Hello David and team, >>Out of curiosity, why would scaling down to 1 and back up to N not be an already supported pattern?
I may be wrong, but generally if you use Solr with only one core/shard you don't use solr cloud/zookeeper. At least in older Solr versions. Kind regards, Alejandro Arrieta On Thu, Mar 12, 2026, 9:29 AM David Eric Pugh via dev <[email protected]> wrote: > Jan, so if my world doesn't include Kubernetes, it would be a reasonable > addition to Solr to ship a placement plugin that scales up and down the > single shard collections that use it. And does the book keeping in > ZooKeeper to not show down nodes or down replicas? > Not sure how complex the engineering on this will be! > Out of curiosity, why would scaling down to 1 and back up to N not be an > already supported pattern? Is it because everyone does that with their own > scripts external to Solr or via the Operator? What am I missing about this > use case? > > On Thursday, March 12, 2026 at 08:27:15 AM EDT, David Eric Pugh < > [email protected]> wrote: > > David --> I oddly struggled to write the email cause I was stumbling > over my words... I wasn't sure if I should have said "shard", and how to > phrase a collection made up of a single core.... And then copies of that > core... After I read your response, I thought, I should check out the > Solr Concepts page and see what it tells me and discovered that we have > nothing under Solr Concepts specific to this topic. I looked up in the > glossary "SolrCloud" and it led me to > https://solr.apache.org/guide/solr/latest/deployment-guide/cluster-types.html#solrcloud-mode. > Only later when I scrolled up in the page did I see the section "Cluster > Concepts". Thoughts on maybe moving that section under the Solr Concepts > hierarchy in Ref Guide? It would have helped me use the right terms! > > > > > On Wednesday, March 11, 2026 at 06:38:17 PM EDT, David Smiley < > [email protected]> wrote: > > An aside: Remember that the leader is a replica too, so your numbers are > off & confusing. "single shard with no replicas" -- I guessed what you > mean but surprised to hear a misuse of SolrCloud lingo from you. AFAICT, > leadership isn't even pertinent to your inquiry either. > > On Wed, Mar 11, 2026 at 5:38 PM David Eric Pugh via dev < > [email protected]> > wrote: > > > Hey all, I wanted to get some feedback from you'all on a recent usecase I > > was asked about. I suspect the answer will be "Use Solr Operator", but > > here goes! > > I have an environment where I have 5 or so single shard collections. > > Much of the time I run just a single node and each collection is a > single > > shard with no replicas. Sometimes, to support load, I'll add another > node > > or two. Then I'll add replicas so cover the new nodes, 1 per node. So > > with three nodes, I have one leader and two replicas. Add two more > nodes, > > move to one leader and four replicas. > > However, when I remove a node by shutting it down, then Zookeeper never > > get's notified about this, and so the replica is listed as down, and the > > node is listed as down in red in the UI. When it isn't really red, it's > > just we don't need it for now, and it's not coming back. > > I'd like to just declare "For this collection, I want one replica per > node > > based on however many nodes are current". I don't want to call the > > various commands myself to add replicas and or remove then as nodes are > > added or removed. And I don't want to call various apis or other complex > > things when I add or remove a node, I just want bin/solr stop and > bin/solr > > start to be run ;-). > > I think this is what Replica Placement Plugins were for maybe? Could I > > have a Replica Placement strategy that when ZK sees a new node added, > then > > creates a new replica on it, and vice versa, when a node goes away, it > just > > removes that replica instead of treating it as "down"? > > Thoughts? > > Eric > > >
