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// Copyright 2016 Google LLC
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// See the License for the specific language governing permissions and
// limitations under the License.
// Package longrunning supports Long Running Operations for the Google Cloud Libraries.
// See for its service definition.
// Users of the Google Cloud Libraries will typically not use this package directly.
// Instead they will call functions returning Operations and call their methods.
// This package is still experimental and subject to change.
package longrunning // import ""
import (
autogen ""
gax ""
pb ""
// ErrNoMetadata is the error returned by Metadata if the operation contains no metadata.
var ErrNoMetadata = errors.New("operation contains no metadata")
// Operation represents the result of an API call that may not be ready yet.
type Operation struct {
c operationsClient
proto *pb.Operation
type operationsClient interface {
GetOperation(context.Context, *pb.GetOperationRequest, ...gax.CallOption) (*pb.Operation, error)
CancelOperation(context.Context, *pb.CancelOperationRequest, ...gax.CallOption) error
DeleteOperation(context.Context, *pb.DeleteOperationRequest, ...gax.CallOption) error
// InternalNewOperation is for use by the google Cloud Libraries only.
// InternalNewOperation returns an long-running operation, abstracting the raw pb.Operation.
// The conn parameter refers to a server that proto was received from.
func InternalNewOperation(inner *autogen.OperationsClient, proto *pb.Operation) *Operation {
return &Operation{
c: inner,
proto: proto,
// Name returns the name of the long-running operation.
// The name is assigned by the server and is unique within the service
// from which the operation is created.
func (op *Operation) Name() string {
return op.proto.Name
// Done reports whether the long-running operation has completed.
func (op *Operation) Done() bool {
return op.proto.Done
// Metadata unmarshals op's metadata into meta.
// If op does not contain any metadata, Metadata returns ErrNoMetadata and meta is unmodified.
func (op *Operation) Metadata(meta proto.Message) error {
if m := op.proto.Metadata; m != nil {
return ptypes.UnmarshalAny(m, meta)
return ErrNoMetadata
// Poll fetches the latest state of a long-running operation.
// If Poll fails, the error is returned and op is unmodified.
// If Poll succeeds and the operation has completed with failure,
// the error is returned and op.Done will return true.
// If Poll succeeds and the operation has completed successfully,
// op.Done will return true; if resp != nil, the response of the operation
// is stored in resp.
func (op *Operation) Poll(ctx context.Context, resp proto.Message, opts ...gax.CallOption) error {
if !op.Done() {
p, err := op.c.GetOperation(ctx, &pb.GetOperationRequest{Name: op.Name()}, opts...)
if err != nil {
return err
op.proto = p
if !op.Done() {
return nil
switch r := op.proto.Result.(type) {
case *pb.Operation_Error:
// TODO(pongad): r.Details may contain further information
return status.Errorf(codes.Code(r.Error.Code), "%s", r.Error.Message)
case *pb.Operation_Response:
if resp == nil {
return nil
return ptypes.UnmarshalAny(r.Response, resp)
return fmt.Errorf("unsupported result type %[1]T: %[1]v", r)
// DefaultWaitInterval is the polling interval used by Operation.Wait.
const DefaultWaitInterval = 60 * time.Second
// Wait is equivalent to WaitWithInterval using DefaultWaitInterval.
func (op *Operation) Wait(ctx context.Context, resp proto.Message, opts ...gax.CallOption) error {
return op.WaitWithInterval(ctx, resp, DefaultWaitInterval, opts...)
// WaitWithInterval blocks until the operation is completed.
// If resp != nil, Wait stores the response in resp.
// WaitWithInterval polls every interval, except initially
// when it polls using exponential backoff.
// See documentation of Poll for error-handling information.
func (op *Operation) WaitWithInterval(ctx context.Context, resp proto.Message, interval time.Duration, opts ...gax.CallOption) error {
bo := gax.Backoff{
Initial: 1 * time.Second,
Max: interval,
if bo.Max < bo.Initial {
bo.Max = bo.Initial
return op.wait(ctx, resp, &bo, gax.Sleep, opts...)
type sleeper func(context.Context, time.Duration) error
// wait implements Wait, taking exponentialBackoff and sleeper arguments for testing.
func (op *Operation) wait(ctx context.Context, resp proto.Message, bo *gax.Backoff, sl sleeper, opts ...gax.CallOption) error {
for {
if err := op.Poll(ctx, resp, opts...); err != nil {
return err
if op.Done() {
return nil
if err := sl(ctx, bo.Pause()); err != nil {
return err
// Cancel starts asynchronous cancellation on a long-running operation. The server
// makes a best effort to cancel the operation, but success is not
// guaranteed. If the server doesn't support this method, it returns
// status.Code(err) == codes.Unimplemented. Clients can use
// Poll or other methods to check whether the cancellation succeeded or whether the
// operation completed despite cancellation. On successful cancellation,
// the operation is not deleted; instead, op.Poll returns an error
// with code Canceled.
func (op *Operation) Cancel(ctx context.Context, opts ...gax.CallOption) error {
return op.c.CancelOperation(ctx, &pb.CancelOperationRequest{Name: op.Name()}, opts...)
// Delete deletes a long-running operation. This method indicates that the client is
// no longer interested in the operation result. It does not cancel the
// operation. If the server doesn't support this method, status.Code(err) == codes.Unimplemented.
func (op *Operation) Delete(ctx context.Context, opts ...gax.CallOption) error {
return op.c.DeleteOperation(ctx, &pb.DeleteOperationRequest{Name: op.Name()}, opts...)