On 8/18/2015 11:50 PM, William Bell wrote: > We sometimes get a spike in Solr, and we get like 3K of threads and then > timeouts... > > In Solr 5.2.1 the defult jetty settings is kinda crazy for threads - since > the value is HIGH! > > What do others recommend?
The setting of 10000 is so that there is effectively no limit. Solr will stop working right if it is not allowed to start threads whenever it wishes. Solr is not a typical web application. As far as I know (any my knowledge could be wrong), a typical web application that serves a website to users will handle all back-end details with the same thread(s) that were created when the connection was opened. Putting a relatively low limit on the number of threads in that situation is sensible. A very small Solr install with a low query volume will work in 200 threads (the default limit in most containers), but it doesn't take very much to exceed that. I have a Solr 4.9.1 dev install with 44 cores, running with the Jetty 8 example included in the 4.x download. 19 of those cores are build cores, with 19 cores for live indexes. The other six cores are always empty, with a shards parameter in the search handler definition for distributed searching. This install does NOT run in SolrCloud mode. This dev server sees very little traffic besides a few indexing requests every minute and load balancer health checks. JConsole shows the number of threads hovering between 230 and 235. If I scroll through the thread list, most of them show a state of WAITING on various locking mechanisms, which explains why my CPUs (8 CPU cores total) are not being overwhelmed with work from all those threads. Solr and Lucene don't really have a runaway thread problem as far as I can tell, but the system does use a fair number of them for basic operation, with more cores/collections adding more threads. SolrCloud mode will also use more threads. If you send requests to Solr at a vary fast rate, the servlet container may also use a lot of threads. Thanks, Shawn
