Hi - You are running mapred jobs on the same nodes as Solr runs right? The first thing i would think of is that your OS file buffer cache is abused. The mappers read all data, presumably residing on the same node. The mapper output and shuffling part would take place on the same node, only the reducer output is sent to your nodes, which i assume are on the same machines. Those same machines have a large Lucene index. All this data, written to and read from the same disk, competes for a nice spot in the OS buffer cache.
Forget it if i misread anything, but when you're using serious figures of size, then do not abuse your caches. Have a separate mapred and Solr cluster, because they both eat cache space. I assume you can see serious IO WAIT times. Split the stuff and maybe even use smaller hardware, but more. M -----Original message----- > From:Wilburn, Scott <scott.wilb...@verizonwireless.com.INVALID> > Sent: Wednesday 13th August 2014 23:09 > To: solr-user@lucene.apache.org > Subject: Solr cloud performance degradation with billions of documents > > Hello everyone, > I am trying to use SolrCloud to index a very large number of simple documents > and have run into some performance and scalability limitations and was > wondering what can be done about it. > > Hardware wise, I have a 32-node Hadoop cluster that I use to run all of the > Solr shards and each node has 128GB of memory. The current SolrCloud setup is > split into 4 separate and individual clouds of 32 shards each thereby giving > four running shards per cloud or one cloud per eight nodes. Each shard is > currently assigned a 6GB heap size. I’d prefer to avoid increasing heap > memory for Solr shards to have enough to run other MapReduce jobs on the > cluster. > > The rate of documents that I am currently inserting into these clouds per day > is 5 Billion each in two clouds, 3 Billion into the third, and 2 Billion into > the fourth ; however to account for capacity, the aim is to scale the > solution to support double that amount of documents. To index these > documents, there are MapReduce jobs that run that generate the Solr XML > documents and will then submit these documents via SolrJ's CloudSolrServer > interface. In testing, I have found that limiting the number of active > parallel inserts to 80 per cloud gave the best performance as anything higher > gave diminishing returns, most likely due to the constant shuffling of > documents internally to SolrCloud. From an index perspective, dated > collections are being created to hold an entire day's of documents and > generally the inserting happens primarily on the current day (the previous > days are only to allow for searching) and the plan is to keep up to 60 days > (or collections) in each cloud. A single shar d index in one collection in the busiest cloud currently takes up 30G disk space or 960G for the entire collection. The documents are being auto committed with a hard commit time of 4 minutes (opensearcher = false) and soft commit time of 8 minutes. > > From a search perspective, the use case is fairly generic and simple searches > of the type :, so there is no need to tune the system to use any of the more > advanced querying features. Therefore, the most important thing for me is to > have the indexing performance be able to keep up with the rate of input. > > In the initial load testing, I was able to achieve a projected indexing rate > of 10 Billion documents per cloud per day for a grand total of 40 Billion per > day. However, the initial load testing was done on fairly empty clouds with > just a few small collections. Now that there have been several days of > documents being indexed, I am starting to see a fairly steep drop-off in > indexing performance once the clouds reached about 15 full collections (or > about 80-100 Billion documents per cloud) in the two biggest clouds. Based on > current application logging I’m seeing a 40% drop off in indexing > performance. Because of this, I have concerns on how performance will hold as > more collections are added. > > My question to the community is if anyone else has had any experience in > using Solr at this scale (hundreds of Billions) and if anyone has observed > such a decline in indexing performance as the number of collections > increases. My understanding is that each collection is a separate index and > therefore the inserting rate should remain constant. Aside from that, what > other tweaks or changes can be done in the SolrCloud configuration to > increase the rate of indexing performance? Am I hitting a hard limitation of > what Solr can handle? > > Thanks, > Scott > >
