Program hangs when modifying u->buffer while using proxy module to talk to upstream backend

[Maxim Dounin]

Hello!

On Mon, Apr 09, 2012 at 07:02:10PM -0700, Ashish S wrote:

> Hi,
> 
> I currently use upstream to talk to a back-end, which sends me some
> response. In my module, i am trying to re-format the plain-text
> upstream backend response, to XML, and I also add some new data to it,
> based on an in-memory lookup within my module.  What would be the best
> way to do this?

Unless you are working on custom protocol module, you may want to 
use filter module to re-format data instead.

> In my setup, I am able to parse response from upstream (u->buffer),
> construct a modified string and assign it back to u->buffer, and am I
> setting  u->headers_in.content_length_n and
> r->headers_out.content_length_n correctly. The issue i face is, every
> *second* request hangs, if i am trying the request through the
> browser. (However, trying through command-line & curl, works
> everytime). And I always see this error message in the logs: "client
> prematurely closed connection, so upstream connection is closed too
> while sending to client, client: 127.0.0.1".   What am i doing wrong?

It's hard to say anything without seeing the code, but most likely 
you fail to set u->length properly.  See e.g. memcached module for 
a simple example of non-buffered protocol handler.

Maxim Dounin