Intermittent latency issues on Solaris10

[Igor Minar]

On Mar 17, 2009, at 2:04 PM, Patrick Giagnocavo wrote:

> Igor Minar wrote:
>> Hi Folks!
>>
>> I'm trying set up a Varnish instance on Solaris 10 and I'm facing  
>> some
>> weird issue there. I was wondering if anyone could give me some
>> insight into what's going on.
>>
>> After applying a few patches (I submited all of them to Trac), I was
>> able compile Varnish 2.0.2 and 2.0.3 with Sun Studio compiler.  
>> Varnish
>> starts and is able to handle requests, but from time to time, I see
>> multi-second latency when executing requests. As if varnish "hung"  
>> for
>> a few seconds. This latency occurs for cache hits and is not caused  
>> by
>> the backed app.
>
> You should look into using DTrace to figure out what is going on.   
> Do a
> search on dtrace at blogs.sun.com, there are many useful scripts and
> snippets of dtrace code there.
>
> --Patrick

I tried truss and dtrace but I don't see anything suspicious.

However what I did notice was an occurrence of "SessionClose c  
timeout" in varnishlog just before every stalled response:

     0 CLI          - Rd ping
     0 CLI          - Wr 0 200 PONG 1238102801 1.0
     0 CLI          - Rd ping
     0 CLI          - Wr 0 200 PONG 1238102804 1.0
    11 SessionClose c timeout
    11 StatSess     c 192.18.43.225 43205 0 1 2 0 0 0 814 677
     8 SessionClose c timeout
     8 StatSess     c 192.18.43.225 54410 0 1 3 0 0 0 1221 1275
     4 SessionClose c timeout
     4 StatSess     c 192.18.43.225 9008 3 1 5 0 0 1 2310 45105
     9 SessionClose c timeout
     9 StatSess     c 192.18.43.225 45298 0 1 3 0 0 0 1304 1986
     4 SessionOpen  c 192.18.43.225 13094 0.0.0.0:8080
     4 ReqStart     c 192.18.43.225 13094 1500381747
     4 RxRequest    c GET

Does anyone know what this means and what I can do to get rid of it?

thanks,
Igor