Explanation

When starting XWiki, the application may appear to hang during startup while initializing Solr. No clear error may be displayed in the logs, but the servlet container remains stuck during the Solr initialization phase.

This can happen when Solr tries to initialize multiple cores at the same time, especially for cores created by older XWiki versions.

Cause

This issue occurs because Solr loads all configured cores during startup. When multiple cores need to be initialized simultaneously, Solr may lock itself and prevent the XWiki application from completing the startup process.

Newer XWiki versions create Solr cores with delayed loading enabled, meaning that the core is initialized only when it is first used. However, existing Solr cores created by older versions may not have this option configured.

Solution

To resolve the issue, configure the existing Solr cores to use delayed loading:

1. Navigate to the XWiki Solr storage directory:

   <permdir>/store/solr/

2. For each Solr core, edit the core.properties file:

   <permdir>/store/solr/<core-name>/core.properties

3. Add the following property:

   loadOnStartup=false

4. Save the changes and restart the servlet container running XWiki.