[Rock-dev] [rock] #442: roby/syskit: Cleanup of Syskit::InstanceRequirements::Task

[rock]

#442: roby/syskit: Cleanup of Syskit::InstanceRequirements::Task
--------------------+--------------------
 Reporter:  thro02  |      Owner:
     Type:  defect  |     Status:  new
 Priority:  normal  |  Milestone:
Component:  base    |   Keywords:  syskit
--------------------+--------------------
 Not all obsolete instances of Syskit::InstanceRequirements::Task are
 picked up by the garbage collector.

 Situation is as follows:
 The orogen task monster_interface::InterfaceModule is used standalone and
 as dependency in an action, i.e.

 -- Modelling in syskit (simplified)
 {{{
 module 'Sherpa'
     profile 'Common' do
         define("monster_interface", monster_interface::InterfaceModule)
     end
 end

 class RobotActions < Roby::Action::Interface
     use_profile Sherpa::Common

     def set_posture(arguments = Hash.new)
         task = Sherpa::Tasks::SetPosture.new(arguments)
         monster = task.depends_on(monster_interface::InterfaceModule,
 :role => 'monster_interface')
         task
     end
 end
 }}}

 -- Calling at runtime via shell --
 1. monster_interface_def!
 2. set_posture!

 leads to a Roby::TaskStructure::PlannedBy
 {{{
 MonsterInterface::InterfaceModule::0x01
  --> Syskit::InstanceRequirements::Task::0x01   [ <--- this one originates
 from the monster_interface_def! call ]
  --> Syskit::InstanceRequirements::Task::0x02   [ <-- this one orignates
 from the set_posture call ]
 }}}

 When the set_posture action ends, one would expect the second
 Syskit::InstanceRequirements::Task to be cleaned up, however it isn't
 since its original dependency was defined on another
 MonsterInterface::InterfaceModule instance (say
 MonsterInterface::InterfaceModule::0x02) which has been merged into
 MonsterInterface::InterfaceModule::0x01.

 Thus only if MonsterInterface::InterfaceModule::0x01 is removed the
 PlannedBy relation is cleaned up properly.
 If calling the set_posture method more frequently we have a 'memory leak'
 and time consuming network merges.

 The current workaround clears the Syskit::InstanceRequirementsTasks in the
 Roby garbage collection based on some general constraints, i.e. checking
 for parents and matching the InstanceRequirementsTask interface. However,
 that should be actually fixed in Syskit and not in Roby.

-- 
Ticket URL: <https://rock.opendfki.de/ticket/442>
rock <https://rock.opendfki.de>
rock: the robot construction kit