[Segment Replication] Add Segment Replication backpressure rejection stats to _nodes/stats

server/src/main/java/org/opensearch/action/admin/cluster/node/stats/NodeStats.java

@@ -46,6 +46,7 @@
 import org.opensearch.core.xcontent.XContentBuilder;
 import org.opensearch.discovery.DiscoveryStats;
 import org.opensearch.http.HttpStats;
+import org.opensearch.index.SegmentReplicationRejectionStats;
 import org.opensearch.index.stats.IndexingPressureStats;
 import org.opensearch.index.stats.ShardIndexingPressureStats;
 import org.opensearch.index.store.remote.filecache.FileCacheStats;
@@ -129,6 +130,9 @@
     @Nullable
     private SearchBackpressureStats searchBackpressureStats;
 
+    @Nullable
+    private SegmentReplicationRejectionStats segmentReplicationRejectionStats;
+
     @Nullable
     private ClusterManagerThrottlingStats clusterManagerThrottlingStats;
 
@@ -211,6 +215,12 @@
         } else {
             resourceUsageStats = null;
         }
+        // TODO: change to V_2_12_0 on main after backport to 2.x
+        if (in.getVersion().onOrAfter(Version.V_3_0_0)) {
+            segmentReplicationRejectionStats = in.readOptionalWriteable(SegmentReplicationRejectionStats::new);
+        } else {
+            segmentReplicationRejectionStats = null;
+        }
         if (in.getVersion().onOrAfter(Version.V_2_12_0)) {
             repositoriesStats = in.readOptionalWriteable(RepositoriesStats::new);
         } else {
@@ -244,6 +254,7 @@
         @Nullable FileCacheStats fileCacheStats,
         @Nullable TaskCancellationStats taskCancellationStats,
         @Nullable SearchPipelineStats searchPipelineStats,
+        @Nullable SegmentReplicationRejectionStats segmentReplicationRejectionStats,
         @Nullable RepositoriesStats repositoriesStats
     ) {
         super(node);
@@ -271,6 +282,7 @@
         this.fileCacheStats = fileCacheStats;
         this.taskCancellationStats = taskCancellationStats;
         this.searchPipelineStats = searchPipelineStats;
+        this.segmentReplicationRejectionStats = segmentReplicationRejectionStats;
         this.repositoriesStats = repositoriesStats;
     }
 
@@ -415,6 +427,10 @@
     }
 
     @Nullable
+    public SegmentReplicationRejectionStats getSegmentReplicationRejectionStats() {
+        return segmentReplicationRejectionStats;
+    }
+
     public RepositoriesStats getRepositoriesStats() {
         return repositoriesStats;
     }
@@ -465,6 +481,10 @@
         if (out.getVersion().onOrAfter(Version.V_2_12_0)) {
             out.writeOptionalWriteable(resourceUsageStats);
         }
+        // TODO: change to V_2_12_0 on main after backport to 2.x
+        if (out.getVersion().onOrAfter(Version.V_3_0_0)) {
+            out.writeOptionalWriteable(segmentReplicationRejectionStats);
+        }
         if (out.getVersion().onOrAfter(Version.V_2_12_0)) {
             out.writeOptionalWriteable(repositoriesStats);
         }
@@ -561,6 +581,10 @@
         if (getResourceUsageStats() != null) {
             getResourceUsageStats().toXContent(builder, params);
         }
+        if (getSegmentReplicationRejectionStats() != null) {
+            getSegmentReplicationRejectionStats().toXContent(builder, params);
+        }
+
         if (getRepositoriesStats() != null) {
             getRepositoriesStats().toXContent(builder, params);
         }

server/src/main/java/org/opensearch/action/admin/cluster/node/stats/NodesStatsRequest.java

@@ -215,6 +215,7 @@ public enum Metric {
         TASK_CANCELLATION("task_cancellation"),
         SEARCH_PIPELINE("search_pipeline"),
         RESOURCE_USAGE_STATS("resource_usage_stats"),
+        SEGMENT_REPLICATION_BACKPRESSURE("segment_replication_backpressure"),
         REPOSITORIES("repositories");
 
         private String metricName;

server/src/main/java/org/opensearch/action/admin/cluster/node/stats/TransportNodesStatsAction.java

@@ -126,6 +126,7 @@ protected NodeStats nodeOperation(NodeStatsRequest nodeStatsRequest) {
             NodesStatsRequest.Metric.TASK_CANCELLATION.containedIn(metrics),
             NodesStatsRequest.Metric.SEARCH_PIPELINE.containedIn(metrics),
             NodesStatsRequest.Metric.RESOURCE_USAGE_STATS.containedIn(metrics),
+            NodesStatsRequest.Metric.SEGMENT_REPLICATION_BACKPRESSURE.containedIn(metrics),
             NodesStatsRequest.Metric.REPOSITORIES.containedIn(metrics)
         );
     }

server/src/main/java/org/opensearch/action/admin/cluster/stats/TransportClusterStatsAction.java

@@ -170,6 +170,7 @@ protected ClusterStatsNodeResponse nodeOperation(ClusterStatsNodeRequest nodeReq
             false,
             false,
             false,
+            false,
             false
         );
         List<ShardStats> shardsStats = new ArrayList<>();

server/src/main/java/org/opensearch/index/SegmentReplicationPressureService.java

@@ -106,10 +106,11 @@ public SegmentReplicationPressureService(
         ClusterService clusterService,
         IndicesService indicesService,
         ShardStateAction shardStateAction,
+        SegmentReplicationStatsTracker tracker,
         ThreadPool threadPool
     ) {
         this.indicesService = indicesService;
-        this.tracker = new SegmentReplicationStatsTracker(this.indicesService);
+        this.tracker = tracker;
         this.shardStateAction = shardStateAction;
         this.threadPool = threadPool;
 

server/src/main/java/org/opensearch/index/SegmentReplicationRejectionStats.java

@@ -0,0 +1,67 @@
+/*
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * The OpenSearch Contributors require contributions made to
+ * this file be licensed under the Apache-2.0 license or a
+ * compatible open source license.
+ */
+
+package org.opensearch.index;
+
+import org.opensearch.Version;
+import org.opensearch.core.common.io.stream.StreamInput;
+import org.opensearch.core.common.io.stream.StreamOutput;
+import org.opensearch.core.common.io.stream.Writeable;
+import org.opensearch.core.xcontent.ToXContentFragment;
+import org.opensearch.core.xcontent.XContentBuilder;
+
+import java.io.IOException;
+
+/**
+ * Segment Replication Rejection Stats.
+ *
+ * @opensearch.internal
+ */
+public class SegmentReplicationRejectionStats implements Writeable, ToXContentFragment {
+
+    /**
+     * Total rejections due to segment replication backpressure
+     */
+    private long totalRejectionCount;
+
+    public SegmentReplicationRejectionStats(final long totalRejectionCount) {
+        this.totalRejectionCount = totalRejectionCount;
+    }
+
+    public SegmentReplicationRejectionStats(StreamInput in) throws IOException {
+        // TODO: change to V_2_12_0 on main after backport to 2.x
+        if (in.getVersion().onOrAfter(Version.V_3_0_0)) {
+            this.totalRejectionCount = in.readVLong();
+        }
+    }
+
+    public long getTotalRejectionCount() {
+        return totalRejectionCount;
+    }
+
+    @Override
+    public XContentBuilder toXContent(XContentBuilder builder, Params params) throws IOException {
+        builder.startObject("segment_replication_backpressure");
+        builder.field("total_rejected_requests", totalRejectionCount);
+        return builder.endObject();
+    }
+
+    @Override
+    public void writeTo(StreamOutput out) throws IOException {
+        // TODO: change to V_2_12_0 on main after backport to 2.x
+        if (out.getVersion().onOrAfter(Version.V_3_0_0)) {
+            out.writeVLong(totalRejectionCount);
+        }
+    }
+
+    @Override
+    public String toString() {
+        return "SegmentReplicationRejectionStats{ totalRejectedRequestCount=" + totalRejectionCount + '}';
+    }
+
+}

server/src/main/java/org/opensearch/index/SegmentReplicationStatsTracker.java

@@ -33,6 +33,14 @@ public SegmentReplicationStatsTracker(IndicesService indicesService) {
         rejectionCount = ConcurrentCollections.newConcurrentMap();
     }
 
+    public SegmentReplicationRejectionStats getTotalRejectionStats() {
+        return new SegmentReplicationRejectionStats(this.rejectionCount.values().stream().mapToInt(AtomicInteger::get).sum());
+    }
+
+    protected Map<ShardId, AtomicInteger> getRejectionCount() {
+        return rejectionCount;
+    }
+
     public SegmentReplicationStats getStats() {
         Map<ShardId, SegmentReplicationPerGroupStats> stats = new HashMap<>();
         for (IndexService indexService : indicesService) {

server/src/main/java/org/opensearch/node/Node.java

@@ -136,6 +136,7 @@
 import org.opensearch.index.IndexModule;
 import org.opensearch.index.IndexSettings;
 import org.opensearch.index.IndexingPressureService;
+import org.opensearch.index.SegmentReplicationStatsTracker;
 import org.opensearch.index.analysis.AnalysisRegistry;
 import org.opensearch.index.engine.EngineFactory;
 import org.opensearch.index.recovery.RemoteStoreRestoreService;
@@ -977,6 +978,7 @@ protected Node(
                 transportService.getTaskManager()
             );
 
+            final SegmentReplicationStatsTracker segmentReplicationStatsTracker = new SegmentReplicationStatsTracker(indicesService);
             RepositoriesModule repositoriesModule = new RepositoriesModule(
                 this.environment,
                 pluginsService.filterPlugins(RepositoryPlugin.class),
@@ -1116,6 +1118,7 @@ protected Node(
                 fileCache,
                 taskCancellationMonitoringService,
                 resourceUsageCollectorService,
+                segmentReplicationStatsTracker,
                 repositoryService
             );
 
@@ -1246,6 +1249,7 @@ protected Node(
                 b.bind(MetricsRegistry.class).toInstance(metricsRegistry);
                 b.bind(RemoteClusterStateService.class).toProvider(() -> remoteClusterStateService);
                 b.bind(PersistedStateRegistry.class).toInstance(persistedStateRegistry);
+                b.bind(SegmentReplicationStatsTracker.class).toInstance(segmentReplicationStatsTracker);
             });
             injector = modules.createInjector();
 

server/src/main/java/org/opensearch/node/NodeService.java

@@ -48,6 +48,7 @@
 import org.opensearch.discovery.Discovery;
 import org.opensearch.http.HttpServerTransport;
 import org.opensearch.index.IndexingPressureService;
+import org.opensearch.index.SegmentReplicationStatsTracker;
 import org.opensearch.index.store.remote.filecache.FileCache;
 import org.opensearch.indices.IndicesService;
 import org.opensearch.ingest.IngestService;
@@ -96,6 +97,8 @@ public class NodeService implements Closeable {
     private final TaskCancellationMonitoringService taskCancellationMonitoringService;
     private final RepositoriesService repositoriesService;
 
+    private final SegmentReplicationStatsTracker segmentReplicationStatsTracker;
+
     NodeService(
         Settings settings,
         ThreadPool threadPool,
@@ -119,6 +122,7 @@ public class NodeService implements Closeable {
         FileCache fileCache,
         TaskCancellationMonitoringService taskCancellationMonitoringService,
         ResourceUsageCollectorService resourceUsageCollectorService,
+        SegmentReplicationStatsTracker segmentReplicationStatsTracker,
         RepositoriesService repositoriesService
     ) {
         this.settings = settings;
@@ -146,6 +150,7 @@ public class NodeService implements Closeable {
         this.repositoriesService = repositoriesService;
         clusterService.addStateApplier(ingestService);
         clusterService.addStateApplier(searchPipelineService);
+        this.segmentReplicationStatsTracker = segmentReplicationStatsTracker;
     }
 
     public NodeInfo info(
@@ -226,6 +231,7 @@ public NodeStats stats(
         boolean taskCancellation,
         boolean searchPipelineStats,
         boolean resourceUsageStats,
+        boolean segmentReplicationTrackerStats,
         boolean repositoriesStats
     ) {
         // for indices stats we want to include previous allocated shards stats as well (it will
@@ -256,6 +262,7 @@ public NodeStats stats(
             fileCacheStats && fileCache != null ? fileCache.fileCacheStats() : null,
             taskCancellation ? this.taskCancellationMonitoringService.stats() : null,
             searchPipelineStats ? this.searchPipelineService.stats() : null,
+            segmentReplicationTrackerStats ? this.segmentReplicationStatsTracker.getTotalRejectionStats() : null,
             repositoriesStats ? this.repositoriesService.getRepositoriesStats() : null
         );
     }

server/src/test/java/org/opensearch/action/admin/cluster/node/stats/NodeStatsTests.java

@@ -49,6 +49,7 @@
 import org.opensearch.discovery.DiscoveryStats;
 import org.opensearch.http.HttpStats;
 import org.opensearch.index.ReplicationStats;
+import org.opensearch.index.SegmentReplicationRejectionStats;
 import org.opensearch.index.remote.RemoteSegmentStats;
 import org.opensearch.index.remote.RemoteTranslogTransferTracker;
 import org.opensearch.index.translog.RemoteTranslogStats;
@@ -417,6 +418,17 @@ public void testSerialization() throws IOException {
                         assertEquals(aResourceUsageStats.getTimestamp(), bResourceUsageStats.getTimestamp());
                     });
                 }
+                SegmentReplicationRejectionStats segmentReplicationRejectionStats = nodeStats.getSegmentReplicationRejectionStats();
+                SegmentReplicationRejectionStats deserializedSegmentReplicationRejectionStats = deserializedNodeStats
+                    .getSegmentReplicationRejectionStats();
+                if (segmentReplicationRejectionStats == null) {
+                    assertNull(deserializedSegmentReplicationRejectionStats);
+                } else {
+                    assertEquals(
+                        segmentReplicationRejectionStats.getTotalRejectionCount(),
+                        deserializedSegmentReplicationRejectionStats.getTotalRejectionCount()
+                    );
+                }
                 ScriptCacheStats scriptCacheStats = nodeStats.getScriptCacheStats();
                 ScriptCacheStats deserializedScriptCacheStats = deserializedNodeStats.getScriptCacheStats();
                 if (scriptCacheStats == null) {
@@ -812,6 +824,11 @@ public static NodeStats createNodeStats(boolean remoteStoreStats) {
             }
             nodesResourceUsageStats = new NodesResourceUsageStats(resourceUsageStatsMap);
         }
+        SegmentReplicationRejectionStats segmentReplicationRejectionStats = null;
+        if (frequently()) {
+            segmentReplicationRejectionStats = new SegmentReplicationRejectionStats(randomNonNegativeLong());
+        }
+
         ClusterManagerThrottlingStats clusterManagerThrottlingStats = null;
         if (frequently()) {
             clusterManagerThrottlingStats = new ClusterManagerThrottlingStats();
@@ -853,6 +870,7 @@ public static NodeStats createNodeStats(boolean remoteStoreStats) {
             null,
             null,
             null,
+            segmentReplicationRejectionStats,
             null
         );
     }

server/src/test/java/org/opensearch/cluster/DiskUsageTests.java

@@ -192,6 +192,7 @@ public void testFillDiskUsage() {
                 null,
                 null,
                 null,
+                null,
                 null
             ),
             new NodeStats(
@@ -220,6 +221,7 @@ public void testFillDiskUsage() {
                 null,
                 null,
                 null,
+                null,
                 null
             ),
             new NodeStats(
@@ -248,6 +250,7 @@ public void testFillDiskUsage() {
                 null,
                 null,
                 null,
+                null,
                 null
             )
         );
@@ -307,6 +310,7 @@ public void testFillDiskUsageSomeInvalidValues() {
                 null,
                 null,
                 null,
+                null,
                 null
             ),
             new NodeStats(
@@ -335,6 +339,7 @@ public void testFillDiskUsageSomeInvalidValues() {
                 null,
                 null,
                 null,
+                null,
                 null
             ),
             new NodeStats(
@@ -363,6 +368,7 @@ public void testFillDiskUsageSomeInvalidValues() {
                 null,
                 null,
                 null,
+                null,
                 null
             )
         );

server/src/test/java/org/opensearch/index/SegmentReplicationPressureServiceTests.java

@@ -278,6 +278,13 @@ private SegmentReplicationPressureService buildPressureService(Settings settings
         ClusterService clusterService = mock(ClusterService.class);
         when(clusterService.getClusterSettings()).thenReturn(new ClusterSettings(settings, ClusterSettings.BUILT_IN_CLUSTER_SETTINGS));
 
-        return new SegmentReplicationPressureService(settings, clusterService, indicesService, shardStateAction, mock(ThreadPool.class));
+        return new SegmentReplicationPressureService(
+            settings,
+            clusterService,
+            indicesService,
+            shardStateAction,
+            new SegmentReplicationStatsTracker(indicesService),
+            mock(ThreadPool.class)
+        );
     }
 }