anchor.diff:  type:: The type of metric to retrieve. The default is `all` to retrieve all metric types. Other possible values are `counter`, `gauge`, `histogram`, `meter`, and `timer`. More than one type can be specified in a request; multiple types should be separated by a comma.
   
   prefix:: The first characters of metric name that will filter the metrics returned to those starting with the provided string. It can be combined with `group` and/or `type` parameters. More than one prefix can be specified in a request; multiple prefixes should be separated by a comma. Prefix matching is also case-sensitive.
  +
  +regex:: A regular expression matching metric names. Note: dot separators in metric names must be escaped, eg.
  +`QUERY\./select\..*` is a valid regex that matches all metrics with the `QUERY./select.` prefix.
   
   property:: Allows requesting only this metric from any compound metric. Multiple `property` parameters can be combined to act as an OR request. For example, to only get the 99th and 999th percentile values from all metric types and groups, you can add `&property=p99_ms&property=p999_ms` to your request. This can be combined with `group`, `type`, and `prefix` as necessary.
   
  
positive.code: [source,text]
  http://localhost:8983/solr/admin/metrics?wt=xml&prefix=INDEX&group=core
  
  Request only "user.name" property of "system.properties" metric from registry "solr.jvm":
  
  [source,text]
  
negative.code: 
  The <<Core Level Metrics,Core (SolrCore) Registry>> includes `solr.core.<collection>`, one for each core. When making requests with the <<Metrics API>>, you can specify `&group=core` to limit to only these metrics.
  
  * all common RequestHandler-s report: request timers / counters, timeouts, errors. Handlers that support
    process distributed shard requests also report `shardRequests` sub-counters for each type of distributed
    request.
  * <<Index Merge Metrics,index-level events>>: meters for minor / major merges, number of merged docs, number of deleted docs, gauges for currently running merges and their size.
  * shard replication and transaction log replay on replicas (TBD, SOLR-9856)
  * open / available / pending connections for shard handler and update handler
  