On 12/1/2016 4:04 AM, kshitij tyagi wrote: > I am using Solr and serving huge number of requests in my application. > > I need to know how can I utilize caching in Solr. > > As of now in then clicking Core Selector → [core name] → Plugins / Stats. > > I am seeing my hit ration as 0 for all the caches. What does this mean and > how this can be optimized.
If your hitratio is zero, then none of the queries related to that cache are finding matches. This means that your client systems are never sending the same query twice. One possible reason for a zero hitratio is using "NOW" in date queries -- NOW changes every millisecond, and the actual timestamp value is what ends up in the cache. This means that the same query with NOW executed more than once will actually be different from the cache's perspective. The solution is date rounding -- using things like NOW/HOUR or NOW/DAY. You could use NOW/MINUTE, but the window for caching would be quite small. 5000 entries for your filterCache is almost certainly too big. Each filterCache entry tends to be quite large. If the core has ten million documents in it, then each filterCache entry would be 1.25 million bytes in size -- the entry is a bitset of all documents in the core. This includes deleted docs that have not yet been reclaimed by merging. If a filterCache for an index that size (which is not all that big) were to actually fill up with 5000 entries, it would require over six gigabytes of memory just for the cache. The 1000 that you have on queryResultCache is also rather large, but probably not a problem. There's also documentCache, which generally is OK to have sized at several thousand -- I have 16384 on mine. If your documents are particularly large, then you probably would want to have a smaller number. It's good that your autowarmCount values are low. High values here tend to make commits take a very long time. You do not need to send your message more than once. The first repeat was after less than 40 minutes. The second was after about two hours. Waiting a day or two for a response, particularly for a difficult problem, is not unusual for a mailing list. I begain this reply as soon as I saw your message -- about 7:30 AM in my timezone. Thanks, Shawn
