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gcp.go
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gcp.go
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package gcp // import "github.com/NYTimes/gizmo/pubsub/gcp"
import (
"errors"
"sync"
"time"
gpubsub "cloud.google.com/go/pubsub"
"github.com/NYTimes/gizmo/pubsub"
"github.com/golang/protobuf/proto"
"golang.org/x/net/context"
"google.golang.org/api/option"
)
// Subscriber is a Google Cloud Platform PubSub client that allows a user to
// consume messages via the pubsub.Subscriber interface.
type Subscriber struct {
sub subscription
ctx context.Context
mtxStop sync.Mutex
stopped bool
cancel func()
err error
}
// NewSubscriber will instantiate a new Subscriber that wraps a pubsub.Iterator.
func NewSubscriber(ctx context.Context, projID, subscription string, opts ...option.ClientOption) (*Subscriber, error) {
client, err := gpubsub.NewClient(ctx, projID, opts...)
if err != nil {
return &Subscriber{}, err
}
sub := client.Subscription(subscription)
sub.ReceiveSettings = gpubsub.ReceiveSettings{
MaxExtension: defaultMaxExtension,
MaxOutstandingMessages: defaultMaxMessages,
}
return &Subscriber{
ctx: ctx,
sub: subscriptionImpl{Sub: sub},
}, nil
}
var (
defaultMaxMessages = 10
defaultMaxExtension = 60 * time.Second
)
// Start will start pulling from pubsub via a pubsub.Iterator.
func (s *Subscriber) Start() <-chan pubsub.SubscriberMessage {
output := make(chan pubsub.SubscriberMessage)
go func(s *Subscriber, output chan pubsub.SubscriberMessage) {
defer close(output)
s.ctx, s.cancel = context.WithCancel(s.ctx)
err := s.sub.Receive(s.ctx, func(ctx context.Context, msg message) {
sm := &SubMessage{
msg: msg,
}
if mi, ok := msg.(messageImpl); ok {
sm.Attributes = mi.Msg.Attributes
}
output <- sm
})
if err != nil {
s.Stop()
s.err = err
}
}(s, output)
return output
}
// Err will contain any error the Subscriber has encountered while processing.
func (s *Subscriber) Err() error {
return s.err
}
// Stop will block until the consumer has stopped consuming messages.
func (s *Subscriber) Stop() error {
s.mtxStop.Lock()
defer s.mtxStop.Unlock()
if s.stopped {
return nil
}
s.stopped = true
if s.cancel != nil {
s.cancel()
}
return nil
}
// SetReceiveSettings sets the ReceivedSettings on the google pubsub Subscription.
// Should be called before Start().
func (s *Subscriber) SetReceiveSettings(settings gpubsub.ReceiveSettings) {
s.sub.(subscriptionImpl).Sub.ReceiveSettings = settings
}
// SubMessage pubsub implementation of pubsub.SubscriberMessage.
type SubMessage struct {
msg message
Attributes map[string]string
}
// Message will return the data of the pubsub Message.
func (m *SubMessage) Message() []byte {
return m.msg.MsgData()
}
// ExtendDoneDeadline will call the deprecated ModifyAckDeadline for a pubsub
// Message. This likely should not be called.
func (m *SubMessage) ExtendDoneDeadline(dur time.Duration) error {
return errors.New("not suppported")
}
// Done will acknowledge the pubsub Message.
func (m *SubMessage) Done() error {
m.msg.Done()
return nil
}
// publisher is a Google Cloud Platform PubSub client that allows a user to
// consume messages via the pubsub.MultiPublisher interface.
type publisher struct {
topic *gpubsub.Topic
}
var _ pubsub.Publisher = &publisher{}
var _ pubsub.MultiPublisher = &publisher{}
// NewPublisher will instantiate a new GCP MultiPublisher.
func NewPublisher(ctx context.Context, cfg Config, opts ...option.ClientOption) (pubsub.MultiPublisher, error) {
if cfg.ProjectID == "" {
return nil, errors.New("project id is required")
}
if cfg.Topic == "" {
return nil, errors.New("topic name is required")
}
c, err := gpubsub.NewClient(ctx, cfg.ProjectID, opts...)
if err != nil {
return nil, err
}
t := c.Topic(cfg.Topic)
// Update PublishSettings from cfg.PublishSettings
// but never set thresholds to 0.
if cfg.PublishSettings.DelayThreshold > 0 {
t.PublishSettings.DelayThreshold = cfg.PublishSettings.DelayThreshold
}
if cfg.PublishSettings.CountThreshold > 0 {
t.PublishSettings.CountThreshold = cfg.PublishSettings.CountThreshold
}
if cfg.PublishSettings.ByteThreshold > 0 {
t.PublishSettings.ByteThreshold = cfg.PublishSettings.ByteThreshold
}
if cfg.PublishSettings.NumGoroutines > 0 {
t.PublishSettings.NumGoroutines = cfg.PublishSettings.NumGoroutines
}
if cfg.PublishSettings.Timeout > 0 {
t.PublishSettings.Timeout = cfg.PublishSettings.Timeout
}
return &publisher{
topic: t,
}, nil
}
// Publish will marshal the proto message and publish it to GCP pubsub.
func (p *publisher) Publish(ctx context.Context, key string, msg proto.Message) error {
mb, err := proto.Marshal(msg)
if err != nil {
return err
}
return p.PublishRaw(ctx, key, mb)
}
// PublishRaw will publish the message to GCP pubsub.
func (p *publisher) PublishRaw(ctx context.Context, key string, m []byte) error {
res := p.topic.Publish(ctx, &gpubsub.Message{
Data: m,
Attributes: map[string]string{"key": key},
})
_, err := res.Get(ctx)
return err
}
// PublishMulti will publish multiple messages to GCP pubsub in a single request.
func (p *publisher) PublishMulti(ctx context.Context, keys []string, messages []proto.Message) error {
if len(keys) != len(messages) {
return errors.New("keys and messages must be equal length")
}
a := make([][]byte, len(messages))
for i := range messages {
b, err := proto.Marshal(messages[i])
if err != nil {
return err
}
a[i] = b
}
return p.PublishMultiRaw(ctx, keys, a)
}
// PublishMultiRaw will publish multiple raw byte array messages to GCP pubsub in a single request.
func (p *publisher) PublishMultiRaw(ctx context.Context, keys []string, messages [][]byte) error {
if len(keys) != len(messages) {
return errors.New("keys and messages must be equal length")
}
for i := range messages {
err := p.PublishRaw(ctx, keys[i], messages[i])
if err != nil {
return err
}
}
return nil
}
// interfaces and types to make this more testable
type (
subscription interface {
Receive(ctx context.Context, f func(context.Context, message)) error
}
message interface {
ID() string
MsgData() []byte
Done()
}
messageImpl struct {
Msg *gpubsub.Message
}
subscriptionImpl struct {
Sub *gpubsub.Subscription
}
)
func (m messageImpl) ID() string {
return m.Msg.ID
}
func (m messageImpl) MsgData() []byte {
return m.Msg.Data
}
func (m messageImpl) Done() {
m.Msg.Ack()
}
func (s subscriptionImpl) Receive(ctx context.Context, f func(context.Context, message)) error {
return s.Sub.Receive(ctx, func(ctx context.Context, msg *gpubsub.Message) {
f(ctx, messageImpl{msg})
})
}