It is important to understand the Liveness and Readiness probes when you run Sitecore on Kubernetes. Their documentation provides more detail around these 2 probes:
- Liveness: Indicates whether the container is running. If the liveness probe fails, the kubelet kills the container, and the container is subjected to its restart policy.
- Readiness: Indicates whether the container is ready to respond to requests. If the readiness probe fails, the endpoints controller removes the Pod’s IP address from the endpoints of all Services that match the Pod.
In Sitecore these probes can be found under /healthz/live and /healthz/ready. The rest of this post will focus on the Readiness probe. There is a great article by Vitalii Tylyk which discusses these probes at a high level. By default, a Sitecore XP install checks a variety of xDB services as well as Solr as part of this probe. If these services are not all healthy then the probe will fail and no requests will be send to this pod.
It is important to understand this default behavior in the context of your Sitecore solution. If having xDB and Solr up are critical to a solution then this default behavior does not need to be changed. The risk with this setup is that all pods can be pulled from the load balancer if there is an issue with Solr or xDB and the site will be completely down. If these services are not critical to the Sitecore site then they can be removed from the readiness probe.
Below patch file shows how to remove all these checks so the readiness probe still returns healthy even if Solr and xDB are completely down. In many real world scenarios only a subset of these will have to be removed, for example removing xDB services but leaving Solr as the solution has a critical dependency on it.
<?xml version="1.0"?>
<configuration xmlns:patch="http://www.sitecore.net/xmlconfig/">
<sitecore>
<services>
<configurator type="Sitecore.ContentSearch.SolrProvider.DependencyInjection.ContentSearchServicesConfigurator, Sitecore.ContentSearch.SolrProvider">
<patch:delete />
</configurator>
<configurator type="Sitecore.XConnect.Client.Configuration.HealthCheckServicesConfigurators.XConnectCollectionHealthCheckServicesConfigurator, Sitecore.XConnect.Client.Configuration">
<patch:delete />
</configurator>
<configurator type="Sitecore.XConnect.Client.Configuration.HealthCheckServicesConfigurators.XConnectConfigurationHealthCheckServicesConfigurator, Sitecore.XConnect.Client.Configuration">
<patch:delete />
</configurator>
<configurator type="Sitecore.XConnect.Client.Configuration.HealthCheckServicesConfigurators.XConnectSearchHealthCheckServicesConfigurator, Sitecore.XConnect.Client.Configuration">
<patch:delete />
</configurator>
<configurator type="Sitecore.Xdb.Common.Web.Xmgmt.XdbEnabledHealthCheckServicesConfigurator`2[[Sitecore.Reporting.Service.Http.XConnectClient.XdbReportingWebClient, Sitecore.Reporting.Service.Http.XConnectClient],[Sitecore.Reporting.Service.Http.Abstractions.Routes, Sitecore.Reporting.Service.Http.Abstractions]], Sitecore.Xdb.Common.Web.Xmgmt">
<patch:delete />
</configurator>
<configurator type="Sitecore.Xdb.Common.Web.Xmgmt.XdbEnabledHealthCheckServicesConfigurator`2[[Sitecore.Xdb.ReferenceData.Client.ReferenceDataHttpClient, Sitecore.Xdb.ReferenceData.Client],[Sitecore.Xdb.ReferenceData.Client.Routes, Sitecore.Xdb.ReferenceData.Client]], Sitecore.Xdb.Common.Web.Xmgmt">
<patch:delete />
</configurator>
<configurator type="Sitecore.Xdb.Common.Web.Xmgmt.XdbEnabledHealthCheckServicesConfigurator`2[[Sitecore.Xdb.ReferenceData.Client.ReadOnlyReferenceDataHttpClient, Sitecore.Xdb.ReferenceData.Client],[Sitecore.Xdb.ReferenceData.Client.Routes, Sitecore.Xdb.ReferenceData.Client]], Sitecore.Xdb.Common.Web.Xmgmt">
<patch:delete />
</configurator>
<configurator type="Sitecore.Xdb.Common.Web.Xmgmt.XdbEnabledHealthCheckServicesConfigurator`2[[Sitecore.Xdb.MarketingAutomation.ReportingClient.AutomationReportingClient, Sitecore.Xdb.MarketingAutomation.ReportingClient],[Sitecore.Xdb.MarketingAutomation.ReportingClient.ReportingRoutes, Sitecore.Xdb.MarketingAutomation.ReportingClient]], Sitecore.Xdb.Common.Web.Xmgmt">
<patch:delete />
</configurator>
<configurator type="Sitecore.Xdb.Common.Web.Xmgmt.XdbEnabledHealthCheckServicesConfigurator`2[[Sitecore.Xdb.MarketingAutomation.OperationsClient.AutomationOperationsClient, Sitecore.Xdb.MarketingAutomation.OperationsClient],[Sitecore.Xdb.MarketingAutomation.OperationsClient.OperationRoutes, Sitecore.Xdb.MarketingAutomation.OperationsClient]], Sitecore.Xdb.Common.Web.Xmgmt">
<patch:delete />
</configurator>
</services>
</sitecore>
</configuration>
Jeroen's Sitecore Blog 