WSGIChunkedRequest

Description:

Enabled support for chunked request content.

Syntax:

WSGIChunkedRequest On|Off

Default:

WSGIChunkedRequest Off

Context:

server config, virtual host, directory, .htaccess

The WSGIChunkedRequest directive can be used to enable support for chunked request content. Rather than Apache rejecting a request using chunked request content, it will be allowed to pass through:

WSGIChunkedRequest On

Do note however that WSGI is technically incapable of supporting chunked request content without all chunked request content having to be first read in and buffered. This is because WSGI requires CONTENT_LENGTH be set when there is any request content.

In mod_wsgi no buffering is done. Thus, to be able to read the request content in the case of a chunked transfer encoding, you need to step outside of the WSGI specification and do things it says you aren’t meant to.

You have two choices for how you can do this. The first choice you have is to call read() on wsgi.input but not supply any argument at all. This will cause all request content to be read in and returned.

The second is to loop on calling read() on wsgi.input with a set block size passed as argument and do this until read() returns an empty string.

Because both calling methods are not allowed under WSGI specification, in using these, your code will not technically be portable to other WSGI hosting mechanisms, although if those other WSGI servers support it, you will be okay.

That all said, although technically not permitted by the WSGI specification, modern WSGI frameworks do now incorporate support for handling chunked request content, as well as the case where compressed request content is expanded by the web server such that CONTENT_LENGTH is no longer accurate. The required behaviour is enabled in these frameworks by the WSGI server passing through the non standard wsgi.input_terminated key set as True in the per request WSGI environ dictionary. When this is done the web frameworks will always read all available input and ignore CONTENT_LENGTH.

Because mod_wsgi guarantees that an empty string is returned when all input is exhausted, it will always set this flag.