Class: ZK::Server::SubProcess

Inherits:
Base
  • Object
show all
Defined in:
lib/zk-server/sub_process.rb

Overview

This encapsulates the logic of running the zookeeper server, as a sub-process. It is intended that it will be stopped and started with the process that starts it. We are not going to do daemonized process management.

By default, we will create a directory in the current working directory called 'zk-server' to store our data under (configurable).

Instance Attribute Summary collapse

Attributes inherited from Base

#config

Instance Method Summary collapse

Methods inherited from Base

#clobber!, #create_files!, #ping?, #wait_until_ping, #write_log4j_properties!, #write_myid!, #write_zoo_cfg!

Methods included from Logging

#logger

Constructor Details

#initialize(opts = {}) ⇒ SubProcess

Returns a new instance of SubProcess.



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# File 'lib/zk-server/sub_process.rb', line 16

def initialize(opts={})
  @exit_watching_thread = nil

  @pid = nil
  @status = nil

  super
end

Instance Attribute Details

#child_startup_timeout ⇒ Object

how long should we wait for the child to start responding to 'ruok'?



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# File 'lib/zk-server/sub_process.rb', line 14

def child_startup_timeout
  @child_startup_timeout
end

#status ⇒ Object (readonly)

Returns the value of attribute status.



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# File 'lib/zk-server/sub_process.rb', line 11

def status
  @status
end

Instance Method Details

#alive? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/zk-server/sub_process.rb', line 39

def alive?
  return false unless spawned?
  false|kill(0)
rescue Errno::ESRCH
  false
end

#fork_and_exec! ⇒ Object (protected) 



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# File 'lib/zk-server/sub_process.rb', line 158

def fork_and_exec!
  @pid ||= 
    fork do                 # gah, use fork because 1.8.7 sucks
      3.upto(255) do |fd|
        begin
          if io = IO.new(fd)
            io.close
          end
        rescue
        end
      end

      $stderr.puts "stdio_redirect_path: #{stdio_redirect_path.inspect}"
      $stdout.reopen($stderr)
      $stderr.reopen(stdio_redirect_path, 'a')

      exec(*command_args)
    end
end

#join ⇒ Object

wait for sub-process to exit



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# File 'lib/zk-server/sub_process.rb', line 26

def join
  @mutex.synchronize do
    logger.debug { "spawned process #{@pid}" }
    @exit_cond.wait_until { @status }
  end
  @status.success?
end

#kill(signal) ⇒ Object 



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# File 'lib/zk-server/sub_process.rb', line 88

def kill(signal)
  raise "No pid yet!" unless @pid
  Process.kill(signal, @pid)
end

#pid ⇒ Object

the pid of our child process



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# File 'lib/zk-server/sub_process.rb', line 84

def pid
  @pid
end

#run ⇒ false, true

start the child, using the Base#config. we create the files necessary, fork the child, and wait 5s for the child to start responding to pings

Returns:

  • (false, true) —

    false if run has already been called on this instance true if we hav



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# File 'lib/zk-server/sub_process.rb', line 99

def run
  return false if @run_called
  @run_called = true

  create_files!

  if ZK::Server.mri_187?
    fork_and_exec!
  elsif ZK::Server.jruby? and not ZK::Server.ruby_19?
    raise "You must run Jruby in 1.9 compatibility mode! I'm very sorry, i need Kernel.spawn"
  else
    spawn!
  end

  spawn_exit_watching_thread

  unless wait_until_ping(@child_startup_timeout)
    raise "Oh noes! something went wrong!" unless running?
  end

  at_exit { self.shutdown }

  true
end

#running? ⇒ Boolean

true if the process was started and is still running

Returns:

  • (Boolean) 


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# File 'lib/zk-server/sub_process.rb', line 35

def running?
  spawned? and !@status and alive?
end

#shutdown ⇒ Object

shutdown the child, wait for it to exit, ensure it is dead



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# File 'lib/zk-server/sub_process.rb', line 52

def shutdown
  if @pid
    return if @status

    @mutex.synchronize do
      %w[HUP TERM KILL].each do |signal|
        logger.debug { "sending #{signal} to #{@pid}" }

        return unless running? # jruby doesn't seem to get @status ?

        begin
          kill(signal)
        rescue Errno::ESRCH
          return true
        end

        @exit_cond.wait(5) # check running? on next pass
      end
    end

    unless @exit_watching_thread.join(3) == @exit_watching_thread
      logger.warn { "exit watching thread didn't exit after 3 sec" }
    end

    @pid = @exit_watching_thread = nil

    logger.debug { "@status: #{@status}" }
  end
  true
end

#spawn! ⇒ Object (protected) 



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# File 'lib/zk-server/sub_process.rb', line 148

def spawn!
  @pid ||= (
    args = command_args()
    args << { :err => [:child, :out], :out => [stdio_redirect_path, 'w'] }
    ::Kernel.spawn({}, *command_args).tap do |pid|
      logger.debug { "Spawned process #{pid}" }
    end
  )
end

#spawn_exit_watching_thread ⇒ Object (protected) 



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# File 'lib/zk-server/sub_process.rb', line 125

def spawn_exit_watching_thread
  @exit_watching_thread ||= Thread.new do
    _, @status = Process.wait2(@pid)
    @mutex.synchronize do
      @exit_cond.broadcast
    end
  end
end

#spawned? ⇒ Boolean

have we started the child process?

Returns:

  • (Boolean) 


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# File 'lib/zk-server/sub_process.rb', line 47

def spawned?
  !!@pid
end

#wait_for_pid(timeout = 2) ⇒ Object (protected)

wait for up to timeout seconds to pass, polling for completion returns nil if the process didn't exit



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# File 'lib/zk-server/sub_process.rb', line 136

def wait_for_pid(timeout=2)
  times_up = timeout ? Time.now + timeout : 0

  while Time.now < times_up
    pid, stat = ::Process.wait2(@pid, ::Process::WNOHANG)
    return stat if stat
    sleep(0.01)
  end

  nil
end