Snapshot _status API to return correct status for partial snapshots

CHANGELOG.md

@@ -98,6 +98,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 - [Bug] Check phase name before SearchRequestOperationsListener onPhaseStart ([#12035](https://github.com/opensearch-project/OpenSearch/pull/12035))
 - Fix Span operation names generated from RestActions ([#12005](https://github.com/opensearch-project/OpenSearch/pull/12005))
 - Fix error in RemoteSegmentStoreDirectory when debug logging is enabled ([#12328](https://github.com/opensearch-project/OpenSearch/pull/12328))
+- Fix snapshot _status API to return correct status for partial snapshots ([#12812](https://github.com/opensearch-project/OpenSearch/pull/12812))
 
 ### Security
 

server/src/internalClusterTest/java/org/opensearch/snapshots/DedicatedClusterSnapshotRestoreIT.java

@@ -572,7 +572,7 @@ public void testRestoreIndexWithMissingShards() throws Exception {
                 List<SnapshotStatus> snapshotStatuses = snapshotsStatusResponse.getSnapshots();
                 assertEquals(snapshotStatuses.size(), 1);
                 logger.trace("current snapshot status [{}]", snapshotStatuses.get(0));
-                assertTrue(snapshotStatuses.get(0).getState().completed());
+                assertThat(getSnapshot("test-repo", "test-snap-2").state(), equalTo(SnapshotState.PARTIAL));
             }, 1, TimeUnit.MINUTES);
             SnapshotsStatusResponse snapshotsStatusResponse = clusterAdmin().prepareSnapshotStatus("test-repo")
                 .setSnapshots("test-snap-2")
@@ -589,7 +589,6 @@ public void testRestoreIndexWithMissingShards() throws Exception {
             // After it was marked as completed in the cluster state - we need to check if it's completed on the file system as well
             assertBusy(() -> {
                 SnapshotInfo snapshotInfo = getSnapshot("test-repo", "test-snap-2");
-                assertTrue(snapshotInfo.state().completed());
                 assertEquals(SnapshotState.PARTIAL, snapshotInfo.state());
             }, 1, TimeUnit.MINUTES);
         } else {

server/src/internalClusterTest/java/org/opensearch/snapshots/SnapshotStatusApisIT.java

@@ -357,6 +357,25 @@ public void testSnapshotStatusOnFailedSnapshot() throws Exception {
         assertEquals(SnapshotsInProgress.State.FAILED, snapshotsStatusResponse.getSnapshots().get(0).getState());
     }
 
+    public void testSnapshotStatusOnPartialSnapshot() throws Exception {
+        final String dataNode = internalCluster().startDataOnlyNode();
+        final String repoName = "test-repo";
+        final String snapshotName = "test-snap";
+        final String indexName = "test-idx";
+        createRepository(repoName, "fs");
+        // create an index with a single shard on the data node, that will be stopped
+        createIndex(indexName, singleShardOneNode(dataNode));
+        index(indexName, "_doc", "some_doc_id", "foo", "bar");
+        logger.info("--> stopping data node before creating snapshot");
+        stopNode(dataNode);
+        startFullSnapshot(repoName, snapshotName, true).get();
+        final List<SnapshotStatus> snapshotStatus = clusterAdmin().snapshotsStatus(
+            new SnapshotsStatusRequest(repoName, new String[] { snapshotName })
+        ).actionGet().getSnapshots();
+        assertThat(snapshotStatus.size(), equalTo(1));
+        assertEquals(SnapshotsInProgress.State.PARTIAL, snapshotStatus.get(0).getState());
+    }
+
     public void testStatusAPICallInProgressShallowSnapshot() throws Exception {
         internalCluster().startClusterManagerOnlyNode();
         internalCluster().startDataOnlyNode();

server/src/main/java/org/opensearch/action/admin/cluster/snapshots/status/TransportSnapshotsStatusAction.java

@@ -356,11 +356,11 @@
                             state = SnapshotsInProgress.State.FAILED;
                             break;
                         case SUCCESS:
-                        case PARTIAL:
-                            // Translating both PARTIAL and SUCCESS to SUCCESS for now
-                            // TODO: add the differentiation on the metadata level in the next major release
                             state = SnapshotsInProgress.State.SUCCESS;
                             break;
+                        case PARTIAL:
+                            state = SnapshotsInProgress.State.PARTIAL;
+                            break;
                         default:
                             throw new IllegalArgumentException("Unknown snapshot state " + snapshotInfo.state());
                     }

server/src/main/java/org/opensearch/cluster/SnapshotsInProgress.java

@@ -747,7 +747,12 @@
             snapshot.writeTo(out);
             out.writeBoolean(includeGlobalState);
             out.writeBoolean(partial);
-            out.writeByte(state.value());
+            if ((out.getVersion().before(Version.V_3_0_0)) && state == State.PARTIAL) {
+                // Setting to SUCCESS for partial snapshots in older versions to maintain backward compatibility
+                out.writeByte(State.SUCCESS.value());
+            } else {
+                out.writeByte(state.value());
+            }
             out.writeList(indices);
             out.writeLong(startTime);
             out.writeMap(shards, (o, v) -> v.writeTo(o), (o, v) -> v.writeTo(o));
@@ -937,7 +942,8 @@
         STARTED((byte) 1, false),
         SUCCESS((byte) 2, true),
         FAILED((byte) 3, true),
-        ABORTED((byte) 4, false);
+        ABORTED((byte) 4, false),
+        PARTIAL((byte) 5, false);
 
         private final byte value;
 
@@ -968,6 +974,8 @@
                     return FAILED;
                 case 4:
                     return ABORTED;
+                case 5:
+                    return PARTIAL;
                 default:
                     throw new IllegalArgumentException("No snapshot state for value [" + value + "]");
             }