Merge pull request #100 from buildkite/feat_s3_copy_on_download

feat: ensure that when we read an object we also copy it

Author: wolfeidau

sam/app/cache-bucket.cfn.yml

@@ -13,6 +13,10 @@ Parameters:
     Type: String
     Description: The prefix for the cache bucket name
     Default: buildkite-caches
+  ExpirationInDays:
+    Type: Number
+    Description: The number of days to expire cache objects
+    Default: 7
 Outputs:
   CacheBucketAccessRole:
     Value:
@@ -95,6 +99,11 @@ Resources:
       NotificationConfiguration:
         EventBridgeConfiguration:
           EventBridgeEnabled: true
+      LifecycleConfiguration:
+        Rules:
+        - Id: ExpireCacheObjects
+          Status: Enabled
+          ExpirationInDays: !Ref ExpirationInDays
 
   CacheBucketPolicy:
     Type: AWS::S3::BucketPolicy

store/s3.go

@@ -329,6 +329,24 @@ func (b *S3Blob) Download(ctx context.Context, key string, destPath string) (*Tr
 		attribute.Int("concurrency", b.concurrency),
 	)
 
+	// Copy the object to itself to reset the LastModified timestamp,
+	// which extends the lifecycle expiration.
+	copySource := fmt.Sprintf("%s/%s", b.bucketName, fullKey)
+	_, err = b.client.CopyObject(ctx, &s3.CopyObjectInput{
+		Bucket:            aws.String(b.bucketName),
+		Key:               aws.String(fullKey),
+		CopySource:        aws.String(copySource),
+		MetadataDirective: "REPLACE",
+	})
+	if err != nil {
+		return nil, fmt.Errorf("failed to refresh object expiration: %w", err)
+	}
+
+	slog.Debug("refreshed object expiration",
+		"key", fullKey,
+		"bucket", b.bucketName,
+	)
+
 	return &TransferInfo{
 		BytesTransferred: bytesWritten,
 		TransferSpeed:    averageSpeed,