CR: handle index recreate and stronger tests

server/src/main/java/org/elasticsearch/repositories/ShardGenerations.java

@@ -54,6 +54,13 @@ private ShardGenerations(Map<IndexId, List<String>> shardGenerations) {
         this.shardGenerations = shardGenerations;
     }
 
+    /**
+     * Returns the total number of shards tracked by this instance.
+     */
+    public int totalShards() {
+        return shardGenerations.values().stream().mapToInt(List::size).sum();
+    }
+
     /**
      * Returns all indices for which shard generations are tracked.
      *

server/src/main/java/org/elasticsearch/snapshots/SnapshotsService.java

@@ -597,14 +597,13 @@ private void cleanupAfterError(Exception exception) {
     private static ShardGenerations buildGenerations(SnapshotsInProgress.Entry snapshot, MetaData metaData) {
         ShardGenerations.Builder builder = ShardGenerations.builder();
         final Map<String, IndexId> indexLookup = new HashMap<>();
-        snapshot.indices().forEach(idx -> {
-            if (metaData.index(idx.getName()) != null) {
-                indexLookup.put(idx.getName(), idx);
-            } else {
-                assert snapshot.partial() : "Index [" + idx + "] was deleted during a snapshot but snapshot was not partial.";
-            }
-        });
+        snapshot.indices().forEach(idx -> indexLookup.put(idx.getName(), idx));
         snapshot.shards().forEach(c -> {
+            if (metaData.index(c.key.getIndex()) == null) {
+                assert snapshot.partial() :
+                    "Index [" + c.key.getIndex() + "] was deleted during a snapshot but snapshot was not partial.";
+                return;
+            }
             final IndexId indexId = indexLookup.get(c.key.getIndexName());
             if (indexId != null) {
                 builder.put(indexId, c.key.id(), c.value.generation());
@@ -1044,12 +1043,13 @@ protected void doRun() {
                         shardFailures.add(new SnapshotShardFailure(status.nodeId(), shardId, status.reason()));
                     }
                 }
+                final ShardGenerations shardGenerations = buildGenerations(entry, metaData);
                 repository.finalizeSnapshot(
                     snapshot.getSnapshotId(),
-                    buildGenerations(entry, metaData),
+                    shardGenerations,
                     entry.startTime(),
                     failure,
-                    entry.shards().size(),
+                    entry.partial() ? shardGenerations.totalShards() : entry.shards().size(),
                     unmodifiableList(shardFailures),
                     entry.repositoryStateId(),
                     entry.includeGlobalState(),

server/src/test/java/org/elasticsearch/snapshots/SnapshotResiliencyTests.java

@@ -21,6 +21,7 @@
 
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
+import org.apache.lucene.util.SetOnce;
 import org.elasticsearch.ExceptionsHelper;
 import org.elasticsearch.Version;
 import org.elasticsearch.action.ActionListener;
@@ -143,6 +144,7 @@
 import org.elasticsearch.env.TestEnvironment;
 import org.elasticsearch.gateway.MetaStateService;
 import org.elasticsearch.gateway.TransportNodesListGatewayStartedShards;
+import org.elasticsearch.index.Index;
 import org.elasticsearch.index.analysis.AnalysisRegistry;
 import org.elasticsearch.index.seqno.GlobalCheckpointSyncAction;
 import org.elasticsearch.index.seqno.RetentionLeaseSyncer;
@@ -504,7 +506,7 @@ public void testConcurrentSnapshotCreateAndDeleteOther() {
         }
     }
 
-    public void testConcurrentSnapshotDeleteAndDeleteIndex() {
+    public void testConcurrentSnapshotDeleteAndDeleteIndex() throws IOException {
         setupTestCluster(randomFrom(1, 3, 5), randomIntBetween(2, 10));
 
         String repoName = "repo";
@@ -517,7 +519,9 @@ public void testConcurrentSnapshotDeleteAndDeleteIndex() {
         final StepListener<Collection<CreateIndexResponse>> createIndicesListener = new StepListener<>();
         final int indices = randomIntBetween(5, 20);
 
+        final SetOnce<Index> firstIndex = new SetOnce<>();
         continueOrDie(createRepoAndIndex(repoName, index, 1), createIndexResponse -> {
+            firstIndex.set(masterNode.clusterService.state().metaData().index(index).getIndex());
             // create a few more indices to make it more likely that the subsequent index delete operation happens before snapshot
             // finalization
             final GroupedActionListener<CreateIndexResponse> listener = new GroupedActionListener<>(createIndicesListener, indices);
@@ -535,21 +539,43 @@ public void testConcurrentSnapshotDeleteAndDeleteIndex() {
                 .setPartial(partialSnapshot).execute(createSnapshotResponseStepListener));
 
         continueOrDie(createSnapshotResponseStepListener,
-            createSnapshotResponse -> client().admin().indices().delete(new DeleteIndexRequest(index), noopListener()));
+            createSnapshotResponse -> client().admin().indices().delete(new DeleteIndexRequest(index), new ActionListener<>() {
+                @Override
+                public void onResponse(AcknowledgedResponse acknowledgedResponse) {
+                    if (partialSnapshot) {
+                        // Recreate index by the same name to test that we don't snapshot conflicting metadata in this scenario
+                        client().admin().indices().create(new CreateIndexRequest(index), noopListener());
+                    }
+                }
+
+                @Override
+                public void onFailure(Exception e) {
+                    if (partialSnapshot) {
+                        throw new AssertionError("Delete index should always work during partial snapshots", e);
+                    }
+                }
+            }));
 
         deterministicTaskQueue.runAllRunnableTasks();
 
         SnapshotsInProgress finalSnapshotsInProgress = masterNode.clusterService.state().custom(SnapshotsInProgress.TYPE);
         assertFalse(finalSnapshotsInProgress.entries().stream().anyMatch(entry -> entry.state().completed() == false));
         final Repository repository = masterNode.repositoriesService.repository(repoName);
-        Collection<SnapshotId> snapshotIds = getRepositoryData(repository).getSnapshotIds();
+        final RepositoryData repositoryData = getRepositoryData(repository);
+        Collection<SnapshotId> snapshotIds = repositoryData.getSnapshotIds();
         assertThat(snapshotIds, hasSize(1));
 
         final SnapshotInfo snapshotInfo = repository.getSnapshotInfo(snapshotIds.iterator().next());
         assertEquals(SnapshotState.SUCCESS, snapshotInfo.state());
         if (partialSnapshot) {
             // Single shard for each index so we either get all indices or all except for the deleted index
             assertThat(snapshotInfo.successfulShards(), either(is(indices + 1)).or(is(indices)));
+            if (snapshotInfo.successfulShards() == indices + 1) {
+                final IndexMetaData indexMetaData =
+                    repository.getSnapshotIndexMetaData(snapshotInfo.snapshotId(), repositoryData.resolveIndexId(index));
+                // Make sure we snapshotted the metadata of this index and not the recreated version
+                assertEquals(indexMetaData.getIndex(), firstIndex.get());
+            }
         } else {
             // Index delete must be blocked for non-partial snapshots and we get a snapshot for every index
             assertEquals(snapshotInfo.successfulShards(), indices + 1);