master: split Select() into new module to reduce wire size.
service.py currently imports master.py(+parent.py) just to get Select().pull/255/head
David Wilson
7 years ago
parent
7a592d1c34
commit
ddf28987a0
@ -0,0 +1,133 @@
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# Copyright 2017, David Wilson
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#
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# Redistribution and use in source and binary forms, with or without
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# modification, are permitted provided that the following conditions are met:
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#
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# 1. Redistributions of source code must retain the above copyright notice,
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# this list of conditions and the following disclaimer.
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#
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# 2. Redistributions in binary form must reproduce the above copyright notice,
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# this list of conditions and the following disclaimer in the documentation
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# and/or other materials provided with the distribution.
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#
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# 3. Neither the name of the copyright holder nor the names of its contributors
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# may be used to endorse or promote products derived from this software without
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# specific prior written permission.
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#
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# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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# AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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# ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
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# LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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# CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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# SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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# INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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# CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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# ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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# POSSIBILITY OF SUCH DAMAGE.
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import mitogen.core
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class Error(mitogen.core.Error):
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pass
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class Select(object):
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notify = None
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@classmethod
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def all(cls, receivers):
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return list(msg.unpickle() for msg in cls(receivers))
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def __init__(self, receivers=(), oneshot=True):
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self._receivers = []
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self._oneshot = oneshot
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self._latch = mitogen.core.Latch()
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for recv in receivers:
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self.add(recv)
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def _put(self, value):
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self._latch.put(value)
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if self.notify:
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self.notify(self)
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def __bool__(self):
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return bool(self._receivers)
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def __enter__(self):
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return self
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def __exit__(self, e_type, e_val, e_tb):
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self.close()
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def __iter__(self):
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while self._receivers:
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yield self.get()
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loop_msg = 'Adding this Select instance would create a Select cycle'
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def _check_no_loop(self, recv):
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if recv is self:
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raise Error(self.loop_msg)
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for recv_ in self._receivers:
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if recv_ == recv:
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raise Error(self.loop_msg)
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if isinstance(recv_, Select):
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recv_._check_no_loop(recv)
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owned_msg = 'Cannot add: Receiver is already owned by another Select'
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def add(self, recv):
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if isinstance(recv, Select):
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recv._check_no_loop(self)
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self._receivers.append(recv)
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if recv.notify is not None:
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raise Error(self.owned_msg)
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recv.notify = self._put
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# Avoid race by polling once after installation.
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if not recv.empty():
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self._put(recv)
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not_present_msg = 'Instance is not a member of this Select'
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def remove(self, recv):
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try:
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if recv.notify != self._put:
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raise ValueError
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self._receivers.remove(recv)
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recv.notify = None
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except (IndexError, ValueError):
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raise Error(self.not_present_msg)
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def close(self):
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for recv in self._receivers[:]:
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self.remove(recv)
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self._latch.close()
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def empty(self):
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return self._latch.empty()
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empty_msg = 'Cannot get(), Select instance is empty'
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def get(self, timeout=None):
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if not self._receivers:
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raise Error(self.empty_msg)
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while True:
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recv = self._latch.get(timeout=timeout)
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try:
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msg = recv.get(block=False)
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if self._oneshot:
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self.remove(recv)
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msg.receiver = recv
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return msg
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except mitogen.core.TimeoutError:
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# A receiver may have been queued with no result if another
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# thread drained it before we woke up, or because another
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# thread drained it between add() calling recv.empty() and
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# self._put(). In this case just sleep again.
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continue
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