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subscription.go
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subscription.go
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package firestore
import (
"context"
"time"
"cloud.google.com/go/firestore"
"golang.org/x/sync/errgroup"
"google.golang.org/api/iterator"
"google.golang.org/grpc/codes"
"google.golang.org/grpc/status"
"github.com/ThreeDotsLabs/watermill"
"github.com/ThreeDotsLabs/watermill/message"
)
type subscription struct {
name string
topic string
config SubscriberConfig
client client
logger watermill.LoggerAdapter
closing chan struct{}
output chan *message.Message
}
func newSubscription(
name, topic string,
config SubscriberConfig,
client client,
logger watermill.LoggerAdapter,
closing chan struct{},
) (*subscription, error) {
s := &subscription{
name: name,
topic: topic,
config: config,
client: client,
logger: logger,
closing: closing,
output: make(chan *message.Message),
}
if err := createFirestoreSubscriptionIfNotExists(s.client, config.PubSubRootCollection, topic, s.config.GenerateSubscriptionName(topic), s.logger, s.config.Timeout); err != nil {
return nil, err
}
return s, nil
}
func (s *subscription) receive(ctx context.Context) {
s.readPendingMessages(ctx)
g, ctx := errgroup.WithContext(ctx)
g.Go(func() error {
return s.readPendingMessagesPeriodically(ctx)
})
g.Go(func() error {
return s.watchIncomingMessages(ctx)
})
if err := g.Wait(); err != nil {
s.logger.Error("Subscription receive failure", err, nil)
}
}
func (s *subscription) readPendingMessagesPeriodically(ctx context.Context) error {
ticker := time.NewTicker(s.config.ReadAllPeriod)
for {
select {
case <-ticker.C:
s.readPendingMessages(ctx)
case <-ctx.Done():
return ctx.Err()
}
}
}
func (s *subscription) readPendingMessages(ctx context.Context) {
docs, err := s.messagesQuery().Documents(ctx).GetAll()
if err != nil {
s.logger.Error("Couldn't read all messages from subscription", err, nil)
return
}
for _, doc := range docs {
s.handleAddedMessage(ctx, doc)
}
}
func (s *subscription) watchIncomingMessages(ctx context.Context) error {
subscriptionSnapshots := s.messagesQuery().Query.Snapshots(ctx)
defer subscriptionSnapshots.Stop()
for {
subscriptionSnapshot, err := subscriptionSnapshots.Next()
if err == iterator.Done {
s.logger.Debug("Listening on subscription done", nil)
return err
} else if status.Code(err) == codes.Canceled {
s.logger.Debug("Receive context canceled", nil)
return err
} else if err != nil {
s.logger.Error("Error receiving", err, nil)
return err
}
if subscriptionSnapshot.Size == 0 {
continue
}
for _, e := range onlyAddedMessages(subscriptionSnapshot.Changes) {
s.handleAddedMessage(ctx, e.Doc)
}
}
}
func (s *subscription) messagesQuery() *firestore.CollectionRef {
return s.client.Collection(s.config.PubSubRootCollection).Doc(s.topic).Collection(s.name)
}
func onlyAddedMessages(changes []firestore.DocumentChange) (added []firestore.DocumentChange) {
for _, ch := range changes {
if ch.Kind == firestore.DocumentAdded {
added = append(added, ch)
}
}
return
}
func (s *subscription) handleAddedMessage(ctx context.Context, doc *firestore.DocumentSnapshot) {
logger := s.logger.With(watermill.LogFields{"document_id": doc.Ref.ID})
msg, err := s.config.Marshaler.Unmarshal(doc)
if err != nil {
logger.Error("Couldn't unmarshal message", err, nil)
return
}
ctx, cancelCtx := context.WithCancel(ctx)
msg.SetContext(ctx)
defer cancelCtx()
select {
case <-s.closing:
logger.Trace("Channel closed when waiting for consuming message", nil)
return
case <-ctx.Done():
logger.Trace("Context done when waiting for consuming message", nil)
return
case s.output <- msg:
logger.Trace("Message consumed, waiting for ack/nack", nil)
// message consumed, wait for ack/nack
}
select {
case <-s.closing:
logger.Trace("Closing when waiting for ack/nack", nil)
case <-msg.Nacked():
logger.Trace("Message nacked", nil)
case <-ctx.Done():
logger.Trace("Context done", nil)
case <-msg.Acked():
if err := s.ackMessage(ctx, doc, logger); err != nil {
logger.Error("Failed to ack message", err, nil)
return
}
logger.Trace("Message acked", nil)
}
}
func (s *subscription) ackMessage(
ctx context.Context,
message *firestore.DocumentSnapshot,
logger watermill.LoggerAdapter,
) error {
deleteCtx, deleteCancel := context.WithTimeout(ctx, s.config.Timeout)
defer deleteCancel()
_, err := message.Ref.Delete(deleteCtx, firestore.Exists)
if status.Code(err) == codes.NotFound {
logger.Trace("Message deleted meanwhile", nil)
return nil
}
if err != nil {
return err
}
return nil
}