If you experience the following on-screen error, or log message:
Unfortunately, the extraction doesn't seem to work with this configuration when clicking Submit and test extraction, try to patch Solarium by running the following command in your Drupal docroot (the vendor folder may also be at the same level as your docroot):
Resolution for Drupal 8
cd vendor/solarium/solarium && wget https://gist.githubusercontent.com/janusman/fc7833a8598e436434899d2b369e04bb/raw/3583b2531fb90edf900e3f3b552ae4d339c40e27/solarium-patch-3.8.1-to-3.x-with-boundary-fix.patch && patch -p1 <solarium-patch-3.8.1-to-3.x-with-boundary-fix.patch
Resolution for Drupal 7
Go to the Search API configuration page, and then click the Search API attachments tab.
Scroll to the Solr Extraction Settings section, and in the Solr extracting servlet path field, enter