I’ve had a lot of luck using the bats testing infrastructure to try out “what if” situations with Solr to see what actually happens. For example, I tested out classic leader/follower replication works when your leader is a single node solr cloud server and your follower is a totally separate single node cloud server!
You may want to write some bats test that simulate these situations to confirm/deny what folks say “should” happen. They would be great to have for integration/regression testing as well. > On May 21, 2024, at 11:30 AM, Matt Kuiper <kuipe...@gmail.com> wrote: > > Thanks for the responses! > > Shawn, > > I believe I understood that Zookeeper does not actually handle the request. > Thanks for the clarification as I did not word it properly. > > More precisely, will a SolrJ CloudSolrClient work for the purpose of > querying SolrCloud if the ZK host list it is configured with represents a > Zookeeper ensemble that has lost its quorum? > > My goal is to learn if this SolrJ client (configured via zkhost list) can > reliably query a SolrCloud even when the ZK ensemble has lost its quorum. > > I have heard that Zookeeper will go into a read-only mode if quorum is > lost. Put another way, will the SolrJ cloud client still be able to talk > to ZK to discover the URLs required to get > to Solr and serve queries (at least will the solrj client be given the > latest state from the remaining ZK nodes for what was last written to > Zookeeper)? > > Our company is reviewing HA/DR scenarios for SolrCloud and I am > investigating if a SolrCloud that has lost its ZK quorum can provide any > value for Solr queries, and how to characterize accuracy of any search > results. > > Thanks for any further information you can provide. > > Matt > > On Mon, May 20, 2024 at 9:02 PM Shawn Heisey <apa...@elyograg.org.invalid> > wrote: > >> On 5/20/2024 17:46, mtn search wrote: >>> Will a SolrJ client connection (configured with a ZKhost list) to a >>> SolrCloud still work for querying a SolrCloud when the Zookeeper ensemble >>> has lost its quorum, but some ZK nodes remain up? I understand that >>> indexing will not work. >>> >>> Follow-on - will the Solr query work to the same SolrCloud if the query >> is >>> sent directly to a Solr node rather than to Zookeeper? >> >> Requests to SolrCloud such as queries or indexing do not go through ZK, >> ever. >> >> The SolrJ cloud client talks to ZK to discover the URLs required to get >> to Solr and which of them are online at any given moment. ZK is used as >> a central database to coordinate the cluster, it does not handle requests. >> >> Thanks, >> Shawn >> >> _______________________ Eric Pugh | Founder | OpenSource Connections, LLC | 434.466.1467 | http://www.opensourceconnections.com <http://www.opensourceconnections.com/> | My Free/Busy <http://tinyurl.com/eric-cal> Co-Author: Apache Solr Enterprise Search Server, 3rd Ed <https://www.packtpub.com/big-data-and-business-intelligence/apache-solr-enterprise-search-server-third-edition-raw> This e-mail and all contents, including attachments, is considered to be Company Confidential unless explicitly stated otherwise, regardless of whether attachments are marked as such.
