Add documentation on GroupMetadataManager Gauges: NumOffsets, NumGrou…

…ps, NumGroups[PreparingRebalance,CompletingRebalance,Empty,Stable,Dead]

docs/ops.html

@@ -963,6 +963,21 @@ <h4><a id="remote_jmx" href="#remote_jmx">Security Considerations for Remote Mon
         <td>kafka.server:type=ReplicaManager,name=IsrExpandsPerSec</td>
         <td>See above</td>
       </tr>
+      <tr>
+        <td>Consumer Group Offset Count</td>
+        <td>kafka.server:type=GroupMetadataManager,name=NumOffsets</td>
+        <td>Total number of committed offsets for Consumer Groups</td>
+      </tr>
+      <tr>
+        <td>Consumer Group Count</td>
+        <td>kafka.server:type=GroupMetadataManager,name=NumGroups</td>
+        <td>Total number of Consumer Groups</td>
+      </tr>
+      <tr>
+        <td>Consumer Group Count, per State</td>
+        <td>kafka.server:type=GroupMetadataManager,name=NumGroups[PreparingRebalance,CompletingRebalance,Empty,Stable,Dead]</td>
+        <td>The number of Consumer Groups in each state: PreparingRebalance, CompletingRebalance, Empty, Stable, Dead</td>
+      </tr>
       <tr>
         <td>Max lag in messages btw follower and leader replicas</td>
         <td>kafka.server:type=ReplicaFetcherManager,name=MaxLag,clientId=Replica</td>