Add heap usage estimate to ClusterInfo

server/src/internalClusterTest/java/org/elasticsearch/index/shard/IndexShardIT.java

@@ -18,6 +18,8 @@
 import org.elasticsearch.cluster.ClusterInfoService;
 import org.elasticsearch.cluster.ClusterInfoServiceUtils;
 import org.elasticsearch.cluster.ClusterState;
+import org.elasticsearch.cluster.HeapUsage;
+import org.elasticsearch.cluster.HeapUsageSupplier;
 import org.elasticsearch.cluster.InternalClusterInfoService;
 import org.elasticsearch.cluster.metadata.IndexMetadata;
 import org.elasticsearch.cluster.node.DiscoveryNode;
@@ -61,6 +63,7 @@
 import org.elasticsearch.indices.IndicesService;
 import org.elasticsearch.indices.breaker.CircuitBreakerService;
 import org.elasticsearch.indices.recovery.RecoveryState;
+import org.elasticsearch.plugins.ClusterPlugin;
 import org.elasticsearch.plugins.Plugin;
 import org.elasticsearch.search.builder.SearchSourceBuilder;
 import org.elasticsearch.test.DummyShardLock;
@@ -81,6 +84,7 @@
 import java.util.Collections;
 import java.util.List;
 import java.util.Locale;
+import java.util.Map;
 import java.util.Optional;
 import java.util.concurrent.BrokenBarrierException;
 import java.util.concurrent.CountDownLatch;
@@ -89,6 +93,7 @@
 import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.concurrent.atomic.AtomicReference;
 import java.util.function.Predicate;
+import java.util.stream.Collectors;
 import java.util.stream.Stream;
 
 import static com.carrotsearch.randomizedtesting.RandomizedTest.randomAsciiLettersOfLength;
@@ -110,12 +115,13 @@
 import static org.hamcrest.Matchers.equalTo;
 import static org.hamcrest.Matchers.greaterThan;
 import static org.hamcrest.Matchers.instanceOf;
+import static org.hamcrest.Matchers.lessThanOrEqualTo;
 
 public class IndexShardIT extends ESSingleNodeTestCase {
 
     @Override
     protected Collection<Class<? extends Plugin>> getPlugins() {
-        return pluginList(InternalSettingsPlugin.class);
+        return pluginList(InternalSettingsPlugin.class, BogusHeapUsagePlugin.class);
     }
 
     public void testLockTryingToDelete() throws Exception {
@@ -253,6 +259,20 @@ public void testExpectedShardSizeIsPresent() throws InterruptedException {
         assertThat(dataSetSize.get(), greaterThan(0L));
     }
 
+    public void testHeapUsageEstimateIsPresent() {
+        InternalClusterInfoService clusterInfoService = (InternalClusterInfoService) getInstanceFromNode(ClusterInfoService.class);
+        ClusterInfoServiceUtils.refresh(clusterInfoService);
+        ClusterState state = getInstanceFromNode(ClusterService.class).state();
+        Map<String, HeapUsage> heapUsages = clusterInfoService.getClusterInfo().getNodesHeapUsage();
+        assertNotNull(heapUsages);
+        assertEquals(state.nodes().size(), heapUsages.size());
+        for (DiscoveryNode node : state.nodes()) {
+            assertTrue(heapUsages.containsKey(node.getId()));
+            HeapUsage heapUsage = heapUsages.get(node.getId());
+            assertThat(heapUsage.freeBytes(), lessThanOrEqualTo(heapUsage.totalBytes()));
+        }
+    }
+
     public void testIndexCanChangeCustomDataPath() throws Exception {
         final String index = "test-custom-data-path";
         final Path sharedDataPath = getInstanceFromNode(Environment.class).sharedDataDir().resolve(randomAsciiLettersOfLength(10));
@@ -795,4 +815,43 @@ private static void assertAllIndicesRemovedAndDeletionCompleted(Iterable<Indices
             assertBusy(() -> assertFalse(indicesService.hasUncompletedPendingDeletes()), 1, TimeUnit.MINUTES);
         }
     }
+
+    private static class BogusHeapUsageSupplier implements HeapUsageSupplier {
+
+        private final ClusterService clusterService;
+
+        private BogusHeapUsageSupplier(ClusterService clusterService) {
+            this.clusterService = clusterService;
+        }
+
+        @Override
+        public void getClusterHeapUsage(ActionListener<Map<String, HeapUsage>> listener) {
+            ActionListener.completeWith(
+                listener,
+                () -> clusterService.state().nodes().stream().collect(Collectors.toUnmodifiableMap(DiscoveryNode::getId, node -> {
+                    final long maxHeap = randomNonNegativeLong();
+                    final long freeHeap = (long) (randomFloat() * maxHeap);
+                    return new HeapUsage(node.getId(), node.getName(), maxHeap, freeHeap);
+                }))
+            );
+        }
+    }
+
+    public static class BogusHeapUsagePlugin extends Plugin implements ClusterPlugin {
+
+        private BogusHeapUsageSupplier bogusHeapUsageSupplier;
+
+        public BogusHeapUsagePlugin() {}
+
+        @Override
+        public Collection<?> createComponents(PluginServices services) {
+            bogusHeapUsageSupplier = new BogusHeapUsageSupplier(services.clusterService());
+            return Collections.singletonList(bogusHeapUsageSupplier);
+        }
+
+        @Override
+        public HeapUsageSupplier getHeapUsageSupplier() {
+            return bogusHeapUsageSupplier;
+        }
+    }
 }

server/src/main/java/org/elasticsearch/TransportVersions.java

@@ -274,6 +274,7 @@ static TransportVersion def(int id) {
     public static final TransportVersion ESQL_LIMIT_ROW_SIZE = def(9_085_0_00);
     public static final TransportVersion ESQL_REGEX_MATCH_WITH_CASE_INSENSITIVITY = def(9_086_0_00);
     public static final TransportVersion IDP_CUSTOM_SAML_ATTRIBUTES = def(9_087_0_00);
+    public static final TransportVersion HEAP_USAGE_IN_CLUSTER_INFO = def(9_088_0_00);
 
     /*
      * STOP! READ THIS FIRST! No, really,

server/src/main/java/org/elasticsearch/cluster/ClusterInfo.java

@@ -36,7 +36,7 @@
 import static org.elasticsearch.cluster.routing.ShardRouting.newUnassigned;
 import static org.elasticsearch.cluster.routing.UnassignedInfo.Reason.REINITIALIZED;
 import static org.elasticsearch.common.xcontent.ChunkedToXContentHelper.chunk;
-import static org.elasticsearch.common.xcontent.ChunkedToXContentHelper.endArray;
+import static org.elasticsearch.common.xcontent.ChunkedToXContentHelper.endObject;
 import static org.elasticsearch.common.xcontent.ChunkedToXContentHelper.startObject;
 
 /**
@@ -57,9 +57,10 @@ public class ClusterInfo implements ChunkedToXContent, Writeable {
     final Map<ShardId, Long> shardDataSetSizes;
     final Map<NodeAndShard, String> dataPath;
     final Map<NodeAndPath, ReservedSpace> reservedSpace;
+    final Map<String, HeapUsage> nodesHeapUsage;
 
     protected ClusterInfo() {
-        this(Map.of(), Map.of(), Map.of(), Map.of(), Map.of(), Map.of());
+        this(Map.of(), Map.of(), Map.of(), Map.of(), Map.of(), Map.of(), Map.of());
     }
 
     /**
@@ -71,6 +72,7 @@ protected ClusterInfo() {
      * @param shardDataSetSizes a shard id to data set size in bytes mapping per shard
      * @param dataPath the shard routing to datapath mapping
      * @param reservedSpace reserved space per shard broken down by node and data path
+     * @param nodesHeapUsage heap usage broken down by node
      * @see #shardIdentifierFromRouting
      */
     public ClusterInfo(
@@ -79,14 +81,16 @@ public ClusterInfo(
         Map<String, Long> shardSizes,
         Map<ShardId, Long> shardDataSetSizes,
         Map<NodeAndShard, String> dataPath,
-        Map<NodeAndPath, ReservedSpace> reservedSpace
+        Map<NodeAndPath, ReservedSpace> reservedSpace,
+        Map<String, HeapUsage> nodesHeapUsage
     ) {
         this.leastAvailableSpaceUsage = Map.copyOf(leastAvailableSpaceUsage);
         this.mostAvailableSpaceUsage = Map.copyOf(mostAvailableSpaceUsage);
         this.shardSizes = Map.copyOf(shardSizes);
         this.shardDataSetSizes = Map.copyOf(shardDataSetSizes);
         this.dataPath = Map.copyOf(dataPath);
         this.reservedSpace = Map.copyOf(reservedSpace);
+        this.nodesHeapUsage = Map.copyOf(nodesHeapUsage);
     }
 
     public ClusterInfo(StreamInput in) throws IOException {
@@ -98,6 +102,11 @@ public ClusterInfo(StreamInput in) throws IOException {
             ? in.readImmutableMap(NodeAndShard::new, StreamInput::readString)
             : in.readImmutableMap(nested -> NodeAndShard.from(new ShardRouting(nested)), StreamInput::readString);
         this.reservedSpace = in.readImmutableMap(NodeAndPath::new, ReservedSpace::new);
+        if (in.getTransportVersion().onOrAfter(TransportVersions.HEAP_USAGE_IN_CLUSTER_INFO)) {
+            this.nodesHeapUsage = in.readImmutableMap(HeapUsage::new);
+        } else {
+            this.nodesHeapUsage = Map.of();
+        }
     }
 
     @Override
@@ -112,6 +121,9 @@ public void writeTo(StreamOutput out) throws IOException {
             out.writeMap(this.dataPath, (o, k) -> createFakeShardRoutingFromNodeAndShard(k).writeTo(o), StreamOutput::writeString);
         }
         out.writeMap(this.reservedSpace);
+        if (out.getTransportVersion().onOrAfter(TransportVersions.HEAP_USAGE_IN_CLUSTER_INFO)) {
+            out.writeMap(this.nodesHeapUsage, StreamOutput::writeWriteable);
+        }
     }
 
     /**
@@ -191,10 +203,29 @@ public Iterator<? extends ToXContent> toXContentChunked(ToXContent.Params params
                 }
                 return builder.endObject(); // NodeAndPath
             }),
-            endArray() // end "reserved_sizes"
+            chunk(
+                (builder, p) -> builder.endArray() // end "reserved_sizes"
+                    .startObject("heap_usage")
+            ),
+            Iterators.map(nodesHeapUsage.entrySet().iterator(), c -> (builder, p) -> {
+                builder.startObject(c.getKey());
+                c.getValue().toShortXContent(builder);
+                builder.endObject();
+                return builder;
+            }),
+            endObject() // end "heap_usage"
         );
     }
 
+    /**
+     * Returns a node id to estimated heap usage mapping for all nodes that we have such data for.
+     * Note that these estimates should be considered minimums. They may be used to determine whether
+     * there IS NOT capacity to do something, but not to determine that there IS capacity to do something.
+     */
+    public Map<String, HeapUsage> getNodesHeapUsage() {
+        return nodesHeapUsage;
+    }
+
     /**
      * Returns a node id to disk usage mapping for the path that has the least available space on the node.
      * Note that this does not take account of reserved space: there may be another path with less available _and unreserved_ space.
@@ -301,7 +332,8 @@ public String toString() {
 
     // exposed for tests, computed here rather than exposing all the collections separately
     int getChunkCount() {
-        return leastAvailableSpaceUsage.size() + shardSizes.size() + shardDataSetSizes.size() + dataPath.size() + reservedSpace.size() + 6;
+        return leastAvailableSpaceUsage.size() + shardSizes.size() + shardDataSetSizes.size() + dataPath.size() + reservedSpace.size()
+            + nodesHeapUsage.size() + 7;
     }
 
     public record NodeAndShard(String nodeId, ShardId shardId) implements Writeable {

server/src/main/java/org/elasticsearch/cluster/ClusterInfoSimulator.java

@@ -153,6 +153,7 @@ public ClusterInfo getClusterInfo() {
             shardSizes.toImmutableMap(),
             shardDataSetSizes,
             dataPath,
+            Map.of(),
             Map.of()
         );
     }

server/src/main/java/org/elasticsearch/cluster/HeapUsage.java

@@ -0,0 +1,70 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the "Elastic License
+ * 2.0", the "GNU Affero General Public License v3.0 only", and the "Server Side
+ * Public License v 1"; you may not use this file except in compliance with, at
+ * your election, the "Elastic License 2.0", the "GNU Affero General Public
+ * License v3.0 only", or the "Server Side Public License, v 1".
+ */
+
+package org.elasticsearch.cluster;
+
+import org.elasticsearch.common.io.stream.StreamInput;
+import org.elasticsearch.common.io.stream.StreamOutput;
+import org.elasticsearch.common.io.stream.Writeable;
+import org.elasticsearch.common.unit.ByteSizeValue;
+import org.elasticsearch.xcontent.ToXContentFragment;
+import org.elasticsearch.xcontent.XContentBuilder;
+
+import java.io.IOException;
+
+/**
+ * Record representing the heap usage for a single cluster node
+ */
+public record HeapUsage(String nodeId, String nodeName, long totalBytes, long freeBytes) implements ToXContentFragment, Writeable {
+
+    public HeapUsage(StreamInput in) throws IOException {
+        this(in.readString(), in.readString(), in.readVLong(), in.readVLong());
+    }
+
+    @Override
+    public void writeTo(StreamOutput out) throws IOException {
+        out.writeString(this.nodeId);
+        out.writeString(this.nodeName);
+        out.writeVLong(this.totalBytes);
+        out.writeVLong(this.freeBytes);
+    }
+
+    public XContentBuilder toShortXContent(XContentBuilder builder) throws IOException {
+        builder.field("node_name", this.nodeName);
+        builder.humanReadableField("total_heap_bytes", "total", ByteSizeValue.ofBytes(this.totalBytes));
+        builder.humanReadableField("used_heap_bytes", "used", ByteSizeValue.ofBytes(this.usedBytes()));
+        builder.humanReadableField("free_heap_bytes", "free", ByteSizeValue.ofBytes(this.freeBytes));
+        builder.field("free_heap_percent", truncatePercent(this.freeHeapAsPercentage()));
+        builder.field("used_heap_percent", truncatePercent(this.usedHeapAsPercentage()));
+        return builder;
+    }
+
+    @Override
+    public XContentBuilder toXContent(XContentBuilder builder, Params params) throws IOException {
+        builder.field("node_id", this.nodeId);
+        toShortXContent(builder);
+        return builder;
+    }
+
+    public double freeHeapAsPercentage() {
+        return 100.0 * freeBytes / (double) totalBytes;
+    }
+
+    public double usedHeapAsPercentage() {
+        return 100.0 - freeHeapAsPercentage();
+    }
+
+    public long usedBytes() {
+        return totalBytes - freeBytes;
+    }
+
+    private static double truncatePercent(double pct) {
+        return Math.round(pct * 10.0) / 10.0;
+    }
+}

server/src/main/java/org/elasticsearch/cluster/HeapUsageSupplier.java

@@ -0,0 +1,29 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the "Elastic License
+ * 2.0", the "GNU Affero General Public License v3.0 only", and the "Server Side
+ * Public License v 1"; you may not use this file except in compliance with, at
+ * your election, the "Elastic License 2.0", the "GNU Affero General Public
+ * License v3.0 only", or the "Server Side Public License, v 1".
+ */
+
+package org.elasticsearch.cluster;
+
+import org.elasticsearch.action.ActionListener;
+
+import java.util.Map;
+
+public interface HeapUsageSupplier {
+
+    /**
+     * This will be used when there are no heap usage suppliers available
+     */
+    HeapUsageSupplier EMPTY = listener -> listener.onResponse(Map.of());
+
+    /**
+     * Get the heap usage for every node in the cluster
+     *
+     * @param listener The listener which will receive the results
+     */
+    void getClusterHeapUsage(ActionListener<Map<String, HeapUsage>> listener);
+}