[Zope] Re: Slow File Access With LocalFS

[Dieter Maurer]

Jonothan Farr writes:
 > It sounds to me like the Apache server is just writing the data directly to the
 > HTTP connection as it is read. I believe that's how HTTP "streaming" works. I
 > also believe this is possible to do using the Zope HTTPResponse object. Does
 > anyone have any ideas?
We use it to deliver images from a multimedia database.

In Zope 2.1.0, it was not at all easy to use the HTTP streaming.
Many proxies and IE require the Content-Length header
to be correct.
To set a correct "Content-Length" was not a problem.
However, ZPublisher.HTTPResponse reset it afterwards to 0,
leading to very strange effects in various situations (i.e.
with IE and some Proxies).

We finally settled it in the following way:

      RESPONSE.setHeader('Content-Length',length)
      RESPONSE.setHeader('transfer-encoding','binary') # to prevent RESPONSE.__str__ to overwrite "Content-Length"
      RESPONSE.headers['Content-Length']= length
      # now do several "RESPONSE.write"

I am not sure, whether 2.1.6 or 2.2 still requires this strange
code sequence.


For Zope 2.1.6, we detected a nasty ZServer bug with the
streaming protocol: missing thread synchronization.
As a result, browsers got a non-deterministic part of the image.
Very nice effects....
DC told me, that this bug is fixed in the CVS and for Zope 2.2.


Thus, do not use the HTTP streaming protocol for the standard
Zope 2.1.6 distribution (or be ready to patch ZServer).


Dieter