Ensure no snapshotted commit when close engine (#38663)

With this change, we can automatically detect an implementation 
that acquires an index commit but fails to release.

server/src/test/java/org/elasticsearch/index/engine/InternalEngineTests.java

@@ -2493,6 +2493,7 @@ public class InternalEngineTests extends EngineTestCase {
                 prevLocalCheckpoint = localCheckpoint;
                 prevMaxSeqNo = maxSeqNo;
             }
+            IOUtils.close(commits);
         }
     }
 

server/src/test/java/org/elasticsearch/index/seqno/RetentionLeaseIT.java

@@ -105,7 +105,7 @@ public class RetentionLeaseIT extends ESIntegTestCase  {
 
             // check retention leases have been committed on the primary
             final RetentionLeases primaryCommittedRetentionLeases = RetentionLeases.decodeRetentionLeases(
-                    primary.acquireLastIndexCommit(false).getIndexCommit().getUserData().get(Engine.RETENTION_LEASES));
+                    primary.commitStats().getUserData().get(Engine.RETENTION_LEASES));
             assertThat(currentRetentionLeases, equalTo(RetentionLeases.toMap(primaryCommittedRetentionLeases)));
 
             // check current retention leases have been synced to all replicas
@@ -120,7 +120,7 @@ public class RetentionLeaseIT extends ESIntegTestCase  {
 
                 // check retention leases have been committed on the replica
                 final RetentionLeases replicaCommittedRetentionLeases = RetentionLeases.decodeRetentionLeases(
-                        replica.acquireLastIndexCommit(false).getIndexCommit().getUserData().get(Engine.RETENTION_LEASES));
+                        replica.commitStats().getUserData().get(Engine.RETENTION_LEASES));
                 assertThat(currentRetentionLeases, equalTo(RetentionLeases.toMap(replicaCommittedRetentionLeases)));
             }
         }

test/framework/src/main/java/org/elasticsearch/test/InternalTestCluster.java

@@ -87,6 +87,7 @@ import org.elasticsearch.index.IndexService;
 import org.elasticsearch.index.engine.CommitStats;
 import org.elasticsearch.index.engine.DocIdSeqNoAndTerm;
 import org.elasticsearch.index.engine.Engine;
+import org.elasticsearch.index.engine.EngineTestCase;
 import org.elasticsearch.index.engine.InternalEngine;
 import org.elasticsearch.index.seqno.SeqNoStats;
 import org.elasticsearch.index.seqno.SequenceNumbers;
@@ -1254,6 +1255,7 @@ public final class InternalTestCluster extends TestCluster {
         //check that shards that have same sync id also contain same number of documents
         assertSameSyncIdSameDocs();
         assertOpenTranslogReferences();
+        assertNoSnapshottedIndexCommit();
     }
 
     private void assertSameSyncIdSameDocs() {
@@ -1324,6 +1326,28 @@ public final class InternalTestCluster extends TestCluster {
         });
     }
 
+    private void assertNoSnapshottedIndexCommit() throws Exception {
+        assertBusy(() -> {
+            final Collection<NodeAndClient> nodesAndClients = nodes.values();
+            for (NodeAndClient nodeAndClient : nodesAndClients) {
+                IndicesService indexServices = getInstance(IndicesService.class, nodeAndClient.name);
+                for (IndexService indexService : indexServices) {
+                    for (IndexShard indexShard : indexService) {
+                        try {
+                            Engine engine = IndexShardTestCase.getEngine(indexShard);
+                            if (engine instanceof InternalEngine) {
+                                assertFalse(indexShard.routingEntry().toString() + " has unreleased snapshotted index commits",
+                                    EngineTestCase.hasSnapshottedCommits(engine));
+                            }
+                        } catch (AlreadyClosedException ignored) {
+
+                        }
+                    }
+                }
+            }
+        });
+    }
+
     /**
      * Asserts that the document history in Lucene index is consistent with Translog's on every index shard of the cluster.
      * This assertion might be expensive, thus we prefer not to execute on every test but only interesting tests.