hanging connections

[Stig Bakken]

Kristian, please let me know whether I should file a ticket for this.

 - Stig

On Mon, Dec 20, 2010 at 4:14 PM, Stig Bakken <stig at zedge.net> wrote:

> On Mon, Dec 20, 2010 at 9:25 AM, Kristian Lyngstol <
> kristian at varnish-software.com> wrote:
>
>> On Fri, Dec 17, 2010 at 03:40:35PM +0100, Stig Bakken wrote:
>> > I have a script processing varnishlog output to give me the serving
>> > latency based on the ReqEnd tag, and frequently see objects served from
>> > cache, size around 25kB, that take 5+ seconds to serve.
>>
>> If there are two requests for an object, request A and request B, the
>> following will happen:
>>
>> Time  |    Action
>> 0s    | A asks for /foo
>>      | Cache-miss - fetch from backend
>> 0.5s  | B asks for /foo
>>      | Cache hit on busy object - wait for it
>> 5s    | Web server is finished delivering /foo
>> 5.1s  | A gets /foo - cache miss
>> 5.1s  | B gets /foo - cache hit
>>
>> It's a bit difficult to spot this as it happens, it's been a matter of
>> discussion recently (Arthur being the one who first became aware of the
>> issue).
>>
>> It sounds like this might be what you are seeing.
>>
>
> Here are some more details.  The attached file is an edited varnishlog
> dump, with elapsed time appended after each ReqEnd.  Notice that one of the
> requests takes 137 seconds, during which time all of the others in the dump
> complete much faster.  The Age: header is high, which rules out the cache
> injection race condition, right?
>
> This is with 2.1.4 installed from the official rpm on RHEL, btw.
>
>  - Stig
>
>
> --
> Stig Bakken
> CTO, Zedge.net - free your phone!
>



-- 
Stig Bakken
CTO, Zedge.net - free your phone!
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