OASIS Team

1

ProActive PDC - MOP - JOnAs

• OASIS Team
• INRIA -- CNRS - I3S -- Univ. of Nice
  Sophia-Antipolis
• www.inria.fr/oasis/ProActive
• Francoise Baude, Denis Caromel, Fabrice Huet,
  Julien Vayssiere,
• Alexandre Bergel, Olivier Nano (IC2D)
• Mickael Bartorello, Helene Manguin, (ProActive -
  Interactions)
• Nico Guillier, Alexandre Guyot, Laurent Vaills
  (ProActive - EJB)
• 1. ProActive Non Functional
  properties
• 2. 1.MOP and 2. Meta-Objet
  for Distribution
• 3. IC2D
• 4. ProActive and EJB JOnAS

2
Non Functional Properties

• Currently in ProActive
• Remotely accessible Objects
• (Classes, not only Interfaces, Dynamic)
• Asynchronous Communications, Futures
• Migration
• Visualization and monitoring (IC2D)
• Others
• Security (worked on)
• Group Communications (thinking about it)
• Communications with disconnected mode

3
1. ProActive PDC Objectives and Rationale
Seamless
Sequential
Multithreaded
Distributed

• Most of the time, activities and distribution are
  not known at the beginning, and change over time
• Seamless implies reuse, smooth and incremental
  transitions

Library !
4
ProActive model

• Active objects coarse-grained structuring
  entities (subsystems)
• Each active object - possibly owns many passive
  objects
• - has exactly one thread.
• No shared passive objects -- Parameters are
  passed by deep-copy
• Asynchronous Communication between active objects
  
• Future objects and wait-by-necessity.
• Full control to serve incoming requests
  (reification)

5
ProActive Active object
Standard object

• An active object is composed of several objects
  
• The object itself (1)
• The body handles synchronization and the
  service of requests (2)
• The queue of pending requests (3)

1
Objet
Active object
Proxy
Object
1
2
Body
6
ProActive Creating active objects
Single inheritance using interface

• An object created with A a new A (obj, 7)
• can be turned into an active object
• Class-based
• class pA extends A implements Active
• A a (A)ProActive.newActive(pA,params,
  node)
• The most general case. Allows to provide a
  specific behavior.
• Instanciation-based
• A a (A)ProActive.newActive(A,params,
  node)
• Object-based
• A a new A (obj, 7)
• a (A)ProActive.turnActive (a, node)

7
ProActive Reuse and seamless

• Two key features
• Polymorphism between standard and active objects
• Type compatibility for classes (and not only
  interfaces)
• Needed and done for the future objects also
• Dynamic mechanism (dynamically achieved if
  needed)
• Wait-by-necessity inter-object synchronization
• Systematic, implicit and transparent futures
• Ease the programming of synchronizations,
  and the reuse of routines

8
2. ProActive Migration of active objects

• Migration is initiated by the active object
  itself through a primitive migrateTo
• Can be initiated from outside through any public
  method
• The active object migrates with
• all pending requests
• all its passive objects
• all its future objects
• Automatic and transparent forwarding of
• requests (remote references remain valid)
• replies (its previous queries will be
  fullfilled)

9
Characteristics and optimizations

• Same semantics guaranteed (RDV, FIFO order point
  to point, asynchronous)
• Safe migration (no agent in the air!)
• Local references if possible when arriving within
  a VM
• Tensionning (removal of forwarder)

10
Characteristics and optimizations

• Same semantics guaranteed (RDV, FIFO order point
  to point, asynchronous)
• Safe migration (no agent in the air!)
• Local references if possible when arriving within
  a VM
• Tensionning (removal of forwarder)

11
Characteristics and optimizations

• Same semantics guaranteed (RDV, FIFO order point
  to point, asynchronous)
• Safe migration (no agent in the air!)
• Local references if possible when arriving within
  a VM
• Tensionning (removal of forwarder)

direct
12
Characteristics and optimizations

• Same semantics guaranteed (RDV, FIFO order point
  to point, asynchronous)
• Safe migration (no agent in the air!)
• Local references if possible when arriving within
  a VM
• Tensionning (removal of forwarder)

direct
direct
13
Characteristics and optimizations

• Same semantics guaranteed (RDV, FIFO order point
  to point, asynchronous)
• Safe migration (no agent in the air!)
• Local references if possible when arriving within
  a VM
• Tensionning (removal of forwarder)

direct
forwarder
direct
14
Characteristics and optimizations

• Same semantics guaranteed (RDV, FIFO order point
  to point, asynchronous)
• Safe migration (no agent in the air!)
• Local references if possible when arriving within
  a VM
• Tensionning (removal of forwarder)

direct
forwarder
direct
15
Characteristics and optimizations

• Same semantics guaranteed (RDV, FIFO order point
  to point, asynchronous)
• Safe migration (no agent in the air!)
• Local references if possible when arriving within
  a VM
• Tensionning (removal of forwarder)

direct
forwarder
direct
16
Characteristics and optimizations

• Same semantics guaranteed (RDV, FIFO order point
  to point, asynchronous)
• Safe migration (no agent in the air!)
• Local references if possible when arriving within
  a VM
• Tensionning (removal of forwarder)

direct
forwarder
direct
17
ProActive API for Mobile Agents

• Mobile agents (active objects) that communicate
• Basic primitive migrateTo
• public static void migrateTo (String u)
• // string to specify the node (VM)
• public static void migrateTo (Object o)
• // joinning another active object
• public static void migrateTo (Node n)
• // ProActive node (VM)
• public static void migrateTo (JiniNode n)
• // ProActive node (VM)

18
2.1 ProActive architecture a simple MOP

• MOP (Meta-Object Protocol)
• Runtime reflection (for dynamicity)
• New semantics for method and constructor calls
• Uses the Java Reflection API
• ProActive
• Implemented on top of the MOP
• Other models can be built on top of ProActive or
  on top of the MOP

19
Principes du MOP

• Génération statique ou dynamique de stub
• Réifie linvocation de méthode
• Représente lobjet réifié
• Sous-classe lobjet réifié typage respecté
• Le stub depend uniquement de lobjet réifié,
• pas du proxy
• Chaque méthode fabrique un objet Call
  représentant son invocation et le passe à un proxy

Objet réifié
Stub
Proxy
20
The MOP - principle
- Object effarray - String methodname - Object
res
Objet classique
- Object reify (Call c)
Objet réifié
PROXY_CLASS_NAME null
Reflect
Proxy
Objet distant
Proxy
Body
Futur
Active
Remote
All interfaces that inherit Reflect are marker
interfaces for reflexion
21
ProActive implementation principle
PROXY_CLASS_NAME null
MOP
ProxyForBody
ProActive
2 aspects of distribution
- PROXY_CLASS_NAME ProxyForBody -
BODY_CLASS_NAME Body
Active
A
Application
PA
- live (Body)
22
Proxy and Body
Based on interface Active and class ProActive
A proxy / body model

• Originalities
• Extensions through inheritance of the Reflect
  interface
• 3 ways to turn a standard object into a reified
  one
• Reuse of existing classes, polymorphism between
  standard and reified objects

23
Interface utilisateur du MOP

• Instanciation dobjets réifiés par le méthode
  statique newInstance de la classe MOP
• Programmation classe par classe par des
  interfaces dérivant de Reflect
• Vector v (Vector) MOP.newInstance ( ltnom classe
  réifiée (impl. Reflect)gt,
• ltparamètres
  passés au proxygt,
• ltparamètres
  du constructeur de lobjet réifiégt )
• Ou instance par instance
• Vector v (Vector) MOP.newInstance ( ltnom de
  classe standardgt,
• ltnom classe
  proxy à utilisergt,
• ltparamètres
  passés au proxygt,
• ltparamètres
  du constructeur de lobjet réifiégt )
• Ou objet par objet
• Vector v (Vector) MOP.turnReified ( ltobjet
  standardgt,
• ltnom
  classe proxy à utilisergt,
• 
  ltparamètres passés au proxygt )

24
Exemple EchoProxy

• public class EchoProxy implements Proxy
• // Attributs
• Object myobject
• // Constructeur
• public EchoProxy (Call c, Object p)
• this.myobject c.execute()
• // Méthode de linterface Proxy
• public Object reify (Call c)
• System.out.println ("Echo-gt"c.methodname")
  
• return result c.execute (myobject)
• public interface Echo extends Reflect
• PROXY_CLASS_NAME "EchoProxy"

A a (A)newInstance ("Echo_A",null,null) A a
(A)newInstance ("A","Echo",null,null) A a
(A)turnReified ( a, "Echo", null)
25
2.2 Meta-Objects for DistributionAn Active Object
Body
FuturePool
RequestLine
Object
26
Composition dun objet actif

• Multiples Objets
• RequestSender Envoie les requetes (proxy body)
• RequestReceiver Recoit les requetes
• ReplySender Envoie le resultat a lappelant
• ReplyReceiver Recoit les mises a jour de futures
• Service Choisit et execute les requetes
• RequestLine Requetes en attente
• FuturePool Futurs en attente

27
Requete a un Objet Actif
28
Listener

• Modele observateur-observe
• Des evenements sont (eventuellement) generes a
  chaque etape importante,
• eventuellement envoyes a un listener
• Ces listeners peuvent etre ajoutes/suprimes
  dynamiquement

29
Types devenements (1)

• 3 grandes categories
• Objet Actif
• Creation
• Migration (activation,
  desactivation Cycle de vie)
• Communications
• Requests
• RequestSent
• RequestReceived
• Reply
• ReplySent
• ReplyReceived
• Service (activite de lOA)
• WaitForRequest
• WaitByNecessity

30
Listener - Modifier

• Idem Listener modifier lexecution dun
  objet actif
• A la creation changer le lieu de creation
• Au debut dune migration changer destination
• Step-by-step sur les toutes communications
• etc.
• Application debug, monitoring, contrôle
  interactif de lexecution

31
Localisation des listeners
32
Reception dune requete avec Listener
1 - Appel
2 - RequestReceived
4 - RequestAccepted
33
3. IC2D
Interactive Control Debug for Distribution
DEMO
C3D Collaborative 3D renderer in
//
(ProActive application)
IC2D Monitoring and Control
34
IC2D on several machines (1)
35
IC2D on several machines (2)
36
4. ProActive -- EJB JOnASReflexion et
Experimentation
37
DIVA Distributed Int. Virtual World in Java
38
C3D distributed-//-collaborative
39
www.inria.fr/oasis/ProActive
40
ProActive Conclusion

• 100 Java
• Both parallelism, distribution, sophisticated
  synchronization (CSCW), and mobile active objects
  
• Multithreaded and distributed
• Mapping of active objects onto hosts and VMs
• Reuse -- seamless
• Polymorphism with existing class types
• Dynamic works on previously unknown objects and
  classes
• Asynchrony -- Wait-by-necessity
• Centralized control
• Extensible
• ProActive vs. RMI alone - 30 of
  code
• www.inria.fr/oasis/ProActive

41
The Level 0 MOP

• Originalities
• Extensions through inheritance of the Reflect
  interface
• 3 ways to turn a standard object into a reified
  one
• Reuse of existing classes, polymorphism between
  standard and reified objects

42
Proxy and Body
Based on interface Active and class ProActive
A proxy / body model
A body is needed (no multiple inheritance)
43
The MOP - implementation

• Either static or dynamic stub generation
• The stub reifies method invocations by overriding
  all inherited methods with methods that build a
  MethodCall object when called and pass it on to
  the proxyobject that implements the actual
  meta-behavior.
• Acts as a type-safe surrogate for the reified
  object (the stub class is a subclass of the
  reified class).
• The stubs depends only on the reified class, not
  on the proxy
• The proxy does not depend on the type of the
  reified object

reified object
reified object
Stub
Proxy
44
ProActive Migration of active objects
Object
Calling Object
Forwarder
Proxy
Body

• Migration is initiated by the active object
  through a request
• The active object migrates with
• - its passive objects - the queue of pending
  requests - its future objects