Riak connection pool silent disconnection

Mikhail Kuznetsov kuznetsov.m.yu at gmail.com
Thu Oct 11 23:54:05 EDT 2012


Yes, I return connection to pool after query. Pool have 30 workers and most of operations is single put. Ulimit in system is equal to 2048. We just started, we store about 200-300 Mb of data on all cluster. We have about terabyte of free space on server disks. Servers mostly stand by and waiting for clients. Heavy load will be later.

I don't understand what is that parameter {checkout,false,5000} for? There are no checkout parameter in erlang pb client, in server config I don't found any too. 
-- 
Sincerely yours,
Mikhail Kuznetsov

When best practices meet everyday life and lead to perfection...

Oct 11, 2012, в 21:26 , Mike Oxford написал(а):

> I think the key may lie here.... ",{checkout,false,5000}"
> 
> Are you releasing your connections back to the pool?   Is your throughput greater than the system can handle due to limited connection pool sizes?  What is your ulimit set to (ulimit -n)  ... maybe you're running out of FD's?
> 
> -mox
> 
> On Wed, Oct 10, 2012 at 10:31 PM, Mikhail Kuznetsov <kuznetsov.m.yu at gmail.com> wrote:
> I got nasty problem in production. We make connection pool with official erlang pb client. Everything works fine. To organize pool we use hottub (we try several,but that is simplest). Each connection used at least once in 3-5 minutes(production is not full loaded now).
> 
> After several days riak server disconnect us. But socket process doesn't die, on any request it answers {error, disconnected}. So far I wrote pool workers checker, if it is_connected(Pid) return not true, we kill worker and pool create new one. I fired it every ten minutes. But it didn't help. It return true, but then I am making request I get {error, disconnected}. Only solution that work so far is pool full reinit if some worker return {error, disconnected}. It is very barbaric and may crash whole app.
> 
> When I checked server logs I found many errors like this two: 2012-09-20 00:10:10.976 [error] <0.803.0>@riak_core_vnode:handle_info:510 296867520082839655260123481645494988367611297792 riak_kv_vnode worker pool crashed {timeout,{gen_server,call,[<0.819.0>,{work,<0.806.0>,{fold,#Fun,#Fun},{raw,59205031,<0.28969.11>}}]}} 2012-09-20 00:10:10.976 [error] <0.862.0>@riak_core_vnode:handle_info:510 365375409332725729550921208179070754913983135744 riak_kv_vnode worker pool crashed {timeout,{gen_fsm,sync_send_event,[<0.866.0>,{checkout,false,5000},5000]}}
> 
> I guess that is real problem, but I think client connection should at least log something, get connection problem failures list or die. I got is_connected(Pid) = true
> 
> How are you organizing connection pools which work 24/7? How you check pool workers or refresh them?
> 
> 
> 
> 
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