How do I copy wsgi.input if I want to process POST data more than once?

Question

In WSGI, post data is consumed by reading the file-like object environ['wsgi.input']. If a second element in the stack also wants to read post data it may hang the program by reading when there's nothing more to read.

How should I copy the POST data so it can be processed multiple times?

Answer 1

You could try putting a file-like replica of the stream back in the environment:

from cStringIO import StringIO

length = int(environ.get('CONTENT_LENGTH', '0'))
body = StringIO(environ['wsgi.input'].read(length))
environ['wsgi.input'] = body

Needing to do this is a bit of a smell, though. Ideally only one piece of code should be parsing the query string and post body, and delivering the results to other components.