Assert in IndexReshardingState.Split ctor that source shards are not …

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

@@ -181,6 +181,9 @@ public static TargetShardState readFrom(StreamInput in) throws IOException {
         private final TargetShardState[] targetShards;
 
         Split(SourceShardState[] sourceShards, TargetShardState[] targetShards) {
+            // The resharding metadata is deleted when the last source shard transitions to done
+            assert Arrays.stream(sourceShards).allMatch((state) -> state == SourceShardState.DONE) == false;
+
             this.sourceShards = sourceShards;
             this.targetShards = targetShards;
 
@@ -375,20 +378,6 @@ public boolean targetStateAtLeast(int shardNum, TargetShardState targetShardStat
             return getTargetShardState(shardNum).ordinal() >= targetShardState.ordinal();
         }
 
-        /**
-         * Check whether this metadata represents an incomplete split
-         * @return true if the split is incomplete (not all source shards are DONE)
-         */
-        public boolean inProgress() {
-            for (int i = 0; i < oldShardCount; i++) {
-                if (sourceShards[i] == SourceShardState.SOURCE) {
-                    return true;
-                }
-            }
-
-            return false;
-        }
-
         public Stream<TargetShardState> targetStates() {
             return Arrays.stream(targetShards);
         }

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

@@ -14,6 +14,8 @@
 import org.elasticsearch.xcontent.XContentParser;
 
 import java.io.IOException;
+import java.util.Arrays;
+import java.util.stream.IntStream;
 
 public class IndexReshardingMetadataSerializationTests extends AbstractXContentSerializingTestCase<IndexReshardingMetadata> {
     @Override
@@ -46,6 +48,10 @@ private IndexReshardingState.Split createTestSplit() {
         for (int i = 0; i < oldShards; i++) {
             sourceShardStates[i] = randomFrom(IndexReshardingState.Split.SourceShardState.values());
         }
+        // All sources done is an invalid state, will fail assert in Split constructor
+        if (Arrays.stream(sourceShardStates).allMatch(state -> state == IndexReshardingState.Split.SourceShardState.DONE)) {
+            sourceShardStates[0] = IndexReshardingState.Split.SourceShardState.SOURCE;
+        }
         for (int i = 0; i < targetShardStates.length; i++) {
             targetShardStates[i] = randomFrom(IndexReshardingState.Split.TargetShardState.values());
         }
@@ -74,16 +80,18 @@ enum Mutation {
         var sourceShardStates = split.sourceShards().clone();
         var targetShardStates = split.targetShards().clone();
 
-        switch (randomFrom(Mutation.values())) {
-            case SOURCE_SHARD_STATES:
-                var is = randomInt(sourceShardStates.length - 1);
-                sourceShardStates[is] = IndexReshardingState.Split.SourceShardState.values()[(sourceShardStates[is].ordinal() + 1)
-                    % IndexReshardingState.Split.SourceShardState.values().length];
-                break;
-            case TARGET_SHARD_STATES:
-                var it = randomInt(targetShardStates.length - 1);
-                targetShardStates[it] = IndexReshardingState.Split.TargetShardState.values()[(targetShardStates[it].ordinal() + 1)
-                    % IndexReshardingState.Split.TargetShardState.values().length];
+        var is = randomInt(sourceShardStates.length - 1);
+        boolean allOtherSourcesDone = IntStream.range(0, sourceShardStates.length)
+            .filter(i -> i != is)
+            .allMatch(i -> sourceShardStates[i] == IndexReshardingState.Split.SourceShardState.DONE);
+        // All sources done is an invalid state, will fail assert in Split constructor
+        if (allOtherSourcesDone || randomFrom(Mutation.values()) == Mutation.TARGET_SHARD_STATES) {
+            var it = randomInt(targetShardStates.length - 1);
+            targetShardStates[it] = IndexReshardingState.Split.TargetShardState.values()[(targetShardStates[it].ordinal() + 1)
+                % IndexReshardingState.Split.TargetShardState.values().length];
+        } else {
+            sourceShardStates[is] = IndexReshardingState.Split.SourceShardState.values()[(sourceShardStates[is].ordinal() + 1)
+                % IndexReshardingState.Split.SourceShardState.values().length];
         }
 
         return new IndexReshardingState.Split(sourceShardStates, targetShardStates);

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

@@ -33,7 +33,7 @@ public void testSplit() {
         }
 
         // advance split state randomly and expect to terminate
-        while (split.inProgress()) {
+        while (true) {
             var splitBuilder = split.builder();
             // pick a shard at random and see if we can advance it
             int idx = randomIntBetween(0, numShards * multiple - 1);
@@ -43,6 +43,11 @@ public void testSplit() {
                 var nextState = randomFrom(IndexReshardingState.Split.SourceShardState.values());
                 if (nextState.ordinal() == sourceState.ordinal() + 1) {
                     if (split.targetsDone(idx)) {
+                        long ongoingSourceShards = split.sourceStates()
+                            .filter(state -> state != IndexReshardingState.Split.SourceShardState.DONE)
+                            .count();
+                        // all source shards done is an invalid state, terminate
+                        if (ongoingSourceShards == 1) break;
                         splitBuilder.setSourceShardState(idx, nextState);
                     } else {
                         assertThrows(AssertionError.class, () -> splitBuilder.setSourceShardState(idx, nextState));
@@ -63,10 +68,10 @@ public void testSplit() {
             split = splitBuilder.build();
         }
 
-        for (int i = 0; i < numShards; i++) {
-            assertSame(IndexReshardingState.Split.SourceShardState.DONE, split.getSourceShardState(i));
-            assertFalse(split.isTargetShard(i));
-        }
+        assertEquals(
+            split.sourceStates().filter(state -> state == IndexReshardingState.Split.SourceShardState.DONE).count(),
+            numShards - 1
+        );
         for (int i = numShards; i < numShards * multiple; i++) {
             assertSame(IndexReshardingState.Split.TargetShardState.DONE, split.getTargetShardState(i));
             assertTrue(split.isTargetShard(i));