worker(val = 0.005)

#warn_if_in_single_mode(hook_name) (private)

.new(options, config) ⇒ `DSL`