source: fedd/federation/thread_pool.py @ bea19b7

#!/usr/local/bin/python

import logging
import time
import sys 
import traceback

from threading import Lock, Thread, Condition
from service_error import service_error

class thread_pool:
    """
    A class to keep track of a set of threads all invoked for the same
    task.  Manages the mutual exclusion of the states.
    """
    def __init__(self, nthreads):
        """
        Start a pool.
        """
        self.changed = Condition()
        self.started = 0
        self.terminated = 0
        self.nthreads = nthreads

    def acquire(self):
        """
        Get the pool's lock.
        """
        self.changed.acquire()

    def release(self):
        """
        Release the pool's lock.
        """
        self.changed.release()

    def wait(self, timeout = None):
        """
        Wait for a pool thread to start or stop.
        """
        self.changed.wait(timeout)

    def start(self):
        """
        Called by a pool thread to report starting.
        """
        self.changed.acquire()
        self.started += 1
        self.changed.notifyAll()
        self.changed.release()

    def terminate(self):
        """
        Called by a pool thread to report finishing.
        """
        self.changed.acquire()
        self.terminated += 1
        self.changed.notifyAll()
        self.changed.release()

    def clear(self):
        """
        Clear all pool data.
        """
        self.changed.acquire()
        self.started = 0
        self.terminated =0
        self.changed.notifyAll()
        self.changed.release()

    def wait_for_slot(self):
        """
        Wait until we have a free slot to start another pooled thread
        """
        self.acquire()
        while self.started - self.terminated >= self.nthreads:
            self.wait()
        self.release()

    def wait_for_all_done(self, timeout=None):
        """
        Wait until all active threads finish (and at least one has
        started).  If a timeout is given, return after waiting that long
        for termination.  If all threads are done (and one has started in
        the since the last clear()) return True, otherwise False.
        """
        if timeout:
            deadline = time.time() + timeout
        self.acquire()
        while self.started == 0 or self.started > self.terminated:
            self.wait(timeout)
            if timeout:
                if time.time() > deadline:
                    break
                timeout = deadline - time.time()
        self.release()
        return not (self.started == 0 or self.started > self.terminated)

class pooled_thread(Thread):
    """
    One of a set of threads dedicated to a specific task.  Uses the
    thread_pool class above for coordination.
    """
    def __init__(self, group=None, target=None, name=None, args=(), 
            kwargs={}, pdata=None, trace_file=None):
        Thread.__init__(self, group, target, name, args, kwargs)
        self.rv = None          # Return value of the ops in this thread
        self.exception = None   # Exception that terminated this thread
        self.target=target      # Target function to run on start()
        self.args = args        # Args to pass to target
        self.kwargs = kwargs    # Additional kw args
        self.pdata = pdata      # thread_pool for this class
        # Logger for this thread
        self.log = logging.getLogger("fedd.experiment_control")
    
    def run(self):
        """
        Emulate Thread.run, except add pool data manipulation and error
        logging.
        """
        if self.pdata:
            self.pdata.start()

        if self.target:
            try:
                self.rv = self.target(*self.args, **self.kwargs)
            except service_error, s:
                self.exception = s
                self.log.error("Thread exception: %s %s" % \
                        (s.code_string(), s.desc))
            except:
                self.exception = sys.exc_info()[1]
                self.log.error(("Unexpected thread exception: %s" +\
                        "Trace %s") % (self.exception,\
                            traceback.format_exc()))
        if self.pdata:
            self.pdata.terminate()