Allow upload of translog-1 generation while migrating to remote (#18713)

Signed-off-by: Gaurav Bafna <[email protected]>

Author: gbbafna

server/src/main/java/org/opensearch/index/translog/transfer/BlobStoreTransferService.java

@@ -40,7 +40,6 @@
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
-import java.util.Objects;
 import java.util.Set;
 
 import static org.opensearch.common.blobstore.BlobContainer.BlobNameSortOrder.LEXICOGRAPHIC;
@@ -192,7 +191,8 @@ private void uploadBlob(
                 listener.onFailure(new FileTransferException(fileSnapshot, ex));
             });
 
-            Objects.requireNonNull(fileSnapshot.getChecksum());
+            // Only the first generation doesn't have checksum
+            assert (fileSnapshot.getChecksum() != null || fileSnapshot.getName().contains("-1."));
             uploadBlobAsyncInternal(
                 fileSnapshot.getName(),
                 fileSnapshot.getName(),
@@ -226,7 +226,7 @@ void uploadBlobAsyncInternal(
         BlobPath blobPath,
         WritePriority writePriority,
         RemoteTransferContainer.OffsetRangeInputStreamSupplier inputStreamSupplier,
-        long expectedChecksum,
+        Long expectedChecksum,
         ActionListener<Void> completionListener,
         Map<String, String> metadata
     ) throws IOException {

server/src/main/java/org/opensearch/indices/recovery/RecoveryTarget.java

@@ -224,8 +224,7 @@ public void prepareForTranslogOperations(int totalTranslogOps, ActionListener<Vo
             indexShard().openEngineAndSkipTranslogRecovery();
             // upload to remote store in migration for primary shard
             if (indexShard.shouldSeedRemoteStore()) {
-                // This cleans up remote translog's 0 generation, as we don't want to get that uploaded
-                indexShard.sync();
+                logger.info("Remote Store seeding starting for {}", indexShard.shardId());
                 threadPool.executor(ThreadPool.Names.GENERIC).execute(() -> { indexShard.refresh("remote store migration"); });
                 indexShard.waitForRemoteStoreSync(this::setLastAccessTime);
                 logger.info("Remote Store is now seeded for {}", indexShard.shardId());