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4:Remote procedure callJava RMI

/ N/

---ORB(Object Request Broker)

RPC--Remote Procedure Call ) RMI--Remote Method Invocation ) Event-based model

bigendianlitterendianmashellAPI CORBAIDL

---Location transparencyCommunication protocols

Interfaces

RPCs Service interface RMIs Remote interface,

IDLsInterface Definition Languages Java RMI javaIDLs. e.g. CORBA IDL (n1), DCE IDL and DCOM IDL

4:Remote procedure callEvents and notificationsJava RMI

The object modelDistributed objectsThe distributed object model

object reference interfaceActions ExceptionsGarbage collection

/server, client. server client.

. E.g. B & FE.g. C E E.g., B

Invocation semantics RRP RRP Retry Request message: Duplicate filtering: Retransmission of result:

Invocation semanticsexactly onceexactly once RRPMaybe maybe

Invocation semanticsAt-least-once Sun RPC ,

Invocation semanticsAt-most-once JavaRMI

failure modelTCP/IP exactly once.at most once.at least once

Invocation semantics

12 serverB, clientBRRMRRM RMI RRMRRM

RMI software proxy, skeleton dispatcher

proxy

proxyserverskeletondispatcher dispatcher ProxydispatchermethodId skeleton Skeletonserver

5:Remote Procedure CallEvents and notificationsJava RMI

Sun RPC case studyRPC RPC /(server)server(client) clientserver

Sun RPC case study continued

Sun RPC case study continuedRPCStub

Sun RPC case study continuedfn() stubstubc_fn()stubs_fn() fn() fn()c_fn() fn(), fn()s_fn()

Sun RPC case study continuedStub marshal() unmarshal( )Marshal DCE RPC Network Data RepresentationNDRunmarshalNDR

Sun RPC case study continuedClient stubmarshal (network data representation , NDR) Client runtime systemunmarshal

Sun RPC case study continuedServer stubunmarshal marshal

Sun RPC case study continuedIDL compilerIDL Header IDL headerClient stubstubServer stubstub

Sun RPC case study continuedClient codeServer code stub

Sun RPC case study continuedstub serverTCP/UDP Server socketServer Stub

Service interface: the procedures that are available for remote callingInvocation semantics choice: at-least-once or at-most-onceGenerally implemented over request-reply protocolBuilding blocksCommunication moduleClient stub procedure (as proxy in RMI): marshalling, sending, unmarshallingDispatcher: select one of the server stub proceduresServer stub procedure (as skeleton in RMI): unmarshalling, calling, marshalling

Sun RPC case studyNFSat-least-once semanticsXDR - Interface definition languageInterface name: Program number, version numberProcedure identifier: procedure numberRpcgen generator of RPC componentsclient stub procedureserver main procedureDispatcherserver stub proceduremarshalling and unmarshalling procedure

Sun RPC case study continuedBinding portmapperServer: register ((program number, version number), port number)Client: request port number by (program number, version number)AuthenticationEach request contains the credentials of the user, e.g. uid and gid of the userAccess control according to the credential information

//RPC struct call_body {unsigned int rpcvers; unsigned int prog; unsigned int vers; unsigned int proc;opaque_auth cred; opaque_auth verf; parameter 1 parameter 2. . .}; Sun Microsystems Open Network Computing. The ONCuses XDR as the external data representation standard

Sun RPC case study RPC Stub DCE RPCIDL stubRPC

5:Remote procedure callEvents and notificationsJava RMI

Publish/subscribe paradigm

Information provider

.

IP

RSS Web "Push" (Protocol)RSSReally Simple Syndication RDF (Resource Description Framework) Site SummaryRich Site Summary SyndicationRSS blog wiki RSS

Jini Jini?JiniSunJini --- ---JiniJiniJini

JiniDiscovery and Join Lookup () LookupNetwork Services ---Other Services ---Leasing ---Transactions ---Distributed Event---Other OS ---Other CPU ---CPU

JiniDiscovery and Join 512 Discovery

JiniJini Lookup DiscoveryLookup Lookup Jini Lookup Discovery and JoinJoinDiscovery LookupLookup ()LookupLookup /

JiniLookup Lookup Lookup Lookup ( postscript) LookupPeer Lookup (Lookup ) LookupPeer Lookup Lookup Discovery and Join

Jini Jini Discovery and Join Lookup

JiniJava Jini Java APIAPI rool back JiniJini JavaSpace

Jini JavaJini Java API () ()

5:

Remote procedure callEvents and notificationsJava RMI

Java RMI remote method invocation(RMI)Jdk1.1(1997.02)Jdk1.2Access to Remote ObjectsClient-Server ProtocolHigh-level APIJava-to-Java onlyTransparentLightweight

Java RMI RPCRMI->->

Java RMI RMI(Remote Interface)(Remote Service)StubSkeletonRMI

Java RMI RMIJavaJavaRMICStubSkeleton (host)Java RMIJava

Java RMI RMIserver, client .RMIserverclientRMI

Java RMI ---import java.rmi.*;public interface compute extends Remote {public int add(int x, int y)throws RemoteException;}

Java RMI ---import java.rmi.*;import java.rmi.server.*;public class AdderImpl extends UnicastRemoteObjectimplements Compute {public AdderImpl() throws RemoteException {}public int add(int x, int y)throws RemoteException {return x + y;}

Java RMI ---

Java RMI ---stubsskeletonStubsskeletons rmicStubskeleton

Java RMI ---Object Serialization( Stream)

Java RMI ---

Java RMI ---RMI RMI Registry, 1099.(object servers will bedynamically assigned ports by theRMI runtime)stub

Java RMI ---Server-sideRMI ( ). RMI Registry

Java RMI ---Client-sidejava.rmi.Naming RMI Registrylookup() URL:rmi://[:]/

Java RMI ---

Java RMI ---

Java RMI ---

Java RMI ---

RMI:

RMIRMI, 1. RMI 2. RMI JavaRMI RMI

RMI:Engin,,task.engin ..:,, engin.server CPU .:RMI.

RMI:,,: engintask,Task ,engin.,

RMICompute engin:1. compute engine ComputeEngine , Compute, executeTask, .2. Client engin.client server.3. ,, .4. execute.

RMI

RMI, :1. 2. 3. 4. enginmain:

package engine;import java.rmi.*; import java.rmi.server.*; import compute.*;public class ComputeEngine extends UnicastRemoteObject implements Compute{ public ComputeEngine() throws RemoteException{ super(); }public Object executeTask(Task t){ return t.execute(); }public static void main(String[] args){ if (System.getSecurityManager() == null){ System.setSecurityManager(new RMISecurityManager()); } String name = "//host/Compute";try { Compute engine = new ComputeEngine(); Naming.rebind(name, engine); System.out.println("ComputeEngine bound");} catch (Exception e) { System.err.println("ComputeEngine exception: " + e.getMessage()); e.printStackTrace(); }}

RMI,super(), a UnicastRemoteObject ,, .engin, , . .

RMI:1. . stub,. 2. . ,.

RMI RMImain computer engincomputer engin

RMI

task

RMIcomputePi1. ,2. 3.

package client;mport java.rmi.*; import java.math.*; import compute.*;public class ComputePi {public static void main(String args[]) {if (System.getSecurityManager() == null){ System.setSecurityManager(new RMISecurityManager()); }try { String name = "//" + args[0] + "/Compute";Compute comp = (Compute) Naming.lookup(name);Pi task = new Pi(Integer.parseInt(args[1]));BigDecimal pi = (BigDecimal) (comp.executeTask(task));System.out.println(pi);} catch (Exception e) {System.err.println("ComputePi exception: " + e.getMessage());e.printStackTrace(); }}

RMI

package client;import compute.*; import java.math.*;public class Pi implements Task {private static final BigDecimal ZERO = BigDecimal.valueOf(0);private static final BigDecimal ONE = BigDecimal.valueOf(1);private static final BigDecimal FOUR = BigDecimal.valueOf(4);private static final int roundingMode = BigDecimal.ROUND_HALF_EVEN;public Pi(int digits){ this.digits = digits; }

public Object execute(){ return computePi(digits); }*************************************************** pi/4 = 4*arctan(1/5) - arctan(1/239)**************************************************public static BigDecimal computePi(int digits) {int scale = digits + 5;BigDecimal arctan1_5 = arctan(5, scale);BigDecimal arctan1_239 = arctan(239, scale);BigDecimal piarctan1_5.multiply(FOUR).subtract(arctan1_239).multiply(FOUR);return pi.setScale(digits, BigDecimal.ROUND_HALF_UP); }

/*** Compute the value, in radians, of the arctangent of* the inverse of the supplied integer to the speficied* number of digits after the decimal point. The value* is computed using the power series expansion for the* arctangent:* arctan(x) = x - (x^3)/3 + (x^5)/5 - (x^7)/7 +*(x^9)/9 ...*/

public static BigDecimal arctan(int inverseX, int scale){ BigDecimal result, numer, term;BigDecimal invX = BigDecimal.valueOf(inverseX);BigDecimal invX2 =BigDecimal.valueOf(inverseX * inverseX);numer = ONE.divide(invX, scale, roundingMode);result = numer;int i = 1;do { numer =numer.divide(invX2, scale, roundingMode);int denom = 2 * i + 1;term = numer.divide(BigDecimal.valueOf(denom),scale, roundingMode);if ((i % 2) != 0) { result = result.subtract(term); }else { result = result.add(term); }i++;} while (term.compareTo(ZERO) != 0);return result;

RMI engin Rmi1. 2. 3. 4.

RMI 1. compute ( Compute and Task interfaces)2. engine ( ComputeEngine implementation class and its stub)3. client ( ComputePi client code and Pi task implementation)

RMI

5:Remote procedure callEvents and notificationsJava RMI

RMISun RPC

project1 atleast-onceatleast-once