[Docs] Coordinator event metrics (#1272)

* [Docs] Add coordinator event metric document

* [Docs] Add coordinator event metric document

Author: zcoo

fluss-common/src/main/java/com/alibaba/fluss/metrics/MetricNames.java

@@ -44,8 +44,8 @@ public class MetricNames {
 
     // for coordinator event processor
     public static final String EVENT_QUEUE_SIZE = "eventQueueSize";
-    public static final String EVENT_PROCESS_TIME_MS = "eventProcessTimeMs";
     public static final String EVENT_QUEUE_TIME_MS = "eventQueueTimeMs";
+    public static final String EVENT_PROCESSING_TIME_MS = "eventProcessingTimeMs";
 
     // --------------------------------------------------------------------------------------------
     // metrics for tablet server

fluss-server/src/main/java/com/alibaba/fluss/server/coordinator/event/CoordinatorEventManager.java

@@ -53,7 +53,7 @@ public final class CoordinatorEventManager implements EventManager {
     private final Lock putLock = new ReentrantLock();
 
     // metrics
-    private Histogram eventProcessTime;
+    private Histogram eventProcessingTime;
     private Histogram eventQueueTime;
 
     private static final int WINDOW_SIZE = 100;
@@ -68,9 +68,9 @@ public CoordinatorEventManager(
     private void registerMetrics() {
         coordinatorMetricGroup.gauge(MetricNames.EVENT_QUEUE_SIZE, queue::size);
 
-        eventProcessTime =
+        eventProcessingTime =
                 coordinatorMetricGroup.histogram(
-                        MetricNames.EVENT_PROCESS_TIME_MS,
+                        MetricNames.EVENT_PROCESSING_TIME_MS,
                         new DescriptiveStatisticsHistogram(WINDOW_SIZE));
 
         eventQueueTime =
@@ -138,7 +138,7 @@ public void doWork() throws Exception {
                 log.error("Uncaught error processing event {}.", coordinatorEvent, e);
             } finally {
                 long eventFinishTimeMs = System.currentTimeMillis();
-                eventProcessTime.update(eventFinishTimeMs - eventStartTimeMs);
+                eventProcessingTime.update(eventFinishTimeMs - eventStartTimeMs);
             }
         }
     }

website/docs/maintenance/observability/monitor-metrics.md

@@ -312,8 +312,8 @@ Some metrics might not be exposed when using other JVM implementations (e.g. IBM
   </thead>
   <tbody>
     <tr>
-      <th rowspan="6"><strong>coordinator</strong></th>
-      <td style={{textAlign: 'center', verticalAlign: 'middle' }} rowspan="6">-</td>
+      <th rowspan="9"><strong>coordinator</strong></th>
+      <td style={{textAlign: 'center', verticalAlign: 'middle' }} rowspan="9">-</td>
       <td>activeCoordinatorCount</td>
       <td>The number of active CoordinatorServer in this cluster.</td>
       <td>Gauge</td>
@@ -343,6 +343,21 @@ Some metrics might not be exposed when using other JVM implementations (e.g. IBM
       <td>The total number of replicas in the progress to be deleted in this cluster.</td>
       <td>Gauge</td>
     </tr>
+    <tr>
+      <td>eventQueueSize</td>
+      <td>The number of events waiting to be processed in the queue.</td>
+      <td>Gauge</td>
+    </tr>
+    <tr>
+      <td>eventQueueTimeMs</td>
+      <td>The time that an event spent waiting in the queue to be processed.</td>
+      <td>Histogram</td>
+    </tr>
+    <tr>
+      <td>eventProcessingTimeMs</td>
+      <td>The time that an event took to be processed.</td>
+      <td>Histogram</td>
+    </tr>
   </tbody>
 </table>