vSphere HA Application Monitoring This chapter discusses vSphere High Availability (HA) and how to use HA Application Monitoring APIs with the Guest SDK. About vSphere HAThe vSphere High Availability (HA) feature for ESXi hosts in a cluster provides protection for a guest OS and its applications, by restarting the virtual machine if a guest OS or application failure occurs. The HA feature provides this reset capability using two different mechanisms: Prerequisites for HA Application MonitoringBefore you start working with the HA Application Monitoring SDK, verify that your vSphere application is running within a VMware cluster that has both the High Availability and VM and Application Monitoring options enabled.Using the HA Application Monitoring APIsYou can use the HA Application Monitoring SDK to create a stand-alone application monitoring program, or to enhance an existing application or script. The purpose of your application monitoring program determines the API call sequence and the application behavior that you write to handle the response data.