private StoredObject createCombinedObjectLarge(CombinedStoredObject combinedObject) {
    URI location = combinedObject.getLocation();
    log.info("starting multipart upload: %s", location);

    String bucket = getS3Bucket(location);
    String key = getS3ObjectKey(location);

    String uploadId =
        s3Service
            .initiateMultipartUpload(new InitiateMultipartUploadRequest(bucket, key))
            .getUploadId();

    try {
      List<PartETag> parts = newArrayList();
      int partNumber = 1;
      for (StoredObject newCombinedObjectPart : combinedObject.getSourceParts()) {
        CopyPartResult part =
            s3Service.copyPart(
                new CopyPartRequest()
                    .withUploadId(uploadId)
                    .withPartNumber(partNumber)
                    .withDestinationBucketName(bucket)
                    .withDestinationKey(key)
                    .withSourceBucketName(getS3Bucket(newCombinedObjectPart.getLocation()))
                    .withSourceKey(getS3ObjectKey(newCombinedObjectPart.getLocation())));
        parts.add(new PartETag(partNumber, part.getETag()));
        partNumber++;
      }

      String etag =
          s3Service
              .completeMultipartUpload(
                  new CompleteMultipartUploadRequest(bucket, key, uploadId, parts))
              .getETag();

      ObjectMetadata newObject = s3Service.getObjectMetadata(bucket, key);
      log.info("completed multipart upload: %s", location);

      if (!etag.equals(newObject.getETag())) {
        // this might happen in rare cases due to S3's eventual consistency
        throw new IllegalStateException("completed etag is different from combined object etag");
      }

      return updateStoredObject(location, newObject);
    } catch (AmazonClientException e) {
      try {
        s3Service.abortMultipartUpload(new AbortMultipartUploadRequest(bucket, key, uploadId));
      } catch (AmazonClientException ignored) {
      }
      throw Throwables.propagate(e);
    }
  }
 @Override
 public StoredObject putObject(URI location, File source) {
   try {
     log.info("starting upload: %s", location);
     PutObjectResult result =
         s3Service.putObject(getS3Bucket(location), getS3ObjectKey(location), source);
     ObjectMetadata metadata =
         s3Service.getObjectMetadata(getS3Bucket(location), getS3ObjectKey(location));
     if (!result.getETag().equals(metadata.getETag())) {
       // this might happen in rare cases due to S3's eventual consistency
       throw new IllegalStateException("uploaded etag is different from retrieved object etag");
     }
     log.info("completed upload: %s", location);
     return updateStoredObject(location, metadata);
   } catch (Exception e) {
     throw Throwables.propagate(e);
   }
 }