Collect JVM memory metrics (#2937)

* add jvm metrics

* include all changes

* Fix tests and lint errors

* Fix formatting

* Instantiate jvmmetrics class in stackdriver module

* add metrics registration behaviour and explicit call

* redo tests

* fix formatting/variable name

* lint

core/src/main/java/google/registry/monitoring/whitebox/JvmMetrics.java

@@ -0,0 +1,103 @@
+// Copyright 2017 The Nomulus Authors. All Rights Reserved.
+//
+// Licensed 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 google.registry.monitoring.whitebox;
+
+import com.google.common.base.Supplier;
+import com.google.common.collect.ImmutableList;
+import com.google.common.collect.ImmutableMap;
+import com.google.common.collect.ImmutableSet;
+import com.google.monitoring.metrics.LabelDescriptor;
+import com.google.monitoring.metrics.MetricRegistry;
+import com.google.monitoring.metrics.MetricRegistryImpl;
+import jakarta.inject.Inject;
+import jakarta.inject.Singleton;
+import java.lang.management.ManagementFactory;
+import java.lang.management.MemoryMXBean;
+import java.lang.management.MemoryUsage;
+
+/** Exposes JVM metrics. */
+@Singleton
+class JvmMetrics {
+
+  private static final ImmutableSet<LabelDescriptor> TYPE_LABEL_SET =
+      ImmutableSet.of(LabelDescriptor.create("type", "Memory type (e.g., heap, non_heap)"));
+  private final MemoryMXBean memoryMxBean;
+
+  @Inject
+  JvmMetrics() {
+    this(ManagementFactory.getMemoryMXBean());
+  }
+
+  /** Constructor for testing. */
+  JvmMetrics(MemoryMXBean memoryMxBean) {
+    this.memoryMxBean = memoryMxBean;
+  }
+
+  /** Registers JVM gauges with the default registry. */
+  void register() {
+    MetricRegistry registry = MetricRegistryImpl.getDefault();
+
+    registry.newGauge(
+        "/jvm/memory/used",
+        "Current memory usage in bytes",
+        "bytes",
+        TYPE_LABEL_SET,
+        (Supplier<ImmutableMap<ImmutableList<String>, Long>>) this::getUsedMemory,
+        Long.class);
+
+    registry.newGauge(
+        "/jvm/memory/committed",
+        "Committed memory in bytes",
+        "bytes",
+        TYPE_LABEL_SET,
+        (Supplier<ImmutableMap<ImmutableList<String>, Long>>) this::getCommittedMemory,
+        Long.class);
+
+    registry.newGauge(
+        "/jvm/memory/max",
+        "Maximum memory in bytes",
+        "bytes",
+        TYPE_LABEL_SET,
+        (Supplier<ImmutableMap<ImmutableList<String>, Long>>) this::getMaxMemory,
+        Long.class);
+  }
+
+  ImmutableMap<ImmutableList<String>, Long> getUsedMemory() {
+    MemoryUsage heapUsage = memoryMxBean.getHeapMemoryUsage();
+    MemoryUsage nonHeapUsage = memoryMxBean.getNonHeapMemoryUsage();
+
+    return ImmutableMap.of(
+        ImmutableList.of("heap"), heapUsage.getUsed(),
+        ImmutableList.of("non_heap"), nonHeapUsage.getUsed());
+  }
+
+  ImmutableMap<ImmutableList<String>, Long> getCommittedMemory() {
+    MemoryUsage heapUsage = memoryMxBean.getHeapMemoryUsage();
+    MemoryUsage nonHeapUsage = memoryMxBean.getNonHeapMemoryUsage();
+
+    return ImmutableMap.of(
+        ImmutableList.of("heap"), heapUsage.getCommitted(),
+        ImmutableList.of("non_heap"), nonHeapUsage.getCommitted());
+  }
+
+  ImmutableMap<ImmutableList<String>, Long> getMaxMemory() {
+    MemoryUsage heapUsage = memoryMxBean.getHeapMemoryUsage();
+    MemoryUsage nonHeapUsage = memoryMxBean.getNonHeapMemoryUsage();
+
+    return ImmutableMap.of(
+        ImmutableList.of("heap"), heapUsage.getMax(),
+        ImmutableList.of("non_heap"), nonHeapUsage.getMax());
+  }
+}

core/src/main/java/google/registry/monitoring/whitebox/StackdriverModule.java

@@ -32,7 +32,7 @@ import jakarta.inject.Named;
 import jakarta.inject.Singleton;
 import org.joda.time.Duration;
 
-/** Dagger module for Google Stackdriver service connection objects. */
+/** Dagger module for monitoring and Google Stackdriver service connection objects. */
 @Module
 public final class StackdriverModule {
 
@@ -77,7 +77,11 @@ public final class StackdriverModule {
 
   @Provides
   static MetricReporter provideMetricReporter(
-      MetricWriter metricWriter, @Config("metricsWriteInterval") Duration writeInterval) {
+      MetricWriter metricWriter,
+      @Config("metricsWriteInterval") Duration writeInterval,
+      JvmMetrics jvmMetrics) {
+    jvmMetrics.register();
+
     return new MetricReporter(
         metricWriter,
         writeInterval.getStandardSeconds(),

core/src/test/java/google/registry/monitoring/whitebox/JvmMetricsTest.java

@@ -0,0 +1,96 @@
+// Copyright 2017 The Nomulus Authors. All Rights Reserved.
+//
+// Licensed 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 google.registry.monitoring.whitebox;
+
+import static com.google.common.truth.Truth.assertThat;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
+
+import com.google.common.collect.ImmutableList;
+import com.google.common.collect.ImmutableMap;
+import com.google.monitoring.metrics.MetricRegistry;
+import com.google.monitoring.metrics.MetricRegistryImpl;
+import java.lang.management.MemoryMXBean;
+import java.lang.management.MemoryUsage;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+/** Unit tests for {@link JvmMetrics}. */
+class JvmMetricsTests {
+
+  private MetricRegistry registry;
+  private JvmMetrics jvmMetrics;
+  private MemoryMXBean mockMemoryMXBean = mock(MemoryMXBean.class);
+
+  private static final MemoryUsage HEAP_USAGE =
+      new MemoryUsage(/*init*/ 100, /*used*/ 200, /*commited*/ 500, /*max*/ 1000);
+  private static final MemoryUsage NON_HEAP_USAGE =
+      new MemoryUsage(/*init*/ 50, /*used*/ 100, /*commited*/ 250, /*max*/ 500);
+
+  @BeforeEach
+  public void setUp() {
+    MetricRegistryImpl.getDefault().unregisterAllMetrics();
+    registry = MetricRegistryImpl.getDefault();
+
+    when(mockMemoryMXBean.getHeapMemoryUsage()).thenReturn(HEAP_USAGE);
+    when(mockMemoryMXBean.getNonHeapMemoryUsage()).thenReturn(NON_HEAP_USAGE);
+
+    jvmMetrics = new JvmMetrics(mockMemoryMXBean);
+  }
+
+  @Test
+  public void metricsRegistered() {
+    jvmMetrics.register();
+
+    assertThat(registry.getRegisteredMetrics()).hasSize(3);
+
+    for (var metric : registry.getRegisteredMetrics()) {
+      assertThat(metric).isInstanceOf(com.google.monitoring.metrics.VirtualMetric.class);
+    }
+  }
+
+  @Test
+  public void testGetUsedMemory() {
+    jvmMetrics.register();
+    ImmutableMap<ImmutableList<String>, Long> values = jvmMetrics.getUsedMemory();
+
+    assertThat(values)
+        .containsExactly(
+            ImmutableList.of("heap"), 200L,
+            ImmutableList.of("non_heap"), 100L);
+  }
+
+  @Test
+  public void testGetCommittedMemory() {
+    jvmMetrics.register();
+    ImmutableMap<ImmutableList<String>, Long> values = jvmMetrics.getCommittedMemory();
+
+    assertThat(values)
+        .containsExactly(
+            ImmutableList.of("heap"), 500L,
+            ImmutableList.of("non_heap"), 250L);
+  }
+
+  @Test
+  public void testGetMaxMemory() {
+    jvmMetrics.register();
+    ImmutableMap<ImmutableList<String>, Long> values = jvmMetrics.getMaxMemory();
+
+    assertThat(values)
+        .containsExactly(
+            ImmutableList.of("heap"), 1000L,
+            ImmutableList.of("non_heap"), 500L);
+  }
+}