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37 lines
1.0 KiB
Python
37 lines
1.0 KiB
Python
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from twisted.internet import defer
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from foolscap.eventual import eventually
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class ConcurrencyLimiter:
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"""I implement a basic concurrency limiter. Add work to it in the form of
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(callable, args, kwargs) tuples. No more than LIMIT callables will be
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outstanding at any one time.
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"""
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def __init__(self, limit=10):
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self.limit = 10
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self.pending = []
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self.active = 0
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def add(self, cb, *args, **kwargs):
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d = defer.Deferred()
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task = (cb, args, kwargs, d)
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self.pending.append(task)
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self.maybe_start_task()
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return d
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def maybe_start_task(self):
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if self.active >= self.limit:
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return
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if not self.pending:
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return
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(cb, args, kwargs, done_d) = self.pending.pop(0)
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self.active += 1
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d = defer.maybeDeferred(cb, *args, **kwargs)
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d.addBoth(self._done, done_d)
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def _done(self, res, done_d):
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self.active -= 1
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eventually(done_d.callback, res)
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self.maybe_start_task()
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