Class: Flamingo::Daemon::Flamingod

Inherits:
Object
  • Object
show all
Includes:
TrapKeeper
Defined in:
lib/flamingo/daemon/flamingod.rb

Overview

Flamingod is the main overseer of the Flamingo flock.

Starts three sets of children:

  • A wader process: initiates stream request, pushes each response into the queue

  • A Sinatra server: lightweight responder to create and manage subscriptions

  • A set of dispatchers: worker processes that handle each stream response.

You can control the flamingod with the following signals:

  • TERM and INT will kill the flamingod parent process, and signal each child with TERM

  • USR1 will restart the wader gracefully.

Instance Method Summary collapse

Methods included from TrapKeeper

trap

Instance Method Details

#children ⇒ Object 



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# File 'lib/flamingo/daemon/flamingod.rb', line 90

def children
  ([@wader,@web_server] + @dispatchers).compact
end

#clear_process_meta_data ⇒ Object 



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# File 'lib/flamingo/daemon/flamingod.rb', line 161

def clear_process_meta_data
  meta = Flamingo.meta
  meta.delete(:start_time)
  meta.delete(:host)
  meta.delete(:pid)
  meta[:running] = false
end

#exit_signaled=(val) ⇒ Object 



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# File 'lib/flamingo/daemon/flamingod.rb', line 27

def exit_signaled=(val)
  Flamingo.logger.info "Exit signal set to #{val}"
  @exit_signaled = val
end

#exit_signaled? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/flamingo/daemon/flamingod.rb', line 23

def exit_signaled?
  @exit_signaled
end

#handle_wader_exit(status) ⇒ Object 



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# File 'lib/flamingo/daemon/flamingod.rb', line 124

def handle_wader_exit(status)
  if WaderProcess.fatal_exit?(status)
    Flamingo.logger.error "Wader exited with status "+
      "#{status.exitstatus} and cannot be automatically restarted"
    $stderr.write("Wader exited with fatal error. Check the the log.")
    terminate!
  else
    @wader = start_new_wader
  end
end

#restart_wader ⇒ Object 



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# File 'lib/flamingo/daemon/flamingod.rb', line 60

def restart_wader
  if @wader
    Flamingo.logger.info "Flamingod restarting wader pid=#{@wader.pid} with SIGINT"
    @wader.kill("INT")
  else
    Flamingo.logger.info "Wader is not started. Attempting to start new wader."
    @wader = start_new_wader
  end
end

#run ⇒ Object 



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# File 'lib/flamingo/daemon/flamingod.rb', line 169

def run
  $0 = 'flamingod'
  Flamingo.logger.info "Flamingod version: #{Flamingo::VERSION}"
  set_process_meta_data
  trap_signals
  start_children
  wait_on_children
  clear_process_meta_data
end

#run_as_daemon ⇒ Object 



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# File 'lib/flamingo/daemon/flamingod.rb', line 135

def run_as_daemon
  pid_file = PidFile.new
  if pid_file.running?
    raise "flamingod process #{pid_file.read} appears to be running"
  end
  pid = fork do
    pid_file.write(Process.pid)
    [$stdout,$stdin,$stderr].each do |io|
      io.reopen '/dev/null' rescue nil
    end
    run
    clear_process_meta_data
    pid_file.delete
  end
  Process.detach(pid)
  pid
end

#set_process_meta_data ⇒ Object 



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# File 'lib/flamingo/daemon/flamingod.rb', line 153

def set_process_meta_data
  meta = Flamingo.meta
  meta[:start_time] = Time.now.utc.to_i
  meta[:host] = `hostname`.chomp rescue nil
  meta[:pid] = Process.pid
  meta[:running] = true
end

#signal_children(sig) ⇒ Object 



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# File 'lib/flamingo/daemon/flamingod.rb', line 70

def signal_children(sig)
  pids = (children.map {|c| c.pid}).join(",")
  Flamingo.logger.info "Flamingod sending SIG#{sig} to pids=#{pids}"
  children.each do |child|
    if child.running?
      begin
        child.signal(sig)
      rescue => e
        Flamingo.logger.info "Failure sending SIG#{sig} to child #{child.pid}: #{e}"
      end
    end
  end
end

#start_children ⇒ Object 



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# File 'lib/flamingo/daemon/flamingod.rb', line 94

def start_children
  Flamingo.logger.info "Flamingod starting children"
  @wader = start_new_wader
  @dispatchers = [start_new_dispatcher]
  @web_server = start_new_web_server
end

#start_new_dispatcher ⇒ Object 



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# File 'lib/flamingo/daemon/flamingod.rb', line 39

def start_new_dispatcher
  Flamingo.logger.info "Flamingod starting new dispatcher"
  dispatcher = DispatcherProcess.new
  dispatcher.start
  dispatcher
end

#start_new_wader ⇒ Object 



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# File 'lib/flamingo/daemon/flamingod.rb', line 32

def start_new_wader
  Flamingo.logger.info "Flamingod starting new wader"
  wader = WaderProcess.new
  wader.start
  wader
end

#start_new_web_server ⇒ Object 



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# File 'lib/flamingo/daemon/flamingod.rb', line 46

def start_new_web_server
  Flamingo.logger.info "Flamingod starting new web server"
  ws = WebServerProcess.new
  ws.start
  ws
end

#terminate! ⇒ Object 



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# File 'lib/flamingo/daemon/flamingod.rb', line 84

def terminate!
  Flamingo.logger.info "Flamingod terminating"
  self.exit_signaled = true
  signal_children("INT")
end

#trap_signals ⇒ Object 



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# File 'lib/flamingo/daemon/flamingod.rb', line 53

def trap_signals
  trap("KILL") { terminate! }
  trap("TERM") { terminate! }
  trap("INT")  { terminate! }
  trap("USR1") { restart_wader }
end

#wait_on_children ⇒ Object

Unless signaled externally, waits in an endless loop. If any child process terminates, it restarts that process. TODO Needs intelligent behavior so we don’t get endless loops



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# File 'lib/flamingo/daemon/flamingod.rb', line 105

def wait_on_children()
  until exit_signaled?
    child_pid = Process.wait(-1)
    child_status = $?
    unless exit_signaled?
      if @wader && @wader.pid == child_pid
        handle_wader_exit(child_status)
      elsif @web_server.pid == child_pid
        @web_server = start_new_web_server
      elsif (to_delete = @dispatchers.find{|d| d.pid == child_pid})
        @dispatchers.delete(to_delete)
        @dispatchers << start_new_dispatcher
      else
        Flamingo.logger.info "Received exit from unknown child #{child_pid}"
      end
    end
  end
end