---
title: "completeMultipartUpload | Grafana k6 documentation"
description: "S3Client.completeMultipartUpload uploads a multipar object to a bucket"
---

> For a curated documentation index, see [llms.txt](/llms.txt). For the complete documentation index, see [llms-full.txt](/llms-full.txt).

# completeMultipartUpload

`S3Client.completeMultipartUpload` uploads a multipart object to an S3 bucket.

### Parameters

Expand table

| Parameter  | Type                                                                              | Description                                                                           |
|------------|-----------------------------------------------------------------------------------|---------------------------------------------------------------------------------------|
| bucketName | string                                                                            | Name of the bucket to delete the object to.                                           |
| objectKey  | string                                                                            | Name of the uploaded object.                                                          |
| uploadId   | number                                                                            | UploadId of the multipart upload to complete.                                         |
| parts      | Array< [S3Part](/docs/k6/latest/javascript-api/jslib/aws/s3client/s3part/)> | The [S3Part](/docs/k6/latest/javascript-api/jslib/aws/s3client/s3part/)s to assemble. |

### Returns

Expand table

| Type                                                                                                    | Description                                                                                                                                                                                                              |
|---------------------------------------------------------------------------------------------------------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| Promise< [S3UploadedObject](/docs/k6/latest/javascript-api/jslib/aws/s3client/s3uploadedobject/)> | A Promise that fulfills with an [S3UploadedObject](/docs/k6/latest/javascript-api/jslib/aws/s3client/s3uploadedobject/) containing metadata about the completed multipart upload, including ETag and optional checksums. |

### Example

JavaScript ![Copy code to clipboard](/media/images/icons/icon-copy-small-2.svg) Copy

```javascript
import crypto from 'k6/crypto';
import exec from 'k6/execution';

import {
  AWSConfig,
  S3Client,
} from 'https://jslib.k6.io/aws/0.14.0/s3.js';

const awsConfig = new AWSConfig({
  region: __ENV.AWS_REGION,
  accessKeyId: __ENV.AWS_ACCESS_KEY_ID,
  secretAccessKey: __ENV.AWS_SECRET_ACCESS_KEY,
  sessionToken: __ENV.AWS_SESSION_TOKEN,
});

const s3 = new S3Client(awsConfig);

const testBucketName = 'test-jslib-aws';
const testFileKey = 'multipart.txt';

export default async function () {
  // List the buckets the AWS authentication configuration
  // gives us access to.
  const buckets = await s3.listBuckets();

  // If our test bucket does not exist, abort the execution.
  if (buckets.filter((b) => b.name === testBucketName).length == 0) {
    exec.test.abort();
  }

  // Produce random bytes to upload of size ~12MB, that
  // we will upload in two 6MB parts. This is done as the
  // minimum part size supported by S3 is 5MB.
  const bigFile = crypto.randomBytes(12 * 1024 * 1024);

  // Initialize a multipart upload
  const multipartUpload = await s3.createMultipartUpload(testBucketName, testFileKey);

  // Upload the first part
  const firstPartData = bigFile.slice(0, 6 * 1024 * 1024);
  const firstPart = await s3.uploadPart(
    testBucketName,
    testFileKey,
    multipartUpload.uploadId,
    1,
    firstPartData
  );

  // Upload the second part
  const secondPartData = bigFile.slice(6 * 1024 * 1024, 12 * 1024 * 1024);
  const secondPart = await s3.uploadPart(
    testBucketName,
    testFileKey,
    multipartUpload.uploadId,
    2,
    secondPartData
  );

  // Complete the multipart upload
  const uploadResult = await s3.completeMultipartUpload(
    testBucketName,
    testFileKey,
    multipartUpload.uploadId,
    [firstPart, secondPart]
  );

  // Access the upload metadata
  console.log('Multipart upload completed! ETag:', uploadResult.eTag);

  if (uploadResult.size) {
    console.log('Total object size:', uploadResult.size);
  }

  // For multipart uploads, the checksum type will typically be "COMPOSITE"
  if (uploadResult.checksumType) {
    console.log('Checksum type:', uploadResult.checksumType);
  }

  // Let's redownload it verify it's correct, and delete it
  const obj = await s3.getObject(testBucketName, testFileKey);
  await s3.deleteObject(testBucketName, testFileKey);
}
```

*A k6 script that will upload a multipart upload to an S3 bucket*