Remove ccs_telemetry feature flag (#113825)

This removes `ccs_telemetry` feature flag, and instead introduces an
undocumented, true by default setting: - `search.ccs.collect_telemetry`
- enables CCS search telemetry collection and
`_cluster/stats?include_remote=true`. Can be disabled if this is causing
any problems.

Author: smalyshev

docs/build.gradle

@@ -123,7 +123,6 @@ testClusters.matching { it.name == "yamlRestTest"}.configureEach {
 
   requiresFeature 'es.index_mode_feature_flag_registered', Version.fromString("8.0.0")
   requiresFeature 'es.failure_store_feature_flag_enabled', Version.fromString("8.12.0")
-  requiresFeature 'es.ccs_telemetry_feature_flag_enabled', Version.fromString("8.16.0")
 
   // TODO Rene: clean up this kind of cross project file references
   extraConfigFile 'op-jwks.json', project(':x-pack:test:idp-fixture').file("src/main/resources/oidc/op-jwks.json")

docs/changelog/113825.yaml

@@ -0,0 +1,12 @@
+pr: 113825
+summary: Cross-cluster search telemetry
+area: Search
+type: feature
+issues: []
+highlight:
+  title: Cross-cluster search telemetry
+  body: |-
+    The cross-cluster search telemetry is collected when cross-cluster searches
+    are performed, and is returned as "ccs" field in `_cluster/stats` output.
+    It also add a new parameter `include_remotes=true` to the `_cluster/stats` API
+    which will collect data from connected remote clusters.

server/src/internalClusterTest/java/org/elasticsearch/action/admin/cluster/stats/ClusterStatsRemoteIT.java

@@ -14,7 +14,6 @@
 import org.elasticsearch.client.internal.Client;
 import org.elasticsearch.cluster.health.ClusterHealthStatus;
 import org.elasticsearch.common.settings.Settings;
-import org.elasticsearch.common.util.FeatureFlag;
 import org.elasticsearch.core.TimeValue;
 import org.elasticsearch.index.query.MatchAllQueryBuilder;
 import org.elasticsearch.search.builder.SearchSourceBuilder;
@@ -23,7 +22,6 @@
 import org.elasticsearch.test.ESIntegTestCase.Scope;
 import org.elasticsearch.test.InternalTestCluster;
 import org.junit.Assert;
-import org.junit.BeforeClass;
 
 import java.util.Collection;
 import java.util.List;
@@ -46,7 +44,6 @@ public class ClusterStatsRemoteIT extends AbstractMultiClustersTestCase {
     private static final String REMOTE2 = "cluster-b";
 
     private static final String INDEX_NAME = "demo";
-    private static final FeatureFlag CCS_TELEMETRY_FEATURE_FLAG = new FeatureFlag("ccs_telemetry");
 
     @Override
     protected boolean reuseClusters() {
@@ -63,11 +60,6 @@ protected Map<String, Boolean> skipUnavailableForRemoteClusters() {
         return Map.of(REMOTE1, false, REMOTE2, true);
     }
 
-    @BeforeClass
-    protected static void skipIfTelemetryDisabled() {
-        assumeTrue("Skipping test as CCS_TELEMETRY_FEATURE_FLAG is disabled", CCS_TELEMETRY_FEATURE_FLAG.isEnabled());
-    }
-
     public void testRemoteClusterStats() throws ExecutionException, InterruptedException {
         setupClusters();
         final Client client = client(LOCAL_CLUSTER);

server/src/internalClusterTest/java/org/elasticsearch/search/ccs/CCSUsageTelemetryIT.java

@@ -25,7 +25,6 @@
 import org.elasticsearch.common.bytes.BytesReference;
 import org.elasticsearch.common.settings.Settings;
 import org.elasticsearch.common.util.CollectionUtils;
-import org.elasticsearch.common.util.FeatureFlag;
 import org.elasticsearch.core.TimeValue;
 import org.elasticsearch.index.query.MatchAllQueryBuilder;
 import org.elasticsearch.plugins.Plugin;
@@ -40,7 +39,6 @@
 import org.elasticsearch.test.InternalTestCluster;
 import org.elasticsearch.usage.UsageService;
 import org.junit.Assert;
-import org.junit.BeforeClass;
 import org.junit.Rule;
 import org.junit.rules.TestRule;
 import org.junit.runner.Description;
@@ -73,7 +71,6 @@ public class CCSUsageTelemetryIT extends AbstractMultiClustersTestCase {
     private static final Logger LOGGER = LogManager.getLogger(CCSUsageTelemetryIT.class);
     private static final String REMOTE1 = "cluster-a";
     private static final String REMOTE2 = "cluster-b";
-    private static final FeatureFlag CCS_TELEMETRY_FEATURE_FLAG = new FeatureFlag("ccs_telemetry");
 
     @Override
     protected boolean reuseClusters() {
@@ -88,11 +85,6 @@ protected Collection<String> remoteClusterAlias() {
     @Rule
     public SkipUnavailableRule skipOverride = new SkipUnavailableRule(REMOTE1, REMOTE2);
 
-    @BeforeClass
-    protected static void skipIfTelemetryDisabled() {
-        assumeTrue("Skipping test as CCS_TELEMETRY_FEATURE_FLAG is disabled", CCS_TELEMETRY_FEATURE_FLAG.isEnabled());
-    }
-
     @Override
     protected Map<String, Boolean> skipUnavailableForRemoteClusters() {
         var map = skipOverride.getMap();

server/src/main/java/org/elasticsearch/action/admin/cluster/stats/ClusterStatsResponse.java

@@ -28,8 +28,6 @@
 import java.util.Map;
 import java.util.Set;
 
-import static org.elasticsearch.action.search.TransportSearchAction.CCS_TELEMETRY_FEATURE_FLAG;
-
 public class ClusterStatsResponse extends BaseNodesResponse<ClusterStatsNodeResponse> implements ToXContentFragment {
 
     final ClusterStatsNodes nodesStats;
@@ -145,14 +143,12 @@ public XContentBuilder toXContent(XContentBuilder builder, Params params) throws
         builder.field("repositories");
         repositoryUsageStats.toXContent(builder, params);
 
-        if (CCS_TELEMETRY_FEATURE_FLAG.isEnabled()) {
-            builder.startObject("ccs");
-            if (remoteClustersStats != null) {
-                builder.field("clusters", remoteClustersStats);
-            }
-            ccsMetrics.toXContent(builder, params);
-            builder.endObject();
+        builder.startObject("ccs");
+        if (remoteClustersStats != null) {
+            builder.field("clusters", remoteClustersStats);
         }
+        ccsMetrics.toXContent(builder, params);
+        builder.endObject();
 
         return builder;
     }

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

@@ -49,6 +49,7 @@
 import org.elasticsearch.injection.guice.Inject;
 import org.elasticsearch.node.NodeService;
 import org.elasticsearch.repositories.RepositoriesService;
+import org.elasticsearch.search.SearchService;
 import org.elasticsearch.tasks.CancellableTask;
 import org.elasticsearch.tasks.Task;
 import org.elasticsearch.tasks.TaskId;
@@ -431,8 +432,8 @@ public Map<String, RemoteClusterStats> getRemoteStats() {
         }
     }
 
-    private static boolean doRemotes(ClusterStatsRequest request) {
-        return request.doRemotes();
+    private boolean doRemotes(ClusterStatsRequest request) {
+        return SearchService.CCS_COLLECT_TELEMETRY.get(settings) && request.doRemotes();
     }
 
     private class RemoteStatsFanout extends CancellableFanOut<String, RemoteClusterStatsResponse, Map<String, RemoteClusterStats>> {

server/src/main/java/org/elasticsearch/action/search/TransportSearchAction.java

@@ -52,9 +52,9 @@
 import org.elasticsearch.common.regex.Regex;
 import org.elasticsearch.common.settings.Setting;
 import org.elasticsearch.common.settings.Setting.Property;
+import org.elasticsearch.common.settings.Settings;
 import org.elasticsearch.common.util.ArrayUtils;
 import org.elasticsearch.common.util.CollectionUtils;
-import org.elasticsearch.common.util.FeatureFlag;
 import org.elasticsearch.common.util.Maps;
 import org.elasticsearch.common.util.concurrent.CountDown;
 import org.elasticsearch.common.util.concurrent.EsExecutors;
@@ -128,8 +128,6 @@ public class TransportSearchAction extends HandledTransportAction<SearchRequest,
     public static final String FROZEN_INDICES_DEPRECATION_MESSAGE = "Searching frozen indices [{}] is deprecated."
         + " Consider cold or frozen tiers in place of frozen indices. The frozen feature will be removed in a feature release.";
 
-    public static final FeatureFlag CCS_TELEMETRY_FEATURE_FLAG = new FeatureFlag("ccs_telemetry");
-
     /** The maximum number of shards for a single search request. */
     public static final Setting<Long> SHARD_COUNT_LIMIT_SETTING = Setting.longSetting(
         "action.search.shard_count.limit",
@@ -162,6 +160,7 @@ public class TransportSearchAction extends HandledTransportAction<SearchRequest,
     private final SearchResponseMetrics searchResponseMetrics;
     private final Client client;
     private final UsageService usageService;
+    private final Settings settings;
 
     @Inject
     public TransportSearchAction(
@@ -194,8 +193,9 @@ public TransportSearchAction(
         this.indexNameExpressionResolver = indexNameExpressionResolver;
         this.namedWriteableRegistry = namedWriteableRegistry;
         this.executorSelector = executorSelector;
-        this.defaultPreFilterShardSize = DEFAULT_PRE_FILTER_SHARD_SIZE.get(clusterService.getSettings());
-        this.ccsCheckCompatibility = SearchService.CCS_VERSION_CHECK_SETTING.get(clusterService.getSettings());
+        this.settings = clusterService.getSettings();
+        this.defaultPreFilterShardSize = DEFAULT_PRE_FILTER_SHARD_SIZE.get(settings);
+        this.ccsCheckCompatibility = SearchService.CCS_VERSION_CHECK_SETTING.get(settings);
         this.searchResponseMetrics = searchResponseMetrics;
         this.client = client;
         this.usageService = usageService;
@@ -372,7 +372,7 @@ void executeRequest(
                     searchPhaseProvider.apply(delegate)
                 );
             } else {
-                if ((listener instanceof TelemetryListener tl) && CCS_TELEMETRY_FEATURE_FLAG.isEnabled()) {
+                if (listener instanceof TelemetryListener tl) {
                     tl.setRemotes(resolvedIndices.getRemoteClusterIndices().size());
                     if (task.isAsync()) {
                         tl.setFeature(CCSUsageTelemetry.ASYNC_FEATURE);
@@ -398,7 +398,7 @@ void executeRequest(
                 }
                 final TaskId parentTaskId = task.taskInfo(clusterService.localNode().getId(), false).taskId();
                 if (shouldMinimizeRoundtrips(rewritten)) {
-                    if ((listener instanceof TelemetryListener tl) && CCS_TELEMETRY_FEATURE_FLAG.isEnabled()) {
+                    if (listener instanceof TelemetryListener tl) {
                         tl.setFeature(CCSUsageTelemetry.MRT_FEATURE);
                     }
                     final AggregationReduceContext.Builder aggregationReduceContextBuilder = rewritten.source() != null
@@ -1868,7 +1868,7 @@ private class SearchResponseActionListener implements ActionListener<SearchRespo
          * Should we collect telemetry for this search?
          */
         private boolean collectTelemetry() {
-            return CCS_TELEMETRY_FEATURE_FLAG.isEnabled() && usageBuilder.getRemotesCount() > 0;
+            return SearchService.CCS_COLLECT_TELEMETRY.get(settings) && usageBuilder.getRemotesCount() > 0;
         }
 
         public void setRemotes(int count) {

server/src/main/java/org/elasticsearch/common/settings/ClusterSettings.java

@@ -467,6 +467,7 @@ public void apply(Settings value, Settings current, Settings previous) {
         SearchService.MAX_KEEPALIVE_SETTING,
         SearchService.ALLOW_EXPENSIVE_QUERIES,
         SearchService.CCS_VERSION_CHECK_SETTING,
+        SearchService.CCS_COLLECT_TELEMETRY,
         MultiBucketConsumerService.MAX_BUCKET_SETTING,
         SearchService.LOW_LEVEL_CANCELLATION_SETTING,
         SearchService.MAX_OPEN_SCROLL_CONTEXT,

server/src/main/java/org/elasticsearch/rest/action/admin/cluster/RestClusterStatsAction.java

@@ -11,8 +11,6 @@
 
 import org.elasticsearch.action.admin.cluster.stats.ClusterStatsRequest;
 import org.elasticsearch.client.internal.node.NodeClient;
-import org.elasticsearch.common.util.FeatureFlag;
-import org.elasticsearch.common.util.set.Sets;
 import org.elasticsearch.rest.BaseRestHandler;
 import org.elasticsearch.rest.RestRequest;
 import org.elasticsearch.rest.Scope;
@@ -33,10 +31,9 @@ public class RestClusterStatsAction extends BaseRestHandler {
 
     private static final Set<String> SUPPORTED_CAPABILITIES = Set.of(
         "human-readable-total-docs-size",
-        "verbose-dense-vector-mapping-stats"
+        "verbose-dense-vector-mapping-stats",
+        "ccs-stats"
     );
-    private static final Set<String> SUPPORTED_CAPABILITIES_CCS_STATS = Set.copyOf(Sets.union(SUPPORTED_CAPABILITIES, Set.of("ccs-stats")));
-    public static final FeatureFlag CCS_TELEMETRY_FEATURE_FLAG = new FeatureFlag("ccs_telemetry");
     private static final Set<String> SUPPORTED_QUERY_PARAMETERS = Set.of("include_remotes", "nodeId", REST_TIMEOUT_PARAM);
 
     @Override
@@ -73,6 +70,6 @@ public boolean canTripCircuitBreaker() {
 
     @Override
     public Set<String> supportedCapabilities() {
-        return CCS_TELEMETRY_FEATURE_FLAG.isEnabled() ? SUPPORTED_CAPABILITIES_CCS_STATS : SUPPORTED_CAPABILITIES;
+        return SUPPORTED_CAPABILITIES;
     }
 }

server/src/main/java/org/elasticsearch/search/SearchService.java

@@ -260,6 +260,13 @@ public class SearchService extends AbstractLifecycleComponent implements IndexEv
         Property.NodeScope
     );
 
+    public static final Setting<Boolean> CCS_COLLECT_TELEMETRY = Setting.boolSetting(
+        "search.ccs.collect_telemetry",
+        true,
+        Property.Dynamic,
+        Property.NodeScope
+    );
+
     public static final int DEFAULT_SIZE = 10;
     public static final int DEFAULT_FROM = 0;