What you _do_ want to do is add replicas so you distribute the CPU load across a bunch of machines.
The QueryResultCache isn't very useful unless you have multiple queries that 1> reference the _exact_ same query, q, fq, sorting and all 2> don't page very far. This cache really only holds the document (internal Lucene) IDs for a "window" of hits. So say your window (configured in solrconfig.xml) is set to 50. For each of the query keys, 50 IDs are stored. Next time that exact query comes in, and _assuming_ start+rows < 50, you'll get the IDs from the cache and not much action occurs. The design intent here is to satisfy a few pages of results. If you mean by "tail queries" that there is very little repetition of queries, then why bother with a cache at all? If the hit ratio is going towards 0 it's not doing you enough good to matter. FWIW, Erick On Thu, Feb 20, 2014 at 1:58 PM, KNitin <nitin.t...@gmail.com> wrote: > Hello > > I have a 4 node cluster running Solr cloud 4.3.1. I have a few large > collections sharded 8 ways across all the 4 nodes (with 2 shards per node). > The size of the shard for the large collections is around 600-700Mb > containing around 250K+ documents. > > Currently the size of the query cache is around 512. We have a few jobs > that run tail queries on these collections. The hit ratio of the cache > drops to 0 when running these queries and also at the same time CPU spikes. > The latencies are in the order of seconds in the above case. I verified GC > behavior is normal (not killing cpu) > > The following are my questions > > > 1. Is it a good practice to vary the Query Result Cache size based on > the size of the collection (large collections have large cache)? > 2. If most of your queries are tail queries, what is a good way to make > your cache usage effective (higher hits) > 3. If lets say all your queries miss the cache, it is an OK behavior if > your CPU spikes (to 90+%) > 4. Is there a recommended shard size (# of doc, size ) to use. A few of > my collections are 100-200 Mb and the large ones are in teh order of > 800-1Gb > > Thanks a lot in advance > Nitin >
