Multipart concurrent chunk upload is inefficient.

[arunj-kp]

Describe the bug
This PR(2804) unblocked us to try concurrent multipart upload and it is a great change. But, unfortunately, there is a bug in this feature. Redundant part uploads are happening. I uploaded a 7.8MB file with two parts (Part1: 5MB, Part2: 2.8MB) as I opted for the smallest chunk size of 5MB. But, AWS SDK uploaded five parts like 2(Part2),1(Part1),2,1,2 (That is, Part2 uploaded three times and Part1 two times) [Screenshot of the part upload sequence attached below]

To Reproduce

• Enable more number of threads (I set 10 threads)
• Upload a file (I uploaded 7.8MB file)
• Monitor network traffic. I used CharlesProxy, I could see concurrent part uploads happening but keeps on uploading already uploaded parts
• Finally succeeds
  This is a major performance issue in this feature and the feature is inefficient to use in a production app (uploaded around 20MB for a 7.8MB file)

A code sample or steps:

        val awsTempCredentials = BasicSessionCredentials(
            uploadKeyMap[ACCESS_KEY], uploadKeyMap[SECRET_KEY], uploadKeyMap[SESSION_TOKEN]
        )
        val awsClient = AmazonS3Client(awsTempCredentials, ClientConfiguration())
        awsClient.setS3ClientOptions(S3ClientOptions.builder().setAccelerateModeEnabled(true).build())
        val tuOptions = TransferUtilityOptions()
        tuOptions.transferThreadPoolSize = 1
        transferUtility = TransferUtility.builder()
            .s3Client(awsClient)
            .context(applicationContext)
            .transferUtilityOptions(tuOptions)
            .defaultBucket(uploadKeyMap[S3_BUCKET_NAME])
            .build()

            val uploadObserver = transferUtility?.upload(uploadKeyMap[UPLOAD_KEY], mediaFile)

            Single.create<TransferState> { emitter ->
                uploadObserver?.setTransferListener(UploadListener(emitter))
            }.blockingGet()

Which AWS service(s) are affected?
S3 file upload

Expected behavior
Redundant part uploads should not be happened. For a 7.8MB file, only 2 parts to be uploaded if the max part size is selected as 5MB.

Screenshots
If applicable, add screenshots to help explain your problem.

Environment Information (please complete the following information):

• AWS Android SDK Version: 2.41.1
• Device: Samsung J7
• Android Version: 9
• Specific to simulators: No

Additional context
Add any other context about the problem here.

[sdhuka]

Discussed this offline with OP and not able to repro, if required please re-open.