Module: Einhorn::Command

Defined in:
lib/einhorn/command.rb,
lib/einhorn/command/interface.rb

Defined Under Namespace

Modules: Interface

Constant Summary collapse

MAX_SPINUP_INTERVAL =

Unbounded exponential backoff is not a thing: we run into problems if e.g., each of our hundred workers simultaneously fail to boot for the same ephemeral reason. Instead cap backoff by some reasonable maximum, so we don’t wait until the heat death of the universe to spin up new capacity.

30.0

Class Method Summary collapse

Class Method Details

.cull ⇒ Object 



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# File 'lib/einhorn/command.rb', line 433

def self.cull
  acked = Einhorn::WorkerPool.ack_count
  unsignaled = Einhorn::WorkerPool.unsignaled_count
  target = Einhorn::WorkerPool.ack_target

  if Einhorn::State.upgrading && acked >= target
    Einhorn::State.upgrading = false
    Einhorn.log_info("Upgraded successfully to version #{Einhorn::State.version} (Einhorn #{Einhorn::VERSION}).", :upgrade)
    Einhorn.send_tagged_message(:upgrade, "Upgrade done", true)
  end

  old_workers = Einhorn::WorkerPool.old_workers
  Einhorn.log_debug("#{acked} acked, #{unsignaled} unsignaled, #{target} target, #{old_workers.length} old workers")
  if !Einhorn::State.upgrading && old_workers.length > 0
    Einhorn.log_info("Killing off #{old_workers.length} old workers.", :upgrade)
    signal_all("USR2", old_workers)
  elsif Einhorn::State.upgrading && Einhorn::State.smooth_upgrade
    # In a smooth upgrade, kill off old workers one by one when we have
    # sufficiently many new workers.
    excess = (old_workers.length + acked) - target
    if excess > 0
      Einhorn.log_info("Smooth upgrade: killing off #{excess} old workers.", :upgrade)
      signal_all("USR2", old_workers.take(excess))
    else
      Einhorn.log_debug("Not killing old workers, as excess is #{excess}.")
    end
  end

  if unsignaled > target
    excess = Einhorn::WorkerPool.unsignaled_modern_workers_with_priority[0...(unsignaled-target)]
    Einhorn.log_info("Have too many workers at the current version, so killing off #{excess.length} of them.")
    signal_all("USR2", excess)
  end
end

.decrement ⇒ Object 



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# File 'lib/einhorn/command.rb', line 162

def self.decrement
  if Einhorn::State.config[:number] <= 1
    output = "Can't decrease number of workers (already at #{Einhorn::State.config[:number]}).  Run kill #{$$} if you really want to kill einhorn."
    $stderr.puts(output)
    return output
  end

  Einhorn::Event.break_loop
  old = Einhorn::State.config[:number]
  new = (Einhorn::State.config[:number] -= 1)
  output = "Decrementing number of workers from #{old} -> #{new}"
  $stderr.puts(output)
  output
end

.dumpable_state ⇒ Object 



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# File 'lib/einhorn/command.rb', line 195

def self.dumpable_state
  global_state = Einhorn::State.dumpable_state
  descriptor_state = Einhorn::Event.persistent_descriptors.map do |descriptor|
    descriptor.to_state
  end

  {
    :state => global_state,
    :persistent_descriptors => descriptor_state,
  }
end

.full_upgrade(options = {}) ⇒ Object

Parameters:

  • options (Hash) (defaults to: {})

Options Hash (options):

  • :smooth (Boolean) — default: false —

    Whether to perform a smooth or fleet upgrade. In a smooth upgrade, bring up new workers and cull old workers one by one as soon as there is a replacement. In a fleet upgrade, bring up all the new workers and don’t cull any old workers until they’re all up.



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# File 'lib/einhorn/command.rb', line 390

def self.full_upgrade(options={})
  options = {:smooth => false}.merge(options)

  Einhorn::State.smooth_upgrade = options.fetch(:smooth)
  reload_for_upgrade
end

.full_upgrade_fleet ⇒ Object 



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# File 'lib/einhorn/command.rb', line 400

def self.full_upgrade_fleet
  full_upgrade(:smooth => false)
end

.full_upgrade_smooth ⇒ Object 



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# File 'lib/einhorn/command.rb', line 397

def self.full_upgrade_smooth
  full_upgrade(:smooth => true)
end

.increment ⇒ Object 



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# File 'lib/einhorn/command.rb', line 153

def self.increment
  Einhorn::Event.break_loop
  old = Einhorn::State.config[:number]
  new = (Einhorn::State.config[:number] += 1)
  output = "Incrementing number of workers from #{old} -> #{new}"
  $stderr.puts(output)
  output
end

.louder(log = true) ⇒ Object 



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# File 'lib/einhorn/command.rb', line 557

def self.louder(log=true)
  Einhorn::State.verbosity -= 1 if Einhorn::State.verbosity > 0
  output = "Verbosity set to #{Einhorn::State.verbosity}"
  Einhorn.log_info(output) if log
  output
end

.mourn(pid) ⇒ Object

Mourn the death of your child



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# File 'lib/einhorn/command.rb', line 24

def self.mourn(pid)
  unless spec = Einhorn::State.children[pid]
    Einhorn.log_error("Could not find any config for exited child #{pid.inspect}! This probably indicates a bug in Einhorn.")
    return
  end

  Einhorn::State.children.delete(pid)

  # Unacked worker
  if spec[:type] == :worker && !spec[:acked]
    Einhorn::State.consecutive_deaths_before_ack += 1
    extra = ' before it was ACKed'
  else
    extra = nil
  end

  case type = spec[:type]
  when :worker
    Einhorn.log_info("===> Exited worker #{pid.inspect}#{extra}", :upgrade)
  when :state_passer
    Einhorn.log_debug("===> Exited state passing process #{pid.inspect}", :upgrade)
  else
    Einhorn.log_error("===> Exited process #{pid.inspect} has unrecgonized type #{type.inspect}: #{spec.inspect}", :upgrade)
  end
end

.next_index ⇒ Object 



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# File 'lib/einhorn/command.rb', line 259

def self.next_index
  all_indexes = Set.new(Einhorn::State.children.map { |k, st| st[:index] })
  0.upto(all_indexes.length) do |i|
    return i unless all_indexes.include?(i)
  end
end

.prepare_child_environment(index) ⇒ Object 



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# File 'lib/einhorn/command.rb', line 325

def self.prepare_child_environment(index)
  # This is run from the child
  ENV['EINHORN_MASTER_PID'] = Process.ppid.to_s
  ENV['EINHORN_SOCK_PATH'] = Einhorn::Command::Interface.socket_path
  if Einhorn::State.command_socket_as_fd
    socket = UNIXSocket.open(Einhorn::Command::Interface.socket_path)
    Einhorn::TransientState.socket_handles << socket
    ENV['EINHORN_SOCK_FD'] = socket.fileno.to_s
  end

  ENV['EINHORN_FD_COUNT'] = Einhorn::State.bind_fds.length.to_s
  Einhorn::State.bind_fds.each_with_index {|fd, i| ENV["EINHORN_FD_#{i}"] = fd.to_s}

  ENV['EINHORN_CHILD_INDEX'] = index.to_s

  # EINHORN_FDS is deprecated. It was originally an attempt to
  # match Upstart's nominal internal support for space-separated
  # FD lists, but nobody uses that in practice, and it makes
  # finding individual FDs more difficult
  ENV['EINHORN_FDS'] = Einhorn::State.bind_fds.map(&:to_s).join(' ')
end

.prepare_child_process ⇒ Object 



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# File 'lib/einhorn/command.rb', line 377

def self.prepare_child_process
  Process.setpgrp
  Einhorn.renice_self
end

.quieter(log = true) ⇒ Object 



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# File 'lib/einhorn/command.rb', line 550

def self.quieter(log=true)
  Einhorn::State.verbosity += 1 if Einhorn::State.verbosity < 2
  output = "Verbosity set to #{Einhorn::State.verbosity}"
  Einhorn.log_info(output) if log
  output
end

.reap ⇒ Object 



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# File 'lib/einhorn/command.rb', line 9

def self.reap
  begin
    while true
      Einhorn.log_debug('Going to reap a child process')

      pid = Process.wait(-1, Process::WNOHANG)
      return unless pid
      mourn(pid)
      Einhorn::Event.break_loop
    end
  rescue Errno::ECHILD
  end
end

.register_ack(pid) ⇒ Object 



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# File 'lib/einhorn/command.rb', line 77

def self.register_ack(pid)
  unless spec = Einhorn::State.children[pid]
    Einhorn.log_error("Could not find state for PID #{pid.inspect}; ignoring ACK.")
    return
  end

  if spec[:acked]
    Einhorn.log_error("Pid #{pid.inspect} already ACKed; ignoring new ACK.")
    return
  end

  if Einhorn::State.consecutive_deaths_before_ack > 0
    extra = ", breaking the streak of #{Einhorn::State.consecutive_deaths_before_ack} consecutive unacked workers dying"
  else
    extra = nil
  end
  Einhorn::State.consecutive_deaths_before_ack = 0

  spec[:acked] = true
  Einhorn.log_info("Up to #{Einhorn::WorkerPool.ack_count} / #{Einhorn::WorkerPool.ack_target} #{Einhorn::State.ack_mode[:type]} ACKs#{extra}")
  # Could call cull here directly instead, I believe.
  Einhorn::Event.break_loop
end

.register_manual_ack(pid) ⇒ Object 



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# File 'lib/einhorn/command.rb', line 50

def self.register_manual_ack(pid)
  ack_mode = Einhorn::State.ack_mode
  unless ack_mode[:type] == :manual
    Einhorn.log_error("Received a manual ACK for #{pid.inspect}, but ack_mode is #{ack_mode.inspect}. Ignoring ACK.")
    return
  end
  Einhorn.log_info("Received a manual ACK from #{pid.inspect}")
  register_ack(pid)
end

.register_timer_ack(time, pid) ⇒ Object 



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# File 'lib/einhorn/command.rb', line 60

def self.register_timer_ack(time, pid)
  ack_mode = Einhorn::State.ack_mode
  unless ack_mode[:type] == :timer
    Einhorn.log_error("Received a timer ACK for #{pid.inspect}, but ack_mode is #{ack_mode.inspect}. Ignoring ACK.")
    return
  end

  unless Einhorn::State.children[pid]
    # TODO: Maybe cancel pending ACK timers upon death?
    Einhorn.log_debug("Worker #{pid.inspect} died before its timer ACK happened.")
    return
  end

  Einhorn.log_info("Worker #{pid.inspect} has been up for #{time}s, so we are considering it alive.")
  register_ack(pid)
end

.reload ⇒ Object 



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# File 'lib/einhorn/command.rb', line 207

def self.reload
  unless Einhorn::State.respawn
    Einhorn.log_info("Not reloading einhorn because we're exiting")
    return
  end

  Einhorn.log_info("Reloading einhorn master (#{Einhorn::TransientState.script_name})...", :reload)

  # In case there's anything lurking
  $stdout.flush

  # Spawn a child to pass the state through the pipe
  read, write = Einhorn::Compat.pipe

  fork do
    Einhorn::TransientState.whatami = :state_passer
    Einhorn::State.children[Process.pid] = {type: :state_passer}
    Einhorn::State.generation += 1
    read.close

    begin
      write.write(YAML.dump(dumpable_state))
    rescue Errno::EPIPE => e
      e.message << " (state worker could not write state, which likely means the parent process has died)"
      raise e
    end
    write.close

    exit(0)
  end
  write.close

  unless Einhorn.can_safely_reload?
    Einhorn.log_error("Can not initiate einhorn master reload safely, aborting", :reload)
    Einhorn::State.reloading_for_upgrade = false
    read.close
    return
  end

  begin
    Einhorn.initialize_reload_environment
    respawn_commandline = Einhorn.upgrade_commandline(['--with-state-fd', read.fileno.to_s])
    respawn_commandline << { :close_others => false }
    Einhorn.log_info("About to re-exec einhorn master as #{respawn_commandline.inspect}", :reload)
    Einhorn::Compat.exec(*respawn_commandline)
  rescue SystemCallError => e
    Einhorn.log_error("Could not reload! Attempting to continue. Error was: #{e}", :reload)
    Einhorn::State.reloading_for_upgrade = false
    read.close
  end
end

.reload_for_upgrade ⇒ Object 



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# File 'lib/einhorn/command.rb', line 404

def self.reload_for_upgrade
  Einhorn::State.reloading_for_upgrade = true
  reload
end

.replenish ⇒ Object 



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# File 'lib/einhorn/command.rb', line 473

def self.replenish
  return unless Einhorn::State.respawn

  if !Einhorn::State.last_spinup
    replenish_immediately
  else
    replenish_gradually
  end
end

.replenish_gradually(max_unacked = nil) ⇒ Object 



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# File 'lib/einhorn/command.rb', line 499

def self.replenish_gradually(max_unacked=nil)
  return if Einhorn::TransientState.has_outstanding_spinup_timer
  return unless Einhorn::WorkerPool.missing_worker_count > 0

  # default to spinning up at most NCPU workers at once
  unless max_unacked
    begin
      @processor_count ||= Einhorn::Compat.processor_count
    rescue => err
      Einhorn.log_error(err.inspect)
      @processor_count = 1
    end
    max_unacked = @processor_count
  end

  if max_unacked <= 0
    raise ArgumentError.new("max_unacked must be positive")
  end

  # Exponentially backoff automated spinup if we're just having
  # things die before ACKing
  spinup_interval = Einhorn::State.config[:seconds] * (1.5 ** Einhorn::State.consecutive_deaths_before_ack)
  spinup_interval = [spinup_interval, MAX_SPINUP_INTERVAL].min
  seconds_ago = (Time.now - Einhorn::State.last_spinup).to_f

  if seconds_ago > spinup_interval
    unacked = Einhorn::WorkerPool.unacked_unsignaled_modern_workers.length
    if unacked >= max_unacked
      Einhorn.log_debug("There are #{unacked} unacked new workers, and max_unacked is #{max_unacked}, so not spinning up a new process")
    else
      msg = "Last spinup was #{seconds_ago}s ago, and spinup_interval is #{spinup_interval}s, so spinning up a new process"

      if Einhorn::State.consecutive_deaths_before_ack > 0
        Einhorn.log_info("#{msg} (there have been #{Einhorn::State.consecutive_deaths_before_ack} consecutive unacked worker deaths)", :upgrade)
      else
        Einhorn.log_debug(msg)
      end

      spinup
    end
  else
    Einhorn.log_debug("Last spinup was #{seconds_ago}s ago, and spinup_interval is #{spinup_interval}s, so not spinning up a new process")
  end

  Einhorn::TransientState.has_outstanding_spinup_timer = true
  Einhorn::Event::Timer.open(spinup_interval) do
    Einhorn::TransientState.has_outstanding_spinup_timer = false
    replenish
  end
end

.replenish_immediately ⇒ Object 



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# File 'lib/einhorn/command.rb', line 483

def self.replenish_immediately
  missing = Einhorn::WorkerPool.missing_worker_count
  if missing <= 0
    Einhorn.log_error("Missing is currently #{missing.inspect}, but should always be > 0 when replenish_immediately is called. This probably indicates a bug in Einhorn.")
    return
  end
  Einhorn.log_info("Launching #{missing} new workers")
  missing.times {spinup}
end

.reseed_random ⇒ Object

Reseed common ruby random number generators.

OpenSSL::Random uses the PID to reseed after fork, which means that if a long-lived master process over its lifetime spawns two workers with the same PID, those workers will start with the same OpenSSL seed.

Ruby >= 1.9 has a guard against this in SecureRandom, but any direct users of OpenSSL::Random will still be affected.

Ruby 1.8 didn’t even reseed the default random number generator used by Kernel#rand in certain releases.

bugs.ruby-lang.org/issues/4579



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# File 'lib/einhorn/command.rb', line 361

def self.reseed_random
  # reseed Kernel#rand
  srand

  # reseed OpenSSL::Random if it's loaded
  if defined?(OpenSSL::Random)
    if defined?(Random)
      seed = Random.new_seed
    else
      # Ruby 1.8
      seed = rand
    end
    OpenSSL::Random.seed(seed.to_s)
  end
end

.set_workers(new) ⇒ Object 



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# File 'lib/einhorn/command.rb', line 177

def self.set_workers(new)
  if new == Einhorn::State.config[:number]
    return ""
  end

  Einhorn::Event.break_loop
  old = Einhorn::State.config[:number]
  Einhorn::State.config[:number] = new
  output = "Altering worker count, #{old} -> #{new}. Will "
  if old < new
    output << "spin up additional workers."
  else
    output << "gracefully terminate workers."
  end
  $stderr.puts(output)
  output
end

.signal_all(signal, children = nil, record = true) ⇒ Object 



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# File 'lib/einhorn/command.rb', line 101

def self.signal_all(signal, children=nil, record=true)
  children ||= Einhorn::WorkerPool.workers

  signaled = {}
  Einhorn.log_info("Sending #{signal} to #{children.inspect}", :upgrade)

  children.each do |child|
    unless spec = Einhorn::State.children[child]
      Einhorn.log_error("Trying to send #{signal} to dead child #{child.inspect}. The fact we tried this probably indicates a bug in Einhorn.", :upgrade)
      next
    end

    if record
      if spec[:signaled].include?(signal)
        Einhorn.log_error("Re-sending #{signal} to already-signaled child #{child.inspect}. It may be slow to spin down, or it may be swallowing #{signal}s.", :upgrade)
      end
      spec[:signaled].add(signal)
    end

    begin
      Process.kill(signal, child)
    rescue Errno::ESRCH
    else
      signaled[child] = spec
    end
  end

  if Einhorn::State.signal_timeout && record
    Einhorn::Event::Timer.open(Einhorn::State.signal_timeout) do
      children.each do |child|
        spec = Einhorn::State.children[child]
        next unless spec # Process is already dead and removed by mourn
        signaled_spec = signaled[child]
        next unless signaled_spec # We got ESRCH when trying to signal
        if spec[:spinup_time] != signaled_spec[:spinup_time]
          Einhorn.log_info("Different spinup time recorded for #{child} after #{Einhorn::State.signal_timeout}s. This probably indicates a PID rollover.", :upgrade)
          next
        end

        Einhorn.log_info("Child #{child.inspect} is still active after #{Einhorn::State.signal_timeout}s. Sending SIGKILL.")
        begin
          Process.kill('KILL', child)
        rescue Errno::ESRCH
        end
        spec[:signaled].add('KILL')
      end
    end
  end

  "Successfully sent #{signal}s to #{signaled.length} processes: #{signaled.keys}"
end

.spinup(cmd = nil) ⇒ Object 



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# File 'lib/einhorn/command.rb', line 266

def self.spinup(cmd=nil)
  cmd ||= Einhorn::State.cmd
  index = next_index
  if Einhorn::TransientState.preloaded
    pid = fork do
      Einhorn::TransientState.whatami = :worker
      prepare_child_process

      Einhorn.log_info('About to tear down Einhorn state and run einhorn_main')
      Einhorn::Command::Interface.uninit
      Einhorn::Event.close_all_for_worker
      Einhorn.set_argv(cmd, true)

      reseed_random

      prepare_child_environment(index)
      einhorn_main
    end
  else
    pid = fork do
      Einhorn::TransientState.whatami = :worker
      prepare_child_process

      Einhorn.log_info("About to exec #{cmd.inspect}")
      # Here's the only case where cloexec would help. Since we
      # have to track and manually close FDs for other cases, we
      # may as well just reuse close_all rather than also set
      # cloexec on everything.
      #
      # Note that Ruby 1.9's close_others option is useful here.
      Einhorn::Event.close_all_for_worker

      prepare_child_environment(index)
      Einhorn::Compat.exec(cmd[0], cmd[1..-1], :close_others => false)
    end
  end

  Einhorn.log_info("===> Launched #{pid} (index: #{index})", :upgrade)
  Einhorn::State.last_spinup = Time.now
  Einhorn::State.children[pid] = {
    :type => :worker,
    :version => Einhorn::State.version,
    :acked => false,
    :signaled => Set.new,
    :index => index,
    :spinup_time => Einhorn::State.last_spinup,
  }

  # Set up whatever's needed for ACKing
  ack_mode = Einhorn::State.ack_mode
  case type = ack_mode[:type]
  when :timer
    Einhorn::Event::ACKTimer.open(ack_mode[:timeout], pid)
  when :manual
  else
    Einhorn.log_error("Unrecognized ACK mode #{type.inspect}")
  end
end

.stop_respawning ⇒ Object 



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# File 'lib/einhorn/command.rb', line 468

def self.stop_respawning
  Einhorn::State.respawn = false
  Einhorn::Event.break_loop
end

.upgrade_workers ⇒ Object 



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# File 'lib/einhorn/command.rb', line 409

def self.upgrade_workers
  if Einhorn::State.upgrading
    Einhorn.log_info("Currently upgrading (#{Einhorn::WorkerPool.ack_count} / #{Einhorn::WorkerPool.ack_target} ACKs; bumping version and starting over)...", :upgrade)
  else
    Einhorn::State.upgrading = true
    u_type = Einhorn::State.smooth_upgrade ? 'smooth' : 'fleet'
    Einhorn.log_info("Starting #{u_type} upgrade from version" +
                     " #{Einhorn::State.version}...", :upgrade)
  end

  # Reset this, since we've just upgraded to a new universe (I'm
  # not positive this is the right behavior, but it's not
  # obviously wrong.)
  Einhorn::State.consecutive_deaths_before_ack = 0
  Einhorn::State.last_upgraded = Time.now

  Einhorn::State.version += 1
  if Einhorn::State.smooth_upgrade
    replenish_gradually
  else
    replenish_immediately
  end
end