Java Distributed Object System

Main Module of a Distributed System Global address space global identifier registry/ name service ( central, distributed, replicated) Transportation system Global Control flow (Invocation/Control flow Protocol) parameter passing across address space method invocation semantic entity activation Failure Behavior exception consistency and persistency 1997.10.22 CS491 presented by Peng Wu

RMI Overview RMI provides distributed computing ability on the specific system(JVM) for the specific language(Java) CORBA, RPC System Heterogeneity Language Heterogeneity RMI based on homogeneity and strength it Language Integration -- distributed object model similar interface, preserve some behavior exception System Integration garbage collection mobile behavior security 1997.10.22 CS491 presented by Peng Wu

Language Integration -- Distributed Object Model Java Object model Object Interface declare a set of methods for Java object without implementation Method Invocation primitive type passed by value object passed by reference Distributed Object model Remote object object whose methods can be accessed from another address space Remote interface an interface that declares the methods of a remote object Remote Implementation RMI non-remote object passed by value remote object passed by reference 1997.10.22 CS491 presented by Peng Wu

RMI Interfaces and Classes Object classes Interfaces Remote RemoteObject IOException RemoteServer RemoteException Client stub ... UnicastRemoteObject ... extension implementation 1997.10.22 CS491 presented by Peng Wu

System Integration Distributed Garbage Collection Dynamic Stub loading specialized class loader security manager pickling system When marshalling remote object, marshal stream embeds URL info of the stub code On demarshalling, marshal stream loads stub code if it’s not available locally 1997.10.22 CS491 presented by Peng Wu

Remote Reference layer System Architecture Stub/Skeleton layer Remote reference layer Transport layer Application Client Server Stubs Skeleton RMI System Remote Reference layer Transport 1997.10.22 CS491 presented by Peng Wu

Distributed object Across Address Space Name Service URL based name lookup, no location transparency Non-persistent database java..rmi.registry.Registry java.rmi.LocateRegistry java.rmi.naming export export Remote Server Remote Server registry registry Locate Reg Locate Reg naming naming client client binding binding 1997.10.22 CS491 presented by Peng Wu

Distributed object Across Address Space Pickling -- Object transmission across address space Serialized representation of objects: object type object persistent state relationships between objects within a stream object implementation info Pickling remote object remote interface remote object reference 1997.10.22 CS491 presented by Peng Wu

RMI Performance Call time (no configuration available) CORBA vs. RMI RMI vs. Local call(PPro 200Mhz, NT, JDK no JIT) Call time (no configuration available) setup time: RMI 40% slower than CORBA binding: RMI 200-1500ms slower than CORBA CORBA vs. RMI 1000 calls, one argument, JDK1.1.1 1997.10.22 CS491 presented by Peng Wu

CORBA and RMI Performance (1000 calls, one argument) 1997.10.22 CS491 presented by Peng Wu

RMI Performance Scalability -- ability of handling multiple connections to one remote object HelloImpl.sayHello() JDK1.1, Win95, 133-Pentium 150 threads in 2 sec interval, 200 threads in 5 sec interval(RMI) 1000 threads(Java IDL) Serialization 100 times, default serialization, buffered stream, primitive type, small array, small object array(10) RMI 64500ms (object) CORBA 3485ms (IDL struct) different serialization schemes Object[1000], each 3 attributes(String, Double,util.Data) 1997.10.22 CS491 presented by Peng Wu

Performance of different serialization scheme (Solaris2 Performance of different serialization scheme (Solaris2.5 Ultra-1 with attributes String, Double,Data) 1997.10.22 CS491 presented by Peng Wu

Summary Pros Integrating distribute object model seamlessly into Java object model Homogeneity Communication with non-Java object may work through JNI and JDBC Cons Make distributed computing in Java easily to approach, but not efficiently Heterogeneity A primitive implementation currently 1997.10.22 CS491 presented by Peng Wu

JavaSpace -- a new distributed computing paradigm JavaSpace -- A reliable distributed storage system Goal -- facilitating cooperate distributed computing Utilization Distributed algorithms as flow of object establish connections between participants(Client/Server, RPC, RMI) build interfaces and protocols between participants establish connections with a broker(JavaSpace) build interfaces and protocols with the broker Distributed persistence 1997.10.22 CS491 presented by Peng Wu

Client read Identities write JavaSpace Write event Client write Event Dispatcher Transaction notify take notify write JavaSpace JavaSpace 1997.10.22 CS491 presented by Peng Wu

JavaSpace model Entry basic unit of JavaSpace, a typed group of objects Template a “partial” entry used to match entries with specific properties Operation read write take notify 1997.10.22 CS491 presented by Peng Wu

A reliable distributed storage system Store and retrieve entries -- object Weak query ability Handle concurrent access Global control flow across multiple JavaSpaces asynchronous retrieval distributed transaction mechanism 1997.10.22 CS491 presented by Peng Wu