openstack team mailing list archive

[Rick Jones <rick.jones2@xxxxxx>]

On 06/04/2013 02:45 AM, Klaus Schürmann wrote:
> Hi Rick,
>
> I found the problem. I placed a hardware balancer in front of the proxy server.
> The balancer lost some packets because of a faulty network interface.
> Your tip was excellent.

I'm glad it helped.  Looking back I see that my math on the cumulative 
time for successive retransmissions of TCP SYNs was completely wrong - 3 
+ 6 + 12 isn't 17, but 21... :)

rick

> Thanks
> Klaus
>
> -----Ursprüngliche Nachricht-----
> Von: Rick Jones [mailto:rick.jones2@xxxxxx]
> Gesendet: Freitag, 31. Mai 2013 19:17
> An: Klaus Schürmann
> Cc: openstack@xxxxxxxxxxxxxxxxxxx
> Betreff: Re: [Openstack] Swift performance issues with requests
>
> On 05/31/2013 04:55 AM, Klaus Schürmann wrote:
> > May 31 10:33:08 swift-proxy1 proxy-logging 10.4.2.99 10.4.2.99 31/May/2013/08/33/08 GET /v1/AUTH_provider1/129450/829188397.31 HTTP/1.0 200 - Wget/1.12%20%28linux-gnu%29 provider1%2CAUTH_tke6408efec4b2439091fb6f4e75911602 - 283354 - txd4a3a4bf3f384936a0bc14dbffddd275 - 0.1020 -
> > May 31 10:33:26 swift-proxy1 proxy-logging 10.4.2.99 10.4.2.99 31/May/2013/08/33/26 GET /v1/AUTH_provider1/129450/829188397.31 HTTP/1.0 200 - Wget/1.12%20%28linux-gnu%29 provider1%2CAUTH_tke6408efec4b2439091fb6f4e75911602 - 283354 - txd8c6b34b8e41460bb2c5f3f4b6def0ef - 17.7330 -   <<<<<<<<<<<<<<
>
> Something I forgot to mention, which was the basis for my TCP
> retransmissions guess.  Depending on your kernel revision, the initial
> TCP retransmission timeout is 3 seconds, and it will double each time -
> eg 3, 6, 12.  As it happens, the cumulative time for that is 17
> seconds...  So, the 17 seconds and change would be consistent with a
> transient problem in establishing a TCP connection.  Of course, it could
> just be a coincidence.
>
> Later kernels - I  forget where in the 3.X stream exactly - have the
> initial retransmission timeout of 1 second.  In that case the timeouts
> would go 1, 2, 4, 8, etc...
>
> rick