Flask上下文管理
Flask上下文管理流程图
1.基于线程实现Threading.local,保证每个线程的隔离
import threading
local_values = threading.local() #线程 Local 类
def func(num):
local_values.name = num
import time
time.sleep(1)
print(local_values.name, threading.current_thread().name)
for i in range(20):
th = threading.Thread(target=func, args=(i,), name='线程%s' % i)
th.start()
# 基于线程get_ident的线程隔离local的基础原理
from threading import Thread
from _thread import get_ident # 每个线程的唯一标示
import time
def task(num):
v = get_ident()
time.sleep(1)
print(v) # 打印每个线程的唯一标示
if __name__ == '__main__':
for i in range(20):
t = Thread(target=task, args=(i,))
t.start()
自定义线程local类(基于线程get_ident)
from _thread import get_ident
import threading
class Local(object):
def __init__(self):
self.storage = {}
self.get_ident = get_ident
def set(self, k, v):
ident = self.get_ident()
origin = self.storage.get(ident)
if not origin:
origin = {k: v}
else:
origin[k] = v
self.storage[ident] = origin
def get(self, k):
ident = self.get_ident()
origin = self.storage.get(ident)
if not origin:
return None
else:
return origin.get(k, None)
local_values = Local()
def task(num):
local_values.set("name", num) # set方法
import time
time.sleep(1)
print(local_values.get("name"), threading.Thread().name)
if __name__ == '__main__':
for i in range(20):
t = threading.Thread(target=task, args=(i,), name="%s" % i)
t.start()
面向对象的基础知识复习
# 面向对象中的 __setattr__ 与 __getattr__ 方法的解释
class Foo(object):
def __init__(self):
object.__setattr__(self, "storage", {})
# 这样写 说明的是 我用他的父类设置值，不会触发本类的setattr
def __setattr__(self, key, value): # 对象.xxx = xxx 触发
#这里面不能这样写，会触发__setattr__方法，出现递归！！
self.storage = {"k1": "v1"}
print(key, value)
def __getattr__(self, item):
print(item)
if __name__ == '__main__':
t = Foo()
Flask内部实现的本地线程(协程--线程--进程)
# _*_ coding:utf-8 _*_
# __author__Zj__
try:
from greenlet import getcurrent as get_ident # 协程
except ImportError:
try:
from thread import get_ident # 线程
except ImportError:
from _thread import get_ident #获取线程的唯一标识 get_ident()
class Local(object):
__slots__ = ('__storage__', '__ident_func__')
def __init__(self):
object.__setattr__(self, '__storage__', {})
object.__setattr__(self, '__ident_func__', get_ident)
def __getattr__(self, name):
try:
return self.__storage__[self.__ident_func__()][name]
except KeyError:
raise AttributeError(name)
def __setattr__(self, name, value):
ident = self.__ident_func__()
storage = self.__storage__
try:
storage[ident][name] = value
except KeyError:
storage[ident] = {name: value}
local_values = Local()
import threading
def task(num):
local_values.name = num
import time
time.sleep(1)
print(local_values.name, threading.Thread().name)
if __name__ == '__main__':
for i in range(20):
t = threading.Thread(target=task, args=(i,), name="%s" % i)
t.start()
2.Flask上下文管理流程图
LocalStack类源码解析(_request_ctx_stack)
class LocalStack(object):
def __init__(self):
self._local = Local() # loacl对象
def __release_local__(self):
self._local.__release_local__()
def _get__ident_func__(self):
return self._local.__ident_func__
def _set__ident_func__(self, value):
object.__setattr__(self._local, '__ident_func__', value)
__ident_func__ = property(_get__ident_func__, _set__ident_func__)
del _get__ident_func__, _set__ident_func__
def __call__(self):
def _lookup():
rv = self.top
if rv is None:
raise RuntimeError('object unbound')
return rv
return LocalProxy(_lookup)
def push(self, obj):
"""Pushes a new item to the stack"""
rv = getattr(self._local, 'stack', None)
if rv is None:
self._local.stack = rv = [] # 对local类设置值 触发local的__setattr__方法，生成rv 与 与 stack对应的list指向同一个地址
rv.append(obj)
return rv
def pop(self):
"""Removes the topmost item from the stack, will return the
old value or `None` if the stack was already empty.
"""
stack = getattr(self._local, 'stack', None)
if stack is None:
return None
elif len(stack) == 1:
release_local(self._local)
return stack[-1]
else:
return stack.pop()
@property
def top(self):
"""The topmost item on the stack. If the stack is empty,
`None` is returned.
"""
try:
return self._local.stack[-1]
except (AttributeError, IndexError):
return None
Local类
class Local(object):
__slots__ = ('__storage__', '__ident_func__')
def __init__(self):
object.__setattr__(self, '__storage__', {})
object.__setattr__(self, '__ident_func__', get_ident)
def __call__(self, proxy):
"""Create a proxy for a name."""
return LocalProxy(self, proxy)
def __release_local__(self):
self.__storage__.pop(self.__ident_func__(), None)
def __getattr__(self, name): # 取值的时候触发 getattr
try:
return self.__storage__[self.__ident_func__()][name]
except KeyError:
raise AttributeError(name)
def __setattr__(self, name, value):
# value = []
ident = self.__ident_func__() # 对每一个线程设置自己的stack栈
storage = self.__storage__
try:
storage[ident][name] = value
except KeyError:
storage[ident] = {name: value}
RequestContext 类
class RequestContext(object):
def __init__(self, app, environ, request=None):
self.app = app
if request is None:
request = app.request_class(environ)
self.request = request
self.url_adapter = app.create_url_adapter(self.request)
self.flashes = None
self.session = None
# Request contexts can be pushed multiple times and interleaved with
# other request contexts. Now only if the last level is popped we
# get rid of them. Additionally if an application context is missing
# one is created implicitly so for each level we add this information
self._implicit_app_ctx_stack = []
# indicator if the context was preserved. Next time another context
# is pushed the preserved context is popped.
self.preserved = False
# remembers the exception for pop if there is one in case the context
# preservation kicks in.
self._preserved_exc = None
# Functions that should be executed after the request on the response
# object. These will be called before the regular "after_request"
# functions.
self._after_request_functions = []
self.match_request()
def _get_g(self):
return _app_ctx_stack.top.g
def _set_g(self, value):
_app_ctx_stack.top.g = value
g = property(_get_g, _set_g)
del _get_g, _set_g
def copy(self):
"""Creates a copy of this request context with the same request object.
This can be used to move a request context to a different greenlet.
Because the actual request object is the same this cannot be used to
move a request context to a different thread unless access to the
request object is locked.
.. versionadded:: 0.10
"""
return self.__class__(self.app,
environ=self.request.environ,
request=self.request
)
def match_request(self):
"""Can be overridden by a subclass to hook into the matching
of the request.
"""
try:
url_rule, self.request.view_args = \
self.url_adapter.match(return_rule=True)
self.request.url_rule = url_rule
except HTTPException as e:
self.request.routing_exception = e
def push(self):
"""Binds the request context to the current context."""
# If an exception occurs in debug mode or if context preservation is
# activated under exception situations exactly one context stays
# on the stack. The rationale is that you want to access that
# information under debug situations. However if someone forgets to
# pop that context again we want to make sure that on the next push
# it's invalidated, otherwise we run at risk that something leaks
# memory. This is usually only a problem in test suite since this
# functionality is not active in production environments.
#
top = _request_ctx_stack.top
if top is not None and top.preserved:
top.pop(top._preserved_exc)
# Before we push the request context we have to ensure that there
# is an application context.
app_ctx = _app_ctx_stack.top
if app_ctx is None or app_ctx.app != self.app:
app_ctx = self.app.app_context()
app_ctx.push()
self._implicit_app_ctx_stack.append(app_ctx)
else:
self._implicit_app_ctx_stack.append(None)
if hasattr(sys, 'exc_clear'):
sys.exc_clear()
#LocalStack.push()
_request_ctx_stack.push(self)
# Open the session at the moment that the request context is available.
# This allows a custom open_session method to use the request context.
# Only open a new session if this is the first time the request was
# pushed, otherwise stream_with_context loses the session.
if self.session is None:
session_interface = self.app.session_interface
self.session = session_interface.open_session(
self.app, self.request
)
if self.session is None:
self.session = session_interface.make_null_session(self.app)
def pop(self, exc=_sentinel):
"""Pops the request context and unbinds it by doing that. This will
also trigger the execution of functions registered by the
:meth:`~flask.Flask.teardown_request` decorator.
.. versionchanged:: 0.9
Added the `exc` argument.
"""
app_ctx = self._implicit_app_ctx_stack.pop()
try:
clear_request = False
if not self._implicit_app_ctx_stack:
self.preserved = False
self._preserved_exc = None
if exc is _sentinel:
exc = sys.exc_info()[1]
self.app.do_teardown_request(exc)
# If this interpreter supports clearing the exception information
# we do that now. This will only go into effect on Python 2.x,
# on 3.x it disappears automatically at the end of the exception
# stack.
if hasattr(sys, 'exc_clear'):
sys.exc_clear()
request_close = getattr(self.request, 'close', None)
if request_close is not None:
request_close()
clear_request = True
finally:
#LocalStack.pop()
rv = _request_ctx_stack.pop()
# get rid of circular dependencies at the end of the request
# so that we don't require the GC to be active.
if clear_request:
rv.request.environ['werkzeug.request'] = None
# Get rid of the app as well if necessary.
if app_ctx is not None:
app_ctx.pop(exc)
assert rv is self, 'Popped wrong request context. ' \
'(%r instead of %r)' % (rv, self)
def auto_pop(self, exc):
if self.request.environ.get('flask._preserve_context') or \
(exc is not None and self.app.preserve_context_on_exception):
self.preserved = True
self._preserved_exc = exc
else:
self.pop(exc)
def __enter__(self):
self.push()
return self
def __exit__(self, exc_type, exc_value, tb):
# do not pop the request stack if we are in debug mode and an
# exception happened. This will allow the debugger to still
# access the request object in the interactive shell. Furthermore
# the context can be force kept alive for the test client.
# See flask.testing for how this works.
self.auto_pop(exc_value)
if BROKEN_PYPY_CTXMGR_EXIT and exc_type is not None:
reraise(exc_type, exc_value, tb)
def __repr__(self):
return '<%s \'%s\' [%s] of %s>' % (
self.__class__.__name__,
self.request.url,
self.request.method,
self.app.name,
)
globals
from functools import partial
from werkzeug.local import LocalStack, LocalProxy
_request_ctx_err_msg = '''\
Working outside of request context.
This typically means that you attempted to use functionality that needed
an active HTTP request. Consult the documentation on testing for
information about how to avoid this problem.\
'''
_app_ctx_err_msg = '''\
Working outside of application context.
This typically means that you attempted to use functionality that needed
to interface with the current application object in some way. To solve
this, set up an application context with app.app_context(). See the
documentation for more information.\
'''
def _lookup_req_object(name):
top = _request_ctx_stack.top
if top is None:
raise RuntimeError(_request_ctx_err_msg)
return getattr(top, name)
def _lookup_app_object(name):
top = _app_ctx_stack.top
if top is None:
raise RuntimeError(_app_ctx_err_msg)
return getattr(top, name)
def _find_app():
top = _app_ctx_stack.top
if top is None:
raise RuntimeError(_app_ctx_err_msg)
return top.app
# context locals
_request_ctx_stack = LocalStack()
_app_ctx_stack = LocalStack()
current_app = LocalProxy(_find_app)
request = LocalProxy(partial(_lookup_req_object, 'request'))
session = LocalProxy(partial(_lookup_req_object, 'session'))
g = LocalProxy(partial(_lookup_app_object, 'g'))
LocalProxy类
class LocalProxy(object):
__slots__ = ('__local', '__dict__', '__name__', '__wrapped__')
def __init__(self, local, name=None):
object.__setattr__(self, '_LocalProxy__local', local)
object.__setattr__(self, '__name__', name)
if callable(local) and not hasattr(local, '__release_local__'):
# "local" is a callable that is not an instance of Local or
# LocalManager: mark it as a wrapped function.
object.__setattr__(self, '__wrapped__', local)
# __str__ 执行此方法
def _get_current_object(self):
"""Return the current object. This is useful if you want the real
object behind the proxy at a time for performance reasons or because
you want to pass the object into a different context.
"""
if not hasattr(self.__local, '__release_local__'):
return self.__local()
try:
return getattr(self.__local, self.__name__)
except AttributeError:
raise RuntimeError('no object bound to %s' % self.__name__)
@property
def __dict__(self):
try:
return self._get_current_object().__dict__
except RuntimeError:
raise AttributeError('__dict__')
def __repr__(self):
try:
obj = self._get_current_object()
except RuntimeError:
return '<%s unbound>' % self.__class__.__name__
return repr(obj)
def __bool__(self):
try:
return bool(self._get_current_object())
except RuntimeError:
return False
def __unicode__(self):
try:
return unicode(self._get_current_object()) # noqa
except RuntimeError:
return repr(self)
def __dir__(self):
try:
return dir(self._get_current_object())
except RuntimeError:
return []
def __getattr__(self, name):
if name == '__members__':
return dir(self._get_current_object())
return getattr(self._get_current_object(), name)
........
__setattr__ = lambda x, n, v: setattr(x._get_current_object(), n, v)
__delattr__ = lambda x, n: delattr(x._get_current_object(), n)
__str__ = lambda x: str(x._get_current_object())
__lt__ = lambda x, o: x._get_current_object() < o
..........
