premature end of msg header

From: Alex Rousskov (
Date: Mon Dec 20 1999 - 09:52:29 MST

Hi All,

        We have received a couple of questions about the "premature end
of msg header" error displayed by polyclt in some tests. While we are
finishing a Web page with description for all errors, here is the
explanation for this particular error.

> What is the exact meaning of errno 259 "premature end of msg header"?

The exact definition is "Polygraph client (server) detected end-of-file
condition on a connection prior to being able to read [the entire] HTTP
response (request) header". This is an error condition detected by
Polygraph, not the OS.

One possible scenario to get this error is when Polygraph server closes
an idle persistent connection at the time when your proxy just started
forwarding a request for that server. To check if that is the case, you
can disable server side timeouts for persistent connections (currently
15 seconds) and see if the "problem" goes away.

If the situation above applies, a proxy has at least these options:
        - retry the request (client sees no errors)
        - report an error to the client
          (client gets "foreign reply" error)
        - simply terminate client connection
          (client gets "premature end of msg header" error)

A proxy can implement one or more of the above options, depending on the
proxy design and installation environment. Also, a proxy can try to
decrease the number of such errors by timing out server-side connections
on its own.

Said that, I must note that we have at least one report of this error
that does not go away with persistent connection timeout turned off.
Hence there are some other cases (possibly a Polygraph and/or proxy bug)
not covered by the description above. We are trying to get more
information to reproduce the problem and will keep you posted.


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