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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
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package pubsub
import (
"context"
"errors"
"fmt"
"io"
"strings"
"sync"
"time"
"cloud.google.com/go/iam"
"cloud.google.com/go/internal/optional"
"github.com/golang/protobuf/ptypes"
durpb "github.com/golang/protobuf/ptypes/duration"
gax "github.com/googleapis/gax-go/v2"
"golang.org/x/sync/errgroup"
pb "google.golang.org/genproto/googleapis/pubsub/v1"
fmpb "google.golang.org/genproto/protobuf/field_mask"
"google.golang.org/grpc"
"google.golang.org/grpc/codes"
)
// Subscription is a reference to a PubSub subscription.
type Subscription struct {
c *Client
// The fully qualified identifier for the subscription, in the format "projects/<projid>/subscriptions/<name>"
name string
// Settings for pulling messages. Configure these before calling Receive.
ReceiveSettings ReceiveSettings
mu sync.Mutex
receiveActive bool
}
// Subscription creates a reference to a subscription.
func (c *Client) Subscription(id string) *Subscription {
return c.SubscriptionInProject(id, c.projectID)
}
// SubscriptionInProject creates a reference to a subscription in a given project.
func (c *Client) SubscriptionInProject(id, projectID string) *Subscription {
return &Subscription{
c: c,
name: fmt.Sprintf("projects/%s/subscriptions/%s", projectID, id),
}
}
// String returns the globally unique printable name of the subscription.
func (s *Subscription) String() string {
return s.name
}
// ID returns the unique identifier of the subscription within its project.
func (s *Subscription) ID() string {
slash := strings.LastIndex(s.name, "/")
if slash == -1 {
// name is not a fully-qualified name.
panic("bad subscription name")
}
return s.name[slash+1:]
}
// Subscriptions returns an iterator which returns all of the subscriptions for the client's project.
func (c *Client) Subscriptions(ctx context.Context) *SubscriptionIterator {
it := c.subc.ListSubscriptions(ctx, &pb.ListSubscriptionsRequest{
Project: c.fullyQualifiedProjectName(),
})
return &SubscriptionIterator{
c: c,
next: func() (string, error) {
sub, err := it.Next()
if err != nil {
return "", err
}
return sub.Name, nil
},
}
}
// SubscriptionIterator is an iterator that returns a series of subscriptions.
type SubscriptionIterator struct {
c *Client
next func() (string, error)
}
// Next returns the next subscription. If there are no more subscriptions, iterator.Done will be returned.
func (subs *SubscriptionIterator) Next() (*Subscription, error) {
subName, err := subs.next()
if err != nil {
return nil, err
}
return &Subscription{c: subs.c, name: subName}, nil
}
// PushConfig contains configuration for subscriptions that operate in push mode.
type PushConfig struct {
// A URL locating the endpoint to which messages should be pushed.
Endpoint string
// Endpoint configuration attributes. See https://cloud.google.com/pubsub/docs/reference/rest/v1/projects.subscriptions#pushconfig for more details.
Attributes map[string]string
}
func (pc *PushConfig) toProto() *pb.PushConfig {
return &pb.PushConfig{
Attributes: pc.Attributes,
PushEndpoint: pc.Endpoint,
}
}
// SubscriptionConfig describes the configuration of a subscription.
type SubscriptionConfig struct {
Topic *Topic
PushConfig PushConfig
// The default maximum time after a subscriber receives a message before
// the subscriber should acknowledge the message. Note: messages which are
// obtained via Subscription.Receive need not be acknowledged within this
// deadline, as the deadline will be automatically extended.
AckDeadline time.Duration
// Whether to retain acknowledged messages. If true, acknowledged messages
// will not be expunged until they fall out of the RetentionDuration window.
RetainAckedMessages bool
// How long to retain messages in backlog, from the time of publish. If
// RetainAckedMessages is true, this duration affects the retention of
// acknowledged messages, otherwise only unacknowledged messages are retained.
// Defaults to 7 days. Cannot be longer than 7 days or shorter than 10 minutes.
RetentionDuration time.Duration
// Expiration policy specifies the conditions for a subscription's expiration.
// A subscription is considered active as long as any connected subscriber is
// successfully consuming messages from the subscription or is issuing
// operations on the subscription. If `expiration_policy` is not set, a
// *default policy* with `ttl` of 31 days will be used. The minimum allowed
// value for `expiration_policy.ttl` is 1 day.
//
// Use time.Duration(0) to indicate that the subscription should never expire.
//
// It is EXPERIMENTAL and subject to change or removal without notice.
ExpirationPolicy optional.Duration
// The set of labels for the subscription.
Labels map[string]string
}
func (cfg *SubscriptionConfig) toProto(name string) *pb.Subscription {
var pbPushConfig *pb.PushConfig
if cfg.PushConfig.Endpoint != "" || len(cfg.PushConfig.Attributes) != 0 {
pbPushConfig = &pb.PushConfig{
Attributes: cfg.PushConfig.Attributes,
PushEndpoint: cfg.PushConfig.Endpoint,
}
}
var retentionDuration *durpb.Duration
if cfg.RetentionDuration != 0 {
retentionDuration = ptypes.DurationProto(cfg.RetentionDuration)
}
return &pb.Subscription{
Name: name,
Topic: cfg.Topic.name,
PushConfig: pbPushConfig,
AckDeadlineSeconds: trunc32(int64(cfg.AckDeadline.Seconds())),
RetainAckedMessages: cfg.RetainAckedMessages,
MessageRetentionDuration: retentionDuration,
Labels: cfg.Labels,
ExpirationPolicy: expirationPolicyToProto(cfg.ExpirationPolicy),
}
}
func protoToSubscriptionConfig(pbSub *pb.Subscription, c *Client) (SubscriptionConfig, error) {
rd := time.Hour * 24 * 7
var err error
if pbSub.MessageRetentionDuration != nil {
rd, err = ptypes.Duration(pbSub.MessageRetentionDuration)
if err != nil {
return SubscriptionConfig{}, err
}
}
var expirationPolicy time.Duration
if ttl := pbSub.ExpirationPolicy.GetTtl(); ttl != nil {
expirationPolicy, err = ptypes.Duration(ttl)
if err != nil {
return SubscriptionConfig{}, err
}
}
return SubscriptionConfig{
Topic: newTopic(c, pbSub.Topic),
AckDeadline: time.Second * time.Duration(pbSub.AckDeadlineSeconds),
PushConfig: PushConfig{
Endpoint: pbSub.PushConfig.PushEndpoint,
Attributes: pbSub.PushConfig.Attributes,
},
RetainAckedMessages: pbSub.RetainAckedMessages,
RetentionDuration: rd,
Labels: pbSub.Labels,
ExpirationPolicy: expirationPolicy,
}, nil
}
// ReceiveSettings configure the Receive method.
// A zero ReceiveSettings will result in values equivalent to DefaultReceiveSettings.
type ReceiveSettings struct {
// MaxExtension is the maximum period for which the Subscription should
// automatically extend the ack deadline for each message.
//
// The Subscription will automatically extend the ack deadline of all
// fetched Messages up to the duration specified. Automatic deadline
// extension beyond the initial receipt may be disabled by specifying a
// duration less than 0.
MaxExtension time.Duration
// MaxOutstandingMessages is the maximum number of unprocessed messages
// (unacknowledged but not yet expired). If MaxOutstandingMessages is 0, it
// will be treated as if it were DefaultReceiveSettings.MaxOutstandingMessages.
// If the value is negative, then there will be no limit on the number of
// unprocessed messages.
MaxOutstandingMessages int
// MaxOutstandingBytes is the maximum size of unprocessed messages
// (unacknowledged but not yet expired). If MaxOutstandingBytes is 0, it will
// be treated as if it were DefaultReceiveSettings.MaxOutstandingBytes. If
// the value is negative, then there will be no limit on the number of bytes
// for unprocessed messages.
MaxOutstandingBytes int
// NumGoroutines is the number of goroutines Receive will spawn to pull
// messages concurrently. If NumGoroutines is less than 1, it will be treated
// as if it were DefaultReceiveSettings.NumGoroutines.
//
// NumGoroutines does not limit the number of messages that can be processed
// concurrently. Even with one goroutine, many messages might be processed at
// once, because that goroutine may continually receive messages and invoke the
// function passed to Receive on them. To limit the number of messages being
// processed concurrently, set MaxOutstandingMessages.
NumGoroutines int
// If Synchronous is true, then no more than MaxOutstandingMessages will be in
// memory at one time. (In contrast, when Synchronous is false, more than
// MaxOutstandingMessages may have been received from the service and in memory
// before being processed.) MaxOutstandingBytes still refers to the total bytes
// processed, rather than in memory. NumGoroutines is ignored.
// The default is false.
Synchronous bool
}
// For synchronous receive, the time to wait if we are already processing
// MaxOutstandingMessages. There is no point calling Pull and asking for zero
// messages, so we pause to allow some message-processing callbacks to finish.
//
// The wait time is large enough to avoid consuming significant CPU, but
// small enough to provide decent throughput. Users who want better
// throughput should not be using synchronous mode.
//
// Waiting might seem like polling, so it's natural to think we could do better by
// noticing when a callback is finished and immediately calling Pull. But if
// callbacks finish in quick succession, this will result in frequent Pull RPCs that
// request a single message, which wastes network bandwidth. Better to wait for a few
// callbacks to finish, so we make fewer RPCs fetching more messages.
//
// This value is unexported so the user doesn't have another knob to think about. Note that
// it is the same value as the one used for nackTicker, so it matches this client's
// idea of a duration that is short, but not so short that we perform excessive RPCs.
const synchronousWaitTime = 100 * time.Millisecond
// This is a var so that tests can change it.
var minAckDeadline = 10 * time.Second
// DefaultReceiveSettings holds the default values for ReceiveSettings.
var DefaultReceiveSettings = ReceiveSettings{
MaxExtension: 10 * time.Minute,
MaxOutstandingMessages: 1000,
MaxOutstandingBytes: 1e9, // 1G
NumGoroutines: 1,
}
// Delete deletes the subscription.
func (s *Subscription) Delete(ctx context.Context) error {
return s.c.subc.DeleteSubscription(ctx, &pb.DeleteSubscriptionRequest{Subscription: s.name})
}
// Exists reports whether the subscription exists on the server.
func (s *Subscription) Exists(ctx context.Context) (bool, error) {
_, err := s.c.subc.GetSubscription(ctx, &pb.GetSubscriptionRequest{Subscription: s.name})
if err == nil {
return true, nil
}
if grpc.Code(err) == codes.NotFound {
return false, nil
}
return false, err
}
// Config fetches the current configuration for the subscription.
func (s *Subscription) Config(ctx context.Context) (SubscriptionConfig, error) {
pbSub, err := s.c.subc.GetSubscription(ctx, &pb.GetSubscriptionRequest{Subscription: s.name})
if err != nil {
return SubscriptionConfig{}, err
}
cfg, err := protoToSubscriptionConfig(pbSub, s.c)
if err != nil {
return SubscriptionConfig{}, err
}
return cfg, nil
}
// SubscriptionConfigToUpdate describes how to update a subscription.
type SubscriptionConfigToUpdate struct {
// If non-nil, the push config is changed.
PushConfig *PushConfig
// If non-zero, the ack deadline is changed.
AckDeadline time.Duration
// If set, RetainAckedMessages is changed.
RetainAckedMessages optional.Bool
// If non-zero, RetentionDuration is changed.
RetentionDuration time.Duration
// If non-zero, Expiration is changed.
ExpirationPolicy optional.Duration
// If non-nil, the current set of labels is completely
// replaced by the new set.
// This field has beta status. It is not subject to the stability guarantee
// and may change.
Labels map[string]string
}
// Update changes an existing subscription according to the fields set in cfg.
// It returns the new SubscriptionConfig.
//
// Update returns an error if no fields were modified.
func (s *Subscription) Update(ctx context.Context, cfg SubscriptionConfigToUpdate) (SubscriptionConfig, error) {
req := s.updateRequest(&cfg)
if err := cfg.validate(); err != nil {
return SubscriptionConfig{}, fmt.Errorf("pubsub: UpdateSubscription %v", err)
}
if len(req.UpdateMask.Paths) == 0 {
return SubscriptionConfig{}, errors.New("pubsub: UpdateSubscription call with nothing to update")
}
rpsub, err := s.c.subc.UpdateSubscription(ctx, req)
if err != nil {
return SubscriptionConfig{}, err
}
return protoToSubscriptionConfig(rpsub, s.c)
}
func (s *Subscription) updateRequest(cfg *SubscriptionConfigToUpdate) *pb.UpdateSubscriptionRequest {
psub := &pb.Subscription{Name: s.name}
var paths []string
if cfg.PushConfig != nil {
psub.PushConfig = cfg.PushConfig.toProto()
paths = append(paths, "push_config")
}
if cfg.AckDeadline != 0 {
psub.AckDeadlineSeconds = trunc32(int64(cfg.AckDeadline.Seconds()))
paths = append(paths, "ack_deadline_seconds")
}
if cfg.RetainAckedMessages != nil {
psub.RetainAckedMessages = optional.ToBool(cfg.RetainAckedMessages)
paths = append(paths, "retain_acked_messages")
}
if cfg.RetentionDuration != 0 {
psub.MessageRetentionDuration = ptypes.DurationProto(cfg.RetentionDuration)
paths = append(paths, "message_retention_duration")
}
if cfg.ExpirationPolicy != nil {
psub.ExpirationPolicy = expirationPolicyToProto(cfg.ExpirationPolicy)
paths = append(paths, "expiration_policy")
}
if cfg.Labels != nil {
psub.Labels = cfg.Labels
paths = append(paths, "labels")
}
return &pb.UpdateSubscriptionRequest{
Subscription: psub,
UpdateMask: &fmpb.FieldMask{Paths: paths},
}
}
const (
// The minimum expiration policy duration is 1 day as per:
// https://github.com/googleapis/googleapis/blob/51145ff7812d2bb44c1219d0b76dac92a8bd94b2/google/pubsub/v1/pubsub.proto#L606-L607
minExpirationPolicy = 24 * time.Hour
// If an expiration policy is not specified, the default of 31 days is used as per:
// https://github.com/googleapis/googleapis/blob/51145ff7812d2bb44c1219d0b76dac92a8bd94b2/google/pubsub/v1/pubsub.proto#L605-L606
defaultExpirationPolicy = 31 * 24 * time.Hour
)
func (cfg *SubscriptionConfigToUpdate) validate() error {
if cfg == nil || cfg.ExpirationPolicy == nil {
return nil
}
policy, min := optional.ToDuration(cfg.ExpirationPolicy), minExpirationPolicy
if policy == 0 || policy >= min {
return nil
}
return fmt.Errorf("invalid expiration policy(%q) < minimum(%q)", policy, min)
}
func expirationPolicyToProto(expirationPolicy optional.Duration) *pb.ExpirationPolicy {
if expirationPolicy == nil {
return nil
}
dur := optional.ToDuration(expirationPolicy)
var ttl *durpb.Duration
// As per:
// https://godoc.org/google.golang.org/genproto/googleapis/pubsub/v1#ExpirationPolicy.Ttl
// if ExpirationPolicy.Ttl is set to nil, the expirationPolicy is toggled to NEVER expire.
if dur != 0 {
ttl = ptypes.DurationProto(dur)
}
return &pb.ExpirationPolicy{
Ttl: ttl,
}
}
// IAM returns the subscription's IAM handle.
func (s *Subscription) IAM() *iam.Handle {
return iam.InternalNewHandle(s.c.subc.Connection(), s.name)
}
// CreateSubscription creates a new subscription on a topic.
//
// id is the name of the subscription to create. It must start with a letter,
// and contain only letters ([A-Za-z]), numbers ([0-9]), dashes (-),
// underscores (_), periods (.), tildes (~), plus (+) or percent signs (%). It
// must be between 3 and 255 characters in length, and must not start with
// "goog".
//
// cfg.Topic is the topic from which the subscription should receive messages. It
// need not belong to the same project as the subscription. This field is required.
//
// cfg.AckDeadline is the maximum time after a subscriber receives a message before
// the subscriber should acknowledge the message. It must be between 10 and 600
// seconds (inclusive), and is rounded down to the nearest second. If the
// provided ackDeadline is 0, then the default value of 10 seconds is used.
// Note: messages which are obtained via Subscription.Receive need not be
// acknowledged within this deadline, as the deadline will be automatically
// extended.
//
// cfg.PushConfig may be set to configure this subscription for push delivery.
//
// If the subscription already exists an error will be returned.
func (c *Client) CreateSubscription(ctx context.Context, id string, cfg SubscriptionConfig) (*Subscription, error) {
if cfg.Topic == nil {
return nil, errors.New("pubsub: require non-nil Topic")
}
if cfg.AckDeadline == 0 {
cfg.AckDeadline = 10 * time.Second
}
if d := cfg.AckDeadline; d < 10*time.Second || d > 600*time.Second {
return nil, fmt.Errorf("ack deadline must be between 10 and 600 seconds; got: %v", d)
}
sub := c.Subscription(id)
_, err := c.subc.CreateSubscription(ctx, cfg.toProto(sub.name))
if err != nil {
return nil, err
}
return sub, nil
}
var errReceiveInProgress = errors.New("pubsub: Receive already in progress for this subscription")
// Receive calls f with the outstanding messages from the subscription.
// It blocks until ctx is done, or the service returns a non-retryable error.
//
// The standard way to terminate a Receive is to cancel its context:
//
// cctx, cancel := context.WithCancel(ctx)
// err := sub.Receive(cctx, callback)
// // Call cancel from callback, or another goroutine.
//
// If the service returns a non-retryable error, Receive returns that error after
// all of the outstanding calls to f have returned. If ctx is done, Receive
// returns nil after all of the outstanding calls to f have returned and
// all messages have been acknowledged or have expired.
//
// Receive calls f concurrently from multiple goroutines. It is encouraged to
// process messages synchronously in f, even if that processing is relatively
// time-consuming; Receive will spawn new goroutines for incoming messages,
// limited by MaxOutstandingMessages and MaxOutstandingBytes in ReceiveSettings.
//
// The context passed to f will be canceled when ctx is Done or there is a
// fatal service error.
//
// Receive will send an ack deadline extension on message receipt, then
// automatically extend the ack deadline of all fetched Messages up to the
// period specified by s.ReceiveSettings.MaxExtension.
//
// Each Subscription may have only one invocation of Receive active at a time.
func (s *Subscription) Receive(ctx context.Context, f func(context.Context, *Message)) error {
s.mu.Lock()
if s.receiveActive {
s.mu.Unlock()
return errReceiveInProgress
}
s.receiveActive = true
s.mu.Unlock()
defer func() { s.mu.Lock(); s.receiveActive = false; s.mu.Unlock() }()
maxCount := s.ReceiveSettings.MaxOutstandingMessages
if maxCount == 0 {
maxCount = DefaultReceiveSettings.MaxOutstandingMessages
}
maxBytes := s.ReceiveSettings.MaxOutstandingBytes
if maxBytes == 0 {
maxBytes = DefaultReceiveSettings.MaxOutstandingBytes
}
maxExt := s.ReceiveSettings.MaxExtension
if maxExt == 0 {
maxExt = DefaultReceiveSettings.MaxExtension
} else if maxExt < 0 {
// If MaxExtension is negative, disable automatic extension.
maxExt = 0
}
var numGoroutines int
switch {
case s.ReceiveSettings.Synchronous:
numGoroutines = 1
case s.ReceiveSettings.NumGoroutines >= 1:
numGoroutines = s.ReceiveSettings.NumGoroutines
default:
numGoroutines = DefaultReceiveSettings.NumGoroutines
}
// TODO(jba): add tests that verify that ReceiveSettings are correctly processed.
po := &pullOptions{
maxExtension: maxExt,
maxPrefetch: trunc32(int64(maxCount)),
synchronous: s.ReceiveSettings.Synchronous,
}
fc := newFlowController(maxCount, maxBytes)
// Wait for all goroutines started by Receive to return, so instead of an
// obscure goroutine leak we have an obvious blocked call to Receive.
group, gctx := errgroup.WithContext(ctx)
for i := 0; i < numGoroutines; i++ {
group.Go(func() error {
return s.receive(gctx, po, fc, f)
})
}
return group.Wait()
}
func (s *Subscription) receive(ctx context.Context, po *pullOptions, fc *flowController, f func(context.Context, *Message)) error {
// Cancel a sub-context when we return, to kick the context-aware callbacks
// and the goroutine below.
ctx2, cancel := context.WithCancel(ctx)
// The iterator does not use the context passed to Receive. If it did, canceling
// that context would immediately stop the iterator without waiting for unacked
// messages.
iter := newMessageIterator(s.c.subc, s.name, po)
// We cannot use errgroup from Receive here. Receive might already be calling group.Wait,
// and group.Wait cannot be called concurrently with group.Go. We give each receive() its
// own WaitGroup instead.
// Since wg.Add is only called from the main goroutine, wg.Wait is guaranteed
// to be called after all Adds.
var wg sync.WaitGroup
wg.Add(1)
go func() {
<-ctx2.Done()
// Call stop when Receive's context is done.
// Stop will block until all outstanding messages have been acknowledged
// or there was a fatal service error.
iter.stop()
wg.Done()
}()
defer wg.Wait()
defer cancel()
for {
var maxToPull int32 // maximum number of messages to pull
if po.synchronous {
if po.maxPrefetch < 0 {
// If there is no limit on the number of messages to pull, use a reasonable default.
maxToPull = 1000
} else {
// Limit the number of messages in memory to MaxOutstandingMessages
// (here, po.maxPrefetch). For each message currently in memory, we have
// called fc.acquire but not fc.release: this is fc.count(). The next
// call to Pull should fetch no more than the difference between these
// values.
maxToPull = po.maxPrefetch - int32(fc.count())
if maxToPull <= 0 {
// Wait for some callbacks to finish.
if err := gax.Sleep(ctx, synchronousWaitTime); err != nil {
// Return nil if the context is done, not err.
return nil
}
continue
}
}
}
msgs, err := iter.receive(maxToPull)
if err == io.EOF {
return nil
}
if err != nil {
return err
}
for i, msg := range msgs {
msg := msg
// TODO(jba): call acquire closer to when the message is allocated.
if err := fc.acquire(ctx, len(msg.Data)); err != nil {
// TODO(jba): test that these "orphaned" messages are nacked immediately when ctx is done.
for _, m := range msgs[i:] {
m.Nack()
}
// Return nil if the context is done, not err.
return nil
}
old := msg.doneFunc
msgLen := len(msg.Data)
msg.doneFunc = func(ackID string, ack bool, receiveTime time.Time) {
defer fc.release(msgLen)
old(ackID, ack, receiveTime)
}
wg.Add(1)
go func() {
defer wg.Done()
f(ctx2, msg)
}()
}
}
}
type pullOptions struct {
maxExtension time.Duration
maxPrefetch int32
// If true, use unary Pull instead of StreamingPull, and never pull more
// than maxPrefetch messages.
synchronous bool
}
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