[SOLR-15017] The core's lib/ folder content is not loaded in the classloader anymore when the core's configuration does not define any <lib> element

• Type: Bug
• Status: Resolved
• Priority: Blocker
• Resolution: Fixed
• Affects Version/s: 8.7
• Fix Version/s: 8.8
• Labels: regression
• Assignee: David Smiley
• Reporter: Thomas Mortagne
• Created: 25/Nov/20 16:21
• Updated: 13/Feb/21 00:09
• Resolved: 01/Dec/20 20:42

Description

I just upgraded solr-core (I'm using Solr in embedded mode) from 8.5.1 to 8.7.0 and it seems that the lib subfolder inside a core folder is not taken into account anymore.

Works fine when I move the lib/ folder one level up (in the Solr home folder) but when the lib folder with the plugins is located in the core folder it cannot find any of the classes.

I debugged it a little and I think the regression was caused by the refactoring done in https://github.com/apache/lucene-solr/commit/732348ec7f9c6b6f7bf9d539a40e50d16198cccc#diff-473fbcdab103c08461ad1b3c3bb1c6d56f1bcd16d6ce341d80855db2cb20a427R749 : the handling of the lib/ core's sub folder was moved to SolrConfig#initLibs() but unfortunately the check to make sure there is at least one <lib> element in the configuration file was not removed which means that if you don't have any of those then the content of the lib/ folder is totally ignored.

That debugging was easy enough but I don't know Solr internals enough to propose something clean to fix the issue in a pull request.

The workaround is to make sure there is at least one <lib/> element (for example {{<lib dir="lib" regex=".*\.jar" />}}) in the core's solrconfig.xml file.

Issue Links

• is related to: SOLR-14197 Reduce API of SolrResourceLoader
• links to: GitHub Pull Request #2107