Kafka Konsumer

Description

Kafka Konsumer provides an easy implementation of Kafka consumer with a built-in retry/exception manager (kafka-cronsumer).

Migration Guide

V2 Release Notes

• Added ability for manipulating kafka message headers.
• Added transactional retry feature. Set false if you want to use exception/retry strategy to only failed messages.
• Enable manuel commit at both single and batch consuming modes.
• Enabling consumer resume/pause functionality. Please refer to its example and how it works documentation.
• Bumped kafka-cronsumer to the latest version:
  • Backoff strategy support (linear, exponential options)
  • Added message key for retried messages
  • Added x-error-message to see what was the error of the message during processing
• Reduce memory allocation.
• Increase TP on changing internal concurrency structure.

How to migrate from v1 to v2?

You can get latest version via go get github.com/Trendyol/kafka-konsumer/v2@latest

• You need to change import path from github.com/Trendyol/kafka-konsumer to github.com/Trendyol/kafka-konsumer/v2

• You need to change your consume function with pointer signature.

• We moved messageGroupDuration from batchConfiguration.messageGroupDuration to root level. Because this field is used single (non-batch) consumer too.

Installation

go get github.com/Trendyol/kafka-konsumer/v2@latest

Examples

You can find a number of ready-to-run examples at this directory.

After running docker-compose up command, you can run any application you want.

Simple Consumer

func main() {
    consumerCfg := &kafka.ConsumerConfig{
        Reader: kafka.ReaderConfig{
            Brokers: []string{"localhost:29092"},
            Topic:   "standart-topic",
            GroupID: "standart-cg",
        },
        ConsumeFn:    consumeFn,
        RetryEnabled: false,
    }

    consumer, _ := kafka.NewConsumer(consumerCfg)
    defer consumer.Stop()
    
    consumer.Consume()
}

func consumeFn(message kafka.Message) error {
    fmt.Printf("Message From %s with value %s", message.Topic, string(message.Value))
    return nil
}

Simple Consumer With Retry/Exception Option

func main() {
    consumerCfg := &kafka.ConsumerConfig{
        Reader: kafka.ReaderConfig{
            Brokers: []string{"localhost:29092"},
            Topic:   "standart-topic",
            GroupID: "standart-cg",
        },
        RetryEnabled: true,
        RetryConfiguration: kafka.RetryConfiguration{
            Topic:         "retry-topic",
            StartTimeCron: "*/1 * * * *",
            WorkDuration:  50 * time.Second,
            MaxRetry:      3,
        },
        ConsumeFn: consumeFn,
    }

    consumer, _ := kafka.NewConsumer(consumerCfg)
    defer consumer.Stop()
    
    consumer.Consume()
}

func consumeFn(message kafka.Message) error {
    fmt.Printf("Message From %s with value %s", message.Topic, string(message.Value))
    return nil
}

With Batch Option

func main() {
    consumerCfg := &kafka.ConsumerConfig{
        Reader: kafka.ReaderConfig{
            Brokers: []string{"localhost:29092"},
            Topic:   "standart-topic",
            GroupID: "standart-cg",
        },
        LogLevel:     kafka.LogLevelDebug,
        RetryEnabled: true,
        RetryConfiguration: kafka.RetryConfiguration{
            Brokers:       []string{"localhost:29092"},
            Topic:         "retry-topic",
            StartTimeCron: "*/1 * * * *",
            WorkDuration:  50 * time.Second,
            MaxRetry:      3,
        },
        MessageGroupDuration: time.Second,
        BatchConfiguration: kafka.BatchConfiguration{
            MessageGroupLimit:    1000,
            BatchConsumeFn:       batchConsumeFn,
        },
    }

    consumer, _ := kafka.NewConsumer(consumerCfg)
    defer consumer.Stop()

    consumer.Consume()
}

func batchConsumeFn(messages []kafka.Message) error {
    fmt.Printf("%d\n comes first %s", len(messages), messages[0].Value)
    return nil
}

With Disabling Transactional Retry

func main() {
    consumerCfg := &kafka.ConsumerConfig{
        Reader: kafka.ReaderConfig{
            Brokers: []string{"localhost:29092"},
            Topic:   "standart-topic",
            GroupID: "standart-cg",
        },
        LogLevel:     kafka.LogLevelDebug,
        RetryEnabled: true,
        TransactionalRetry: kafka.NewBoolPtr(false),
        RetryConfiguration: kafka.RetryConfiguration{
            Brokers:       []string{"localhost:29092"},
            Topic:         "retry-topic",
            StartTimeCron: "*/1 * * * *",
            WorkDuration:  50 * time.Second,
            MaxRetry:      3,
        },
        MessageGroupDuration: time.Second,
        BatchConfiguration: kafka.BatchConfiguration{
            MessageGroupLimit:    1000,
            BatchConsumeFn:       batchConsumeFn,
        },
    }

    consumer, _ := kafka.NewConsumer(consumerCfg)
    defer consumer.Stop()

    consumer.Consume()
}

func batchConsumeFn(messages []kafka.Message) error {
    // you can add custom error handling here & flag messages
    for i := range messages {
        if i%2 == 0 {
            messages[i].IsFailed = true
        }
    }

    // you must return err here to retry failed messages
    return errors.New("err")
}

With Distributed Tracing Support

Please refer to Tracing Example

With Pause & Resume Consumer

Please refer to Pause Resume Example

With Grafana & Prometheus

In this example, we are demonstrating how to create Grafana dashboard and how to define alerts in Prometheus. You can see the example by going to the with-grafana folder in the examples folder and running the infrastructure with docker compose up and then the application.

With SASL-PLAINTEXT Authentication

Under the examples - with-sasl-plaintext folder, you can find an example of a consumer integration with SASL/PLAIN mechanism. To try the example, you can run the command docker compose up under the specified folder and then start the application.

Configurations

config	description	default
reader	Describes all segmentio kafka reader configurations
consumeFn	Kafka consumer function, if retry enabled it, is also used to consume retriable messages
skipMessageByHeaderFn	Function to filter messages based on headers, return true if you want to skip the message	nil
logLevel	Describes log level; valid options are debug, info, warn, and error	info
concurrency	Number of goroutines used at listeners	1
retryEnabled	Retry/Exception consumer is working or not	false
transactionalRetry	Set false if you want to use exception/retry strategy to only failed messages	true
commitInterval	indicates the interval at which offsets are committed to the broker.	1s
rack	see doc
clientId	see doc
messageGroupDuration	Maximum time to wait for a batch	1s
metricPrefix	MetricPrefix is used for prometheus fq name prefix. If not provided, default metric prefix value is kafka_konsumer. Currently, there are two exposed prometheus metrics. processed_messages_total and unprocessed_messages_total So, if default metric prefix used, metrics names are kafka_konsumer_processed_messages_total_current and kafka_konsumer_unprocessed_messages_total_current.	kafka_konsumer
dial.Timeout	see doc	no timeout
dial.KeepAlive	see doc	not enabled
transport.DialTimeout	see doc	5s
transport.IdleTimeout	see doc	30s
transport.MetadataTTL	see doc	6s
transport.MetadataTopics	see doc	all topics in cluster
distributedTracingEnabled	indicates open telemetry support on/off for consume and produce operations.	false
distributedTracingConfiguration.TracerProvider	see doc	otel.GetTracerProvider()
distributedTracingConfiguration.Propagator	see doc	otel.GetTextMapPropagator()
retryConfiguration.clientId	see doc
retryConfiguration.startTimeCron	Cron expression when retry consumer (kafka-cronsumer) starts to work at
retryConfiguration.metricPrefix	MetricPrefix is used for prometheus fq name prefix. If not provided, default metric prefix value is kafka_cronsumer. Currently, there are two exposed prometheus metrics. retried_messages_total_current and discarded_messages_total_current. So, if default metric prefix used, metrics names are kafka_cronsumer_retried_messages_total_current and kafka_cronsumer_discarded_messages_total_current	kafka_cronsumer
retryConfiguration.workDuration	Work duration exception consumer actively consuming messages
retryConfiguration.topic	Retry/Exception topic names
retryConfiguration.brokers	Retry topic brokers urls
retryConfiguration.maxRetry	Maximum retry value for attempting to retry a message	3
retryConfiguration.tls.rootCAPath	see doc	""
retryConfiguration.tls.intermediateCAPath	Same with rootCA, if you want to specify two rootca you can use it with rootCAPath	""
retryConfiguration.sasl.authType	SCRAM or PLAIN
retryConfiguration.sasl.username	SCRAM OR PLAIN username
retryConfiguration.sasl.password	SCRAM OR PLAIN password
retryConfiguration.skipMessageByHeaderFn	Function to filter messages based on headers, return true if you want to skip the message	nil
batchConfiguration.messageGroupLimit	Maximum number of messages in a batch
batchConfiguration.batchConsumeFn	Kafka batch consumer function, if retry enabled it, is also used to consume retriable messages
batchConfiguration.preBatchFn	This function enable for transforming messages before batch consuming starts
batchConfiguration.balancer	see doc	leastBytes
tls.rootCAPath	see doc	""
tls.intermediateCAPath	Same with rootCA, if you want to specify two rootca you can use it with rootCAPath	""
sasl.authType	SCRAM or PLAIN
sasl.username	SCRAM OR PLAIN username
sasl.password	SCRAM OR PLAIN password
logger	If you want to custom logger	info
apiEnabled	Enabled metrics	false
apiConfiguration.port	Set API port	8090
apiConfiguration.healtCheckPath	Set Health check path	healthcheck
metricConfiguration.path	Set metric endpoint path	/metrics

Monitoring

Kafka Konsumer offers an API that handles exposing several metrics.

Exposed Metrics

Metric Name	Description	Value Type
kafka_konsumer_processed_messages_total_current	Total number of processed messages.	Counter
kafka_konsumer_unprocessed_messages_total_current	Total number of unprocessed messages.	Counter