Hi Justin,
not that I know anything about your problem, but we've seen this kind of
behavior, when our Apaches were dying while processing the request. The
apache log would not show any 503 (because there is no-one to log it),
but Varnish was returning 503. In this case, you should see something
like Segmentation fault in your error log on the backend (but I guess
that depends on your platform).
Hope this helps.
Michal
Dne 30.3.2010 17:02, Justin Pasher napsal(a):
Hello,
I'm currently running Varnish r4633 (I can upgrade if absolutely
necessary), and we've been receiving very sporadic 503 errors listed
in the log files generated by varnishncsa. It's a very small
percentage, but nonetheless, when it happens on an important page,
it's noticeable.
Stats from yesterday's log file show 116 "503" errors out of about 4.1
million hits. About 80% of the failed requests are POST requests,
which it setup in my VCL as a "pass through". If I look in the apache
logs (the backend server), I only see one 503 error returned by apache
itself, so maybe there's a timeout issue somewhere. I'm trying to
figure out the best way to troubleshoot this, since it's too
inconsistent to just sit watching the output of varnishlog.
Perhaps it's hitting the default value for between_bytes_timeout (60
seconds)? If processing the data on the backend takes too long, then
varnish would time out after 60 seconds of no data, even if the
backend is still churning, right? I guess the question is what
situations cause Varnish to return a 503 aside from when the backend
itself returns a 503.
I can post details of my VCL if needed, but it's pretty simple (mostly
taken from examples on the site).
--
Michal Táborský
chief systems architect
Netretail Holding, B.V.
http://www.nrholding.com
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