During the day, almost every day, I get a handful of
408 Request Timeout pages when doing stuff on Stack Overflow or Meta Stack Overflow.
Is this an Australia thing, or are others experiencing this intermittently?
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We send our web logs to SQL so we can query them. It turns out that we have a bug that prevents 408s from being logged to SQL.
I did take several random samples of 10,000,000 requests each from our raw logs and have found ~ 30 per 10,000,000 requests that come through as 408. HAProxy records termination states, for all of them I have found they are logged as "cR--" which means:
c : the client-side timeout expired while waiting for the client to send or receive data. R : the proxy was waiting for a complete, valid REQUEST from the client (HTTP mode only). Nothing was sent to any server.
Since 99.99972% of the requests sampled don't have this problem, for now I am going to regard these as a negligible error. If you are receiving a lot more of these over a long period of time (i.e. more that 30 for every 10 million requests you make) I think there is likely a client side issue.
However, since it is possible that my samples are missing spurts of 408s I will do more extensive research when our 408s are part of queryable logs (should be a week or two, the person who maintains our logging system is on vacation at the moment). I will also look closely at the IPs of people who are reporting the issue to see if I can get any more detail -- but right now it is hard with raw data due to the size of it.
Update May 26, 2014:
It is possible this related to tcp-reconnect in modern browsers and our client timeout settings in haproxy. I'm going to have our latest SRE member Shane Madden investigate this now that I have a reasonable hypothesis.
Update May 28, 2014:
Shane has investigated and this should now be resolved for Chrome users, see answer on 408 Request Time-outs still continues. Anyone else seeing these issues, let us know.