Merge branch 'main' into exp-histo-codegen-support

Author: JonasKunz

docs/reference/query-languages/esql/_snippets/commands/layout/fork.md

@@ -17,6 +17,8 @@ FORK ( <processing_commands> ) ( <processing_commands> ) ... ( <processing_comma
 The `FORK` processing command creates multiple execution branches to operate
 on the same input data and combines the results in a single output table. A discriminator column (`_fork`) is added to identify which branch each row came from.
 
+Together with the [`FUSE`](/reference/query-languages/esql/commands/fuse.md) command, `FORK` enables hybrid search to combine and score results from multiple queries. To learn more about using {{esql}} for search, refer to [ES|QL for search](docs-content://solutions/search/esql-for-search.md).
+
 **Branch identification:**
 - The `_fork` column identifies each branch with values like `fork1`, `fork2`, `fork3`
 - Values correspond to the order branches are defined

x-pack/plugin/downsample/src/internalClusterTest/java/org/elasticsearch/xpack/downsample/DownsampleTransportFailureIT.java

@@ -30,6 +30,7 @@
 import org.elasticsearch.search.aggregations.bucket.histogram.DateHistogramInterval;
 import org.elasticsearch.test.ESIntegTestCase;
 import org.elasticsearch.test.InternalTestCluster;
+import org.elasticsearch.test.junit.annotations.TestIssueLogging;
 import org.elasticsearch.test.transport.MockTransportService;
 import org.elasticsearch.xcontent.XContentBuilder;
 import org.elasticsearch.xcontent.XContentFactory;
@@ -264,6 +265,10 @@ private void assertIndexDoesNotExist(final String nodeName, final String indexNa
         assertEquals("no such index [" + indexName + "]", targetIndexNotFoundException.getMessage());
     }
 
+    @TestIssueLogging(
+        value = "org.elasticsearch.xpack.downsample.TransportDownsampleAction:DEBUG",
+        issueUrl = "https://github.com/elastic/elasticsearch/issues/137148"
+    )
     public void testNoDisruption() {
         // GIVEN
 
@@ -278,6 +283,7 @@ public void testNoDisruption() {
         // WHEN nothing happens
 
         // THEN
+        logger.info("Executing downsample action from [{}] to [{}]", SOURCE_INDEX_NAME, TARGET_INDEX_NAME);
         final AcknowledgedResponse downsampleResponse = testCluster.masterClient()
             .execute(DownsampleAction.INSTANCE, downsampleRequest)
             .actionGet(TimeValue.timeValueMillis(DOWNSAMPLE_ACTION_TIMEOUT_MILLIS));

x-pack/plugin/downsample/src/main/java/org/elasticsearch/xpack/downsample/TransportDownsampleAction.java

@@ -238,6 +238,11 @@ protected void masterOperation(
         ClusterState state,
         ActionListener<AcknowledgedResponse> listener
     ) {
+        logger.debug(
+            "Starting downsampling [{}] with [{}] interval",
+            request.getSourceIndex(),
+            request.getDownsampleConfig().getFixedInterval()
+        );
         long startTime = nowSupplier.get();
         String sourceIndexName = request.getSourceIndex();
         IndexNameExpressionResolver.assertExpressionHasNullOrDataSelector(sourceIndexName);
@@ -1025,6 +1030,7 @@ private void createDownsampleIndex(
         taskQueue.submitTask("create-downsample-index [" + downsampleIndexName + "]", new DownsampleClusterStateUpdateTask(listener) {
             @Override
             public ClusterState execute(ClusterState currentState) throws Exception {
+                logger.debug("Creating downsample index [{}]", downsampleIndexName);
                 return metadataCreateIndexService.applyCreateIndexRequest(
                     currentState,
                     createIndexClusterStateUpdateRequest,
@@ -1086,6 +1092,7 @@ class UpdateDownsampleIndexSettingsActionListener implements ActionListener<Ackn
 
         @Override
         public void onResponse(final AcknowledgedResponse response) {
+            logger.debug("Preparing to refresh downsample index [{}]", downsampleIndexName);
             final RefreshRequest request = new RefreshRequest(downsampleIndexName);
             request.setParentTask(parentTask);
             client.admin()
@@ -1150,6 +1157,7 @@ public void onResponse(final BroadcastResponse response) {
 
                     @Override
                     public ClusterState execute(ClusterState currentState) {
+                        logger.debug("Updating downsample index status for [{}]", downsampleIndexName);
                         final ProjectMetadata project = currentState.metadata().getProject(projectId);
                         final IndexMetadata downsampleIndex = project.index(downsampleIndexName);
                         if (IndexMetadata.INDEX_DOWNSAMPLE_STATUS.get(downsampleIndex.getSettings()) == DownsampleTaskStatus.SUCCESS) {
@@ -1201,6 +1209,7 @@ class FlushActionListener implements ActionListener<AcknowledgedResponse> {
 
         @Override
         public void onResponse(final AcknowledgedResponse response) {
+            logger.debug("Preparing to flush downsample index [{}]", downsampleIndexName);
             FlushRequest request = new FlushRequest(downsampleIndexName);
             request.setParentTask(parentTask);
             client.admin()
@@ -1239,12 +1248,14 @@ class MeasurementActionListener implements ActionListener<AcknowledgedResponse>
         @Override
         public void onResponse(final AcknowledgedResponse response) {
             recordSuccessMetrics(startTime);
+            logger.debug("Downsampling measured successfully");
             actionListener.onResponse(AcknowledgedResponse.TRUE);
         }
 
         @Override
         public void onFailure(Exception e) {
             recordSuccessMetrics(startTime);
+            logger.debug("Downsampling measured successfully", e);
             this.actionListener.onFailure(e);
         }