Hi Justin, I had a similar problem with receiving fairly consistent 503 errors on POST requests. In my case, the 503 errors were returning generally in less than a second, despite my having set the various timeout limits to be substantially higher. If it's the same problem, then it's possibly not a timeout problem.
I wrote to the list earlier this year and posted some logs [1], but was asked to post a tcpdump of all communications for further investigation which was (is) beyond my skills. I hope you have more success resolving this, Torrace [1] http://lists.varnish-cache.org/pipermail/varnish-misc/2010-February/003799.html On 31/03/10 4:02 AM, Justin Pasher wrote: > 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). >
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