Can Sitecore be configured to automatically recover after restarting the Solr service?

Question

We are hosting Sitecore 9 on Azure App Services using Solr as the search provider.

Microsoft will occasionally restart the server that is hosting Solr (due to ... updates made by Microsoft to the underlying Azure platform to improve overall reliability, performance, and security of the platform infrastructure).

When this happens Sitecore goes down as well (components that are based on content search are broken), however, it does not recover automatically after Solr is back online (which takes less than 1 minute), and we need to manually restart Sitecore as well, otherwise it will stay stuck in a corrupted state.

Why doesn't Sitecore detect that Solr is back online? Can Sitecore be configured to automatically resume normal operation once Solr has completed the restart?

Answer 1

There is a scheduling agent IsSolrAliveAgent available out of the box and is configured in Sitecore.ContentSearch.Solr.DefaultIndexConfiguration.config. By default, it is configured to run with interval of 10 minutes.

<agent type="Sitecore.ContentSearch.SolrProvider.Agents.IsSolrAliveAgent, Sitecore.ContentSearch.SolrProvider" method="Run" interval="00:10:00" />

You can verify that the aforementioned settings are in place and re-configure the interval to a desired value. For troubleshooting, you can also check the logs files for "IsSolrAliveAgent".