Query regarding "http first read error: EOF" error in varnish

[Geoff Simmons]

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On 1/14/16 6:29 AM, Jayanth Kalyanasundaram wrote:
> 
> Hey, like you said the issue only happens sometimes. But the 
> first_byte_timeout for all the backends is set to 300 seconds.
> 
> [root at varnish ~]# sudo varnishadm "param.show first_byte_timeout" 
> first_byte_timeout Value is: 300.000 [seconds] Default is: 60.000 
> Minimum is: 0.000
> 
> Also the time difference between the backend request and backend 
> response seems to be different each time this issue occurs. For 
> instance, in this case http://pastebin.com/eS2Ldnbv the difference
> is just 0.6 seconds. So I don't think it can be an issue with
> timeouts.
> 
> Would this also happen if the backend server gives an empty
> response to the request ?

Yes, that would also happen, or if the connection is prematurely
closed. Since your backend apparently responds with times ranging from
0.6s to 27s to 54s, and sometimes either drops the connection or sends
an empty response, it looks like your problem is the backend and not
Varnish.

If I may add, "set the Varnish timeout really high" (as in 5 minutes)
is a common reaction from backend developers, but is usually not the
way to solve a such a problem. With that timeout, your worker threads
could be idle for up to five minutes, and you could rapidly exhaust
your thread pool. There's no way around it -- the backend needs to be
fixed.


Best,
Geoff
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