8 nodes, 4 shards apiece? All in the same JVM? People have gotten by the GC pain by running in separate JVMs with less Java memory each on big beefy machines.... That's not a recommendation as much as an observation.
That aside, unless you have some very strange stuff going on this is totally weird. Are you hitting OOM errors at any time you have this problem? Once you hit an OOM error, all bets are off about how Java behaves. If you are hitting those, you can't hope for stability until you fix that issue. In your writeup there's some evidence for this when you say that if you index multiple docs at a time you get failures. Do your Solr logs show any anomalies? My guess is that you'll see exceptions in your Solr logs that will shed light on the issue. Best, Erick On Mon, May 16, 2016 at 8:03 AM, Stephen Weiss <steve.we...@wgsn.com> wrote: > Hi everyone, > > I'm running into a problem with SolrCloud replicas and thought I would ask > the list to see if anyone else has seen this / gotten past it. > > Right now, we are running with only one replica per shard. This is obviously > a problem because if one node goes down anywhere, the whole collection goes > offline, and due to garbage collection issues, this happens about once or > twice a week, causing a great deal of instability. If we try to increase to > 2 replicas per shard, once we index new documents and the shards autocommit, > the shards all get out of sync with each other, with different numbers of > documents, different numbers of documents deleted, different facet counts - > pretty much totally divergent indexes. Shards always show green and > available, and never go into recovery or any other state as to indicate > there's a mismatch. There are also no errors in the logs to indicate > anything is going wrong. Even long after indexing has finished, the replicas > never come back into sync. The only way to get consistency again is to > delete one set of replicas and then add them back in. Unfortunately, when we > do this, we invariably discover that many documents (2-3%) are missing from > the index. > > We have tried setting the min_rf parameter, and have found that when setting > min_rf=2, we almost never get back rf=2. We almost always get rf=1, resend > the request, and it basically just goes into an infinite loop. The only way > to get rf=2 to come back is to only index one document at a time. > Unfortunately, we have to update millions of documents a day and it isn't > really feasible to index this way, and even when indexing one document at a > time, we still occasionally find ourselves in an infinite loop. This doesn't > appear to be related to the documents we are indexing - if we stop the index > process and bounce solr, the exact same document will go through fine the > next time until indexing stops up on another random document. > > We have 8 nodes, with 4 shards a piece, all running one collection with about > 900M documents. An important note is that we have a block join system with 3 > tiers of documents (products -> skus -> sku_history). During indexing, we > are forced to delete all documents for a product prior to adding the product > back into the index, in order to avoid orphaned children / grandchildren. > All documents are consistently indexed with the top-level product ID so that > we can delete all child/grandchild documents prior to updating the document. > So, for each updated document, we are sending through a delete call followed > by an add call. We have tried putting both the delete and add in the same > update request with the same results. > > All we see out there on Google is that none of what we're seeing should be > happening. > > We are currently running Solr 6.0 with Zookeeper 3.4.6. We experienced the > same behavior on 5.4 as well. > > -- > Steve > > ________________________________ > > WGSN is a global foresight business. 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