[8.16] Report JVM stats for all memory pools (97046) (#115117)

docs/changelog/115117.yaml

@@ -0,0 +1,6 @@
+pr: 115117
+summary: Report JVM stats for all memory pools (97046)
+area: Infra/Core
+type: bug
+issues:
+ - 97046

server/src/main/java/org/elasticsearch/monitor/jvm/GcNames.java

@@ -15,8 +15,14 @@ public class GcNames {
     public static final String OLD = "old";
     public static final String SURVIVOR = "survivor";
 
+    private GcNames() {}
+
     /**
-     * Resolves the GC type by its memory pool name ({@link java.lang.management.MemoryPoolMXBean#getName()}.
+     * Resolves the memory area name by the memory pool name provided by {@link java.lang.management.MemoryPoolMXBean#getName()}
+     *
+     * @param poolName the name of the memory pool from {@link java.lang.management.MemoryPoolMXBean}
+     * @param defaultName the name to return if the pool name does not match any known memory area
+     * @return memory area name corresponding to the pool name or {@code defaultName} if no match is found
      */
     public static String getByMemoryPoolName(String poolName, String defaultName) {
         if ("Eden Space".equals(poolName)
@@ -40,6 +46,13 @@ public static String getByMemoryPoolName(String poolName, String defaultName) {
         return defaultName;
     }
 
+    /**
+     * Resolves the GC type by the GC name provided by {@link java.lang.management.GarbageCollectorMXBean#getName()}
+     *
+     * @param gcName the name of the GC from {@link java.lang.management.GarbageCollectorMXBean}
+     * @param defaultName the name to return if the GC name does not match any known GC type
+     * @return GC type corresponding to the GC name or {@code defaultName} if no match is found
+     */
     public static String getByGcName(String gcName, String defaultName) {
         if ("Copy".equals(gcName) || "PS Scavenge".equals(gcName) || "ParNew".equals(gcName) || "G1 Young Generation".equals(gcName)) {
             return YOUNG;

server/src/main/java/org/elasticsearch/monitor/jvm/JvmStats.java

@@ -64,10 +64,7 @@ public static JvmStats jvmStats() {
         List<MemoryPool> pools = new ArrayList<>();
         for (MemoryPoolMXBean memoryPoolMXBean : memoryPoolMXBeans) {
             try {
-                String name = GcNames.getByMemoryPoolName(memoryPoolMXBean.getName(), null);
-                if (name == null) { // if we can't resolve it, its not interesting.... (Per Gen, Code Cache)
-                    continue;
-                }
+                String name = GcNames.getByMemoryPoolName(memoryPoolMXBean.getName(), memoryPoolMXBean.getName());
                 MemoryUsage usage = memoryPoolMXBean.getUsage();
                 MemoryUsage peakUsage = memoryPoolMXBean.getPeakUsage();
                 pools.add(

server/src/test/java/org/elasticsearch/monitor/jvm/JvmStatsTests.java

@@ -13,17 +13,22 @@
 import org.elasticsearch.common.unit.ByteSizeValue;
 import org.elasticsearch.test.ESTestCase;
 
-import java.io.IOException;
 import java.util.Arrays;
 import java.util.List;
+import java.util.Map;
+import java.util.function.Function;
+import java.util.stream.Collectors;
+import java.util.stream.StreamSupport;
 
 import static org.hamcrest.Matchers.anyOf;
 import static org.hamcrest.Matchers.equalTo;
 import static org.hamcrest.Matchers.greaterThan;
 import static org.hamcrest.Matchers.greaterThanOrEqualTo;
+import static org.hamcrest.Matchers.hasKey;
+import static org.hamcrest.Matchers.hasSize;
 
 public class JvmStatsTests extends ESTestCase {
-    public void testJvmStats() throws IOException {
+    public void testJvmStats() {
         JvmStats stats = JvmStats.jvmStats();
         assertNotNull(stats);
         assertNotNull(stats.getUptime());
@@ -40,6 +45,17 @@ public void testJvmStats() throws IOException {
         assertNotNull(mem.getHeapUsedPercent());
         assertThat(mem.getHeapUsedPercent(), anyOf(equalTo((short) -1), greaterThanOrEqualTo((short) 0)));
 
+        // Memory pools
+        Map<String, JvmStats.MemoryPool> memoryPools = StreamSupport.stream(stats.getMem().spliterator(), false)
+            .collect(Collectors.toMap(JvmStats.MemoryPool::getName, Function.identity()));
+        assertThat(memoryPools, hasKey(GcNames.YOUNG));
+        assertThat(memoryPools, hasKey(GcNames.OLD));
+        assertThat(memoryPools, hasKey("Metaspace"));
+        assertThat(memoryPools.keySet(), hasSize(greaterThan(3)));
+        for (JvmStats.MemoryPool memoryPool : memoryPools.values()) {
+            assertThat(memoryPool.getUsed().getBytes(), greaterThan(0L));
+        }
+
         // Threads
         JvmStats.Threads threads = stats.getThreads();
         assertNotNull(threads);