Threads + thread queue length

[Viktor Villafuerte]

I'm bumping this 'thread' up to the top since CJ Ess has just asked a
question related to threads also.. I hate doing this but I'm hoping that
somebody could (maybe) answer this too..?

v

On Mon 12 Oct 2015 15:17:05, Viktor Villafuerte wrote:
> Hi all you carpenters and other Varnish using folk,
> 
> There are couple of things in the output of varnishstat that puzzle me a
> little..
> 
> MAIN.sess_drop               0         0.00 Sessions dropped
> MAIN.sess_dropped            3809332         0.32 Sessions dropped for
> thread
> MAIN.fetch_no_thread           58746         0.01 Fetch failed (no
> thread)
> MAIN.pools                         2          .   Number of thread pools
> MAIN.threads                    1255          .   Total number of
> threads
> 
> I've got 2 pools of 4000 threads set in Varnish config and
> man varnish-counters says:
> 
> sess_drop
> Count of sessions silently dropped due to lack of worker thread.
> 
> sess_dropped
> Number of times session was dropped because the queue were too long
> already. See also parameter queue_max.
> 
> fetch_no_thread
> beresp fetch failed, no thread available
> 
> 
> This tells me that there's no lack of worker threads (good!), but the
> thread queue length does get too long and subsequently sessions get
> dropped (bad!). Also backend fetch failed due to no threads being
> available (what?)
> 
> 
> Now the puzzling bit :)
> 
> 1) why would the thread queue get too long if there seems to be NO lack
> of threads to use?
> 
> 2) why would there be no threads if there seems to be NO lack of threads
> 
> 3) 'See also the parameter queue_max' - but I cannot find any mention of
> such parameter anywhere around? Where does this ellusive paramater live
> then?
> 
> 
> Could anybody shed bit of light on this for me?
> 
> 
> 
> 
> -- 
> Regards
> 
> Viktor Villafuerte
> Optus Internet Engineering
> t: +61 2 80825265
> 
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-- 
Regards

Viktor Villafuerte
Optus Internet Engineering
t: +61 2 80825265