/
subscriber.go
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/
subscriber.go
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// Copyright © 2022 Meroxa, Inc.
//
// 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 clients
import (
"context"
"fmt"
"sync"
"cloud.google.com/go/pubsub"
"github.com/conduitio-labs/conduit-connector-gcp-pubsub/config"
sdk "github.com/conduitio/conduit-connector-sdk"
"github.com/gammazero/deque"
"github.com/google/uuid"
"go.uber.org/multierr"
)
// Subscriber represents a struct with a GCP Pub/Sub client,
// queues for messages, an error channel.
type Subscriber struct {
*pubSub
*subscriber
}
type subscriber struct {
// mutex to lock subscriber during queue operation
mu sync.Mutex
// queue to store all messages until they are read
msgDeque *deque.Deque[*pubsub.Message]
// queue to acknowledge messages
ackDeque *deque.Deque[*pubsub.Message]
// error chanel for the receiver's error
errorCh chan error
// context with close to close the goroutine with the receiver
ctxCancel context.CancelFunc
}
// NewSubscriber initializes a new subscriber client of GCP Pub/Sub
// and starts receiving a messages to the message queue.
func NewSubscriber(ctx context.Context, cfg config.Source) (*Subscriber, error) {
ps, err := newClient(ctx, cfg.General)
if err != nil {
return nil, err
}
cctx, cancel := context.WithCancel(ctx)
sub := &Subscriber{
pubSub: ps,
subscriber: &subscriber{
msgDeque: deque.New[*pubsub.Message](),
ackDeque: deque.New[*pubsub.Message](),
errorCh: make(chan error),
ctxCancel: cancel,
},
}
go func() {
err = sub.pubSub.client.Subscription(cfg.SubscriptionID).Receive(cctx,
func(_ context.Context, m *pubsub.Message) {
sub.mu.Lock()
defer sub.mu.Unlock()
sub.msgDeque.PushBack(m)
},
)
if err != nil {
sub.errorCh <- fmt.Errorf("subscription receive: %w", err)
return
}
sub.errorCh <- nil
}()
return sub, nil
}
// Next returns the next record or an error.
func (s *subscriber) Next(ctx context.Context) (sdk.Record, error) {
select {
case err := <-s.errorCh:
return sdk.Record{}, err
case <-ctx.Done():
return sdk.Record{}, ctx.Err()
default:
s.mu.Lock()
defer s.mu.Unlock()
if s.msgDeque.Len() == 0 {
return sdk.Record{}, sdk.ErrBackoffRetry
}
msg := s.msgDeque.PopFront()
s.ackDeque.PushBack(msg)
metadata := sdk.Metadata{}
if len(msg.Attributes) > 0 {
metadata = msg.Attributes
}
metadata.SetCreatedAt(msg.PublishTime)
return sdk.Util.Source.NewRecordCreate(
sdk.Position(uuid.NewString()),
metadata,
nil,
sdk.RawData(msg.Data),
), nil
}
}
// Ack indicates successful processing of a Message passed.
func (s *subscriber) Ack(ctx context.Context) error {
select {
case <-ctx.Done():
return ctx.Err()
default:
s.mu.Lock()
defer s.mu.Unlock()
s.ackDeque.PopFront().Ack()
return nil
}
}
// Stop calls stop method and releases the GCP Pub/Sub client.
func (s *Subscriber) Stop() error {
return multierr.Append(s.stop(), s.pubSub.close())
}
// stop cancels the context to release the goroutine with the receiver,
// marks all received messages as not acknowledged,
// and waits until the goroutine with the receiver is closed.
func (s *subscriber) stop() error {
s.ctxCancel()
s.mu.Lock()
defer s.mu.Unlock()
for s.msgDeque.Len() > 0 {
s.msgDeque.PopFront().Nack()
}
for s.ackDeque.Len() > 0 {
s.ackDeque.PopFront().Nack()
}
return <-s.errorCh
}