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// Copyright 2017 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 pubsub
import (
pb ""
// Snapshot is a reference to a PubSub snapshot.
type Snapshot struct {
c *Client
// The fully qualified identifier for the snapshot, in the format "projects/<projid>/snapshots/<snap>"
name string
// ID returns the unique identifier of the snapshot within its project.
func (s *Snapshot) ID() string {
slash := strings.LastIndex(, "/")
if slash == -1 {
// name is not a fully-qualified name.
panic("bad snapshot name")
// SnapshotConfig contains the details of a Snapshot.
type SnapshotConfig struct {
Topic *Topic
Expiration time.Time
// Snapshot creates a reference to a snapshot.
func (c *Client) Snapshot(id string) *Snapshot {
return &Snapshot{
c: c,
name: fmt.Sprintf("projects/%s/snapshots/%s", c.projectID, id),
// Snapshots returns an iterator which returns snapshots for this project.
func (c *Client) Snapshots(ctx context.Context) *SnapshotConfigIterator {
it := c.subc.ListSnapshots(ctx, &pb.ListSnapshotsRequest{
Project: c.fullyQualifiedProjectName(),
next := func() (*SnapshotConfig, error) {
snap, err := it.Next()
if err != nil {
return nil, err
return toSnapshotConfig(snap, c)
return &SnapshotConfigIterator{next: next}
// SnapshotConfigIterator is an iterator that returns a series of snapshots.
type SnapshotConfigIterator struct {
next func() (*SnapshotConfig, error)
// Next returns the next SnapshotConfig. Its second return value is iterator.Done if there are no more results.
// Once Next returns iterator.Done, all subsequent calls will return iterator.Done.
func (snaps *SnapshotConfigIterator) Next() (*SnapshotConfig, error) {
// Delete deletes a snapshot.
func (s *Snapshot) Delete(ctx context.Context) error {
return s.c.subc.DeleteSnapshot(ctx, &pb.DeleteSnapshotRequest{Snapshot:})
// SeekToTime seeks the subscription to a point in time.
// Messages retained in the subscription that were published before this
// time are marked as acknowledged, and messages retained in the
// subscription that were published after this time are marked as
// unacknowledged. Note that this operation affects only those messages
// retained in the subscription (configured by SnapshotConfig). For example,
// if `time` corresponds to a point before the message retention
// window (or to a point before the system's notion of the subscription
// creation time), only retained messages will be marked as unacknowledged,
// and already-expunged messages will not be restored.
func (s *Subscription) SeekToTime(ctx context.Context, t time.Time) error {
ts := timestamppb.New(t)
_, err := s.c.subc.Seek(ctx, &pb.SeekRequest{
Target: &pb.SeekRequest_Time{Time: ts},
return err
// CreateSnapshot creates a new snapshot from this subscription.
// The snapshot will be for the topic this subscription is subscribed to.
// If the name is empty string, a unique name is assigned.
// The created snapshot is guaranteed to retain:
// (a) The existing backlog on the subscription. More precisely, this is
// defined as the messages in the subscription's backlog that are
// unacknowledged when Snapshot returns without error.
// (b) Any messages published to the subscription's topic following
// Snapshot returning without error.
func (s *Subscription) CreateSnapshot(ctx context.Context, name string) (*SnapshotConfig, error) {
if name != "" {
name = fmt.Sprintf("projects/%s/snapshots/%s", strings.Split(, "/")[1], name)
snap, err := s.c.subc.CreateSnapshot(ctx, &pb.CreateSnapshotRequest{
Name: name,
if err != nil {
return nil, err
return toSnapshotConfig(snap, s.c)
// SeekToSnapshot seeks the subscription to a snapshot.
// The snapshot need not be created from this subscription,
// but it must be for the topic this subscription is subscribed to.
func (s *Subscription) SeekToSnapshot(ctx context.Context, snap *Snapshot) error {
_, err := s.c.subc.Seek(ctx, &pb.SeekRequest{
Target: &pb.SeekRequest_Snapshot{Snapshot:},
return err
func toSnapshotConfig(snap *pb.Snapshot, c *Client) (*SnapshotConfig, error) {
exp := snap.ExpireTime.AsTime()
return &SnapshotConfig{
Snapshot: &Snapshot{c: c, name: snap.Name},
Topic: newTopic(c, snap.Topic),
Expiration: exp,
}, nil