349 lines
12 KiB
Python
349 lines
12 KiB
Python
# Copyright 2019, David Wilson
|
|
#
|
|
# Redistribution and use in source and binary forms, with or without
|
|
# modification, are permitted provided that the following conditions are met:
|
|
#
|
|
# 1. Redistributions of source code must retain the above copyright notice,
|
|
# this list of conditions and the following disclaimer.
|
|
#
|
|
# 2. Redistributions in binary form must reproduce the above copyright notice,
|
|
# this list of conditions and the following disclaimer in the documentation
|
|
# and/or other materials provided with the distribution.
|
|
#
|
|
# 3. Neither the name of the copyright holder nor the names of its contributors
|
|
# may be used to endorse or promote products derived from this software without
|
|
# specific prior written permission.
|
|
#
|
|
# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
|
|
# AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
|
|
# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
|
|
# ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
|
|
# LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
|
|
# CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
|
|
# SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
|
|
# INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
|
|
# CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
|
|
# ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
|
|
# POSSIBILITY OF SUCH DAMAGE.
|
|
|
|
# !mitogen: minify_safe
|
|
|
|
import mitogen.core
|
|
|
|
|
|
class Error(mitogen.core.Error):
|
|
pass
|
|
|
|
|
|
class Event(object):
|
|
"""
|
|
Represents one selected event.
|
|
"""
|
|
#: The first Receiver or Latch the event traversed.
|
|
source = None
|
|
|
|
#: The :class:`mitogen.core.Message` delivered to a receiver, or the object
|
|
#: posted to a latch.
|
|
data = None
|
|
|
|
|
|
class Select(object):
|
|
"""
|
|
Support scatter/gather asynchronous calls and waiting on multiple
|
|
:class:`receivers <mitogen.core.Receiver>`,
|
|
:class:`channels <mitogen.core.Channel>`,
|
|
:class:`latches <mitogen.core.Latch>`, and
|
|
:class:`sub-selects <Select>`.
|
|
|
|
If `oneshot` is :data:`True`, then remove each receiver as it yields a
|
|
result; since :meth:`__iter__` terminates once the final receiver is
|
|
removed, this makes it convenient to respond to calls made in parallel::
|
|
|
|
total = 0
|
|
recvs = [c.call_async(long_running_operation) for c in contexts]
|
|
|
|
for msg in mitogen.select.Select(recvs):
|
|
print('Got %s from %s' % (msg, msg.receiver))
|
|
total += msg.unpickle()
|
|
|
|
# Iteration ends when last Receiver yields a result.
|
|
print('Received total %s from %s receivers' % (total, len(recvs)))
|
|
|
|
:class:`Select` may drive a long-running scheduler:
|
|
|
|
.. code-block:: python
|
|
|
|
with mitogen.select.Select(oneshot=False) as select:
|
|
while running():
|
|
for msg in select:
|
|
process_result(msg.receiver.context, msg.unpickle())
|
|
for context, workfunc in get_new_work():
|
|
select.add(context.call_async(workfunc))
|
|
|
|
:class:`Select` may be nested:
|
|
|
|
.. code-block:: python
|
|
|
|
subselects = [
|
|
mitogen.select.Select(get_some_work()),
|
|
mitogen.select.Select(get_some_work()),
|
|
mitogen.select.Select([
|
|
mitogen.select.Select(get_some_work()),
|
|
mitogen.select.Select(get_some_work())
|
|
])
|
|
]
|
|
|
|
for msg in mitogen.select.Select(selects):
|
|
print(msg.unpickle())
|
|
|
|
:class:`Select` may be used to mix inter-thread and inter-process IO::
|
|
|
|
latch = mitogen.core.Latch()
|
|
start_thread(latch)
|
|
recv = remote_host.call_async(os.getuid)
|
|
|
|
sel = Select([latch, recv])
|
|
event = sel.get_event()
|
|
if event.source is latch:
|
|
# woken by a local thread
|
|
else:
|
|
# woken by function call result
|
|
"""
|
|
|
|
notify = None
|
|
|
|
def __init__(self, receivers=(), oneshot=True):
|
|
self._receivers = []
|
|
self._oneshot = oneshot
|
|
self._latch = mitogen.core.Latch()
|
|
for recv in receivers:
|
|
self.add(recv)
|
|
|
|
@classmethod
|
|
def all(cls, receivers):
|
|
"""
|
|
Take an iterable of receivers and retrieve a :class:`Message
|
|
<mitogen.core.Message>` from each, returning the result of calling
|
|
:meth:`Message.unpickle() <mitogen.core.Message.unpickle>` on each in
|
|
turn. Results are returned in the order they arrived.
|
|
|
|
This is sugar for handling batch :meth:`Context.call_async
|
|
<mitogen.parent.Context.call_async>` invocations:
|
|
|
|
.. code-block:: python
|
|
|
|
print('Total disk usage: %.02fMiB' % (sum(
|
|
mitogen.select.Select.all(
|
|
context.call_async(get_disk_usage)
|
|
for context in contexts
|
|
) / 1048576.0
|
|
),))
|
|
|
|
However, unlike in a naive comprehension such as:
|
|
|
|
.. code-block:: python
|
|
|
|
recvs = [c.call_async(get_disk_usage) for c in contexts]
|
|
sum(recv.get().unpickle() for recv in recvs)
|
|
|
|
Result processing happens in the order results arrive, rather than the
|
|
order requests were issued, so :meth:`all` should always be faster.
|
|
"""
|
|
return list(msg.unpickle() for msg in cls(receivers))
|
|
|
|
def _put(self, value):
|
|
self._latch.put(value)
|
|
if self.notify:
|
|
self.notify(self)
|
|
|
|
def __bool__(self):
|
|
"""
|
|
Return :data:`True` if any receivers are registered with this select.
|
|
"""
|
|
return bool(self._receivers)
|
|
|
|
__nonzero__ = __bool__
|
|
|
|
def __enter__(self):
|
|
return self
|
|
|
|
def __exit__(self, e_type, e_val, e_tb):
|
|
self.close()
|
|
|
|
def iter_data(self):
|
|
"""
|
|
Yield :attr:`Event.data` until no receivers remain in the select,
|
|
either because `oneshot` is :data:`True`, or each receiver was
|
|
explicitly removed via :meth:`remove`.
|
|
|
|
:meth:`__iter__` is an alias for :meth:`iter_data`, allowing loops
|
|
like::
|
|
|
|
for msg in Select([recv1, recv2]):
|
|
print msg.unpickle()
|
|
"""
|
|
while self._receivers:
|
|
yield self.get_event().data
|
|
|
|
__iter__ = iter_data
|
|
|
|
def iter_events(self):
|
|
"""
|
|
Yield :class:`Event` instances until no receivers remain in the select.
|
|
"""
|
|
while self._receivers:
|
|
yield self.get_event()
|
|
|
|
loop_msg = 'Adding this Select instance would create a Select cycle'
|
|
|
|
def _check_no_loop(self, recv):
|
|
if recv is self:
|
|
raise Error(self.loop_msg)
|
|
|
|
for recv_ in self._receivers:
|
|
if recv_ == recv:
|
|
raise Error(self.loop_msg)
|
|
if isinstance(recv_, Select):
|
|
recv_._check_no_loop(recv)
|
|
|
|
owned_msg = 'Cannot add: Receiver is already owned by another Select'
|
|
|
|
def add(self, recv):
|
|
"""
|
|
Add a :class:`mitogen.core.Receiver`, :class:`Select` or
|
|
:class:`mitogen.core.Latch` to the select.
|
|
|
|
:raises mitogen.select.Error:
|
|
An attempt was made to add a :class:`Select` to which this select
|
|
is indirectly a member of.
|
|
"""
|
|
if isinstance(recv, Select):
|
|
recv._check_no_loop(self)
|
|
|
|
self._receivers.append(recv)
|
|
if recv.notify is not None:
|
|
raise Error(self.owned_msg)
|
|
|
|
recv.notify = self._put
|
|
# After installing the notify function, _put() will potentially begin
|
|
# receiving calls from other threads immediately, but not for items
|
|
# they already had buffered. For those we call _put(), possibly
|
|
# duplicating the effect of other _put() being made concurrently, such
|
|
# that the Select ends up with more items in its buffer than exist in
|
|
# the underlying receivers. We handle the possibility of receivers
|
|
# marked notified yet empty inside Select.get(), so this should be
|
|
# robust.
|
|
for _ in range(recv.size()):
|
|
self._put(recv)
|
|
|
|
not_present_msg = 'Instance is not a member of this Select'
|
|
|
|
def remove(self, recv):
|
|
"""
|
|
Remove an object from from the select. Note that if the receiver has
|
|
notified prior to :meth:`remove`, it will still be returned by a
|
|
subsequent :meth:`get`. This may change in a future version.
|
|
"""
|
|
try:
|
|
if recv.notify != self._put:
|
|
raise ValueError
|
|
self._receivers.remove(recv)
|
|
recv.notify = None
|
|
except (IndexError, ValueError):
|
|
raise Error(self.not_present_msg)
|
|
|
|
def close(self):
|
|
"""
|
|
Remove the select's notifier function from each registered receiver,
|
|
mark the associated latch as closed, and cause any thread currently
|
|
sleeping in :meth:`get` to be woken with
|
|
:class:`mitogen.core.LatchError`.
|
|
|
|
This is necessary to prevent memory leaks in long-running receivers. It
|
|
is called automatically when the Python :keyword:`with` statement is
|
|
used.
|
|
"""
|
|
for recv in self._receivers[:]:
|
|
self.remove(recv)
|
|
self._latch.close()
|
|
|
|
def size(self):
|
|
"""
|
|
Return the number of items currently buffered.
|
|
|
|
As with :class:`Queue.Queue`, `0` may be returned even though a
|
|
subsequent call to :meth:`get` will succeed, since a message may be
|
|
posted at any moment between :meth:`size` and :meth:`get`.
|
|
|
|
As with :class:`Queue.Queue`, `>0` may be returned even though a
|
|
subsequent call to :meth:`get` will block, since another waiting thread
|
|
may be woken at any moment between :meth:`size` and :meth:`get`.
|
|
"""
|
|
return sum(recv.size() for recv in self._receivers)
|
|
|
|
def empty(self):
|
|
"""
|
|
Return `size() == 0`.
|
|
|
|
.. deprecated:: 0.2.8
|
|
Use :meth:`size` instead.
|
|
"""
|
|
return self._latch.empty()
|
|
|
|
empty_msg = 'Cannot get(), Select instance is empty'
|
|
|
|
def get(self, timeout=None, block=True):
|
|
"""
|
|
Call `get_event(timeout, block)` returning :attr:`Event.data` of the
|
|
first available event.
|
|
"""
|
|
return self.get_event(timeout, block).data
|
|
|
|
def get_event(self, timeout=None, block=True):
|
|
"""
|
|
Fetch the next available :class:`Event` from any source, or raise
|
|
:class:`mitogen.core.TimeoutError` if no value is available within
|
|
`timeout` seconds.
|
|
|
|
On success, the message's :attr:`receiver
|
|
<mitogen.core.Message.receiver>` attribute is set to the receiver.
|
|
|
|
:param float timeout:
|
|
Timeout in seconds.
|
|
:param bool block:
|
|
If :data:`False`, immediately raise
|
|
:class:`mitogen.core.TimeoutError` if the select is empty.
|
|
:return:
|
|
:class:`Event`.
|
|
:raises mitogen.core.TimeoutError:
|
|
Timeout was reached.
|
|
:raises mitogen.core.LatchError:
|
|
:meth:`close` has been called, and the underlying latch is no
|
|
longer valid.
|
|
"""
|
|
if not self._receivers:
|
|
raise Error(self.empty_msg)
|
|
|
|
while True:
|
|
recv = self._latch.get(timeout=timeout, block=block)
|
|
try:
|
|
if isinstance(recv, Select):
|
|
event = recv.get_event(block=False)
|
|
else:
|
|
event = Event()
|
|
event.source = recv
|
|
event.data = recv.get(block=False)
|
|
if self._oneshot:
|
|
self.remove(recv)
|
|
if isinstance(recv, mitogen.core.Receiver):
|
|
# Remove in 0.3.x.
|
|
event.data.receiver = recv
|
|
return event
|
|
except mitogen.core.TimeoutError:
|
|
# A receiver may have been queued with no result if another
|
|
# thread drained it before we woke up, or because another
|
|
# thread drained it between add() calling recv.empty() and
|
|
# self._put(), or because Select.add() caused duplicate _put()
|
|
# calls. In this case simply retry.
|
|
continue
|