Fix some lazy rollover code (#124153) (#124306)

The main goal of the PR is to fix the "rollover failed" log in the
`IndexTemplateRegistry`. We were logging this on every upgrade because
`rolloverResponse.isRolledOver()` is always `false` when we do a lazy
rollover request - which is the default for index template updates.

While I was looking at this, I noticed we don't actually return early
when we process a lazy rollover _dry run_. The end result happened to be
ok (i.e. side-effects and response), but I figured I might as well fix
the behavior to return early.

Finally, we add an `INFO` log in the lazy rollover action to aid the
debugging process.

(cherry picked from commit 954420495df0dc4be4ab826724d2b21fab889203)

# Conflicts:
#	server/src/main/java/org/elasticsearch/action/admin/indices/rollover/TransportRolloverAction.java

server/src/main/java/org/elasticsearch/action/admin/indices/rollover/LazyRolloverAction.java

@@ -260,6 +260,11 @@ public final class LazyRolloverAction extends ActionType<RolloverResponse> {
 
             final var rolloverIndexName = rolloverResult.rolloverIndexName();
             final var sourceIndexName = rolloverResult.sourceIndexName();
+            logger.info(
+                "rolling over data stream [{}] to index [{}] because it was marked for lazy rollover",
+                dataStream.getName(),
+                rolloverIndexName
+            );
 
             final var waitForActiveShardsTimeout = rolloverRequest.masterNodeTimeout().millis() < 0
                 ? null

server/src/main/java/org/elasticsearch/action/admin/indices/rollover/TransportRolloverAction.java

@@ -212,44 +212,17 @@ public class TransportRolloverAction extends TransportMasterNodeAction<RolloverR
         final String trialRolloverIndexName = trialRolloverNames.rolloverName();
         MetadataCreateIndexService.validateIndexName(trialRolloverIndexName, metadata, clusterState.routingTable());
 
-        boolean isDataStream = metadata.dataStreams().containsKey(resolvedRolloverTarget.resource());
         if (rolloverRequest.isLazy()) {
-            if (isDataStream == false || rolloverRequest.getConditions().hasConditions()) {
-                String message;
-                if (isDataStream) {
-                    message = "Lazy rollover can be used only without any conditions."
-                        + " Please remove the conditions from the request body or the query parameter 'lazy'.";
-                } else if (rolloverRequest.getConditions().hasConditions() == false) {
-                    message = "Lazy rollover can be applied only on a data stream." + " Please remove the query parameter 'lazy'.";
-                } else {
-                    message = "Lazy rollover can be applied only on a data stream with no conditions."
-                        + " Please remove the query parameter 'lazy'.";
-                }
-                listener.onFailure(new IllegalArgumentException(message));
-                return;
-            }
-            if (rolloverRequest.isDryRun() == false) {
-                metadataDataStreamsService.setRolloverOnWrite(
-                    resolvedRolloverTarget.resource(),
-                    true,
-                    targetFailureStore,
-                    rolloverRequest.ackTimeout(),
-                    rolloverRequest.masterNodeTimeout(),
-                    listener.map(
-                        response -> new RolloverResponse(
-                            trialSourceIndexName,
-                            trialRolloverIndexName,
-                            Map.of(),
-                            false,
-                            false,
-                            response.isAcknowledged(),
-                            false,
-                            response.isAcknowledged()
-                        )
-                    )
-                );
-                return;
-            }
+            markForLazyRollover(
+                rolloverRequest,
+                listener,
+                metadata,
+                resolvedRolloverTarget,
+                targetFailureStore,
+                trialSourceIndexName,
+                trialRolloverIndexName
+            );
+            return;
         }
 
         final IndexAbstraction rolloverTargetAbstraction = clusterState.metadata()
@@ -345,7 +318,7 @@ public class TransportRolloverAction extends TransportMasterNodeAction<RolloverR
                     false,
                     false,
                     false,
-                    rolloverRequest.isLazy()
+                    false
                 );
 
                 // If this is a dry run, return with the results without invoking a cluster state update
@@ -373,6 +346,57 @@ public class TransportRolloverAction extends TransportMasterNodeAction<RolloverR
         );
     }
 
+    private void markForLazyRollover(
+        RolloverRequest rolloverRequest,
+        ActionListener<RolloverResponse> listener,
+        Metadata metadata,
+        ResolvedExpression resolvedRolloverTarget,
+        boolean targetFailureStore,
+        String trialSourceIndexName,
+        String trialRolloverIndexName
+    ) {
+        boolean isDataStream = metadata.dataStreams().containsKey(resolvedRolloverTarget.resource());
+        if (isDataStream == false || rolloverRequest.getConditions().hasConditions()) {
+            String message;
+            if (isDataStream) {
+                message = "Lazy rollover can be used only without any conditions."
+                    + " Please remove the conditions from the request body or the query parameter 'lazy'.";
+            } else if (rolloverRequest.getConditions().hasConditions() == false) {
+                message = "Lazy rollover can be applied only on a data stream. Please remove the query parameter 'lazy'.";
+            } else {
+                message = "Lazy rollover can be applied only on a data stream with no conditions."
+                    + " Please remove the query parameter 'lazy'.";
+            }
+            listener.onFailure(new IllegalArgumentException(message));
+            return;
+        }
+        if (rolloverRequest.isDryRun()) {
+            listener.onResponse(
+                new RolloverResponse(trialSourceIndexName, trialRolloverIndexName, Map.of(), true, false, false, false, true)
+            );
+            return;
+        }
+        metadataDataStreamsService.setRolloverOnWrite(
+            resolvedRolloverTarget.resource(),
+            true,
+            targetFailureStore,
+            rolloverRequest.ackTimeout(),
+            rolloverRequest.masterNodeTimeout(),
+            listener.map(
+                response -> new RolloverResponse(
+                    trialSourceIndexName,
+                    trialRolloverIndexName,
+                    Map.of(),
+                    false,
+                    false,
+                    response.isAcknowledged(),
+                    false,
+                    true
+                )
+            )
+        );
+    }
+
     private void initializeFailureStore(
         RolloverRequest rolloverRequest,
         ActionListener<RolloverResponse> listener,

server/src/test/java/org/elasticsearch/action/admin/indices/rollover/TransportRolloverActionTests.java

@@ -466,19 +466,39 @@ public class TransportRolloverActionTests extends ESTestCase {
             mockMetadataDataStreamService,
             dataStreamAutoShardingService
         );
-        final PlainActionFuture<RolloverResponse> future = new PlainActionFuture<>();
-        RolloverRequest rolloverRequest = new RolloverRequest("logs-ds", null);
-        rolloverRequest.lazy(true);
-        transportRolloverAction.masterOperation(mock(CancellableTask.class), rolloverRequest, stateBefore, future);
-        RolloverResponse rolloverResponse = future.actionGet();
-        assertThat(rolloverResponse.getOldIndex(), equalTo(".ds-logs-ds-000001"));
-        assertThat(rolloverResponse.getNewIndex(), Matchers.startsWith(".ds-logs-ds-"));
-        assertThat(rolloverResponse.getNewIndex(), Matchers.endsWith("-000002"));
-        assertThat(rolloverResponse.isLazy(), equalTo(true));
-        assertThat(rolloverResponse.isDryRun(), equalTo(false));
-        assertThat(rolloverResponse.isRolledOver(), equalTo(false));
-        assertThat(rolloverResponse.getConditionStatus().size(), equalTo(0));
-        assertThat(rolloverResponse.isAcknowledged(), is(true));
+        {
+            // Regular lazy rollover
+            final PlainActionFuture<RolloverResponse> future = new PlainActionFuture<>();
+            RolloverRequest rolloverRequest = new RolloverRequest("logs-ds", null);
+            rolloverRequest.lazy(true);
+            transportRolloverAction.masterOperation(mock(CancellableTask.class), rolloverRequest, stateBefore, future);
+            RolloverResponse rolloverResponse = future.actionGet();
+            assertThat(rolloverResponse.getOldIndex(), equalTo(".ds-logs-ds-000001"));
+            assertThat(rolloverResponse.getNewIndex(), Matchers.startsWith(".ds-logs-ds-"));
+            assertThat(rolloverResponse.getNewIndex(), Matchers.endsWith("-000002"));
+            assertThat(rolloverResponse.isLazy(), equalTo(true));
+            assertThat(rolloverResponse.isDryRun(), equalTo(false));
+            assertThat(rolloverResponse.isRolledOver(), equalTo(false));
+            assertThat(rolloverResponse.getConditionStatus().size(), equalTo(0));
+            assertThat(rolloverResponse.isAcknowledged(), is(true));
+        }
+        {
+            // Dry-run lazy rollover
+            final PlainActionFuture<RolloverResponse> future = new PlainActionFuture<>();
+            RolloverRequest rolloverRequest = new RolloverRequest("logs-ds", null);
+            rolloverRequest.lazy(true);
+            rolloverRequest.dryRun(true);
+            transportRolloverAction.masterOperation(mock(CancellableTask.class), rolloverRequest, stateBefore, future);
+            RolloverResponse rolloverResponse = future.actionGet();
+            assertThat(rolloverResponse.getOldIndex(), equalTo(".ds-logs-ds-000001"));
+            assertThat(rolloverResponse.getNewIndex(), Matchers.startsWith(".ds-logs-ds-"));
+            assertThat(rolloverResponse.getNewIndex(), Matchers.endsWith("-000002"));
+            assertThat(rolloverResponse.isLazy(), equalTo(true));
+            assertThat(rolloverResponse.isDryRun(), equalTo(true));
+            assertThat(rolloverResponse.isRolledOver(), equalTo(false));
+            assertThat(rolloverResponse.getConditionStatus().size(), equalTo(0));
+            assertThat(rolloverResponse.isAcknowledged(), is(false));
+        }
     }
 
     public void testLazyRolloverFails() throws Exception {

x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/template/IndexTemplateRegistry.java

@@ -33,6 +33,7 @@ import org.elasticsearch.cluster.metadata.MetadataIndexTemplateService;
 import org.elasticsearch.cluster.metadata.Template;
 import org.elasticsearch.cluster.node.DiscoveryNode;
 import org.elasticsearch.cluster.service.ClusterService;
+import org.elasticsearch.common.Strings;
 import org.elasticsearch.common.regex.Regex;
 import org.elasticsearch.common.settings.Settings;
 import org.elasticsearch.core.Nullable;
@@ -840,9 +841,8 @@ public abstract class IndexTemplateRegistry implements ClusterStateListener {
 
     void onRolloversBulkResponse(Collection<RolloverResponse> rolloverResponses) {
         for (RolloverResponse rolloverResponse : rolloverResponses) {
-            if (rolloverResponse.isRolledOver() == false) {
-                logger.warn("rollover of the [{}] index [{}] failed", getOrigin(), rolloverResponse.getOldIndex());
-            }
+            assert rolloverResponse.isLazy() && rolloverResponse.isRolledOver() == false
+                : Strings.format("Expected rollover of the [%s] index [%s] to be lazy", getOrigin(), rolloverResponse.getOldIndex());
         }
     }