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.
71 public Hashtable<String,String> properties;
74 * The name of the process.
76 protected String name;
78 * The PID of the process
80 protected int pid = -1;
82 * The PPID of the process
84 protected int ppid = -1;
86 * The host of the process
88 protected Host host = null;
90 /** The arguments of the method function of the process. */
91 public Vector<String> args;
93 /* process synchronization tools */
95 /* give the full path to semaphore to ensure that our own implementation don't get selected */
96 protected java.util.concurrent.Semaphore schedBegin, schedEnd;
97 private boolean nativeStop = false;
100 * Default constructor (used in ApplicationHandler to initialize it)
102 protected Process() {
104 this.id = nextProcessId++;
107 this.args = new Vector<String>();
108 this.properties = null;
109 schedBegin = new java.util.concurrent.Semaphore(0);
110 schedEnd = new java.util.concurrent.Semaphore(0);
115 * Constructs a new process from the name of a host and his name. The method
116 * function of the process doesn't have argument.
118 * @param hostname The name of the host of the process to create.
119 * @param name The name of the process.
121 * @exception HostNotFoundException if no host with this name exists.
125 public Process(String hostname, String name) throws HostNotFoundException {
126 this(Host.getByName(hostname), name, null);
129 * Constructs a new process from the name of a host and his name. The arguments
130 * of the method function of the process are specified by the parameter args.
132 * @param hostname The name of the host of the process to create.
133 * @param name The name of the process.
134 * @param args The arguments of the main function of the process.
136 * @exception HostNotFoundException if no host with this name exists.
138 * @throws NativeException
141 public Process(String hostname, String name, String args[]) throws HostNotFoundException, NativeException {
142 this(Host.getByName(hostname), name, args);
145 * Constructs a new process from a host and his name. The method function of the
146 * process doesn't have argument.
148 * @param host The host of the process to create.
149 * @param name The name of the process.
152 public Process(Host host, String name) {
153 this(host, name, null);
156 * Constructs a new process from a host and his name, the arguments of here method function are
157 * specified by the parameter args.
159 * @param host The host of the process to create.
160 * @param name The name of the process.
161 * @param args The arguments of main method of the process.
164 public Process(Host host, String name, String[]args) {
165 /* This is the constructor called by all others */
169 throw new NullPointerException("Process name cannot be NULL");
172 this.args = new Vector<String>();
174 this.args.addAll(Arrays.asList(args));
177 create(host.getName());
178 } catch (HostNotFoundException e) {
179 throw new RuntimeException("The impossible happened (yet again): the host that I have were not found",e);
182 this.properties = new Hashtable<String,String>();
186 * The natively implemented method to create an MSG process.
187 * @param host A valid (binded) host where create the process.
189 protected native void create(String hostName) throws HostNotFoundException;
191 * This method kills all running process of the simulation.
193 * @param resetPID Should we reset the PID numbers. A negative number means no reset
194 * and a positive number will be used to set the PID of the next newly
197 * @return The function returns the PID of the next created process.
200 public static native int killAll(int resetPID);
202 * This method sets a flag to indicate that this thread must be killed. End user must use static method kill
207 public void nativeStop() {
211 * getter for the flag that indicates that this thread must be killed
216 public boolean getNativeStop() {
221 * This method kill a process.
222 * @param process the process to be killed.
227 Msg.info("Process " + msgName() + " will be killed.");
231 * Suspends the process by suspending the task on which it was
232 * waiting for the completion.
235 public native void pause();
237 * Resumes a suspended process by resuming the task on which it was
238 * waiting for the completion.
242 public native void restart();
244 * Tests if a process is suspended.
246 * @return The method returns true if the process is suspended.
247 * Otherwise the method returns false.
249 public native boolean isSuspended();
251 * Returns the name of the process
253 public String msgName() {
257 * Returns the host of the process.
258 * @return The host instance of the process.
260 public Host getHost() {
264 * This static method gets a process from a PID.
266 * @param PID The process identifier of the process to get.
268 * @return The process with the specified PID.
270 * @exception NativeException on error in the native SimGrid code
272 public static native Process fromPID(int PID) throws NativeException;
274 * This method returns the PID of the process.
276 * @return The PID of the process.
279 public int getPID() {
283 * This method returns the PID of the parent of a process.
285 * @return The PID of the parent of the process.
288 public int getPPID() {
292 * This static method returns the currently running process.
294 * @return The current process.
297 public static native Process currentProcess();
299 * Kills a MSG process
300 * @param process Valid java process to kill
302 final static native void kill(Process process);
304 * Migrates a process to another host.
306 * @param process The process to migrate.
307 * @param host The host where to migrate the process.
310 public static void migrate(Process process, Host host) {
311 MsgNative.processMigrate(process, host);
315 * Makes the current process sleep until millis millisecondes have elapsed.
316 * You should note that unlike "waitFor" which takes seconds, this method takes milliseconds.
317 * FIXME: Not optimal, maybe we should have two native functions.
318 * @param millis the length of time to sleep in milliseconds.
320 public static void sleep(long millis) {
324 * Makes the current process sleep until millis milliseconds and nanos nanoseconds
326 * You should note that unlike "waitFor" which takes seconds, this method takes milliseconds and nanoseconds.
327 * Overloads Thread.sleep.
328 * @param millis the length of time to sleep in milliseconds.
329 * @param nanos additionnal nanoseconds to sleep.
331 public native static void sleep(long millis, int nanos);
333 * Makes the current process sleep until time seconds have elapsed.
334 * @param seconds The time the current process must sleep.
336 public native void waitFor(double seconds);
340 public void showArgs() {
341 Msg.info("[" + this.name + "/" + this.getHost().getName() + "] argc=" +
343 for (int i = 0; i < this.args.size(); i++)
344 Msg.info("[" + this.msgName() + "/" + this.getHost().getName() +
345 "] args[" + i + "]=" + (String) (this.args.get(i)));
350 public native void exit();
353 * This method runs the process. Il calls the method function that you must overwrite.
357 String[] args = null; /* do not fill it before the signal or this.args will be empty */
359 //waitSignal(); /* wait for other people to fill the process in */
363 schedBegin.acquire();
364 } catch(InterruptedException e) {
368 args = new String[this.args.size()];
369 if (this.args.size() > 0) {
370 this.args.toArray(args);
376 } catch(MsgException e) {
378 Msg.info("Unexpected behavior. Stopping now");
381 catch(ProcessKilled pk) {
385 } catch (ProcessKilled pk2) {
386 /* Ignore that other exception that *will* occur all the time.
387 * This is because the C mechanic gives the control to the now-killed process
388 * so that it does some garbage collecting on its own. When it does so here,
389 * the Java thread checks when starting if it's supposed to be killed (to inform
390 * the C world). To avoid the infinite loop or anything similar, we ignore that
391 * exception now. This should be ok since we ignore only a very specific exception
392 * class and not a generic (such as any RuntimeException).
394 System.err.println(currentThread().getName()+": I ignore that other exception");
396 Msg.info(" Process " + ((Process) Thread.currentThread()).msgName() + " has been killed.");
400 pk.printStackTrace();
401 Msg.info("Unexpected behavior. Stopping now");
408 * The main function of the process (to implement).
411 * @throws MsgException
413 public abstract void main(String[]args) throws MsgException;
416 /** @brief Gives the control from the given user thread back to the maestro
418 * schedule() and unschedule() are the basis of interactions between the user threads
419 * (executing the user code), and the maestro thread (executing the platform models to decide
420 * which user thread should get executed when. Once it decided which user thread should be run
421 * (because the blocking action it were blocked onto are terminated in the simulated world), the
422 * maestro passes the control to this uthread by calling uthread.schedule() in the maestro thread
423 * (check its code for the simple semaphore-based synchronization schema).
425 * The uthread executes (while the maestro is blocked), until it starts another blocking
426 * action, such as a communication or so. In that case, uthread.unschedule() gets called from
429 * As other complications, these methods are called directly by the C through a JNI upcall in
430 * response to the JNI downcalls done by the Java code. For example, you have this (simplified)
432 * - a process calls the Task.send() method in java
433 * - this calls Java_org_simgrid_msg_MsgNative_taskSend() in C through JNI
434 * - this ends up calling jprocess_unschedule(), still in C
435 * - this calls the java method "org/simgrid/msg/Process/unschedule()V" through JNI
436 * - that is to say, the unschedule() method that you are reading the documentation of.
438 * To understand all this, you must keep in mind that there is no difference between the C thread
439 * describing a process, and the Java thread doing the same. Most of the time, they are system
440 * threads from the kernel anyway. In the other case (such as when using green java threads when
441 * the OS does not provide any thread feature), I'm unsure of what happens: it's a very long time
442 * that I didn't see any such OS.
444 * The synchronization itself is implemented using simple semaphores in Java, as you can see by
445 * checking the code of these functions (and run() above). That's super simple, and thus welcome
446 * given the global complexity of the synchronization architecture: getting C and Java cooperate
447 * with regard to thread handling in a portable manner is very uneasy. A simple and straightforward
448 * implementation of each synchronization point is precious.
450 * But this kinda limits the system scalability. It may reveal difficult to simulate dozens of
451 * thousands of processes this way, both for memory limitations and for hard limits pushed by the
452 * system on the amount of threads and semaphores (we have 2 semaphores per user process).
454 * At time of writing, the best source of information on how to simulate large systems within the
455 * Java bindings of simgrid is here: http://tomp2p.net/dev/simgrid/
458 public void unschedule() {
459 /* this function is called from the user thread only */
462 /* unlock the maestro before going to sleep */
464 /* Here, the user thread is locked, waiting for the semaphore, and maestro executes instead */
465 schedBegin.acquire();
466 /* now that the semaphore is acquired, it means that maestro gave us the control back */
468 /* the user thread is starting again after giving the control to maestro.
469 * Let's check if we were asked to die in between */
470 if ( (Thread.currentThread() instanceof Process) &&((Process) Thread.currentThread()).getNativeStop()) {
471 throw new ProcessKilled();
474 } catch (InterruptedException e) {
475 /* ignore this exception because this is how we get killed on process.kill or end of simulation.
476 * I don't like hiding exceptions this way, but fail to see any other solution
482 /** @brief Gives the control from the maestro back to the given user thread
484 * Must be called from the maestro thread -- see unschedule() for details.
487 public void schedule() {
489 /* unlock the user thread before going to sleep */
490 schedBegin.release();
491 /* Here, maestro is locked, waiting for the schedEnd semaphore to get signaled by used thread, that executes instead */
493 /* Maestro now has the control back and the user thread went to sleep gently */
495 } catch(InterruptedException e) {
496 throw new RuntimeException("The impossible did happend once again: I got interrupted in schedEnd.acquire()",e);
501 * Class initializer, to initialize various JNI stuff
503 public static native void nativeInit();