On 12/12/2016 3:13 AM, Alfonso Muñoz-Pomer Fuentes wrote: > I’m writing because in our web application we’re using Solr 5.1.0 and > currently we’re hosting it on a VM with 32 GB of RAM (of which 30 are > dedicated to Solr and nothing else is running there). We have four > cores, that are this size: > - 25.56 GB, Num Docs = 57,860,845 > - 12.09 GB, Num Docs = 173,491,631 > > (The other two cores are about 10 MB, 20k docs)
An OOM indicates that a Java application is requesting more memory than it has been told it can use. There are only two remedies for OOM errors: Increase the heap, or make the program use less memory. In this email, I have concentrated on ways to reduce the memory requirements. These index sizes and document counts are relatively small to Solr -- as long as you have enough memory and are smart about how it's used. Solr 5.1.0 comes with GC tuning built into the startup scripts, using some well-tested CMS settings. If you are using those startup scripts, then the parallel collector will NOT be default. No matter what collector is in use, it cannot fix OOM problems. It may change when and how frequently they occur, but it can't do anything about them. > We aren’t indexing on this machine, and we’re getting OOM relatively > quickly (after about 14 hours of regular use). Right now we have a > Cron job that restarts Solr every 12 hours, so it’s not pretty. We use > faceting quite heavily and mostly as a document storage server (we > want full data sets instead of the n most relevant results). Like Toke, I suspect two things: a very large filterCache, and the heavy facet usage, maybe both. Enabling docValues on the fields you're using for faceting and reindexing will make the latter more memory efficient, and likely faster. Reducing the filterCache size would help the former. Note that if you have a completely static index, then it is more likely that you will fill up the filterCache over time. > I don’t know if what we’re experiencing is usual given the index size > and memory constraint of the VM, or something looks like it’s wildly > misconfigured. What do you think? Any useful pointers for some tuning > we could do to improve the service? Would upgrading to Solr 6 make sense? As I already mentioned, the first thing I'd check is the size of the filterCache. Reduce it, possibly so it's VERY small. Do everything you can to assure that you are re-using filters, not sending many unique filters. One of the most common things that leads to low filter re-use is using the bare NOW keyword in date filters and queries. Use NOW/HOUR or NOW/DAY instead -- NOW changes once a millisecond, so it is typically unique for every query. FilterCache entries are huge, as you were told in another reply. Unless you use docValues, or utilize the facet.method parameter VERY carefully, each field you facet on will tie up a large section of memory containing the value for that field in EVERY document in the index. With the document counts you've got, this is a LOT of memory. It is strongly recommended to have docValues enabled on every field you're using for faceting. If you change the schema in this manner, a full reindex will be required before you can use that field again. There is another problem lurking here that Toke already touched on: Leaving only 2GB of RAM for the OS to handle disk caching will result in terrible performance. What you've been told by me and and in other replies is discussed here: https://wiki.apache.org/solr/SolrPerformanceProblems Thanks, Shawn
