Add balancer meter fixes #4470

core/src/main/java/org/apache/accumulo/core/metrics/MetricsProducer.java

@@ -649,6 +649,10 @@ public interface MetricsProducer {
   String METRICS_UPDATE_WALOG_WRITE = METRICS_UPDATE_PREFIX + "walog.write";
   String METRICS_UPDATE_MUTATION_ARRAY_SIZE = METRICS_UPDATE_PREFIX + "mutation.arrays.size";
 
+  // balancer
+  String METRICS_MANAGER_BALANCER_MIGRATING = "manager.balancer.balancing.total";
+  String METRICS_MANAGER_BALANCER_NEED_MIGRATION = "manager.balancer.need.balancing.total";
+
   /**
    * Build Micrometer Meter objects and register them with the registry
    */

server/manager/src/main/java/org/apache/accumulo/manager/Manager.java

@@ -112,6 +112,7 @@
 import org.apache.accumulo.core.util.Retry;
 import org.apache.accumulo.core.util.threads.ThreadPools;
 import org.apache.accumulo.core.util.threads.Threads;
+import org.apache.accumulo.manager.metrics.BalancerMetrics;
 import org.apache.accumulo.manager.metrics.ManagerMetrics;
 import org.apache.accumulo.manager.recovery.RecoveryManager;
 import org.apache.accumulo.manager.state.TableCounts;
@@ -208,6 +209,7 @@ public class Manager extends AbstractServer
   private TServer clientService = null;
   private volatile TabletBalancer tabletBalancer;
   private final BalancerEnvironment balancerEnvironment;
+  private final BalancerMetrics balancerMetrics = new BalancerMetrics();
 
   private ManagerState state = ManagerState.INITIAL;
 
@@ -561,6 +563,10 @@ public void clearMigrations(TableId tableId) {
     }
   }
 
+  public MetricsProducer getBalancerMetrics() {
+    return balancerMetrics;
+  }
+
   enum TabletGoalState {
     HOSTED(TUnloadTabletGoal.UNKNOWN),
     UNASSIGNED(TUnloadTabletGoal.UNASSIGNED),
@@ -934,7 +940,11 @@ private long balanceTablets() {
         synchronized (balancedNotifier) {
           balancedNotifier.notifyAll();
         }
+        balancerMetrics.setMigratingCount(0);
+        balancerMetrics.setNeedMigrationCount(0);
       } else {
+        balancerMetrics.setMigratingCount(params.migrationsOut().size());
+        balancerMetrics.setNeedMigrationCount(migrations.size());
         nextEvent.event("Migrating %d more tablets, %d total", params.migrationsOut().size(),
             migrations.size());
       }
@@ -1104,6 +1114,7 @@ public void run() {
     metricsInfo.addServiceTags(getApplicationName(), sa.getAddress());
 
     var producers = ManagerMetrics.getProducers(getConfiguration(), this);
+    producers.add(balancerMetrics);
     metricsInfo.addMetricsProducers(producers.toArray(new MetricsProducer[0]));
     metricsInfo.init();
 

server/manager/src/main/java/org/apache/accumulo/manager/metrics/BalancerMetrics.java

@@ -0,0 +1,58 @@
+/*
+ * 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
+ *
+ *   https://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.accumulo.manager.metrics;
+
+import java.util.concurrent.atomic.AtomicLong;
+
+import org.apache.accumulo.core.metrics.MetricsProducer;
+
+import io.micrometer.core.instrument.Gauge;
+import io.micrometer.core.instrument.MeterRegistry;
+
+public class BalancerMetrics implements MetricsProducer {
+
+  AtomicLong migratingCount = new AtomicLong();
+  AtomicLong needMigrationCount = new AtomicLong();
+
+  public long getMigratingCount() {
+    return migratingCount.get();
+  }
+
+  public void setMigratingCount(final long migratingCount) {
+    this.migratingCount.set(migratingCount);
+  }
+
+  public long getNeedMigrationCount() {
+    return needMigrationCount.get();
+  }
+
+  public void setNeedMigrationCount(final long needMigrationCount) {
+    this.needMigrationCount.set(needMigrationCount);
+  }
+
+  @Override
+  public void registerMetrics(MeterRegistry registry) {
+    Gauge.builder(METRICS_MANAGER_BALANCER_MIGRATING, this, BalancerMetrics::getMigratingCount)
+        .description("Snapshot count of tablets currently being migrated").register(registry);
+    Gauge
+        .builder(METRICS_MANAGER_BALANCER_NEED_MIGRATION, this,
+            BalancerMetrics::getNeedMigrationCount)
+        .description("Snapshot count of tablets that need to be migrated").register(registry);
+  }
+}

server/manager/src/main/java/org/apache/accumulo/manager/metrics/ManagerMetrics.java

@@ -26,13 +26,9 @@
 import org.apache.accumulo.core.metrics.MetricsProducer;
 import org.apache.accumulo.manager.Manager;
 import org.apache.accumulo.manager.metrics.fate.FateMetrics;
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
 
 public class ManagerMetrics {
 
-  private final static Logger log = LoggerFactory.getLogger(ManagerMetrics.class);
-
   public static List<MetricsProducer> getProducers(AccumuloConfiguration conf, Manager m) {
     ArrayList<MetricsProducer> producers = new ArrayList<>();
     @SuppressWarnings("deprecation")

test/src/main/java/org/apache/accumulo/test/metrics/MetricsIT.java

@@ -101,7 +101,8 @@ public void confirmMetricsPublished() throws Exception {
 
     Set<String> unexpectedMetrics = Set.of(METRICS_SCAN_YIELDS, METRICS_UPDATE_ERRORS,
         METRICS_REPLICATION_QUEUE, METRICS_COMPACTOR_MAJC_STUCK, METRICS_SCAN_BUSY_TIMEOUT);
-    Set<String> flakyMetrics = Set.of(METRICS_GC_WAL_ERRORS, METRICS_FATE_TYPE_IN_PROGRESS);
+    Set<String> flakyMetrics = Set.of(METRICS_GC_WAL_ERRORS, METRICS_FATE_TYPE_IN_PROGRESS,
+        METRICS_MANAGER_BALANCER_NEED_MIGRATION, METRICS_MANAGER_BALANCER_MIGRATING);
 
     Map<String,String> expectedMetricNames = this.getMetricFields();
     flakyMetrics.forEach(expectedMetricNames::remove); // might not see these