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Re: imports failing over dav.

From: Greg Stein <gstein_at_lyra.org>
Date: 2001-09-10 22:30:09 CEST

On Mon, Sep 10, 2001 at 02:42:02PM -0500, Ben Collins-Sussman wrote:
> Here's everything I know about this bug. First, here's one of many
> reproducible examples:

Yup. I saw the same thing.

> I traced this with a network sniffer, and indeed, we're right in the
> middle of a PUT of svndiff data (with a Content-Length of 31116 bytes)
> -- then suddenly a bunch of "RST" (reset) TCP windows, and poof, the
> connection is dead.

I'd need to see who first issued that RST, but I'm guessing the Apache side.
That means Apache closed the connection. I would guess there is some kind of
timeout associated with the connection, and Apache doesn't realize that it
is in use. i.e. something needs to "ping" it

> When I run this process in gdb, we get a SIGPIPE (broken pipe) right
> inside libc, in the middle of attempt to write() data to a socket.
> The gdb traceback shows us inside ne_socket.c:sock_fullwrite() line
> 440. Neon is simply writing 1024 bytes of data to a socket.

First order of business is to get Neon to set a signal handler to ignore
SIGPIPE, and look for EPIPE from that write() call. We can then properly
bubble the error up.

> More frustrating, not a single interesting thing is logged in the
> httpd error_log. The access_log shows nothing but the PUT request.

IMO, the answer is probably in Apache's connection-timeout logic.

> I'm not sure how to debug from here. Do I need to run httpd inside
> gdb? How to proceed?

It probably does not make sense for you to spend time tracing through Apache
to figure out why it decides to close the socket. Maybe there are some other
items to fix?

Looks like I need to revamp the props right quick -- that would appear to be
our biggest blocker. I ought to be able to do that this week.


Greg Stein, http://www.lyra.org/
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Received on Sat Oct 21 14:36:40 2006

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