Fix AWS S3 Large File Upload Failures: InvalidPart Error

by Sebastian Müller 57 views

Uploading large files to AWS S3 can sometimes be tricky, especially when dealing with the dreaded InvalidPart error. This article dives into a common issue encountered when using the AWS SDK for Go v2, specifically the InvalidPart error during multipart uploads. We'll explore the problem, discuss potential causes, and provide a comprehensive guide to troubleshooting and resolving this frustrating issue.

Understanding the InvalidPart Error

When you're working with large files in AWS S3, you'll often use multipart uploads. This process breaks the file into smaller parts, uploads them individually, and then assembles them on the S3 side. This approach is more efficient and resilient for large files, but it also introduces complexity. The InvalidPart error typically arises during the final stage of the multipart upload process, when S3 attempts to assemble the parts. The error message, "One or more of the specified parts could not be found. The part may not have been uploaded, or the specified entity tag may not match the part's entity tag," can be cryptic, but it essentially means that something went wrong with one or more of the parts.

Common Causes of the InvalidPart Error

To effectively troubleshoot this error, it's essential to understand the common culprits. Here are some frequent reasons why you might encounter the InvalidPart error:

  1. Incomplete Uploads: One or more parts may have failed to upload completely due to network issues, timeouts, or other transient errors. This is perhaps the most common cause. When dealing with large files, network hiccups can interrupt the upload process, leaving some parts stranded.
  2. Incorrect Part Numbers: The part numbers are crucial for S3 to assemble the file correctly. If there's a mismatch between the part numbers sent during the upload and the part numbers in the final CompleteMultipartUpload request, you'll encounter this error. Ensuring the correct sequence and numbering of parts is vital.
  3. ETag Mismatches: Each part uploaded to S3 has an associated ETag (Entity Tag), which is a unique identifier. When S3 assembles the parts, it verifies that the ETags match the ones provided in the CompleteMultipartUpload request. If an ETag doesn't match, it indicates that the part may have been corrupted or replaced. Think of ETags as fingerprints for your file parts, ensuring integrity during the upload.
  4. Concurrency Issues: When uploading parts concurrently, especially without proper synchronization, you might run into issues where parts are not uploaded in the correct order or some uploads are interrupted. While concurrency can speed up uploads, it also adds complexity in managing the upload sequence.
  5. Insufficient Retries: Transient errors can occur during uploads. If your code doesn't implement retries for failed uploads, a temporary network issue could lead to a permanent InvalidPart error. Implementing a robust retry mechanism is essential for handling flaky connections.
  6. Incorrect SDK Configuration: Misconfigured SDK settings, such as incorrect region or credentials, can also lead to upload failures and the InvalidPart error. Always double-check your SDK configuration to ensure it aligns with your S3 bucket settings.

Analyzing the Provided Code Snippet

Let's examine the provided Go code snippet to identify potential issues and areas for improvement.

s3UploadManager := manager.NewUploader(s3Client, func(u *manager.Uploader) {
    // Use larger part size for better performance with large files
    u.PartSize = 100 * 1024 * 1024 // 100MB parts
    u.Concurrency = 1 // No concurrency to avoid overwhelming the system
    u.LeavePartsOnError = false // Clean up failed parts
})
file, err := os.Open(filePath) // filepath of a large file
if err != nil {
    return fmt.Errorf("could not open file %v to upload. Here's why: %v", filePath, err)
}
defer file.Close()
_, err = s3UploadManager.Upload(ctx, &s3.PutObjectInput{
    Bucket:               aws.String(s.bucket),
    Key:                  aws.String(key),
    Body:                 file,
    ContentLength:        aws.Int64(fileSize),
    ACL:                  types.ObjectCannedACLBucketOwnerFullControl,
    ServerSideEncryption: types.ServerSideEncryptionAes256,
})

Key Observations

  1. Uploader Configuration: The code configures the manager.Uploader with a 100MB part size and a concurrency of 1. This means that parts are uploaded sequentially, which reduces the risk of concurrency issues but may increase the overall upload time. The LeavePartsOnError is set to false, which is good practice for cleaning up failed uploads.
  2. File Handling: The code opens the file using os.Open and defers the file.Close() call. This ensures that the file is closed properly, even if errors occur.
  3. Upload Call: The s3UploadManager.Upload function is used to upload the file. This function handles the multipart upload process behind the scenes.
  4. Error Handling: The code checks for errors when opening the file and returns an error if one occurs. However, it doesn't explicitly handle errors during the upload process itself.

Potential Problem Areas

While the code appears to be well-structured, there are some areas where improvements can be made to address the InvalidPart error:

  1. Lack of Retry Mechanism: The code doesn't include a retry mechanism for failed uploads. Transient errors can occur, and retrying the upload can often resolve the issue. Implementing a retry strategy is crucial for robust file uploads.
  2. Missing Error Logging: The code doesn't log detailed information about the error, which makes it difficult to diagnose the root cause. Adding logging to capture the specific error message, request ID, and other relevant details can significantly aid in troubleshooting.
  3. No Part-Level Verification: The code relies on the manager.Uploader to handle the multipart upload process, but it doesn't explicitly verify that each part was uploaded successfully. Adding part-level verification can help identify issues with individual parts.

Troubleshooting Steps and Solutions

Now, let's delve into specific troubleshooting steps and solutions to address the InvalidPart error.

1. Implement a Retry Mechanism

As mentioned earlier, transient errors are a common cause of upload failures. Implementing a retry mechanism can automatically handle these errors, improving the reliability of your uploads. You can use a simple retry loop with exponential backoff to retry failed uploads.

Here's an example of how to add a retry mechanism to your code:

import (
	"fmt"
	"github.com/aws/aws-sdk-go-v2/aws"
	"github.com/aws/aws-sdk-go-v2/service/s3"
	"github.com/aws/aws-sdk-go-v2/service/s3/types"
	"github.com/aws/aws-sdk-go-v2/feature/s3/manager"
	"os"
	"time"
)

// retryUploadWithBackoff retries the upload with exponential backoff.
func retryUploadWithBackoff(ctx aws.Context, s3UploadManager *manager.Uploader, input *s3.PutObjectInput, maxRetries int) error {
	for i := 0; i <= maxRetries; i++ {
		_, err := s3UploadManager.Upload(ctx, input)
		if err == nil {
			return nil // Upload successful
		}
		fmt.Printf("Upload failed (attempt %d): %v\n", i+1, err)
		if i == maxRetries {
			return fmt.Errorf("upload failed after %d retries: %v", maxRetries, err)
		}
		// Exponential backoff
		delay := time.Duration(i) * time.Second
		time.Sleep(delay)
	}
	return fmt.Errorf("unknown error occurred during retry") // should not reach here
}


// UploadFile uploads a file to S3 with retries.
func UploadFile(ctx aws.Context, s3Client *s3.Client, bucket, key, filePath string, fileSize int64) error {
	s3UploadManager := manager.NewUploader(s3Client, func(u *manager.Uploader) {
		// Use larger part size for better performance with large files
		u.PartSize = 100 * 1024 * 1024 // 100MB parts
		u.Concurrency = 1             // No concurrency to avoid overwhelming the system
		u.LeavePartsOnError = false    // Clean up failed parts
	})

	file, err := os.Open(filePath) // filepath of a large file
	if err != nil {
		return fmt.Errorf("could not open file %v to upload: %v", filePath, err)
	}
	defer file.Close()

	input := &s3.PutObjectInput{
		Bucket:               aws.String(bucket),
		Key:                  aws.String(key),
		Body:                 file,
		ContentLength:        aws.Int64(fileSize),
		ACL:                  types.ObjectCannedACLBucketOwnerFullControl,
		ServerSideEncryption: types.ServerSideEncryptionAes256,
	}

	maxRetries := 3 // Define the maximum number of retries
	err = retryUploadWithBackoff(ctx, s3UploadManager, input, maxRetries)
	if err != nil {
		return fmt.Errorf("upload failed: %v", err)
	}

	fmt.Println("File uploaded successfully.")
	return nil
}

In this example, the retryUploadWithBackoff function attempts to upload the file multiple times, with an increasing delay between each attempt. This helps to mitigate transient network issues.

2. Add Detailed Logging

Detailed logging is essential for diagnosing upload failures. Add logging statements to capture the specific error message, request ID, and other relevant details. This information can help you pinpoint the root cause of the InvalidPart error.

Here's how you can add logging to your code:

import (
	"fmt"
	"github.com/aws/aws-sdk-go-v2/aws"
	"github.com/aws/aws-sdk-go-v2/service/s3"
	"github.com/aws/aws-sdk-go-v2/service/s3/types"
	"github.com/aws/aws-sdk-go-v2/feature/s3/manager"
	"os"
	"time"
	"log"
)

// retryUploadWithBackoff retries the upload with exponential backoff.
func retryUploadWithBackoff(ctx aws.Context, s3UploadManager *manager.Uploader, input *s3.PutObjectInput, maxRetries int) error {
	for i := 0; i <= maxRetries; i++ {
		_, err := s3UploadManager.Upload(ctx, input)
		if err == nil {
			return nil // Upload successful
		}

		// Log the error with details
		log.Printf("Upload failed (attempt %d): %v", i+1, err)
		if apiErr, ok := err.(aws.APIError); ok {
			log.Printf("  Request ID: %s", apiErr.RequestID())
			log.Printf("  Code: %s", apiErr.Code())
		}

		if i == maxRetries {
			return fmt.Errorf("upload failed after %d retries: %v", maxRetries, err)
		}
		// Exponential backoff
		delay := time.Duration(i) * time.Second
		time.Sleep(delay)
	}
	return fmt.Errorf("unknown error occurred during retry") // should not reach here
}

// UploadFile uploads a file to S3 with retries and logging.
func UploadFile(ctx aws.Context, s3Client *s3.Client, bucket, key, filePath string, fileSize int64) error {
	s3UploadManager := manager.NewUploader(s3Client, func(u *manager.Uploader) {
		// Use larger part size for better performance with large files
		u.PartSize = 100 * 1024 * 1024 // 100MB parts
		u.Concurrency = 1             // No concurrency to avoid overwhelming the system
		u.LeavePartsOnError = false    // Clean up failed parts
	})

	file, err := os.Open(filePath) // filepath of a large file
	if err != nil {
		return fmt.Errorf("could not open file %v to upload: %v", filePath, err)
	}
	defer file.Close()

	input := &s3.PutObjectInput{
		Bucket:               aws.String(bucket),
		Key:                  aws.String(key),
		Body:                 file,
		ContentLength:        aws.Int64(fileSize),
		ACL:                  types.ObjectCannedACLBucketOwnerFullControl,
		ServerSideEncryption: types.ServerSideEncryptionAes256,
	}

	maxRetries := 3 // Define the maximum number of retries
	err = retryUploadWithBackoff(ctx, s3UploadManager, input, maxRetries)
	if err != nil {
		return fmt.Errorf("upload failed: %v", err)
	}

	fmt.Println("File uploaded successfully.")
	return nil
}

This code logs the error message and, if the error is an aws.APIError, it also logs the request ID and error code. This additional information can be invaluable for troubleshooting.

3. Consider Part-Level Verification

While the manager.Uploader simplifies the multipart upload process, it doesn't provide explicit feedback on the success of individual part uploads. For critical uploads, you might want to consider implementing part-level verification.

This involves:

  1. Using Low-Level API: Instead of using manager.Uploader, you can use the low-level S3 API to upload parts individually.
  2. Tracking Uploaded Parts: Keep track of the parts that have been successfully uploaded, including their part numbers and ETags.
  3. Verifying Parts Before Completion: Before calling CompleteMultipartUpload, verify that all parts have been uploaded successfully and that their ETags match the expected values.

Here's a conceptual outline of how you might implement part-level verification:

// 1. Initialize a multipart upload
createMultipartUploadOutput, err := s3Client.CreateMultipartUpload(ctx, &s3.CreateMultipartUploadInput{ /* ... */ })
if err != nil {
    // Handle error
}
uploadID := *createMultipartUploadOutput.UploadId

// 2. Upload parts individually
var completedParts []types.CompletedPart
partNumber := 1
for {
    // Read a part from the file
    // ...

    // Upload the part
    uploadPartOutput, err := s3Client.UploadPart(ctx, &s3.UploadPartInput{ /* ... */ })
    if err != nil {
        // Handle error, retry if necessary
    }

    // Store the completed part information
    completedParts = append(completedParts, types.CompletedPart{
        ETag:       uploadPartOutput.ETag,
        PartNumber: int32(partNumber),
    })

    partNumber++
    // Break if end of file
    // ...
}

// 3. Complete the multipart upload
completeMultipartUploadOutput, err := s3Client.CompleteMultipartUpload(ctx, &s3.CompleteMultipartUploadInput{
    Bucket:          aws.String(bucket),
    Key:             aws.String(key),
    UploadId:        aws.String(uploadID),
    MultipartUpload: &types.CompletedMultipartUpload{
        Parts: completedParts,
    },
})
if err != nil {
    // Handle error
}

This approach provides more control over the upload process and allows you to verify that each part is uploaded correctly.

4. Check SDK and Dependency Versions

Ensure that you're using the latest versions of the AWS SDK for Go v2 and its dependencies. Outdated versions may contain bugs or issues that have been resolved in newer releases.

You can update your dependencies using go get:

go get -u github.com/aws/aws-sdk-go-v2/...
go get -u github.com/aws/aws-sdk-go-v2/config
go get -u github.com/aws/aws-sdk-go-v2/feature/s3/manager
go get -u github.com/aws/aws-sdk-go-v2/service/s3

5. Review S3 Bucket Configuration

Double-check your S3 bucket configuration, including:

  • Permissions: Ensure that your IAM role or user has the necessary permissions to upload objects to the bucket.
  • Bucket Policy: Verify that the bucket policy doesn't have any restrictions that might prevent uploads.
  • Encryption: If server-side encryption is enabled, ensure that you're providing the correct encryption headers in your upload requests.

6. Network Connectivity

Ensure that your application has a stable network connection to S3. Network issues can interrupt uploads and lead to the InvalidPart error. Consider testing your network connection and monitoring it during uploads.

7. Increase Timeout Values

In some cases, the default timeout values for S3 operations may be too short for large file uploads. You can try increasing the timeout values to allow more time for uploads to complete.

Here's how you can configure timeout values in the AWS SDK for Go v2:

import (
	"context"
	"time"

	"github.com/aws/aws-sdk-go-v2/config"
	"github.com/aws/aws-sdk-go-v2/aws"
	"github.com/aws/aws-sdk-go-v2/service/s3"
)

func main() {
	// Load the Shared AWS Configuration (~/.aws/config)
	cfg, err := config.LoadDefaultConfig(context.TODO(),
		config.WithRegion("YOUR_REGION"),
		config.WithClientOptions(func(options *aws.ClientOptions) {
			options.Timeout = time.Duration(15 * time.Minute) // Set the global timeout to 15 minutes
		}),
	)
	if err != nil {
		panic("error loading AWS configuration: " + err.Error())
	}

	// Create an Amazon S3 service client
	client := s3.NewFromConfig(cfg)

	// Use the client to perform S3 operations
	_ = client
}

8. Monitor S3 Performance

AWS provides tools for monitoring S3 performance, such as CloudWatch metrics. Monitor your S3 bucket's performance to identify any potential bottlenecks or issues that might be affecting uploads.

Conclusion

The InvalidPart error during S3 multipart uploads can be a challenging issue to troubleshoot, but by understanding the common causes and following the steps outlined in this article, you can effectively diagnose and resolve the problem. Remember to implement a retry mechanism, add detailed logging, consider part-level verification, and check your SDK and S3 bucket configuration. By taking these steps, you can ensure the reliable and efficient upload of large files to AWS S3. Happy uploading, guys!

If you're still scratching your head, don't hesitate to reach out to the AWS support community or dive deeper into the AWS documentation. There's a wealth of information and expertise out there to help you conquer those tricky S3 upload challenges. Keep experimenting, keep learning, and you'll become an S3 upload master in no time!