Allow a tsdb data stream to rolled over to a logsdb data stream

and the other way around.

This doesn't make much sense. However, if a data stream's index mode differs from the index mode of most recent backing index, then this can cause confusion. Typically, misconfiguration is a reason this can happen.

Related to #126637

Author: martijnvg

server/src/main/java/org/elasticsearch/cluster/metadata/DataStream.java

@@ -610,6 +610,10 @@ public DataStream unsafeRollover(
         } else if (dsIndexMode == IndexMode.LOGSDB && (indexModeFromTemplate == null || indexModeFromTemplate == IndexMode.STANDARD)) {
             // Allow downgrading a time series data stream to a regular data stream
             dsIndexMode = null;
+        } else if (dsIndexMode == IndexMode.TIME_SERIES && indexModeFromTemplate == IndexMode.LOGSDB) {
+            dsIndexMode = IndexMode.LOGSDB;
+        } else if (dsIndexMode == IndexMode.LOGSDB && indexModeFromTemplate == IndexMode.TIME_SERIES) {
+            dsIndexMode = IndexMode.TIME_SERIES;
         }
 
         List<Index> backingIndices = new ArrayList<>(this.backingIndices.indices);

server/src/test/java/org/elasticsearch/cluster/metadata/DataStreamTests.java

@@ -277,6 +277,39 @@ public void testRolloverUpgradeToLogsdbDataStream() {
         assertThat(rolledDs.getIndexMode(), equalTo(IndexMode.LOGSDB));
     }
 
+    public void testRolloverFromTSdbToLogsdb() {
+        DataStream ds = DataStreamTestHelper.randomInstance().copy().setReplicated(false).setIndexMode(IndexMode.TIME_SERIES).build();
+        final var project = ProjectMetadata.builder(randomProjectIdOrDefault()).build();
+        var newCoordinates = ds.nextWriteIndexAndGeneration(project, ds.getDataComponent());
+
+        var rolledDs = ds.rollover(new Index(newCoordinates.v1(), UUIDs.randomBase64UUID()), newCoordinates.v2(), IndexMode.LOGSDB, null);
+        assertThat(rolledDs.getName(), equalTo(ds.getName()));
+        assertThat(rolledDs.getGeneration(), equalTo(ds.getGeneration() + 1));
+        assertThat(rolledDs.getIndices().size(), equalTo(ds.getIndices().size() + 1));
+        assertTrue(rolledDs.getIndices().containsAll(ds.getIndices()));
+        assertTrue(rolledDs.getIndices().contains(rolledDs.getWriteIndex()));
+        assertThat(rolledDs.getIndexMode(), equalTo(IndexMode.LOGSDB));
+    }
+
+    public void testRolloverFromLogsdbToTsdb() {
+        DataStream ds = DataStreamTestHelper.randomInstance().copy().setReplicated(false).setIndexMode(IndexMode.LOGSDB).build();
+        final var project = ProjectMetadata.builder(randomProjectIdOrDefault()).build();
+        var newCoordinates = ds.nextWriteIndexAndGeneration(project, ds.getDataComponent());
+
+        var rolledDs = ds.rollover(
+            new Index(newCoordinates.v1(), UUIDs.randomBase64UUID()),
+            newCoordinates.v2(),
+            IndexMode.TIME_SERIES,
+            null
+        );
+        assertThat(rolledDs.getName(), equalTo(ds.getName()));
+        assertThat(rolledDs.getGeneration(), equalTo(ds.getGeneration() + 1));
+        assertThat(rolledDs.getIndices().size(), equalTo(ds.getIndices().size() + 1));
+        assertTrue(rolledDs.getIndices().containsAll(ds.getIndices()));
+        assertTrue(rolledDs.getIndices().contains(rolledDs.getWriteIndex()));
+        assertThat(rolledDs.getIndexMode(), equalTo(IndexMode.TIME_SERIES));
+    }
+
     public void testRolloverDowngradeFromTsdbToRegularDataStream() {
         DataStream ds = DataStreamTestHelper.randomInstance().copy().setReplicated(false).setIndexMode(IndexMode.TIME_SERIES).build();
         final var project = ProjectMetadata.builder(randomProjectIdOrDefault()).build();