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update docs about contexts

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David Lord 2022-07-08 07:08:54 -07:00
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docs/reqcontext.rst
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@ -37,12 +37,14 @@ context, which also pushes an :doc:`app context </appcontext>`. When the
request ends it pops the request context then the application context.
The context is unique to each thread (or other worker type).
:data:`request` cannot be passed to another thread, the other thread
will have a different context stack and will not know about the request
the parent thread was pointing to.
:data:`request` cannot be passed to another thread, the other thread has
a different context space and will not know about the request the parent
thread was pointing to.
Context locals are implemented in Werkzeug. See :doc:`werkzeug:local`
for more information on how this works internally.
Context locals are implemented using Python's :mod:`contextvars` and
Werkzeug's :class:`~werkzeug.local.LocalProxy`. Python manages the
lifetime of context vars automatically, and local proxy wraps that
low-level interface to make the data easier to work with.
Manually Push a Context
@ -87,10 +89,9 @@ How the Context Works
The :meth:`Flask.wsgi_app` method is called to handle each request. It
manages the contexts during the request. Internally, the request and
application contexts work as stacks, :data:`_request_ctx_stack` and
:data:`_app_ctx_stack`. When contexts are pushed onto the stack, the
application contexts work like stacks. When contexts are pushed, the
proxies that depend on them are available and point at information from
the top context on the stack.
the top item.
When the request starts, a :class:`~ctx.RequestContext` is created and
pushed, which creates and pushes an :class:`~ctx.AppContext` first if
@ -99,10 +100,10 @@ these contexts are pushed, the :data:`current_app`, :data:`g`,
:data:`request`, and :data:`session` proxies are available to the
original thread handling the request.
Because the contexts are stacks, other contexts may be pushed to change
the proxies during a request. While this is not a common pattern, it
can be used in advanced applications to, for example, do internal
redirects or chain different applications together.
Other contexts may be pushed to change the proxies during a request.
While this is not a common pattern, it can be used in advanced
applications to, for example, do internal redirects or chain different
applications together.
After the request is dispatched and a response is generated and sent,
the request context is popped, which then pops the application context.