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);
184 * The natively implemented method to create an MSG process.
185 * @param host A valid (binded) host where create the process.
187 protected native void create(String hostName) throws HostNotFoundException;
189 * This method kills all running process of the simulation.
191 * @param resetPID Should we reset the PID numbers. A negative number means no reset
192 * and a positive number will be used to set the PID of the next newly
195 * @return The function returns the PID of the next created process.
198 public static native int killAll(int resetPID);
200 * This method sets a flag to indicate that this thread must be killed. End user must use static method kill
205 public void nativeStop() {
209 * getter for the flag that indicates that this thread must be killed
214 public boolean getNativeStop() {
219 * This method kill a process.
220 * @param process the process to be killed.
225 Msg.info("Process " + msgName() + " will be killed.");
229 * Suspends the process by suspending the task on which it was
230 * waiting for the completion.
233 public native void pause();
235 * Resumes a suspended process by resuming the task on which it was
236 * waiting for the completion.
240 public native void restart();
242 * Tests if a process is suspended.
244 * @return The method returns true if the process is suspended.
245 * Otherwise the method returns false.
247 public native boolean isSuspended();
249 * Returns the name of the process
251 public String msgName() {
255 * Returns the host of the process.
256 * @return The host instance of the process.
258 public Host getHost() {
262 * This static method gets a process from a PID.
264 * @param PID The process identifier of the process to get.
266 * @return The process with the specified PID.
268 * @exception NativeException on error in the native SimGrid code
270 public static native Process fromPID(int PID) throws NativeException;
272 * This method returns the PID of the process.
274 * @return The PID of the process.
277 public int getPID() {
281 * This method returns the PID of the parent of a process.
283 * @return The PID of the parent of the process.
286 public int getPPID() {
290 * This static method returns the currently running process.
292 * @return The current process.
295 public static native Process currentProcess();
297 * Kills a MSG process
298 * @param process Valid java process to kill
300 final static native void kill(Process process);
302 * Migrates a process to another host.
304 * @param process The process to migrate.
305 * @param host The host where to migrate the process.
308 public static void migrate(Process process, Host host) {
309 MsgNative.processMigrate(process, host);
313 * Makes the current process sleep until millis millisecondes have elapsed.
314 * You should note that unlike "waitFor" which takes seconds, this method takes milliseconds.
315 * FIXME: Not optimal, maybe we should have two native functions.
316 * @param millis the length of time to sleep in milliseconds.
318 public static void sleep(long millis) {
322 * Makes the current process sleep until millis milliseconds and nanos nanoseconds
324 * You should note that unlike "waitFor" which takes seconds, this method takes milliseconds and nanoseconds.
325 * Overloads Thread.sleep.
326 * @param millis the length of time to sleep in milliseconds.
327 * @param nanos additionnal nanoseconds to sleep.
329 public native static void sleep(long millis, int nanos);
331 * Makes the current process sleep until time seconds have elapsed.
332 * @param seconds The time the current process must sleep.
334 public native void waitFor(double seconds);
338 public void showArgs() {
339 Msg.info("[" + this.name + "/" + this.getHost().getName() + "] argc=" +
341 for (int i = 0; i < this.args.size(); i++)
342 Msg.info("[" + this.msgName() + "/" + this.getHost().getName() +
343 "] args[" + i + "]=" + (String) (this.args.get(i)));
348 public native void exit();
351 * This method runs the process. Il calls the method function that you must overwrite.
355 String[] args = null; /* do not fill it before the signal or this.args will be empty */
357 //waitSignal(); /* wait for other people to fill the process in */
361 schedBegin.acquire();
362 } catch(InterruptedException e) {
366 args = new String[this.args.size()];
367 if (this.args.size() > 0) {
368 this.args.toArray(args);
374 } catch(MsgException e) {
376 Msg.info("Unexpected behavior. Stopping now");
379 catch(ProcessKilled pk) {
383 } catch (ProcessKilled pk2) {
384 /* Ignore that other exception that *will* occur all the time.
385 * This is because the C mechanic gives the control to the now-killed process
386 * so that it does some garbage collecting on its own. When it does so here,
387 * the Java thread checks when starting if it's supposed to be killed (to inform
388 * the C world). To avoid the infinite loop or anything similar, we ignore that
389 * exception now. This should be ok since we ignore only a very specific exception
390 * class and not a generic (such as any RuntimeException).
392 System.err.println(currentThread().getName()+": I ignore that other exception");
394 Msg.info(" Process " + ((Process) Thread.currentThread()).msgName() + " has been killed.");
398 pk.printStackTrace();
399 Msg.info("Unexpected behavior. Stopping now");
406 * The main function of the process (to implement).
409 * @throws MsgException
411 public abstract void main(String[]args) throws MsgException;
414 /** @brief Gives the control from the given user thread back to the maestro
416 * schedule() and unschedule() are the basis of interactions between the user threads
417 * (executing the user code), and the maestro thread (executing the platform models to decide
418 * which user thread should get executed when. Once it decided which user thread should be run
419 * (because the blocking action it were blocked onto are terminated in the simulated world), the
420 * maestro passes the control to this uthread by calling uthread.schedule() in the maestro thread
421 * (check its code for the simple semaphore-based synchronization schema).
423 * The uthread executes (while the maestro is blocked), until it starts another blocking
424 * action, such as a communication or so. In that case, uthread.unschedule() gets called from
427 * As other complications, these methods are called directly by the C through a JNI upcall in
428 * response to the JNI downcalls done by the Java code. For example, you have this (simplified)
430 * - a process calls the Task.send() method in java
431 * - this calls Java_org_simgrid_msg_MsgNative_taskSend() in C through JNI
432 * - this ends up calling jprocess_unschedule(), still in C
433 * - this calls the java method "org/simgrid/msg/Process/unschedule()V" through JNI
434 * - that is to say, the unschedule() method that you are reading the documentation of.
436 * To understand all this, you must keep in mind that there is no difference between the C thread
437 * describing a process, and the Java thread doing the same. Most of the time, they are system
438 * threads from the kernel anyway. In the other case (such as when using green java threads when
439 * the OS does not provide any thread feature), I'm unsure of what happens: it's a very long time
440 * that I didn't see any such OS.
442 * The synchronization itself is implemented using simple semaphores in Java, as you can see by
443 * checking the code of these functions (and run() above). That's super simple, and thus welcome
444 * given the global complexity of the synchronization architecture: getting C and Java cooperate
445 * with regard to thread handling in a portable manner is very uneasy. A simple and straightforward
446 * implementation of each synchronization point is precious.
448 * But this kinda limits the system scalability. It may reveal difficult to simulate dozens of
449 * thousands of processes this way, both for memory limitations and for hard limits pushed by the
450 * system on the amount of threads and semaphores (we have 2 semaphores per user process).
452 * At time of writing, the best source of information on how to simulate large systems within the
453 * Java bindings of simgrid is here: http://tomp2p.net/dev/simgrid/
456 public void unschedule() {
457 /* this function is called from the user thread only */
460 /* unlock the maestro before going to sleep */
462 /* Here, the user thread is locked, waiting for the semaphore, and maestro executes instead */
463 schedBegin.acquire();
464 /* now that the semaphore is acquired, it means that maestro gave us the control back */
466 /* the user thread is starting again after giving the control to maestro.
467 * Let's check if we were asked to die in between */
468 if ( (Thread.currentThread() instanceof Process) &&((Process) Thread.currentThread()).getNativeStop()) {
469 throw new ProcessKilled();
472 } catch (InterruptedException e) {
473 /* ignore this exception because this is how we get killed on process.kill or end of simulation.
474 * I don't like hiding exceptions this way, but fail to see any other solution
480 /** @brief Gives the control from the maestro back to the given user thread
482 * Must be called from the maestro thread -- see unschedule() for details.
485 public void schedule() {
487 /* unlock the user thread before going to sleep */
488 schedBegin.release();
489 /* Here, maestro is locked, waiting for the schedEnd semaphore to get signaled by used thread, that executes instead */
491 /* Maestro now has the control back and the user thread went to sleep gently */
493 } catch(InterruptedException e) {
494 throw new RuntimeException("The impossible did happend once again: I got interrupted in schedEnd.acquire()",e);
499 * Class initializer, to initialize various JNI stuff
501 public static native void nativeInit();