Class: Puma::Cluster

Inherits:
Runner show all
Defined in:
lib/puma/cluster.rb,
lib/puma/cluster/worker.rb,
lib/puma/cluster/worker_handle.rb

Overview

This class is instantiated by the ‘Puma::Launcher` and used to boot and serve a Ruby application when puma “workers” are needed i.e. when using multi-processes. For example `$ puma -w 5`

An instance of this class will spawn the number of processes passed in via the ‘spawn_workers` method call. Each worker will have it’s own instance of a ‘Puma::Server`.

Defined Under Namespace

Classes: Worker, WorkerHandle

Instance Attribute Summary collapse

Attributes inherited from Runner

#app, #options, #ruby_engine

Instance Method Summary collapse

Methods inherited from Runner

#close_control_listeners, #debug, #development?, #error, #load_and_bind, #log, #output_header, #redirected_io?, #start_control, #start_server, #stop_control, #test?, #wakeup!

Constructor Details

#initialize(launcher) ⇒ Cluster

Returns a new instance of Cluster.



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# File 'lib/puma/cluster.rb', line 18

def initialize(launcher)
  super(launcher)

  @phase = 0
  @workers = []
  @next_check = Time.now

  @phased_restart = false
end

Instance Attribute Details

#next_worker_index ⇒ Object (readonly) 



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# File 'lib/puma/cluster.rb', line 142

def next_worker_index
  occupied_positions = @workers.map(&:index)
  idx = 0
  idx += 1 until !occupied_positions.include?(idx)
  idx
end

#stats ⇒ Object (readonly)

Inside of a child process, this will return all zeroes, as @workers is only populated in the master process.



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# File 'lib/puma/cluster.rb', line 255

def stats
  old_worker_count = @workers.count { |w| w.phase != @phase }
  worker_status = @workers.map do |w|
    {
      started_at: utc_iso8601(w.started_at),
      pid: w.pid,
      index: w.index,
      phase: w.phase,
      booted: w.booted?,
      last_checkin: utc_iso8601(w.last_checkin),
      last_status: w.last_status,
    }
  end

  {
    started_at: utc_iso8601(@started_at),
    workers: @workers.size,
    phase: @phase,
    booted_workers: worker_status.count { |w| w[:booted] },
    old_workers: old_worker_count,
    worker_status: worker_status,
  }.merge(super)
end

#workers ⇒ Array<Puma::Cluster::WorkerHandle> (readonly)

Returns the list of cluster worker handles.

Returns:



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# File 'lib/puma/cluster.rb', line 30

def workers
  @workers
end

Instance Method Details

#all_workers_booted? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/puma/cluster.rb', line 153

def all_workers_booted?
  @workers.count { |w| !w.booted? } == 0
end

#all_workers_in_phase? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/puma/cluster.rb', line 157

def all_workers_in_phase?
  @workers.all? { |w| w.phase == @phase }
end

#check_workers ⇒ Object 



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# File 'lib/puma/cluster.rb', line 161

def check_workers
  return if @next_check >= Time.now

  @next_check = Time.now + @options[:worker_check_interval]

  timeout_workers
  wait_workers
  cull_workers
  spawn_workers

  if all_workers_booted?
    # If we're running at proper capacity, check to see if
    # we need to phase any workers out (which will restart
    # in the right phase).
    #
    w = @workers.find { |x| x.phase != @phase }

    if w
      log "- Stopping #{w.pid} for phased upgrade..."
      unless w.term?
        w.term
        log "- #{w.signal} sent to #{w.pid}..."
      end
    end
  end

  t = @workers.reject(&:term?)
  t.map!(&:ping_timeout)

  @next_check = [t.min, @next_check].compact.min
end

#cull_start_index(diff) ⇒ Object 



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# File 'lib/puma/cluster.rb', line 132

def cull_start_index(diff)
  case @options[:worker_culling_strategy]
  when :oldest
    0
  else # :youngest
    -diff
  end
end

#cull_workers ⇒ Object 



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# File 'lib/puma/cluster.rb', line 108

def cull_workers
  diff = @workers.size - @options[:workers]
  return if diff < 1
  debug "Culling #{diff} workers"

  workers = workers_to_cull(diff)
  debug "Workers to cull: #{workers.inspect}"

  workers.each do |worker|
    log "- Worker #{worker.index} (PID: #{worker.pid}) terminating"
    worker.term
  end
end

#fork_worker! ⇒ Object

Version:

  • 5.0.0



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# File 'lib/puma/cluster.rb', line 284

def fork_worker!
  if (worker = worker_at 0)
    worker.phase += 1
  end
  phased_restart(true)
end

#halt ⇒ Object 



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# File 'lib/puma/cluster.rb', line 241

def halt
  @status = :halt
  wakeup!
end

#phased_restart(refork = false) ⇒ Object 



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# File 'lib/puma/cluster.rb', line 220

def phased_restart(refork = false)
  return false if @options[:preload_app] && !refork

  @phased_restart = true
  wakeup!

  true
end

#preload? ⇒ Boolean

Returns:

  • (Boolean) 


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

def preload?
  @options[:preload_app]
end

#redirect_io ⇒ Object 



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# File 'lib/puma/cluster.rb', line 59

def redirect_io
  super

  @workers.each { |x| x.hup }
end

#reload_worker_directory ⇒ Object 



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# File 'lib/puma/cluster.rb', line 246

def reload_worker_directory
  dir = @launcher.restart_dir
  log "+ Changing to #{dir}"
  Dir.chdir dir
end

#restart ⇒ Object 



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# File 'lib/puma/cluster.rb', line 215

def restart
  @restart = true
  stop
end

#run ⇒ Object 



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# File 'lib/puma/cluster.rb', line 344

def run
  @status = :run

  output_header "cluster"

  # This is aligned with the output from Runner, see Runner#output_header
  log "*      Workers: #{@options[:workers]}"

  if preload?
    # Threads explicitly marked as fork safe will be ignored. Used in Rails,
    # but may be used by anyone. Note that we need to explicit
    # Process::Waiter check here because there's a bug in Ruby 2.6 and below
    # where calling thread_variable_get on a Process::Waiter will segfault.
    # We can drop that clause once those versions of Ruby are no longer
    # supported.
    fork_safe = ->(t) { !t.is_a?(Process::Waiter) && t.thread_variable_get(:fork_safe) }

    before = Thread.list.reject(&fork_safe)

    log "*     Restarts: (\u2714) hot (\u2716) phased"
    log "* Preloading application"
    load_and_bind

    after = Thread.list.reject(&fork_safe)

    if after.size > before.size
      threads = (after - before)
      if threads.first.respond_to? :backtrace
        log "! WARNING: Detected #{after.size-before.size} Thread(s) started in app boot:"
        threads.each do |t|
          log "! #{t.inspect} - #{t.backtrace ? t.backtrace.first : ''}"
        end
      else
        log "! WARNING: Detected #{after.size-before.size} Thread(s) started in app boot"
      end
    end
  else
    log "*     Restarts: (\u2714) hot (\u2714) phased"

    unless @config.app_configured?
      error "No application configured, nothing to run"
      exit 1
    end

    @launcher.binder.parse @options[:binds]
  end

  read, @wakeup = Puma::Util.pipe

  setup_signals

  # Used by the workers to detect if the master process dies.
  # If select says that @check_pipe is ready, it's because the
  # master has exited and @suicide_pipe has been automatically
  # closed.
  #
  @check_pipe, @suicide_pipe = Puma::Util.pipe

  # Separate pipe used by worker 0 to receive commands to
  # fork new worker processes.
  @fork_pipe, @fork_writer = Puma::Util.pipe

  log "Use Ctrl-C to stop"

  single_worker_warning

  redirect_io

  Plugins.fire_background

  @launcher.write_state

  start_control

  @master_read, @worker_write = read, @wakeup

  @config.run_hooks(:before_fork, nil, @log_writer)

  spawn_workers

  Signal.trap "SIGINT" do
    stop
  end

  begin
    booted = false
    in_phased_restart = false
    workers_not_booted = @options[:workers]

    while @status == :run
      begin
        if @phased_restart
          start_phased_restart
          @phased_restart = false
          in_phased_restart = true
          workers_not_booted = @options[:workers]
        end

        check_workers

        if read.wait_readable([0, @next_check - Time.now].max)
          req = read.read_nonblock(1)

          @next_check = Time.now if req == "!"
          next if !req || req == "!"

          result = read.gets
          pid = result.to_i

          if req == "b" || req == "f"
            pid, idx = result.split(':').map(&:to_i)
            w = worker_at idx
            w.pid = pid if w.pid.nil?
          end

          if w = @workers.find { |x| x.pid == pid }
            case req
            when "b"
              w.boot!
              log "- Worker #{w.index} (PID: #{pid}) booted in #{w.uptime.round(2)}s, phase: #{w.phase}"
              @next_check = Time.now
              workers_not_booted -= 1
            when "e"
              # external term, see worker method, Signal.trap "SIGTERM"
              w.term!
            when "t"
              w.term unless w.term?
            when "p"
              status = result.sub(/^\d+/,'').chomp
              w.ping!(status)
              @events.fire(:ping!, w)

              if in_phased_restart && workers_not_booted.positive? && w0 = worker_at(0)
                w0.ping!(status)
                @events.fire(:ping!, w0)
              end

              if !booted && @workers.none? {|worker| worker.last_status.empty?}
                @events.fire_on_booted!
                debug_loaded_extensions("Loaded Extensions - master:") if @log_writer.debug?
                booted = true
              end
            end
          else
            log "! Out-of-sync worker list, no #{pid} worker"
          end
        end
        if in_phased_restart && workers_not_booted.zero?
          @events.fire_on_booted!
          debug_loaded_extensions("Loaded Extensions - master:") if @log_writer.debug?
          in_phased_restart = false
        end

      rescue Interrupt
        @status = :stop
      end
    end

    stop_workers unless @status == :halt
  ensure
    @check_pipe.close
    @suicide_pipe.close
    read.close
    @wakeup.close
  end
end

#setup_signals ⇒ Object

We do this in a separate method to keep the lambda scope of the signals handlers as small as possible.



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# File 'lib/puma/cluster.rb', line 293

def setup_signals
  if @options[:fork_worker]
    Signal.trap "SIGURG" do
      fork_worker!
    end

    # Auto-fork after the specified number of requests.
    if (fork_requests = @options[:fork_worker].to_i) > 0
      @events.register(:ping!) do |w|
        fork_worker! if w.index == 0 &&
          w.phase == 0 &&
          w.last_status[:requests_count] >= fork_requests
      end
    end
  end

  Signal.trap "SIGCHLD" do
    wakeup!
  end

  Signal.trap "TTIN" do
    @options[:workers] += 1
    wakeup!
  end

  Signal.trap "TTOU" do
    @options[:workers] -= 1 if @options[:workers] >= 2
    wakeup!
  end

  master_pid = Process.pid

  Signal.trap "SIGTERM" do
    # The worker installs their own SIGTERM when booted.
    # Until then, this is run by the worker and the worker
    # should just exit if they get it.
    if Process.pid != master_pid
      log "Early termination of worker"
      exit! 0
    else
      @launcher.close_binder_listeners

      stop_workers
      stop
      @events.fire_on_stopped!
      raise(SignalException, "SIGTERM") if @options[:raise_exception_on_sigterm]
      exit 0 # Clean exit, workers were stopped
    end
  end
end

#spawn_worker(idx, master) ⇒ Object

Version:

  • 5.0.0



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# File 'lib/puma/cluster.rb', line 94

def spawn_worker(idx, master)
  @config.run_hooks(:before_worker_fork, idx, @log_writer)

  pid = fork { worker(idx, master) }
  if !pid
    log "! Complete inability to spawn new workers detected"
    log "! Seppuku is the only choice."
    exit! 1
  end

  @config.run_hooks(:after_worker_fork, idx, @log_writer)
  pid
end

#spawn_workers ⇒ Object 



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# File 'lib/puma/cluster.rb', line 65

def spawn_workers
  diff = @options[:workers] - @workers.size
  return if diff < 1

  master = Process.pid
  if @options[:fork_worker]
    @fork_writer << "-1\n"
  end

  diff.times do
    idx = next_worker_index

    if @options[:fork_worker] && idx != 0
      @fork_writer << "#{idx}\n"
      pid = nil
    else
      pid = spawn_worker(idx, master)
    end

    debug "Spawned worker: #{pid}"
    @workers << WorkerHandle.new(idx, pid, @phase, @options)
  end

  if @options[:fork_worker] && all_workers_in_phase?
    @fork_writer << "0\n"
  end
end

#start_phased_restart ⇒ Object 



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# File 'lib/puma/cluster.rb', line 47

def start_phased_restart
  @events.fire_on_restart!
  @phase += 1
  log "- Starting phased worker restart, phase: #{@phase}"

  # Be sure to change the directory again before loading
  # the app. This way we can pick up new code.
  dir = @launcher.restart_dir
  log "+ Changing to #{dir}"
  Dir.chdir dir
end

#stop ⇒ Object 



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# File 'lib/puma/cluster.rb', line 229

def stop
  @status = :stop
  wakeup!
end

#stop_blocked ⇒ Object 



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# File 'lib/puma/cluster.rb', line 234

def stop_blocked
  @status = :stop if @status == :run
  wakeup!
  @control&.stop true
  Process.waitall
end

#stop_workers ⇒ Object 



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# File 'lib/puma/cluster.rb', line 32

def stop_workers
  log "- Gracefully shutting down workers..."
  @workers.each { |x| x.term }

  begin
    loop do
      wait_workers
      break if @workers.reject {|w| w.pid.nil?}.empty?
      sleep 0.2
    end
  rescue Interrupt
    log "! Cancelled waiting for workers"
  end
end

#worker(index, master) ⇒ Object 



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# File 'lib/puma/cluster.rb', line 193

def worker(index, master)
  @workers = []

  @master_read.close
  @suicide_pipe.close
  @fork_writer.close

  pipes = { check_pipe: @check_pipe, worker_write: @worker_write }
  if @options[:fork_worker]
    pipes[:fork_pipe] = @fork_pipe
    pipes[:wakeup] = @wakeup
  end

  server = start_server if preload?
  new_worker = Worker.new index: index,
                          master: master,
                          launcher: @launcher,
                          pipes: pipes,
                          server: server
  new_worker.run
end

#worker_at(idx) ⇒ Object 



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# File 'lib/puma/cluster.rb', line 149

def worker_at(idx)
  @workers.find { |w| w.index == idx }
end

#workers_to_cull(diff) ⇒ Object 



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# File 'lib/puma/cluster.rb', line 122

def workers_to_cull(diff)
  workers = @workers.sort_by(&:started_at)

  # In fork_worker mode, worker 0 acts as our master process.
  # We should avoid culling it to preserve copy-on-write memory gains.
  workers.reject! { |w| w.index == 0 } if @options[:fork_worker]

  workers[cull_start_index(diff), diff]
end