"""SCons.Job This module defines the Serial and Parallel classes that execute tasks to complete a build. The Jobs class provides a higher level interface to start, stop, and wait on jobs. """ __revision__ = "__FILE__ __REVISION__ __DATE__ __DEVELOPER__" class Jobs: """An instance of this class initializes N jobs, and provides methods for starting, stopping, and waiting on all N jobs. """ def __init__(self, num, taskmaster): """ create 'num' jobs using the given taskmaster. If 'num' is equal to 0, then a serial job will be used, otherwise 'num' parallel jobs will be used. """ if num > 1: self.jobs = [] for i in range(num): self.jobs.append(Parallel(taskmaster, self)) else: self.jobs = [Serial(taskmaster)] def start(self): """start the jobs""" for job in self.jobs: job.start() def wait(self): """ wait for the jobs started with start() to finish""" for job in self.jobs: job.wait() def stop(self): """ stop the jobs started with start() This function does not wait for the jobs to finish. """ for job in self.jobs: job.stop() class Serial: """This class is used to execute tasks in series, and is more efficient than Parallel, but is only appropriate for non-parallel builds. Only one instance of this class should be in existence at a time. This class is not thread safe. """ def __init__(self, taskmaster): """Create a new serial job given a taskmaster. The taskmaster's next_task() method should return the next task that needs to be executed, or None if there are no more tasks. The taskmaster's executed() method will be called for each task when it is successfully executed or failed() will be called if it failed to execute (e.g. execute() raised an exception). The taskmaster's is_blocked() method will not be called. """ self.taskmaster = taskmaster def start(self): """Start the job. This will begin pulling tasks from the taskmaster and executing them, and return when there are no more tasks. If a task fails to execute (i.e. execute() raises an exception), then the job will stop.""" while 1: task = self.taskmaster.next_task() if task is None: break try: task.execute() except: self.taskmaster.failed(task) return else: self.taskmaster.executed(task) def stop(self): """Serial jobs are always finished when start() returns, so there is nothing to do here""" pass def wait(self): """Serial jobs are always finished when start() returns, so there is nothing to do here""" pass # The will hold a condition variable once the first parallel task # is created. cv = None class Parallel: """This class is used to execute tasks in parallel, and is less efficient than Serial, but is appropriate for parallel builds. Create an instance of this class for each job or thread you want. This class is thread safe. """ def __init__(self, taskmaster, jobs): """Create a new parallel job given a taskmaster, and a Jobs instance. Multiple jobs will be using the taskmaster in parallel, but all method calls to taskmaster methods are serialized by the jobs themselves. The taskmaster's next_task() method should return the next task that needs to be executed, or None if there are no more tasks. The taskmaster's executed() method will be called for each task when it is successfully executed or failed() will be called if the task failed to execute (i.e. execute() raised an exception). The taskmaster's is_blocked() method should return true iff there are more tasks, but they can't be executed until one or more other tasks have been executed. next_task() will be called iff is_blocked() returned false. Note: calls to taskmaster are serialized, but calls to execute() on distinct tasks are not serialized, because that is the whole point of parallel jobs: they can execute multiple tasks simultaneously. """ global cv # import threading here so that everything in the Job module # but the Parallel class will work if the interpreter doesn't # support threads import threading self.taskmaster = taskmaster self.jobs = jobs self.thread = threading.Thread(None, self.__run) self.stop_running = 0 if cv is None: cv = threading.Condition() def start(self): """Start the job. This will spawn a thread that will begin pulling tasks from the task master and executing them. This method returns immediately and doesn't wait for the jobs to be executed. If a task fails to execute (i.e. execute() raises an exception), all jobs will be stopped. To stop the job, call stop(). To wait for the job to finish, call wait(). """ self.thread.start() def stop(self): """Stop the job. This will cause the job to finish after the currently executing task is done. A job that has been stopped can not be restarted. To wait for the job to finish, call wait(). """ cv.acquire() self.stop_running = 1 # wake up the sleeping jobs so this job will end as soon as possible: cv.notifyAll() cv.release() def wait(self): """Wait for the job to finish. A job is finished when either there are no more tasks or the job has been stopped and it is no longer executing a task. This method should only be called after start() has been called. To stop the job, call stop(). """ self.thread.join() def __run(self): """private method that actually executes the tasks""" cv.acquire() try: while 1: while self.taskmaster.is_blocked() and not self.stop_running: cv.wait(None) # check this before calling next_task(), because # this job may have been stopped because of a build # failure: if self.stop_running: break task = self.taskmaster.next_task() if task == None: break cv.release() try: try: task.execute() finally: cv.acquire() except: self.taskmaster.failed(task) # stop all jobs since there was a failure: # (this will wake up any waiting jobs, so # it isn't necessary to explicitly wake them # here) self.jobs.stop() else: self.taskmaster.executed(task) if not self.taskmaster.is_blocked(): cv.notifyAll() finally: cv.release()