Solr Failure Issues

If your build fails on a step that connects to Apache Solr - or the build completes but your site cannot reach its search index - the most common cause is an incompatible Solr core, or a core that was uploaded in an incorrect format.

Recognizing the Problem

Look at the log output for the failing Solr step on your build page. A core that Solr cannot load will show up as an error connecting to the core, an HTTP 404 or 500 from the Solr server, or a message that the core or its configuration set could not be found.

Why It Happens

Solr is strict about the version and layout of the configuration set that defines a core. The usual causes are:

• A version mismatch. The config-set bundled with your archive was built for a different major version of Solr than the one running in your build. A core config set for Solr 7 will not load on a Solr 8 or 9 server, and vice versa.
• An incorrect archive format. The core archive must contain the configuration set inside a folder, compressed in the format your .probo.yaml declares. If the files are zipped at the wrong level - for example, the conf directory at the root of the archive instead of nested inside the core folder - Solr cannot find the configuration and the core fails to come up.

Triaging on the Build

To see the Solr back end directly, add /solr to the end of your Probo build URL. This opens the Solr admin interface, where you can confirm whether your core loaded, view the cores Solr actually started with, and read the specific error Solr reported for a core that failed to initialize. This is usually the fastest way to tell an incompatible core apart from one that was simply packaged incorrectly.

Fixing It

Make sure the Solr version and core config set in your .probo.yaml match, and that the archive is laid out correctly with the configuration nested inside the core folder. For the full walkthrough of declaring the Solr version, building the core archive, and uploading it as a build asset, see the Using Apache Solr with Drupal documentation. General configuration options are covered on the Solr Configuration page.

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