[GitHub] [druid] mghosh4 commented on a change in pull request #10379: Adding task slot count metrics to Druid Overlord

[GitBox <gi...@apache.org>]

mghosh4 commented on a change in pull request #10379:
URL: https://github.com/apache/druid/pull/10379#discussion_r493974286



##########
File path: server/src/main/java/org/apache/druid/server/metrics/TaskSlotCountStatsMonitor.java
##########
@@ -0,0 +1,56 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+package org.apache.druid.server.metrics;
+
+import com.google.inject.Inject;
+import org.apache.druid.java.util.emitter.service.ServiceEmitter;
+import org.apache.druid.java.util.emitter.service.ServiceMetricEvent;
+import org.apache.druid.java.util.metrics.AbstractMonitor;
+
+public class TaskSlotCountStatsMonitor extends AbstractMonitor
+{
+  private final TaskSlotCountStatsProvider statsProvider;
+
+  @Inject
+  public TaskSlotCountStatsMonitor(
+          TaskSlotCountStatsProvider statsProvider
+  )
+  {
+    this.statsProvider = statsProvider;
+  }
+
+  @Override
+  public boolean doMonitor(ServiceEmitter emitter)
+  {
+    emit(emitter, "taskSlot/total/count", statsProvider.getTotalTaskSlotCount());

Review comment:
       This is controlled from TaskMaster and it is the same design as `TaskCountStatsMonitor`. If you check that code, taskRunner is only set if the current overlord is the leader https://github.com/apache/druid/blob/master/indexing-service/src/main/java/org/apache/druid/indexing/overlord/TaskMaster.java#L113. Then check the implementation of `getSuccessfulTaskCount`. It only returns a value if the `taskRunner` is set correctly or else `null`.




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