void maybeNotifyForFirstChunkCreation() {
      if (indexToChunkIdsAndChunkSizes.get(0) != null) {
        // reason to check for not null: there are chances that 2nd chunk would completes before the first chunk and
        // the first chunk failed later. In such cases, even though metadata chunk might return some successfully
        // completed chunkIds, the first chunk may be null
        String chunkId = firstChunkIdAndProperties.getFirst().getID();
        BlobProperties chunkProperties = firstChunkIdAndProperties.getSecond();
        Pair<Account, Container> accountContainer =
            RouterUtils.getAccountContainer(accountService, chunkProperties.getAccountId(),
                chunkProperties.getContainerId());
        notificationSystem.onBlobCreated(chunkId, chunkProperties, accountContainer.getFirst(),
            accountContainer.getSecond(), NotificationBlobType.DataChunk);
      }
    }
Notify for the creation of the first chunk. To be called after the overall operation is completed if the overall
blob is composite. If no first chunk was put successfully, this will do nothing.
ambry-router/src/main/java/com/github/ambry/router/PutOperation.java