AWS iOS: How to resume a multipart upload

Question

Based on this sample http://aws.amazon.com/articles/0006282245644577 , it is clear how to use multipart upload using the AWS iOS SDK. However, it seems that my uploads are not stitched together correctly when I try to resume an interrupted upload.

I use the code below to resume an upload. Is this the correct way to set the upload id of a multipart upload?

S3InitiateMultipartUploadRequest *initiateRequest = [[S3InitiateMultipartUploadRequest alloc] initWithKey:key inBucket:bucketName];
S3InitiateMultipartUploadResponse *initiateResponse = [self.amazonS3Client initiateMultipartUpload:initiateRequest];
self.multipartUpload = [initiateResponse multipartUpload];

// Set upload id to resume upload
self.multipartUpload.uploadId = uploadId;

I'd appreciate any help or pointers.

Answer 1

Your code should be robust enough to handle cases where you may need to track which parts were uploaded. Part Uploads of the multipart upload can be done in many ways (either in parallel, multithreaded manner or one after the other in sequence).

Whatever the above approach may be, you can use the listParts API to determine how many parts were successfully uploaded. Since you would already have the upload ID your design must support the ability to continue from the following part upload.

  GET /ObjectName?uploadId=UploadId HTTP/1.1
  Host: BucketName.s3.amazonaws.com
  Date: Date
  Authorization: Signature

Another useful resource to help optimize multipart uploads: http://aws.typepad.com/aws/2010/11/amazon-s3-multipart-upload.html