[jira] [Created] (SOLR-15549) Old SolrJ implementations (8.x) are incompatible with 9.0 Clouds

["Houston Putman (Jira)" <ji...@apache.org>]

Houston Putman created SOLR-15549:
-------------------------------------

             Summary: Old SolrJ implementations (8.x) are incompatible with 9.0 Clouds
                 Key: SOLR-15549
                 URL: https://issues.apache.org/jira/browse/SOLR-15549
             Project: Solr
          Issue Type: Bug
      Security Level: Public (Default Security Level. Issues are Public)
          Components: SolrJ
    Affects Versions: 8.0
            Reporter: Houston Putman
            Assignee: Houston Putman


The {{ZkStateReader}} in 8.x (and previous versions) checks that a {{/clusterstate.json}} node exists in the ZK ChRoot, to ensure that the ChRoot hosts a Solr Cloud. However, starting in 9.0, {{/clusterstate.json}} has been removed, and it is auto-deleted if a user tries to create one.

That means that the ZkStateReader from SolrJ 8.x will error when trying to connect with a Solr 9 cloud, with the message:
{quote}Cannot connect to cluster at localhost:2181/: cluster not found/not ready
{quote}
The solution, is to have the ZK State Reader check both {{/clusterstate.json}} and {{/collections}} and only error if both are missing.  {{/clusterstate.json}} is long-deprecated in 8.x anyways, so adding this additional check is good practice in general.

While it would be nice for every user to use the same SolrJ version as the version they are running for Solr, it can be difficult in practice, especially when upgrading major Solr versions. It would be preferable to support at least version + 1 clouds in SolrJ, for the purpose of upgrades.



--
This message was sent by Atlassian Jira
(v8.3.4#803005)

---------------------------------------------------------------------
To unsubscribe, e-mail: issues-unsubscribe@solr.apache.org
For additional commands, e-mail: issues-help@solr.apache.org