S3 EntityTooSmall error encountered during multipart upload.

What is S3 EntityTooSmall error encountered during multipart upload.

Understanding Amazon S3 and Its Purpose

Amazon Simple Storage Service (S3) is a scalable object storage service provided by AWS. It is designed to store and retrieve any amount of data from anywhere on the web. S3 is commonly used for backup and restore, data archiving, and as a data lake for analytics.

Identifying the Symptom: EntityTooSmall Error

When using Amazon S3 for multipart uploads, you might encounter the EntityTooSmall error. This error typically occurs when one of the parts uploaded is smaller than the minimum required size.

What You Observe

During a multipart upload, you receive an error message indicating that the entity is too small. This interrupts the upload process and prevents the completion of the file upload.

Explaining the EntityTooSmall Issue

The EntityTooSmall error is triggered when a part of a multipart upload is less than 5 MB in size, except for the last part. Amazon S3 requires each part to meet this minimum size requirement to ensure efficient storage and retrieval.

Why This Happens

This issue often arises when the logic for dividing a file into parts does not account for the minimum size requirement, or when the file size is miscalculated.

Steps to Resolve the EntityTooSmall Error

To resolve this issue, follow these steps:

Step 1: Verify Part Sizes

Ensure that each part of your multipart upload is at least 5 MB in size, except for the last part. You can use the AWS SDKs or the AWS CLI to check the size of each part before uploading.

aws s3api list-parts --bucket your-bucket-name --key your-object-key --upload-id your-upload-id

Step 2: Adjust Part Size Logic

Modify your application logic to ensure that each part meets the minimum size requirement. This might involve adjusting the chunk size or the way the file is split.

Step 3: Re-upload Parts

If you have identified parts that are too small, re-upload those parts with the correct size. You can use the AWS CLI or an SDK to upload the corrected parts.

aws s3api upload-part --bucket your-bucket-name --key your-object-key --part-number part-number --upload-id your-upload-id --body file-part

Additional Resources

For more information on multipart uploads and handling errors, refer to the AWS S3 Multipart Upload Overview and the AWS S3 Error Responses documentation.