Somebody on the solr-user mailing list has posed a question about whether they can use ZK 3.4.12 on the server side and a specific version of Solr on the client side. The specific version of Solr they're asking about includes ZK 3.4.10 for its client code.
I would not anticipate any issues running with 3.4.10 on the client side and 3.4.12 on the server side, so I think I can safely answer their question, but I have a more general question to ask. Are there ANY mixed version matchups that present problems, assuming the server is running a newer version than the client? I would never advise running a server version that's older than the client. The very first release of Solr to feature ZK integration was 4.0-ALPHA, and eventually the stable 4.0.0 release, which included ZK 3.3.6. The subsequent version of Solr, which was 4.1.0, included ZK 3.4.5. We expect to include ZK 3.4.12 with the next release of Solr - 7.4.0. I did a simple test with Solr 4.0.0 against a single ZK 3.4.12 server. It started just fine. The testing was not exhaustive, but I saw zero problems. What I intend to say on the solr-user thread is that ZK 3.4.12 can be used with ALL SolrCloud versions, but I thought I should sanity-check that statement here before I make it. Thanks, Shawn
