AsyncCallThread.py

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#  This module was kindly provided by the Ganga developer
#
#    Jakub (Kuba) Moscicki Jakub.Moscicki@cern.ch
#
#  to provide a timeout wrapper for commands that might possibly hang.

from threading import Thread
import time

class AsyncCallThread(Thread):
    """Asynchronous function call thread.  The result of call
    func(*args,**kwds) is stored in the result attribute.  If an exception is
    raised the exception object is stored in the exception
    attribute. Otherwise the exception attribute is None.  The caller is
    notified with the callback(t) where t is this thread object.
    """
    def __init__(self, callback, func, *args, **kwds):
        Thread.__init__(self,name = 'async_call_%s'%func.__name__)
        self.callback = callback
        self.func = func
        self.args = args
        self.kwds = kwds
        self.result = None
        self.exception = None
        self.start_time = 0
        self.stop_time = 0
        self.setDaemon(True)  #This allows python to end even if thread still active.
        
    def run(self):
        self.start_time = time.time()

        try:
            print "Making asynchronous call:",self.func.__name__,self.args,self.kwds
            self.result = self.func(*self.args,**self.kwds)
        except Exception,x:
            self.exception = x

        self.stop_time = time.time()
        self.callback(self)

        
def async_call(callback,func, *args, **kwds):
    """Call func asynchronously in a separate thread. See AsyncCallThread class for details."""
    t = AsyncCallThread(callback,func,*args,**kwds)
    t.start()
    return t


def timeout_call(caller,func, timeout, *args, **kwds):
    def callback(t):
        print 'completed'

    t = AsyncCallThread(callback,func,*args,**kwds)
    t.start()
    time.sleep(1)
    while time.time()-t.start_time < timeout:
        if t.stop_time:
            if t.exception:
                raise t.exception
            else:
                return t.result

        time.sleep(1)

    #  Extension to Kuba's code

    from GBSLogger    import GetLoggerThreshold, Log, logger 
    from GBSUtilities import RemoveChildProcesses
    from GBSTimeStamp import GBSTimeStamp
    
    Log(caller,logger.ERROR,"Timeout reached before asynchronous call ended ...")
    Log(caller,logger.ERROR,"...Attempting to delete child processes to unblock before raising timeout exception...")
    RemoveChildProcesses()    
    raise Exception('timeout!')

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