The PingRequestHandler checks the healthcheck file first (if configured) and returns an error if the instance is disabled. It then executes the configured ping query to ensure that the index is accessible. Advantages:
- Enable/Disable and index availability can both be checked by the load balancer via a single URL.
- The URL accessed by the load balancer is outside /admin, making it easier to restrict access to /admin.
- is depended upon by
SOLR-335 solrj and ping / PingRequestHandler