Emit more granular data points for troubleshooting Eureka instances

Problem Statement

Eureka service registry instances gets registrations and peer replicate these with other instances. When there are issues with registration, client lookups and peer replication it can be difficult to figure out where the root of the problem is.

Emit more granular metrics

• Peer replication - replication time for each replicant
• Registration - time to register, number of instances per service
• Total registrants
• Client request times to fetch service locations

Enhance health actuator

A Eureka server should provide more details on what factors may have affected during peer replication, registration and client lookups when it is unhealthy.

Additional context

Many organizations I talk with have Eureka dashboards showing health. They also have observability tools but are not able to get sufficient data points to help in troubleshooting Eureka instances.

No files or tests are named. Start by tracing the Eureka server paths for peer replication, registration, client service-location lookups, and the health actuator. Done means exposing the requested timing and count data points and providing additional health details for affected replication, registration, and lookup factors.