def handle_exception(self, typ, value, tb):
if not self.running and not self.finished:
self.future = TracebackFuture()
self.future.set_exc_info((typ, value, tb))
self.run()
return True
else:
return False
def start_yield_point():
try:
yielded.start(self)
if yielded.is_ready():
self.future.set_result(yielded.get_result())
else:
self.yield_point = yielded
except Exception:
self.future = TracebackFuture()
self.future.set_exc_info(sys.exc_info())
def next(self):
"""Returns a `.Future` that will yield the next available result.
Note that this `.Future` will not be the same object as any of
the inputs.
"""
self._running_future = TracebackFuture()
if self._finished:
self._return_result(self._finished.popleft())
return self._running_future
def handle_yield(self, yielded):
# Lists containing YieldPoints require stack contexts;
# other lists are handled in convert_yielded.
if _contains_yieldpoint(yielded):
yielded = multi(yielded)
if isinstance(yielded, YieldPoint):
# YieldPoints are too closely coupled to the Runner to go
# through the generic convert_yielded mechanism.
self.future = TracebackFuture()
def start_yield_point():
try:
yielded.start(self)
if yielded.is_ready():
self.future.set_result(yielded.get_result())
else:
self.yield_point = yielded
except Exception:
self.future = TracebackFuture()
self.future.set_exc_info(sys.exc_info())
if self.stack_context_deactivate is None:
# Start a stack context if this is the first
# YieldPoint we've seen.
with stack_context.ExceptionStackContext(
self.handle_exception) as deactivate:
self.stack_context_deactivate = deactivate
def cb():
start_yield_point()
self.run()
self.io_loop.add_callback(cb)
return False
else:
start_yield_point()
else:
try:
self.future = convert_yielded(yielded)
except BadYieldError:
self.future = TracebackFuture()
self.future.set_exc_info(sys.exc_info())
if not self.future.done() or self.future is moment:
self.io_loop.add_future(self.future, lambda f: self.run())
return False
return True
def run():
try:
result = func()
if result is not None:
from hurray.server.gen import convert_yielded
result = convert_yielded(result)
except Exception:
future_cell[0] = TracebackFuture()
future_cell[0].set_exc_info(sys.exc_info())
else:
if is_future(result):
future_cell[0] = result
else:
future_cell[0] = TracebackFuture()
future_cell[0].set_result(result)
self.add_future(future_cell[0], lambda future: self.stop())
class Runner(object):
"""Internal implementation of `hurray.server.gen.engine`.
Maintains information about pending callbacks and their results.
The results of the generator are stored in ``result_future`` (a
`.TracebackFuture`)
"""
def __init__(self, gen, result_future, first_yielded):
self.gen = gen
self.result_future = result_future
self.future = _null_future
self.yield_point = None
self.pending_callbacks = None
self.results = None
self.running = False
self.finished = False
self.had_exception = False
self.io_loop = IOLoop.current()
# For efficiency, we do not create a stack context until we
# reach a YieldPoint (stack contexts are required for the historical
# semantics of YieldPoints, but not for Futures). When we have
# done so, this field will be set and must be called at the end
# of the coroutine.
self.stack_context_deactivate = None
if self.handle_yield(first_yielded):
self.run()
def register_callback(self, key):
"""Adds ``key`` to the list of callbacks."""
if self.pending_callbacks is None:
# Lazily initialize the old-style YieldPoint data structures.
self.pending_callbacks = set()
self.results = {}
if key in self.pending_callbacks:
raise KeyReuseError("key %r is already pending" % (key, ))
self.pending_callbacks.add(key)
def is_ready(self, key):
"""Returns true if a result is available for ``key``."""
if self.pending_callbacks is None or key not in self.pending_callbacks:
raise UnknownKeyError("key %r is not pending" % (key, ))
return key in self.results
def set_result(self, key, result):
"""Sets the result for ``key`` and attempts to resume the generator."""
self.results[key] = result
if self.yield_point is not None and self.yield_point.is_ready():
try:
self.future.set_result(self.yield_point.get_result())
except:
self.future.set_exc_info(sys.exc_info())
self.yield_point = None
self.run()
def pop_result(self, key):
"""Returns the result for ``key`` and unregisters it."""
self.pending_callbacks.remove(key)
return self.results.pop(key)
def run(self):
"""Starts or resumes the generator, running until it reaches a
yield point that is not ready.
"""
if self.running or self.finished:
return
try:
self.running = True
while True:
future = self.future
if not future.done():
return
self.future = None
try:
orig_stack_contexts = stack_context._state.contexts
exc_info = None
try:
value = future.result()
except Exception:
self.had_exception = True
exc_info = sys.exc_info()
if exc_info is not None:
yielded = self.gen.throw(*exc_info)
exc_info = None
else:
yielded = self.gen.send(value)
if stack_context._state.contexts is not orig_stack_contexts:
self.gen.throw(
stack_context.StackContextInconsistentError(
'stack_context inconsistency (probably caused '
'by yield within a "with StackContext" block)')
)
except (StopIteration, Return) as e:
self.finished = True
self.future = _null_future
if self.pending_callbacks and not self.had_exception:
# If we ran cleanly without waiting on all callbacks
# raise an error (really more of a warning). If we
# had an exception then some callbacks may have been
# orphaned, so skip the check in that case.
raise LeakedCallbackError(
"finished without waiting for callbacks %r" %
self.pending_callbacks)
self.result_future.set_result(_value_from_stopiteration(e))
self.result_future = None
self._deactivate_stack_context()
return
except Exception:
self.finished = True
self.future = _null_future
self.result_future.set_exc_info(sys.exc_info())
self.result_future = None
self._deactivate_stack_context()
return
if not self.handle_yield(yielded):
return
finally:
self.running = False
def handle_yield(self, yielded):
# Lists containing YieldPoints require stack contexts;
# other lists are handled in convert_yielded.
if _contains_yieldpoint(yielded):
yielded = multi(yielded)
if isinstance(yielded, YieldPoint):
# YieldPoints are too closely coupled to the Runner to go
# through the generic convert_yielded mechanism.
self.future = TracebackFuture()
def start_yield_point():
try:
yielded.start(self)
if yielded.is_ready():
self.future.set_result(yielded.get_result())
else:
self.yield_point = yielded
except Exception:
self.future = TracebackFuture()
self.future.set_exc_info(sys.exc_info())
if self.stack_context_deactivate is None:
# Start a stack context if this is the first
# YieldPoint we've seen.
with stack_context.ExceptionStackContext(
self.handle_exception) as deactivate:
self.stack_context_deactivate = deactivate
def cb():
start_yield_point()
self.run()
self.io_loop.add_callback(cb)
return False
else:
start_yield_point()
else:
try:
self.future = convert_yielded(yielded)
except BadYieldError:
self.future = TracebackFuture()
self.future.set_exc_info(sys.exc_info())
if not self.future.done() or self.future is moment:
self.io_loop.add_future(self.future, lambda f: self.run())
return False
return True
def result_callback(self, key):
return stack_context.wrap(
_argument_adapter(functools.partial(self.set_result, key)))
def handle_exception(self, typ, value, tb):
if not self.running and not self.finished:
self.future = TracebackFuture()
self.future.set_exc_info((typ, value, tb))
self.run()
return True
else:
return False
def _deactivate_stack_context(self):
if self.stack_context_deactivate is not None:
self.stack_context_deactivate()
self.stack_context_deactivate = None
class WaitIterator(object):
"""Provides an iterator to yield the results of futures as they finish.
Yielding a set of futures like this:
``results = yield [future1, future2]``
pauses the coroutine until both ``future1`` and ``future2``
return, and then restarts the coroutine with the results of both
futures. If either future is an exception, the expression will
raise that exception and all the results will be lost.
If you need to get the result of each future as soon as possible,
or if you need the result of some futures even if others produce
errors, you can use ``WaitIterator``::
wait_iterator = gen.WaitIterator(future1, future2)
while not wait_iterator.done():
try:
result = yield wait_iterator.next()
except Exception as e:
print("Error {} from {}".format(e, wait_iterator.current_future))
else:
print("Result {} received from {} at {}".format(
result, wait_iterator.current_future,
wait_iterator.current_index))
Because results are returned as soon as they are available the
output from the iterator *will not be in the same order as the
input arguments*. If you need to know which future produced the
current result, you can use the attributes
``WaitIterator.current_future``, or ``WaitIterator.current_index``
to get the index of the future from the input list. (if keyword
arguments were used in the construction of the `WaitIterator`,
``current_index`` will use the corresponding keyword).
On Python 3.5, `WaitIterator` implements the async iterator
protocol, so it can be used with the ``async for`` statement (note
that in this version the entire iteration is aborted if any value
raises an exception, while the previous example can continue past
individual errors)::
async for result in gen.WaitIterator(future1, future2):
print("Result {} received from {} at {}".format(
result, wait_iterator.current_future,
wait_iterator.current_index))
.. versionadded:: 4.1
.. versionchanged:: 4.3
Added ``async for`` support in Python 3.5.
"""
def __init__(self, *args, **kwargs):
if args and kwargs:
raise ValueError("You must provide args or kwargs, not both")
if kwargs:
self._unfinished = dict((f, k) for (k, f) in kwargs.items())
futures = list(kwargs.values())
else:
self._unfinished = dict((f, i) for (i, f) in enumerate(args))
futures = args
self._finished = collections.deque()
self.current_index = self.current_future = None
self._running_future = None
for future in futures:
future.add_done_callback(self._done_callback)
def done(self):
"""Returns True if this iterator has no more results."""
if self._finished or self._unfinished:
return False
# Clear the 'current' values when iteration is done.
self.current_index = self.current_future = None
return True
def next(self):
"""Returns a `.Future` that will yield the next available result.
Note that this `.Future` will not be the same object as any of
the inputs.
"""
self._running_future = TracebackFuture()
if self._finished:
self._return_result(self._finished.popleft())
return self._running_future
def _done_callback(self, done):
if self._running_future and not self._running_future.done():
self._return_result(done)
else:
self._finished.append(done)
def _return_result(self, done):
"""Called set the returned future's state that of the future
we yielded, and set the current future for the iterator.
"""
chain_future(done, self._running_future)
self.current_future = done
self.current_index = self._unfinished.pop(done)
@coroutine
def __aiter__(self):
raise Return(self)
def __anext__(self):
if self.done():
# Lookup by name to silence pyflakes on older versions.
raise getattr(builtins, 'StopAsyncIteration')()
return self.next()
def wrapper(*args, **kwargs):
future = TracebackFuture()
if replace_callback and 'callback' in kwargs:
callback = kwargs.pop('callback')
IOLoop.current().add_future(
future, lambda future: callback(future.result()))
try:
result = func(*args, **kwargs)
except (Return, StopIteration) as e:
result = _value_from_stopiteration(e)
except Exception:
future.set_exc_info(sys.exc_info())
return future
else:
if isinstance(result, GeneratorType):
# Inline the first iteration of Runner.run. This lets us
# avoid the cost of creating a Runner when the coroutine
# never actually yields, which in turn allows us to
# use "optional" coroutines in critical path code without
# performance penalty for the synchronous case.
try:
orig_stack_contexts = stack_context._state.contexts
yielded = next(result)
if stack_context._state.contexts is not orig_stack_contexts:
yielded = TracebackFuture()
yielded.set_exception(
stack_context.StackContextInconsistentError(
'stack_context inconsistency (probably caused '
'by yield within a "with StackContext" block)')
)
except (StopIteration, Return) as e:
future.set_result(_value_from_stopiteration(e))
except Exception:
future.set_exc_info(sys.exc_info())
else:
Runner(result, future, yielded)
try:
return future
finally:
# Subtle memory optimization: if next() raised an exception,
# the future's exc_info contains a traceback which
# includes this stack frame. This creates a cycle,
# which will be collected at the next full GC but has
# been shown to greatly increase memory usage of
# benchmarks (relative to the refcount-based scheme
# used in the absence of cycles). We can avoid the
# cycle by clearing the local variable after we return it.
future = None
future.set_result(result)
return future