api: add x-amz-bucket-region header to HeadBucket response

api/api.go

@@ -48,6 +48,12 @@ type API struct {
 	config Config
 }
 
+// BucketLocationGetter is an interface for getting bucket location.
+// This is implemented by the gateway layer to fetch bucket region/location.
+type BucketLocationGetter interface {
+	GetBucketLocation(ctx context.Context, bucketName string) (string, error)
+}
+
 // New constructs a new S3-compatible HTTP API.
 func New(objectAPI cmd.ObjectLayer, credsProvider awsig.CredentialsProvider[AuthData], config Config) *API {
 	v2v4 := awsig.NewV2V4(credsProvider, awsig.V4Config{

api/buckethandlers.go

@@ -302,9 +302,24 @@ func (api *API) HeadBucketHandler(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	if _, err := api.objectAPI.GetBucketInfo(ctx, bucketName); err != nil {
-		writeErrorResponseHeadersOnly(w, cmd.ToAPIError(ctx, err))
-		return
+	// TODO: Add GetBucketLocation to the object layer interface in storj/minio
+	// instead of using type assertion. This would allow us to make a single call
+	// instead of two separate calls (GetBucketInfo + GetBucketLocation).
+	if locationGetter, ok := api.objectAPI.(BucketLocationGetter); ok {
+		location, err := locationGetter.GetBucketLocation(ctx, bucketName)
+		if err != nil {
+			writeErrorResponseHeadersOnly(w, cmd.ToAPIError(ctx, err))
+			return
+		}
+		if location != "" {
+			w.Header().Set(xhttp.AmzBucketRegion, location)
+		}
+	} else {
+		// Fallback to GetBucketInfo if GetBucketLocation is not available
+		if _, err := api.objectAPI.GetBucketInfo(ctx, bucketName); err != nil {
+			writeErrorResponseHeadersOnly(w, cmd.ToAPIError(ctx, err))
+			return
+		}
 	}
 
 	writeSuccessResponseHeadersOnly(w)

miniogw/gateway.go

@@ -346,6 +346,27 @@ func (layer *gatewayLayer) GetBucketInfo(ctx context.Context, bucketName string)
 	}, nil
 }
 
+// GetBucketLocation returns the location/region of a bucket.
+func (layer *gatewayLayer) GetBucketLocation(ctx context.Context, bucketName string) (location string, err error) {
+	defer mon.Task()(&ctx)(&err)
+
+	if err := ValidateBucket(ctx, bucketName); err != nil {
+		return "", minio.BucketNameInvalid{Bucket: bucketName}
+	}
+
+	project, err := projectFromContext(ctx, bucketName, "")
+	if err != nil {
+		return "", err
+	}
+
+	location, err = bucket.GetBucketLocation(ctx, project, bucketName)
+	if err != nil {
+		return "", ConvertError(err, bucketName, "")
+	}
+
+	return location, nil
+}
+
 func (layer *gatewayLayer) ListBuckets(ctx context.Context) (items []minio.BucketInfo, err error) {
 	defer mon.Task()(&ctx)(&err)