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consumer.go
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consumer.go
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package kafka
import (
"context"
"github.com/Shopify/sarama"
"github.com/ThreeDotsLabs/watermill"
wmkafka "github.com/ThreeDotsLabs/watermill-kafka/v2/pkg/kafka"
"github.com/ThreeDotsLabs/watermill/message"
"github.com/rs/zerolog"
)
type Consumer struct {
subscriber *wmkafka.Subscriber
topic string
logger *zerolog.Logger
}
// NewConsumer sets up watermill subscriber and returns our consumer
func NewConsumer(config *Config, logger *zerolog.Logger) (*Consumer, error) {
saramaSubscriberConfig := wmkafka.DefaultSaramaSubscriberConfig()
// equivalent of auto.offset.reset: earliest
saramaSubscriberConfig.Consumer.Offsets.Initial = sarama.OffsetOldest
// note that autocommit is enabled
saramaSubscriberConfig.Version = sarama.V2_6_0_0
subscriber, err := wmkafka.NewSubscriber(
wmkafka.SubscriberConfig{
Brokers: config.BrokerAddresses,
Unmarshaler: wmkafka.DefaultMarshaler{},
OverwriteSaramaConfig: saramaSubscriberConfig,
ConsumerGroup: config.GroupID,
},
watermill.NewStdLogger(false, false), // if we don't like this logger we'll need an adapter for zerologger
)
if err != nil {
return nil, err
}
return &Consumer{
subscriber: subscriber,
topic: config.Topic,
logger: logger,
}, nil
}
// Start reads messages from subscriber and processes them with passed in function.
//
// eg: for msg := range messages {
// fmt.Printf("received message: %s, payload: %s", msg.UUID, string(msg.Payload))
// msg.Ack() }
func (c *Consumer) Start(ctx context.Context, process func(messages <-chan *message.Message)) {
messages, err := c.subscriber.Subscribe(ctx, c.topic)
if err != nil {
c.logger.Fatal().Err(err).Msgf("could not subscribe to topic: %s", c.topic)
}
go process(messages)
}