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From Shawn Heisey <s...@elyograg.org>
Subject Re: ping query frequency
Date Sun, 03 Mar 2013 16:21:13 GMT
On 3/3/2013 2:15 AM, adm1n wrote:
> I'm wonderring how frequent this query should be made. Currently it is done
> before each select request (some very old legacy). I googled a little and
> found out that it is bad practice and has performance impact. So the
> question is should I completely remove it or just do it once in some period
> of time.

Can you point me at the place where it says that it's bad practice to do 
frequent pings?  I use the ping functionality in my haproxy load 
balancer that sits in front of Solr.  It executes a ping request against 
all my Solr instances every five seconds.  Most of the time, the ping 
request (which is distributed) finishes in single-digit milliseconds. If 
that is considered bad practice, I want to figure out why and submit 
issues to get the problem fixed.

I can imagine that sending a ping before every query would be a bad 
idea, but I am hoping that the way I'm using it is OK.

The only problem with ping requests that I have ever noticed was caused 
by long garbage collection pauses on my 8GB Solr heap.  Those pauses 
caused the load balancer to incorrectly mark the active Solr instance(s) 
as down and send requests to a backup.

Through experimentation with -XX memory tuning options, I have now 
eliminated the GC pause problem.  For machines running Solr 
4.2-SNAPSHOT, I have reduced the heap to 6GB, the 3.5.0 machines are 
still running with 8GB.

Thanks,
Shawn


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