Our SOLR instance seems to be single-threading and therefore not taking advantage of its multi-proc host

Question

We are running SOLR 1.4.1 (Lucene 2.9.3) on a 2-CPU Linux host, but it seems that only 1 CPU is ever being used. It almost seems like something is single-threading inside the SOLR application. The CPU utilization is very seldom over 0.9 even under load.

We are running on virtual Linux hosts and but our other apps in the same cluster are multi-threading w/o issue. Some more info on our stack and versions:

Linux 2.6.16.33-xenU Apache 2.2.3 Tomcat 6.0.16 Java SE Runtime Environment (build 1.6.0_10-ea-b11)

Has anyone else noticed this problem?

Might there be some SOLR config aspect to enable multi-threading that we're missing? Any suggestions for troubleshooting?

Judging by SOLR's logs, we do see that multiple requests are processing simultaneously inside SOLR so we do not believe we're sequentially feeding requests to SOLR, ie. bottle-necking things outside of SOLR.

Thx much! Oliver

Answer 1

I don't see anything in the data you provide that indicates that Solr is behaving single-threadedly. Solr does work in a multi-threaded way.

In order to diagnose your problem we need more information, like: do you experience slow performance when querying? What qtimes are reported by Solr? What kind of queries are you issuing? What's your commit/optimize frequency?

To benchmark your Solr instance, try JMeter or ab.