503 due to content-length error? microwave issue?

Alan Dixon alan.g.dixon at gmail.com
Wed Nov 10 21:32:58 CET 2010

On Wed, Nov 10, 2010 at 12:54 PM, Caunter, Stefan <scaunter at topscms.com> wrote:
> There's nothing theoretical. Varnish talks HTTP. HTTP knows nothing, and needs to know nothing, about TCP/IP or MTU; it is a client and server protocol with various implementations of the relevant RFCs.
> You cannot troubleshoot network or transport layer issues at the application layer.
> A more accurate conclusion would be that adding Varnish exposed existing TCP/IP (network/transport layer) issues. They were there before adding Varnish, and would still have been there had Varnish been removed. Changing the MTU corrected the issue.

Yes, expose rather than create is more accurate.

But at the point of discovering the symptom, it's not clear which it
is so I'm trying to provide helpful information for others with a
similar problem.

>From a symptom point of view, the problems were invisible to the user
before varnish, so her experience was that varnish 'caused' the

Alan Dixon, Web Developer

Drupal and CiviCRM for Canadian nonprofits.

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