[232] | 1 | """Easy to use object-oriented thread pool framework. |
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| 2 | |
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| 3 | A thread pool is an object that maintains a pool of worker threads to perform |
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| 4 | time consuming operations in parallel. It assigns jobs to the threads |
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| 5 | by putting them in a work request queue, where they are picked up by the |
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| 6 | next available thread. This then performs the requested operation in the |
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| 7 | background and puts the results in a another queue. |
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| 8 | |
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| 9 | The thread pool object can then collect the results from all threads from |
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| 10 | this queue as soon as they become available or after all threads have |
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| 11 | finished their work. It's also possible, to define callbacks to handle |
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| 12 | each result as it comes in. |
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| 13 | |
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| 14 | The basic concept and some code was taken from the book "Python in a Nutshell" |
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| 15 | by Alex Martelli, copyright 2003, ISBN 0-596-00188-6, from section 14.5 |
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| 16 | "Threaded Program Architecture". I wrapped the main program logic in the |
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| 17 | ThreadPool class, added the WorkRequest class and the callback system and |
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| 18 | tweaked the code here and there. Kudos also to Florent Aide for the exception |
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| 19 | handling mechanism. |
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| 20 | |
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| 21 | Basic usage: |
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| 22 | |
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| 23 | >>> pool = TreadPool(poolsize) |
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| 24 | >>> requests = makeRequests(some_callable, list_of_args, callback) |
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| 25 | >>> [pool.putRequest(req) for req in requests] |
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| 26 | >>> pool.wait() |
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| 27 | |
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| 28 | See the end of the module code for a brief, annotated usage example. |
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| 29 | |
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| 30 | Website : http://chrisarndt.de/en/software/python/threadpool/ |
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| 31 | """ |
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| 32 | |
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| 33 | __all__ = [ |
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| 34 | 'makeRequests', |
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| 35 | 'NoResultsPending', |
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| 36 | 'NoWorkersAvailable', |
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| 37 | 'ThreadPool', |
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| 38 | 'WorkRequest', |
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| 39 | 'WorkerThread' |
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| 40 | ] |
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| 41 | |
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| 42 | __author__ = "Christopher Arndt" |
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| 43 | __version__ = "1.2.3" |
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| 44 | __revision__ = "$Revision: 1.5 $" |
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| 45 | __date__ = "$Date: 2006/06/23 12:32:25 $" |
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| 46 | __license__ = 'Python license' |
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| 47 | |
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| 48 | # standard library modules |
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| 49 | import sys |
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| 50 | import threading |
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| 51 | import Queue |
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| 52 | |
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| 53 | # exceptions |
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| 54 | class NoResultsPending(Exception): |
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| 55 | """All work requests have been processed.""" |
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| 56 | pass |
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| 57 | |
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| 58 | class NoWorkersAvailable(Exception): |
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| 59 | """No worker threads available to process remaining requests.""" |
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| 60 | pass |
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| 61 | |
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| 62 | # classes |
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| 63 | class WorkerThread(threading.Thread): |
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| 64 | """Background thread connected to the requests/results queues. |
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| 65 | |
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| 66 | A worker thread sits in the background and picks up work requests from |
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| 67 | one queue and puts the results in another until it is dismissed. |
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| 68 | """ |
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| 69 | |
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| 70 | def __init__(self, requestsQueue, resultsQueue, **kwds): |
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| 71 | """Set up thread in daemonic mode and start it immediatedly. |
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| 72 | |
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| 73 | requestsQueue and resultQueue are instances of Queue.Queue passed |
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| 74 | by the ThreadPool class when it creates a new worker thread. |
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| 75 | """ |
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| 76 | |
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| 77 | threading.Thread.__init__(self, **kwds) |
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| 78 | self.setDaemon(1) |
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| 79 | self.workRequestQueue = requestsQueue |
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| 80 | self.resultQueue = resultsQueue |
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| 81 | self._dismissed = threading.Event() |
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| 82 | self.start() |
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| 83 | |
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| 84 | def run(self): |
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| 85 | """Repeatedly process the job queue until told to exit.""" |
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| 86 | |
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| 87 | while not self._dismissed.isSet(): |
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| 88 | # thread blocks here, if queue empty |
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| 89 | request = self.workRequestQueue.get() |
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| 90 | if self._dismissed.isSet(): |
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| 91 | # if told to exit, return the work request we just picked up |
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| 92 | self.workRequestQueue.put(request) |
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| 93 | break # and exit |
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| 94 | try: |
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| 95 | self.resultQueue.put( |
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| 96 | (request, request.callable(*request.args, **request.kwds)) |
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| 97 | ) |
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| 98 | except: |
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| 99 | request.exception = True |
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| 100 | self.resultQueue.put((request, sys.exc_info())) |
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| 101 | |
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| 102 | def dismiss(self): |
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| 103 | """Sets a flag to tell the thread to exit when done with current job. |
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| 104 | """ |
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| 105 | |
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| 106 | self._dismissed.set() |
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| 107 | |
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| 108 | |
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| 109 | class WorkRequest: |
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| 110 | """A request to execute a callable for putting in the request queue later. |
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| 111 | |
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| 112 | See the module function makeRequests() for the common case |
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| 113 | where you want to build several WorkRequests for the same callable |
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| 114 | but with different arguments for each call. |
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| 115 | """ |
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| 116 | |
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| 117 | def __init__(self, callable, args=None, kwds=None, requestID=None, |
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| 118 | callback=None, exc_callback=None): |
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| 119 | """Create a work request for a callable and attach callbacks. |
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| 120 | |
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| 121 | A work request consists of the a callable to be executed by a |
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| 122 | worker thread, a list of positional arguments, a dictionary |
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| 123 | of keyword arguments. |
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| 124 | |
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| 125 | A callback function can be specified, that is called when the results |
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| 126 | of the request are picked up from the result queue. It must accept |
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| 127 | two arguments, the request object and the results of the callable, |
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| 128 | in that order. If you want to pass additional information to the |
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| 129 | callback, just stick it on the request object. |
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| 130 | |
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| 131 | You can also give a callback for when an exception occurs. It should |
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| 132 | also accept two arguments, the work request and a tuple with the |
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| 133 | exception details as returned by sys.exc_info(). |
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| 134 | |
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| 135 | requestID, if given, must be hashable since it is used by the |
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| 136 | ThreadPool object to store the results of that work request in a |
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| 137 | dictionary. It defaults to the return value of id(self). |
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| 138 | """ |
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| 139 | |
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| 140 | if requestID is None: |
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| 141 | self.requestID = id(self) |
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| 142 | else: |
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| 143 | try: |
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| 144 | hash(requestID) |
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| 145 | except TypeError: |
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| 146 | raise TypeError("requestID must be hashable.") |
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| 147 | self.requestID = requestID |
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| 148 | self.exception = False |
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| 149 | self.callback = callback |
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| 150 | self.exc_callback = exc_callback |
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| 151 | self.callable = callable |
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| 152 | self.args = args or [] |
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| 153 | self.kwds = kwds or {} |
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| 154 | |
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| 155 | |
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| 156 | class ThreadPool: |
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| 157 | """A thread pool, distributing work requests and collecting results. |
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| 158 | |
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| 159 | See the module doctring for more information. |
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| 160 | """ |
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| 161 | |
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| 162 | def __init__(self, num_workers, q_size=0): |
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| 163 | """Set up the thread pool and start num_workers worker threads. |
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| 164 | |
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| 165 | num_workers is the number of worker threads to start initialy. |
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| 166 | If q_size > 0 the size of the work request queue is limited and |
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| 167 | the thread pool blocks when the queue is full and it tries to put |
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| 168 | more work requests in it (see putRequest method). |
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| 169 | """ |
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| 170 | |
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| 171 | self.requestsQueue = Queue.Queue(q_size) |
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| 172 | self.resultsQueue = Queue.Queue() |
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| 173 | self.workers = [] |
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| 174 | self.workRequests = {} |
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| 175 | self.createWorkers(num_workers) |
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| 176 | |
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| 177 | def createWorkers(self, num_workers): |
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| 178 | """Add num_workers worker threads to the pool.""" |
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| 179 | |
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| 180 | for i in range(num_workers): |
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| 181 | self.workers.append(WorkerThread(self.requestsQueue, |
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| 182 | self.resultsQueue)) |
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| 183 | |
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| 184 | def dismissWorkers(self, num_workers): |
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| 185 | """Tell num_workers worker threads to quit after their current task. |
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| 186 | """ |
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| 187 | |
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| 188 | for i in range(min(num_workers, len(self.workers))): |
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| 189 | worker = self.workers.pop() |
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| 190 | worker.dismiss() |
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| 191 | |
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| 192 | def putRequest(self, request, block=True, timeout=0): |
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| 193 | """Put work request into work queue and save its id for later.""" |
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| 194 | |
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| 195 | assert isinstance(request, WorkRequest) |
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[236] | 196 | self.requestsQueue.put(item=request, block=block)#,timeout=timeout) |
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[232] | 197 | self.workRequests[request.requestID] = request |
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| 198 | |
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| 199 | def poll(self, block=False): |
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| 200 | """Process any new results in the queue.""" |
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| 201 | |
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| 202 | while True: |
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| 203 | # still results pending? |
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| 204 | if not self.workRequests: |
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| 205 | raise NoResultsPending |
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| 206 | # are there still workers to process remaining requests? |
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| 207 | elif block and not self.workers: |
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| 208 | raise NoWorkersAvailable |
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| 209 | try: |
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| 210 | # get back next results |
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| 211 | request, result = self.resultsQueue.get(block=block) |
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| 212 | # has an exception occured? |
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| 213 | if request.exception and request.exc_callback: |
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| 214 | request.exc_callback(request, result) |
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| 215 | # hand results to callback, if any |
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| 216 | if request.callback and not \ |
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| 217 | (request.exception and request.exc_callback): |
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| 218 | request.callback(request, result) |
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| 219 | del self.workRequests[request.requestID] |
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| 220 | except Queue.Empty: |
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| 221 | break |
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| 222 | |
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| 223 | def wait(self): |
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| 224 | """Wait for results, blocking until all have arrived.""" |
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| 225 | while 1: |
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| 226 | try: |
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| 227 | self.poll(True) |
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| 228 | except NoResultsPending: |
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| 229 | break |
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| 230 | # helper functions |
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| 231 | def makeRequests(callable, args_list, callback=None, exc_callback=None): |
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| 232 | """Create several work requests for same callable with different arguments. |
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| 233 | |
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| 234 | Convenience function for creating several work requests for the same |
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| 235 | callable where each invocation of the callable receives different values |
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| 236 | for its arguments. |
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| 237 | |
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| 238 | args_list contains the parameters for each invocation of callable. |
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| 239 | Each item in 'args_list' should be either a 2-item tuple of the list of |
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| 240 | positional arguments and a dictionary of keyword arguments or a single, |
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| 241 | non-tuple argument. |
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| 242 | |
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| 243 | See docstring for WorkRequest for info on callback and exc_callback. |
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| 244 | """ |
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| 245 | |
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| 246 | requests = [] |
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| 247 | for item in args_list: |
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| 248 | if isinstance(item, tuple): |
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| 249 | requests.append( |
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| 250 | WorkRequest(callable, item[0], item[1], callback=callback, |
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| 251 | exc_callback=exc_callback) |
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| 252 | ) |
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| 253 | else: |
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| 254 | requests.append( |
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| 255 | WorkRequest(callable, [item], None, callback=callback, |
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| 256 | exc_callback=exc_callback) |
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| 257 | ) |
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| 258 | return requests |
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| 259 | |
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| 260 | |
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| 261 | #------------------------------ EoF ------------------------------# |
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