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Kafka Consumer Lag Monitoring - Lightweight and Cloud Native Ready

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A client tool that exports the consumer lag of a Kafka consumer group to different implementations such as Prometheus or your terminal. It utlizes Kafka's AdminClient and Kafka's Consumer's client in order to fetch such metrics. Consumer lag calculated as follows:

sum(topic_offset_per_partition-consumer_offset_per_partition)

What is Consumer Lag and why is important?

Quoting this article:

What is Kafka Consumer Lag? Kafka Consumer Lag is the indicator of how much lag there is between Kafka producers and consumers....

Why is Consumer Lag Important? Many applications today are based on being able to process (near) real-time data. Think about performance monitoring system like Sematext Monitoring or log management service like Sematext Logs. They continuously process infinite streams of near real-time data. If they were to show you metrics or logs with too much delay – if the Consumer Lag were too big – they’d be nearly useless. This Consumer Lag tells us how far behind each Consumer (Group) is in each Partition. The smaller the lag the more real-time the data consumption.

In summary, consumer lag tells us 2 things:

Supported Kafka Versions

Since this client uses Kafka Admin Client and Kafka Consumer client version of 2+, therefore this client supportes Kafka brokers from version 0.10.2+.

Features

Changelog

0.1.1

0.1.0

Major Release:

0.0.8:

0.0.7:

0.0.6:

Installation and Usage

Native Application

You can downland the latest release of the Native application from here, currently it only supports Mac and Linux. An example from Prometheus component:

./kafka-consumer-lag-monitoring-prometheus-0.1.0 config.properties

Note to Mac users: You will need to verify the application, to do this, run:

xattr -r -d com.apple.quarantine kafka-consumer-lag-monitoring-prometheus-0.1.0

Uber JAR

You can downland the latest release of the Uber JAR from here. This client requires at least Java 8 in order to run. You can run it like this for example from Console component:

java -jar kafka-consumer-lag-monitoring-console-0.1.0-all.jar -b kafka1:9092,kafka2:9092,kafka3:9092 -c "my_awesome_consumer_group_01" -p 5000

Docker

There two types of docker images:

  1. Docker images based on the native application: This docker image is built using the natively compiled application, the benefit is, you will get faster and small image which is beneficial for your cloud native environment. However, since the native compilation is pretty new to this client, is still an evolving work.
  2. Docker images based on the Uber Jar: This docker image is built using the uber Jar. Although it might be slower and larger, it is the more stable than the Docker native images but is still optimized to run in container orchestration frameworks such as kubernetes as efficient as possible.

Example:

docker run omarsmak/kafka-consumer-lag-monitoring-prometheus-native -p 9739:9739  \
-e kafka_bootstrap_servers=localhost:9092 \
-e kafka_retry_backoff.ms = 200 \
-e monitoring_lag_consumer_groups="test*" \
-e monitoring_lag_prometheus_http_port=9739 \
-e monitoring_lag_logging_rootLogger_appenderRef_stdout_ref=LogToConsole \
-e monitoring_lag_logging_rootLogger_level=info

Usage

Console Component:

This mode will print the consumer lag per partition and the total lag among all partitions and continuously refreshing the metrics per the value of --poll.interval startup parameter. It accepts the following parameters:

./kafka-consumer-lag-monitoring-console-0.1.0 -h    
                                                                                                                                                                                                  130 ↵ omaral-safi@Omars-MBP-2
Usage: kafka-consumer-lag-monitoring-console [-hV] [-b=<kafkaBootstrapServers>]
      [-c=<kafkaConsumerGroups>] [-f=<kafkaPropertiesFile>] [-p=<pollInterval>]
Prints the kafka consumer lag to the console.
 -b, --bootstrap.servers=<kafkaBootstrapServers>
                 A list of host/port pairs to use for establishing the initial
                   connection to the Kafka cluster
 -c, --consumer.groups=<kafkaConsumerGroups>
                 A list of Kafka consumer groups or list ending with star (*)
                   to fetch all consumers with matching pattern, e.g: 'test_v*'
 -f, --properties.file=<kafkaPropertiesFile>
                 Optional. Properties file for Kafka AdminClient
                   configurations, this is the typical Kafka properties file
                   that can be used in the AdminClient. For more info, please
                   take a look at Kafka AdminClient configurations
                   documentation.
 -h, --help      Show this help message and exit.
 -p, --poll.interval=<pollInterval>
                 Interval delay in ms to that refreshes the client lag
                   metrics, default to 2000ms
 -V, --version   Print version information and exit.

An example output:

./kafka-consumer-lag-monitoring-console-0.1.0 -b kafka1:9092,kafka2:9092,kafka3:9092 -c "my_awesome_consumer_group_01" -p 5000
        Consumer group: my_awesome_consumer_group_01
        ==============================================================================
        
        Topic name: topic_example_1
        Total topic offsets: 211132248
        Total consumer offsets: 187689403
        Total lag: 23442845
        
        Topic name: topic_example_2
        Total topic offsets: 15763247
        Total consumer offsets: 15024564
        Total lag: 738683
        
        Topic name: topic_example_3
        Total topic offsets: 392
        Total consumer offsets: 392
        Total lag: 0
        
        Topic name: topic_example_4
        Total topic offsets: 24572
        Total consumer offsets: 24570
        Total lag: 2
        
        Topic name: topic_example_5
        Total topic offsets: 430
        Total consumer offsets: 430
        Total lag: 0
        
        Topic name: topic_example_6
        Total topic offsets: 6342
        Total consumer offsets: 6335    
        Total lag: 7
Example Usage Native Application:
./kafka-consumer-lag-monitoring-console-0.1.0 -c "test*" -b localhost:9092 -p 500
Example Usage Uber Jar Application:
java -jar kafka-consumer-lag-monitoring-console-0.1.0-all.jar -c "test*" -b localhost:9092 -p 500
Example Usage Docker Native Application:
docker run omarsmak/kafka-consumer-lag-monitoring-console-native -c "test*" -b localhost:9092 -p 500
Example Usage Docker Uber Jar Application:
docker run omarsmak/kafka-consumer-lag-monitoring-console -c "test*" -b localhost:9092 -p 500

Prometheus Component:

In this mode, the tool will start an http server on a port that being set in monitoring.lag.prometheus.http.port config and it will expose an endpoint that is reachable via localhost:<http.port>/metrics or localhost:<http.port>/prometheus so prometheus server can scrap these metrics and expose them for example to grafana. You will need to pass the configuration as properties file or via environment variables. An example config file:

kafka.bootstrap.servers=localhost:9092
kafka.retry.backoff.ms = 200
monitoring.lag.consumer.groups=group-a-*,*-b-*,*-c
monitoring.lag.consumer.groups.exclude=*test*
monitoring.lag.prometheus.http.port=9772
monitoring.lag.logging.rootLogger.appenderRef.stdout.ref=LogToConsole
monitoring.lag.logging.rootLogger.level=info

This will include consumer groups that either start with group-a-, contain -b-, or end with -c, excluding those containing test.

You can then run it like the following:

Example Usage Native Application:
./kafka-consumer-lag-monitoring-prometheus-0.1.0 config.proprties
Example Usage Uber Jar Application:
java -jar kafka-consumer-lag-monitoring-prometheus-0.1.0-all.jar config.proprties
Example Usage Docker Native Application:

For Docker, we will use the environment variables instead:

docker run omarsmak/kafka-consumer-lag-monitoring-prometheus-native -p 9739:9739  \
-e kafka_bootstrap_servers=localhost:9092 \
-e kafka_retry_backoff.ms = 200 \
-e monitoring_lag_consumer_groups="test*" \
-e monitoring_lag_prometheus_http_port=9739 \
-e monitoring_lag_logging_rootLogger_appenderRef_stdout_ref=LogToConsole \
-e monitoring_lag_logging_rootLogger_level=info
Example Usage Docker Uber Jar Application:

For Docker, we will use the environment variables instead:

docker run omarsmak/kafka-consumer-lag-monitoring-prometheus -p 9739:9739  \
-e kafka_bootstrap_servers=localhost:9092 \
-e kafka_retry_backoff.ms = 200 \
-e monitoring_lag_consumer_groups="test*" \
-e monitoring_lag_prometheus_http_port=9739 \
-e monitoring_lag_logging_rootLogger_appenderRef_stdout_ref=LogToConsole \
-e monitoring_lag_logging_rootLogger_level=info

Note: By default, port 9739 is exposed by the docker image, hence you should avoid overrding the client's HTTP port through the client's startup arguments (--http.port) as described below when you run the client through docker container and leave it to the default of 9739. However you can still change the corresponding docker mapped port to anything of your choice.

Exposed Metrics:
kafka_consumer_group_offset{group, topic, partition}

The latest committed offset of a consumer group in a given partition of a topic.

kafka_consumer_group_partition_lag{group, topic, partition}

The lag of a consumer group behind the head of a given partition of a topic. Calculated like this: current_topic_offset_per_partition - current_consumer_offset_per_partition.

kafka_topic_latest_offsets{group, topic, partition}

The latest committed offset of a topic in a given partition.

kafka_consumer_group_total_lag{group, topic}

The total lag of a consumer group behind the head of a topic. This gives the total lags from all partitions over each topic, it provides good visibility but not a precise measurement since is not partition aware.

kafka_consumer_group_member_lag{group, member, topic}

The total lag of a consumer group member behind the head of a topic. This gives the total lags over each consumer member within consumer group.

kafka_consumer_group_member_partition_lag{group, member, topic, partition}

The lag of a consumer member within consumer group behind the head of a given partition of a topic.

Configuration

Majority of the components here, for example Prometheus components supports two types of configurations:

  1. Application Properties File: You can provide the application a config properties file as argument e.g: ./kafka-consumer-lag-monitoring-prometheus-0.1.0 config.properties, this is an example config:

     ```
 kafka.bootstrap.servers=localhost:9092
 kafka.retry.backoff.ms = 200
 monitoring.lag.consumer.groups=test*
 monitoring.lag.prometheus.http.port=9772
 monitoring.lag.logging.rootLogger.appenderRef.stdout.ref=LogToConsole
 monitoring.lag.logging.rootLogger.level=info
 ```

    Note here the application accepts configs with two prefixes:

    • kafka.: Use the kafka prefix for any config related to Kafka admin client, these configs are basically the same configs that you will find here: https://kafka.apache.org/documentation/#adminclientconfigs/.
    • monitoring.lag. : Use the monitoring.lag prefix to pass any config specific to this client, you will take a look which configs that the client will accept later.

  2. Environment Variables: You can as well pass the configs as environment variables, this is useful when running the application in environment like Docker, for example:

     ```
 docker run --rm -p 9739:9739 \
 -e monitoring_lag_logging_rootLogger_appenderRef_stdout_ref=LogToConsole \
 -e monitoring_lag_consumer_groups="test-*" \
 -e kafka_bootstrap_servers=host.docker.internal:9092  \
 omarsmak/kafka-consumer-lag-monitoring-prometheus-native:latest 
 ```

    Similar to the application properties file, it supports kafka and monitoring.lag. However, you will need to replace all dot . with underscore _ for all the configs, for example the config kafka.bootstrap.servers its environment equivalent is kafka_bootstrap_servers.

Available Configurations

Logging

The client ships with Log4j bindings and supports JSON and standard logging. The default log4j properties that it uses:

# Log to console
appender.console.type = Console
appender.console.name = LogToConsole
appender.console.layout.type = PatternLayout
appender.console.layout.pattern = [%-5level] %d{yyyy-MM-dd HH:mm:ss.SSS} [%t] %c{1} - %msg%n

# Log to console as JSON
appender.json.type = Console
appender.json.name = LogInJSON
appender.json.layout.type = JsonLayout
appender.json.layout.complete = true
appender.json.layout.compact = false

rootLogger.level = info
rootLogger.appenderRef.stdout.ref = LogInJSON

By default, LogInJSON is enabled. However, you can customtize all of this by providing these configurations prefixed with monitoring.lag.logging.. For example, to enable the standard logging, you will need to add this config monitoring.lag.logging.rootLogger.appenderRef.stdout.ref=LogToConsole or as environment variable: monitoring_lag_logging_rootLogger_appenderRef_stdout_ref=LogToConsole.

Note: When configuring the logging through the environment variables, note that the configuration are case sensitive.

Usage as Library

If you want to use this client embedded into your application, you can achieve that by adding a dependency to this tool in your pom.xml or gradle.build as explained below:

Maven

<dependency>
  <groupId>com.omarsmak.kafka</groupId>
  <artifactId>consumer-lag-monitoring</artifactId>
  <version>0.1.1</version>
</dependency>

Gradle

compile 'com.omarsmak.kafka:consumer-lag-monitoring:0.1.1'

Usage

Java

import com.omarsmak.kafka.consumer.lag.monitoring.client.KafkaConsumerLagClient;
import com.omarsmak.kafka.consumer.lag.monitoring.client.KafkaConsumerLagClientFactory;
import org.apache.kafka.clients.admin.AdminClientConfig;

import java.util.Properties;

public class ConsumerLagClientTest {
    
    public static void main(String[] args){
        // Create a Properties object to hold the Kafka bootstrap servers
        final Properties properties = new Properties();
        properties.setProperty(AdminClientConfig.BOOTSTRAP_SERVERS_CONFIG, "kafka1:9092");
        
        // Create the client, we will use the Java client 
        final KafkaConsumerLagClient kafkaConsumerLagClient = KafkaConsumerLagClientFactory.create(properties);
        
        // Print the lag of a Kafka consumer
        System.out.println(kafkaConsumerLagClient.getConsumerLag("awesome-consumer"));
    }
}

Kotlin

import com.omarsmak.kafka.consumer.lag.monitoring.client.KafkaConsumerLagClientFactory
import org.apache.kafka.clients.admin.AdminClientConfig
import java.util.Properties

object ConsumerLagClientTest {

    @JvmStatic
    fun main(arg: Array<String>) {
        // Create a Properties object to hold the Kafka bootstrap servers
        val properties = Properties().apply {
            this[AdminClientConfig.BOOTSTRAP_SERVERS_CONFIG] = "kafka1:9092"
        }

        // Create the client, we will use the Kafka AdminClient Java client
        val kafkaConsumerLagClient = KafkaConsumerLagClientFactory.create(properties)

        // Print the lag of a Kafka consumer
        println(kafkaConsumerLagClient.getConsumerLag("awesome-consumer"))
    }
}

Build The Project

Run ./gradlew clean build on the top project folder which is as result, it will run all tests and build the Uber jar.

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