[SOLR-15134] Solr upgrade order / documentation

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Duplicate
• Affects Version/s: 8.8
• Fix Version/s: 8.8.1
• Assignee: Unassigned
• Reporter: Bernd Wahlen
• Created: 04/Feb/21 16:45
• Updated: 23/Feb/21 16:20
• Resolved: 12/Feb/21 09:16

Description

I updated a our solr cluster of 3 servers today 8.7 -> 8.8 and found the following difficulties:

1. solrj 8.7 was crashing when trying to connect to solr 8.8 with something like this:

Caused by: org.apache.solr.client.solrj.SolrServerException: java.lang.NullPointerException: Cannot invoke "String.endsWith(String)" because "baseUrl" is null
        at org.apache.solr.client.solrj.impl.BaseCloudSolrClient.requestWithRetryOnStaleState(BaseCloudSolrClient.java:1053) ~[solr-solrj-8.7.0.jar:8.7.0 2dc63e901c60cda27ef3b744bc554f1481b3b067 - atrisharma - 2020-10-29 19:39:18]

After upgrade of solrj to 8.8 also, everything is fine.
I mean this is more like a documentation issue. Most of the time solrj and solrj are compatible up- and down-version.
I read changes:
https://lucene.apache.org/solr/8_8_0/changes/Changes.html#v8.8.0.bug_fixes
There should be some warning that client library must be upgraded before server.
=> https://issues.apache.org/jira/browse/SOLR-15145

2. when updating servers in a rolling manner, after update of 1 server: only the 8.8 server is showing all 3 members of the cluster in the web interface. The 8.7 servers show nothing at all (not even the 2 remaining 8.7 instances). After upgrading all 3, everything recovered. Is the rolling-upgrade not working or is that, because i did it in the wrong order?

Issue Links

• Blocked: SOLR-15145 Older versions of SolrJ (pre-8.8.0) hit an NPE when computing the base_url for core node props