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Diffstat (limited to 'scripts/external_libs/pyzmq-14.5.0/python3/ucs4/32bit/zmq/eventloop/minitornado/stack_context.py')
| -rw-r--r-- | scripts/external_libs/pyzmq-14.5.0/python3/ucs4/32bit/zmq/eventloop/minitornado/stack_context.py | 376 |
1 files changed, 376 insertions, 0 deletions
diff --git a/scripts/external_libs/pyzmq-14.5.0/python3/ucs4/32bit/zmq/eventloop/minitornado/stack_context.py b/scripts/external_libs/pyzmq-14.5.0/python3/ucs4/32bit/zmq/eventloop/minitornado/stack_context.py new file mode 100644 index 00000000..226d8042 --- /dev/null +++ b/scripts/external_libs/pyzmq-14.5.0/python3/ucs4/32bit/zmq/eventloop/minitornado/stack_context.py @@ -0,0 +1,376 @@ +#!/usr/bin/env python +# +# Copyright 2010 Facebook +# +# Licensed under the Apache License, Version 2.0 (the "License"); you may +# not use this file except in compliance with the License. You may obtain +# a copy of the License at +# +# http://www.apache.org/licenses/LICENSE-2.0 +# +# Unless required by applicable law or agreed to in writing, software +# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT +# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the +# License for the specific language governing permissions and limitations +# under the License. + +"""`StackContext` allows applications to maintain threadlocal-like state +that follows execution as it moves to other execution contexts. + +The motivating examples are to eliminate the need for explicit +``async_callback`` wrappers (as in `tornado.web.RequestHandler`), and to +allow some additional context to be kept for logging. + +This is slightly magic, but it's an extension of the idea that an +exception handler is a kind of stack-local state and when that stack +is suspended and resumed in a new context that state needs to be +preserved. `StackContext` shifts the burden of restoring that state +from each call site (e.g. wrapping each `.AsyncHTTPClient` callback +in ``async_callback``) to the mechanisms that transfer control from +one context to another (e.g. `.AsyncHTTPClient` itself, `.IOLoop`, +thread pools, etc). + +Example usage:: + + @contextlib.contextmanager + def die_on_error(): + try: + yield + except Exception: + logging.error("exception in asynchronous operation",exc_info=True) + sys.exit(1) + + with StackContext(die_on_error): + # Any exception thrown here *or in callback and its desendents* + # will cause the process to exit instead of spinning endlessly + # in the ioloop. + http_client.fetch(url, callback) + ioloop.start() + +Most applications shouln't have to work with `StackContext` directly. +Here are a few rules of thumb for when it's necessary: + +* If you're writing an asynchronous library that doesn't rely on a + stack_context-aware library like `tornado.ioloop` or `tornado.iostream` + (for example, if you're writing a thread pool), use + `.stack_context.wrap()` before any asynchronous operations to capture the + stack context from where the operation was started. + +* If you're writing an asynchronous library that has some shared + resources (such as a connection pool), create those shared resources + within a ``with stack_context.NullContext():`` block. This will prevent + ``StackContexts`` from leaking from one request to another. + +* If you want to write something like an exception handler that will + persist across asynchronous calls, create a new `StackContext` (or + `ExceptionStackContext`), and make your asynchronous calls in a ``with`` + block that references your `StackContext`. +""" + +from __future__ import absolute_import, division, print_function, with_statement + +import sys +import threading + +from .util import raise_exc_info + + +class StackContextInconsistentError(Exception): + pass + + +class _State(threading.local): + def __init__(self): + self.contexts = (tuple(), None) +_state = _State() + + +class StackContext(object): + """Establishes the given context as a StackContext that will be transferred. + + Note that the parameter is a callable that returns a context + manager, not the context itself. That is, where for a + non-transferable context manager you would say:: + + with my_context(): + + StackContext takes the function itself rather than its result:: + + with StackContext(my_context): + + The result of ``with StackContext() as cb:`` is a deactivation + callback. Run this callback when the StackContext is no longer + needed to ensure that it is not propagated any further (note that + deactivating a context does not affect any instances of that + context that are currently pending). This is an advanced feature + and not necessary in most applications. + """ + def __init__(self, context_factory): + self.context_factory = context_factory + self.contexts = [] + self.active = True + + def _deactivate(self): + self.active = False + + # StackContext protocol + def enter(self): + context = self.context_factory() + self.contexts.append(context) + context.__enter__() + + def exit(self, type, value, traceback): + context = self.contexts.pop() + context.__exit__(type, value, traceback) + + # Note that some of this code is duplicated in ExceptionStackContext + # below. ExceptionStackContext is more common and doesn't need + # the full generality of this class. + def __enter__(self): + self.old_contexts = _state.contexts + self.new_contexts = (self.old_contexts[0] + (self,), self) + _state.contexts = self.new_contexts + + try: + self.enter() + except: + _state.contexts = self.old_contexts + raise + + return self._deactivate + + def __exit__(self, type, value, traceback): + try: + self.exit(type, value, traceback) + finally: + final_contexts = _state.contexts + _state.contexts = self.old_contexts + + # Generator coroutines and with-statements with non-local + # effects interact badly. Check here for signs of + # the stack getting out of sync. + # Note that this check comes after restoring _state.context + # so that if it fails things are left in a (relatively) + # consistent state. + if final_contexts is not self.new_contexts: + raise StackContextInconsistentError( + 'stack_context inconsistency (may be caused by yield ' + 'within a "with StackContext" block)') + + # Break up a reference to itself to allow for faster GC on CPython. + self.new_contexts = None + + +class ExceptionStackContext(object): + """Specialization of StackContext for exception handling. + + The supplied ``exception_handler`` function will be called in the + event of an uncaught exception in this context. The semantics are + similar to a try/finally clause, and intended use cases are to log + an error, close a socket, or similar cleanup actions. The + ``exc_info`` triple ``(type, value, traceback)`` will be passed to the + exception_handler function. + + If the exception handler returns true, the exception will be + consumed and will not be propagated to other exception handlers. + """ + def __init__(self, exception_handler): + self.exception_handler = exception_handler + self.active = True + + def _deactivate(self): + self.active = False + + def exit(self, type, value, traceback): + if type is not None: + return self.exception_handler(type, value, traceback) + + def __enter__(self): + self.old_contexts = _state.contexts + self.new_contexts = (self.old_contexts[0], self) + _state.contexts = self.new_contexts + + return self._deactivate + + def __exit__(self, type, value, traceback): + try: + if type is not None: + return self.exception_handler(type, value, traceback) + finally: + final_contexts = _state.contexts + _state.contexts = self.old_contexts + + if final_contexts is not self.new_contexts: + raise StackContextInconsistentError( + 'stack_context inconsistency (may be caused by yield ' + 'within a "with StackContext" block)') + + # Break up a reference to itself to allow for faster GC on CPython. + self.new_contexts = None + + +class NullContext(object): + """Resets the `StackContext`. + + Useful when creating a shared resource on demand (e.g. an + `.AsyncHTTPClient`) where the stack that caused the creating is + not relevant to future operations. + """ + def __enter__(self): + self.old_contexts = _state.contexts + _state.contexts = (tuple(), None) + + def __exit__(self, type, value, traceback): + _state.contexts = self.old_contexts + + +def _remove_deactivated(contexts): + """Remove deactivated handlers from the chain""" + # Clean ctx handlers + stack_contexts = tuple([h for h in contexts[0] if h.active]) + + # Find new head + head = contexts[1] + while head is not None and not head.active: + head = head.old_contexts[1] + + # Process chain + ctx = head + while ctx is not None: + parent = ctx.old_contexts[1] + + while parent is not None: + if parent.active: + break + ctx.old_contexts = parent.old_contexts + parent = parent.old_contexts[1] + + ctx = parent + + return (stack_contexts, head) + + +def wrap(fn): + """Returns a callable object that will restore the current `StackContext` + when executed. + + Use this whenever saving a callback to be executed later in a + different execution context (either in a different thread or + asynchronously in the same thread). + """ + # Check if function is already wrapped + if fn is None or hasattr(fn, '_wrapped'): + return fn + + # Capture current stack head + # TODO: Any other better way to store contexts and update them in wrapped function? + cap_contexts = [_state.contexts] + + def wrapped(*args, **kwargs): + ret = None + try: + # Capture old state + current_state = _state.contexts + + # Remove deactivated items + cap_contexts[0] = contexts = _remove_deactivated(cap_contexts[0]) + + # Force new state + _state.contexts = contexts + + # Current exception + exc = (None, None, None) + top = None + + # Apply stack contexts + last_ctx = 0 + stack = contexts[0] + + # Apply state + for n in stack: + try: + n.enter() + last_ctx += 1 + except: + # Exception happened. Record exception info and store top-most handler + exc = sys.exc_info() + top = n.old_contexts[1] + + # Execute callback if no exception happened while restoring state + if top is None: + try: + ret = fn(*args, **kwargs) + except: + exc = sys.exc_info() + top = contexts[1] + + # If there was exception, try to handle it by going through the exception chain + if top is not None: + exc = _handle_exception(top, exc) + else: + # Otherwise take shorter path and run stack contexts in reverse order + while last_ctx > 0: + last_ctx -= 1 + c = stack[last_ctx] + + try: + c.exit(*exc) + except: + exc = sys.exc_info() + top = c.old_contexts[1] + break + else: + top = None + + # If if exception happened while unrolling, take longer exception handler path + if top is not None: + exc = _handle_exception(top, exc) + + # If exception was not handled, raise it + if exc != (None, None, None): + raise_exc_info(exc) + finally: + _state.contexts = current_state + return ret + + wrapped._wrapped = True + return wrapped + + +def _handle_exception(tail, exc): + while tail is not None: + try: + if tail.exit(*exc): + exc = (None, None, None) + except: + exc = sys.exc_info() + + tail = tail.old_contexts[1] + + return exc + + +def run_with_stack_context(context, func): + """Run a coroutine ``func`` in the given `StackContext`. + + It is not safe to have a ``yield`` statement within a ``with StackContext`` + block, so it is difficult to use stack context with `.gen.coroutine`. + This helper function runs the function in the correct context while + keeping the ``yield`` and ``with`` statements syntactically separate. + + Example:: + + @gen.coroutine + def incorrect(): + with StackContext(ctx): + # ERROR: this will raise StackContextInconsistentError + yield other_coroutine() + + @gen.coroutine + def correct(): + yield run_with_stack_context(StackContext(ctx), other_coroutine) + + .. versionadded:: 3.1 + """ + with context: + return func() |