calibre-web/vendor/tornado/stack_context.py
OzzieIsaacs bbf6d9b026 Translation of UI (german and english)
Bugfix for feeds
    - removed categories related and up
    - load new books now working
    - category random now working
login page is free of non accessible elements
boolean custom column is vivible in UI
books with only with certain languages can be shown
book shelfs can be deleted from UI
Anonymous user view is more resticted
Added browse of series in sidebar
Dependencys in vendor folder are updated to newer versions (licencs files are now present)
Bugfix editing Authors names
Made upload on windows working
2016-11-09 19:24:33 +01:00

389 lines
13 KiB
Python

#!/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 descendants*
# will cause the process to exit instead of spinning endlessly
# in the ioloop.
http_client.fetch(url, callback)
ioloop.start()
Most applications shouldn'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 tornado.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]
if not cap_contexts[0][0] and not cap_contexts[0][1]:
# Fast path when there are no active contexts.
def null_wrapper(*args, **kwargs):
try:
current_state = _state.contexts
_state.contexts = cap_contexts[0]
return fn(*args, **kwargs)
finally:
_state.contexts = current_state
null_wrapper._wrapped = True
return null_wrapper
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()