Class: Ruote::EngineParticipant

Inherits:
Object
  • Object
show all
Includes:
LocalParticipant
Defined in:
lib/ruote/part/engine_participant.rb

Overview

A participant for pushing the execution of [segments of] processes to other engines.

It works by giving the participant the connection information to the storage of the other engine.

For instance :

engine0 =
  Ruote::Engine.new(
    Ruote::Worker.new(
      Ruote::FsStorage.new('work0', 'engine_id' => 'engine0')))
engine1 =
  Ruote::Engine.new(
    Ruote::Worker.new(
      Ruote::FsStorage.new('work1', 'engine_id' => 'engine1')))

engine0.register_participant('engine1',
  Ruote::EngineParticipant,
  'storage_class' => Ruote::FsStorage,
  'storage_path' => 'ruote/storage/fs_storage',
  'storage_args' => 'work1')
engine1.register_participant('engine0',
  Ruote::EngineParticipant,
  'storage_class' => Ruote::FsStorage,
  'storage_path' => 'ruote/storage/fs_storage',
  'storage_args' => 'work0')

In this example, two engines are created (note that their ‘engine_id’ is explicitely set (else it would default to ‘engine’)). Each engine is then registered as participant in the other engine. The registration parameters detail the class and the arguments to the storage of the target engine.

This example is a bit dry / flat. A real world example would perhaps detail a ‘master’ engine connected to ‘departmental’ engines, something more hierarchical.

The example also binds reciprocally engines. If the delegated processes are always ‘forgotten’, one could imagine not binding the source engine as a participant in the target engine (not need to answer back).

There are then two variants for calling a subprocess

subprocess :ref => 'subprocess_name', :engine => 'engine1'
  # or
participant :ref => 'engine1', :pdef => 'subprocess_name'

It’s OK to go for the shorter versions :

subprocess_name :engine => 'engine1'
  # or
participant 'engine1', :pdef => 'subprocess_name'
engine1 :pdef => 'subprocess_name'

The subprocess is defined in the current process, or it’s given via its URL. The third variant is a subprocess bound as an engine variable.

engine.variables['variant_3'] = Ruote.process_definition do
  participant 'hello_world_3'
end

pdef = Ruote.process_definition do
  sequence do
    engine1 :pdef => 'variant_1'
    engine1 :pdef => 'http://pdefs.example.com/variant_2.rb'
    engine1 :pdef => 'variant_3'
  end
  define 'variant_1' do
    participant 'hello_world_1'
  end
end

Instance Attribute Summary

Attributes included from LocalParticipant

#context

Instance Method Summary collapse

Methods included from LocalParticipant

#re_dispatch, #unschedule_re_dispatch

Methods included from ReceiverMixin

#applied_workitem, #fetch_flow_expression, #launch, #receive, #reply_to_engine, #sign

Constructor Details

#initialize(opts) ⇒ EngineParticipant

Returns a new instance of EngineParticipant.

Raises:

  • (ArgumentError) 


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# File 'lib/ruote/part/engine_participant.rb', line 108

def initialize(opts)

  if pa = opts['storage_path']
    require pa
  end

  kl = opts['storage_class']

  raise(ArgumentError.new("missing 'storage_class' parameter")) unless kl

  args = opts['storage_args']
  args = args.is_a?(Hash) ? [ args ] : Array(args)
  args << {} unless args.last.is_a?(Hash)
  args.last['preserve_configuration'] = true

  @storage = Ruote.constantize(kl).new(*args)
end

Instance Method Details

#cancel(fei, flavour) ⇒ Object 



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# File 'lib/ruote/part/engine_participant.rb', line 149

def cancel(fei, flavour)

  exps = @storage.get_many('expressions', /^0![^!]+!#{fei.wfid}$/)

  return true if exps.size < 1
    # participant expression will reply to its parent

  @storage.put_msg(
    'cancel',
    'fei' => exps.first['fei'],
    'flavour' => flavour)

  false
    # participant expression will NOT reply to its parent
end

#consume(workitem) ⇒ Object 



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# File 'lib/ruote/part/engine_participant.rb', line 126

def consume(workitem)

  wi = workitem.to_h
  fexp = Ruote::Exp::FlowExpression.fetch(@context, wi['fei'])
  params = wi['fields'].delete('params')

  forget = (fexp.attribute(:forget).to_s == 'true')

  @storage.put_msg(
    'launch',
    'wfid' => wi['fei']['wfid'],
    'parent_id' => forget ? nil : wi['fei'],
    'tree' => determine_tree(fexp, params),
    'workitem' => wi,
    'variables' => fexp.compile_variables)

  fexp.unpersist if forget
    #
    # special behaviour here in case of :forget => true :
    # parent_id of remote expression is set to nil and local expression
    # is unpersisted immediately
end

#reply(fei, workitem) ⇒ Object 



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# File 'lib/ruote/part/engine_participant.rb', line 165

def reply(fei, workitem)

  @storage.put_msg(
    'reply',
    'fei' => fei,
    'workitem' => workitem)
end