4 * Copyright 2006,2007 Martin Quinson, Malek Cherier
7 * This program is free software; you can redistribute
8 * it and/or modify it under the terms of the license
9 *(GNU LGPL) which comes with this package.
12 package org.simgrid.msg;
14 import java.util.Arrays;
15 import java.util.Hashtable;
16 import java.util.Vector;
17 import java.util.concurrent.Semaphore;
20 * A process may be defined as a code, with some private data, executing
21 * in a location (host). All the process used by your simulation must be
22 * declared in the deployment file (XML format).
23 * To create your own process you must inherit your own process from this
24 * class and override the method "main()". For example if you want to use
25 * a process named Slave proceed as it :
27 * (1) import the class Process of the package simgrid.msg
28 * import simgrid.msg.Process;
30 * public class Slave extends simgrid.msg.Process {
32 * (2) Override the method function
35 * public void main(String[] args) {
36 * System.out.println("Hello MSG");
40 * The name of your process must be declared in the deployment file of your simulation.
41 * For the example, for the previous process Slave this file must contains a line :
42 * <process host="Maxims" function="Slave"/>, where Maxims is the host of the process
43 * Slave. All the process of your simulation are automatically launched and managed by Msg.
44 * A process use tasks to simulate communications or computations with another process.
45 * For more information see Task. For more information on host concept
50 public abstract class Process extends Thread {
52 * This attribute represents a bind between a java process object and
53 * a native process. Even if this attribute is public you must never
54 * access to it. It is set automatically during the build of the object.
59 * Even if this attribute is public you must never access to it.
60 * It is used to compute the id of an MSG process.
62 public static long nextProcessId = 0;
65 * Even if this attribute is public you must never access to it.
66 * It is compute automatically during the creation of the object.
67 * The native functions use this identifier to synchronize the process.
74 public Hashtable<String,String> properties;
77 * The name of the process.
79 protected String name;
81 * The PID of the process
83 protected int pid = -1;
85 * The PPID of the process
87 protected int ppid = -1;
89 * The host of the process
91 protected Host host = null;
96 public String msgName() {
99 /** The arguments of the method function of the process. */
100 public Vector<String> args;
102 /* process synchronization tools */
104 /* give the full path to semaphore to ensure that our own implementation don't get selected */
105 protected java.util.concurrent.Semaphore schedBegin, schedEnd;
106 private boolean nativeStop = false;
109 * Default constructor (used in ApplicationHandler to initialize it)
111 protected Process() {
113 this.id = nextProcessId++;
116 this.args = new Vector<String>();
117 this.properties = null;
118 schedBegin = new java.util.concurrent.Semaphore(0);
119 schedEnd = new java.util.concurrent.Semaphore(0);
124 * Constructs a new process from the name of a host and his name. The method
125 * function of the process doesn't have argument.
127 * @param hostname The name of the host of the process to create.
128 * @param name The name of the process.
130 * @exception HostNotFoundException if no host with this name exists.
134 public Process(String hostname, String name) throws HostNotFoundException {
135 this(Host.getByName(hostname), name, null);
138 * Constructs a new process from the name of a host and his name. The arguments
139 * of the method function of the process are specified by the parameter args.
141 * @param hostname The name of the host of the process to create.
142 * @param name The name of the process.
143 * @param args The arguments of the main function of the process.
145 * @exception HostNotFoundException if no host with this name exists.
147 * @throws NativeException
150 public Process(String hostname, String name, String args[]) throws HostNotFoundException, NativeException {
151 this(Host.getByName(hostname), name, args);
154 * Constructs a new process from a host and his name. The method function of the
155 * process doesn't have argument.
157 * @param host The host of the process to create.
158 * @param name The name of the process.
161 public Process(Host host, String name) {
162 this(host, name, null);
165 * Constructs a new process from a host and his name, the arguments of here method function are
166 * specified by the parameter args.
168 * @param host The host of the process to create.
169 * @param name The name of the process.
170 * @param args The arguments of main method of the process.
173 public Process(Host host, String name, String[]args) {
174 /* This is the constructor called by all others */
178 throw new NullPointerException("Process name cannot be NULL");
181 this.args = new Vector<String>();
183 this.args.addAll(Arrays.asList(args));
186 MsgNative.processCreate(this, host.getName());
187 } catch (HostNotFoundException e) {
188 throw new RuntimeException("The impossible happened (yet again): the host that I have were not found",e);
195 * This method kills all running process of the simulation.
197 * @param resetPID Should we reset the PID numbers. A negative number means no reset
198 * and a positive number will be used to set the PID of the next newly
201 * @return The function returns the PID of the next created process.
204 public static int killAll(int resetPID) {
205 return MsgNative.processKillAll(resetPID);
209 * This method sets a flag to indicate that this thread must be killed. End user must use static method kill
214 public void nativeStop()
219 * getter for the flag that indicates that this thread must be killed
224 public boolean getNativeStop()
230 * This method kill a process.
231 * @param process the process to be killed.
236 Msg.info("Process " + msgName() + " will be killed.");
241 * Suspends the process by suspending the task on which it was
242 * waiting for the completion.
245 public void pause() {
246 MsgNative.processSuspend(this);
249 * Resumes a suspended process by resuming the task on which it was
250 * waiting for the completion.
254 public void restart() {
255 MsgNative.processResume(this);
258 * Tests if a process is suspended.
260 * @return The method returns true if the process is suspended.
261 * Otherwise the method returns false.
263 public boolean isSuspended() {
264 return MsgNative.processIsSuspended(this);
267 * Returns the host of a process.
269 * @return The host instance of the process.
273 public Host getHost() {
274 if (this.host == null) {
275 this.host = MsgNative.processGetHost(this);
280 * This static method gets a process from a PID.
282 * @param PID The process identifier of the process to get.
284 * @return The process with the specified PID.
286 * @exception NativeException on error in the native SimGrid code
288 public static Process fromPID(int PID) throws NativeException {
289 return MsgNative.processFromPID(PID);
292 * This method returns the PID of the process.
294 * @return The PID of the process.
297 public int getPID() {
299 pid = MsgNative.processGetPID(this);
304 * This method returns the PID of the parent of a process.
306 * @return The PID of the parent of the process.
309 public int getPPID() {
311 ppid = MsgNative.processGetPPID(this);
316 * This static method returns the currently running process.
318 * @return The current process.
321 public static Process currentProcess() {
322 return MsgNative.processSelf();
325 * Migrates a process to another host.
327 * @param process The process to migrate.
328 * @param host The host where to migrate the process.
331 public static void migrate(Process process, Host host) {
332 MsgNative.processMigrate(process, host);
336 * Makes the current process sleep until time seconds have elapsed.
338 * @param seconds The time the current process must sleep.
340 * @exception HostFailureException on error in the native SimGrid code
342 public static void waitFor(double seconds) throws HostFailureException {
343 MsgNative.processWaitFor(seconds);
348 public void showArgs() {
349 Msg.info("[" + this.name + "/" + this.getHost().getName() + "] argc=" +
351 for (int i = 0; i < this.args.size(); i++)
352 Msg.info("[" + this.msgName() + "/" + this.getHost().getName() +
353 "] args[" + i + "]=" + (String) (this.args.get(i)));
356 * Let the simulated process sleep for the given amount of millisecond in the simulated world.
358 * You don't want to use sleep instead, because it would freeze your simulation
359 * run without any impact on the simulated world.
362 public native void simulatedSleep(double seconds);
365 * This method runs the process. Il calls the method function that you must overwrite.
369 String[]args = null; /* do not fill it before the signal or this.args will be empty */
371 //waitSignal(); /* wait for other people to fill the process in */
375 schedBegin.acquire();
376 } catch(InterruptedException e) {
380 args = new String[this.args.size()];
381 if (this.args.size() > 0) {
382 this.args.toArray(args);
386 MsgNative.processExit(this);
388 } catch(MsgException e) {
390 Msg.info("Unexpected behavior. Stopping now");
393 catch(ProcessKilled pk) {
396 MsgNative.processExit(this);
397 } catch (ProcessKilled pk2) {
398 /* Ignore that other exception that *will* occur all the time.
399 * This is because the C mechanic gives the control to the now-killed process
400 * so that it does some garbage collecting on its own. When it does so here,
401 * the Java thread checks when starting if it's supposed to be killed (to inform
402 * the C world). To avoid the infinite loop or anything similar, we ignore that
403 * exception now. This should be ok since we ignore only a very specific exception
404 * class and not a generic (such as any RuntimeException).
406 System.err.println(currentThread().getName()+": I ignore that other exception");
408 Msg.info(" Process " + ((Process) Thread.currentThread()).msgName() + " has been killed.");
412 pk.printStackTrace();
413 Msg.info("Unexpected behavior. Stopping now");
420 * The main function of the process (to implement).
423 * @throws MsgException
425 public abstract void main(String[]args) throws MsgException;
428 /** @brief Gives the control from the given user thread back to the maestro
430 * schedule() and unschedule() are the basis of interactions between the user threads
431 * (executing the user code), and the maestro thread (executing the platform models to decide
432 * which user thread should get executed when. Once it decided which user thread should be run
433 * (because the blocking action it were blocked onto are terminated in the simulated world), the
434 * maestro passes the control to this uthread by calling uthread.schedule() in the maestro thread
435 * (check its code for the simple semaphore-based synchronization schema).
437 * The uthread executes (while the maestro is blocked), until it starts another blocking
438 * action, such as a communication or so. In that case, uthread.unschedule() gets called from
441 * As other complications, these methods are called directly by the C through a JNI upcall in
442 * response to the JNI downcalls done by the Java code. For example, you have this (simplified)
444 * - a process calls the Task.send() method in java
445 * - this calls Java_org_simgrid_msg_MsgNative_taskSend() in C through JNI
446 * - this ends up calling jprocess_unschedule(), still in C
447 * - this calls the java method "org/simgrid/msg/Process/unschedule()V" through JNI
448 * - that is to say, the unschedule() method that you are reading the documentation of.
450 * To understand all this, you must keep in mind that there is no difference between the C thread
451 * describing a process, and the Java thread doing the same. Most of the time, they are system
452 * threads from the kernel anyway. In the other case (such as when using green java threads when
453 * the OS does not provide any thread feature), I'm unsure of what happens: it's a very long time
454 * that I didn't see any such OS.
456 * The synchronization itself is implemented using simple semaphores in Java, as you can see by
457 * checking the code of these functions (and run() above). That's super simple, and thus welcome
458 * given the global complexity of the synchronization architecture: getting C and Java cooperate
459 * with regard to thread handling in a portable manner is very uneasy. A simple and straightforward
460 * implementation of each synchronization point is precious.
462 * But this kinda limits the system scalability. It may reveal difficult to simulate dozens of
463 * thousands of processes this way, both for memory limitations and for hard limits pushed by the
464 * system on the amount of threads and semaphores (we have 2 semaphores per user process).
466 * At time of writing, the best source of information on how to simulate large systems within the
467 * Java bindings of simgrid is here: http://tomp2p.net/dev/simgrid/
470 public void unschedule() {
471 /* this function is called from the user thread only */
474 /* unlock the maestro before going to sleep */
476 /* Here, the user thread is locked, waiting for the semaphore, and maestro executes instead */
477 schedBegin.acquire();
478 /* now that the semaphore is acquired, it means that maestro gave us the control back */
480 /* the user thread is starting again after giving the control to maestro.
481 * Let's check if we were asked to die in between */
482 if ( (Thread.currentThread() instanceof Process) &&((Process) Thread.currentThread()).getNativeStop()) {
483 throw new ProcessKilled();
486 } catch (InterruptedException e) {
487 /* ignore this exception because this is how we get killed on process.kill or end of simulation.
488 * I don't like hiding exceptions this way, but fail to see any other solution
494 /** @brief Gives the control from the maestro back to the given user thread
496 * Must be called from the maestro thread -- see unschedule() for details.
499 public void schedule() {
501 /* unlock the user thread before going to sleep */
502 schedBegin.release();
503 /* Here, maestro is locked, waiting for the schedEnd semaphore to get signaled by used thread, that executes instead */
505 /* Maestro now has the control back and the user thread went to sleep gently */
507 } catch(InterruptedException e) {
508 throw new RuntimeException("The impossible did happend once again: I got interrupted in schedEnd.acquire()",e);
512 /** Send the given task in the mailbox associated with the specified alias (waiting at most given time)
516 * @throws TimeoutException
517 * @throws HostFailureException
518 * @throws TransferFailureException */
519 public void taskSend(String mailbox, Task task, double timeout) throws NativeException, TransferFailureException, HostFailureException, TimeoutException {
520 task.send(mailbox, timeout);
523 /** Send the given task in the mailbox associated with the specified alias
526 * @throws TimeoutException
527 * @throws HostFailureException
528 * @throws TransferFailureException */
529 public void taskSend(String mailbox, Task task) throws NativeException, TransferFailureException, HostFailureException, TimeoutException {
530 task.send(mailbox, -1);
533 /** Receive a task on mailbox associated with the specified mailbox
536 * @throws TransferFailureException
537 * @throws HostFailureException
538 * @throws TimeoutException
540 public Task taskReceive(String mailbox) throws TransferFailureException, HostFailureException, TimeoutException {
541 return Task.receive(mailbox, -1.0, null);
544 /** Receive a task on mailbox associated with the specified alias (waiting at most given time)
548 * @throws TransferFailureException
549 * @throws HostFailureException
550 * @throws TimeoutException
552 public Task taskReceive(String mailbox, double timeout) throws TransferFailureException, HostFailureException, TimeoutException {
553 return Task.receive(mailbox, timeout, null);
556 /** Receive a task on mailbox associated with the specified alias from given sender
561 * @throws TransferFailureException
562 * @throws HostFailureException
563 * @throws TimeoutException
565 public Task taskReceive(String mailbox, double timeout, Host host) throws TransferFailureException, HostFailureException, TimeoutException {
566 return Task.receive(mailbox, timeout, host);
569 /** Receive a task on mailbox associated with the specified alias from given sender
573 * @throws TransferFailureException
574 * @throws HostFailureException
575 * @throws TimeoutException
577 public Task taskReceive(String mailbox, Host host) throws TransferFailureException, HostFailureException, TimeoutException {
578 return Task.receive(mailbox, -1.0, host);