Module: Angael::Worker

Includes:
ProcessHelper
Defined in:
lib/angael/worker.rb

Overview

Usage

include Angael::Worker
def work
  # Do something interesting, without raising an exception.
end

You can also add some optional behavior by defining the following methods:

#after_fork - This is run once, immediately after the child process is forked
#fork_child - This actually does the forking. You can overwrite this method
              to do wrap the child process in a block. This is useful for
              exception handling. Be sure to actually fork or you may break
              something important.
#log        - If defined, this will be called at various points of interest
              with 1 String as the argument. Log levels are not supported.
#timeout    - Number of seconds to wait for the child process to exit after
              it is sent SIGINT. If you don't define this method, it waits
              60 seconds.

Defined Under Namespace

Classes: ChildProcessNotStoppedError

Instance Attribute Summary collapse

Instance Method Summary collapse

Methods included from ProcessHelper

#exit_status, #send_signal

Instance Attribute Details

#pid ⇒ Object (readonly)

Returns the value of attribute pid.



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# File 'lib/angael/worker.rb', line 23

def pid
  @pid
end

Instance Method Details

#restart! ⇒ Object

This only exists for the sake of testing. I need a way to stub the restart! but not the original start! Note: this method is not tested directly. Users of this library should not call this method or depend on its existence or behavior.



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# File 'lib/angael/worker.rb', line 64

def restart!
  start!
end

#start! ⇒ Object

Loops forever, taking jobs off the queue. SIGINT will stop it after allowing any jobs already taken from the queue to be processed.



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# File 'lib/angael/worker.rb', line 27

def start!
  @stopping = false

  @pid = fork_child do
    __log("Started")

    if respond_to?(:after_fork)
      __log("Running after fork callback")
      after_fork
      __log("Finished running after fork callback")
    end

    @interrupted = false
    trap("INT") do
      __log("SIGINT Received")
      @interrupted = true
    end
    trap("TERM") do
      __log("SIGTERM Received")
      @interrupted = true
    end

    loop do
      if @interrupted
        __log("Child process exiting gracefully")
        exit 0
      end
      work
    end
  end
end

#started? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/angael/worker.rb', line 117

def started?
  !!(pid && pid_running?)
end

#stop_with_wait ⇒ Object

Keeps sending SIGINT until the child process exits. If #timeout seconds pass, then it sends 1 SIGKILL. If that also fails, it raises ChildProcessNotStoppedError.



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# File 'lib/angael/worker.rb', line 89

def stop_with_wait
  return false unless stop_without_wait

  __log("Waiting for child process with pid #{pid} to stop.")

  counter = 0

  while pid_running? && counter < timeout
    sleep 1
    counter += 1
    __log("Sending SIGINT to child process with pid #{pid}. Attempt Count: #{counter}.")
    send_signal('INT', pid)
  end

  if pid_running?
    __log("Child process with pid #{pid} did not stop within #{timeout} seconds of SIGINT. Sending SIGKILL to child process.")
    send_signal('KILL', pid)
    sleep 1
  end

  if pid_running?
    # SIGKILL didn't work.
    msg = "Unable to kill child process with PID: #{pid}"
    __log(msg)
    raise ChildProcessNotStoppedError, msg
  end
end

#stop_without_wait ⇒ Object

Returns true if SIGINT was sent to the child process, even if the child process does not exists. Returns false if started? is true. Sets stopping? to false.



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# File 'lib/angael/worker.rb', line 72

def stop_without_wait
  unless started?
    __log("Tried to stop worker with PID #{pid} but it is not started")
    return false
  end

  # This informs the Manager (through #stopping?) that we intentionally
  # stopped the child process.
  @stopping = true

  __log("Sending SIGINT to child process with pid #{pid}.")
  send_signal('INT', pid)
  true
end

#stopped? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/angael/worker.rb', line 120

def stopped?
  !started?
end

#stopping? ⇒ Boolean

TODO: test this

Returns:

  • (Boolean) 


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# File 'lib/angael/worker.rb', line 124

def stopping?
  @stopping
end