Chapter 16. Kafka Exporter
Chapter 16. Kafka Exporter Kafka Exporter is an open source project to enhance monitoring of Apache Kafka brokers and clients. Kafka Exporter is provided with AMQ Streams for deployment with a Kafka cluster to extract additional metrics data from Kafka brokers related to offsets, consumer groups, consumer lag, and topics. The metrics data is used, for example, to help identify slow consumers. Lag data is exposed as Prometheus metrics, which can then be presented in Grafana for analysis. If you are already using Prometheus and Grafana for monitoring of built-in Kafka metrics, you can configure Prometheus to also scrape the Kafka Exporter Prometheus endpoint. Additional resources Kafka exposes metrics through JMX, which can then be exported as Prometheus metrics. Chapter 7, Monitoring your cluster using JMX 16.1. Consumer lag Consumer lag indicates the difference in the rate of production and consumption of messages. Specifically, consumer lag for a given consumer group indicates the delay between the last message in the partition and the message being currently picked up by that consumer. The lag reflects the position of the consumer offset in relation to the end of the partition log. This difference is sometimes referred to as the delta between the producer offset and consumer offset, the read and write positions in the Kafka broker topic partitions. Suppose a topic streams 100 messages a second. A lag of 1000 messages between the producer offset (the topic partition head) and the last offset the consumer has read means a 10-second delay. The importance of monitoring consumer lag For applications that rely on the processing of (near) real-time data, it is critical to monitor consumer lag to check that it does not become too big. The greater the lag becomes, the further the process moves from the real-time processing objective. Consumer lag, for example, might be a result of consuming too much old data that has not been purged, or through unplanned shutdowns. Reducing consumer lag Typical actions to reduce lag include: Scaling-up consumer groups by adding new consumers Increasing the retention time for a message to remain in a topic Adding more disk capacity to increase the message buffer Actions to reduce consumer lag depend on the underlying infrastructure and the use cases AMQ Streams is supporting. For instance, a lagging consumer is less likely to benefit from the broker being able to service a fetch request from its disk cache. And in certain cases, it might be acceptable to automatically drop messages until a consumer has caught up. 16.2. Kafka Exporter alerting rule examples The sample alert notification rules specific to Kafka Exporter are as follows: UnderReplicatedPartition An alert to warn that a topic is under-replicated and the broker is not replicating enough partitions. The default configuration is for an alert if there are one or more under-replicated partitions for a topic. The alert might signify that a Kafka instance is down or the Kafka cluster is overloaded. A planned restart of the Kafka broker may be required to restart the replication process. TooLargeConsumerGroupLag An alert to warn that the lag on a consumer group is too large for a specific topic partition. The default configuration is 1000 records. A large lag might indicate that consumers are too slow and are falling behind the producers. NoMessageForTooLong An alert to warn that a topic has not received messages for a period of time. The default configuration for the time period is 10 minutes. The delay might be a result of a configuration issue preventing a producer from publishing messages to the topic. You can adapt alerting rules according to your specific needs. Additional resources For more information about setting up alerting rules, see Configuration in the Prometheus documentation. 16.3. Kafka Exporter metrics Lag information is exposed by Kafka Exporter as Prometheus metrics for presentation in Grafana. Kafka Exporter exposes metrics data for brokers, topics, and consumer groups. Table 16.1. Broker metrics output Name Information kafka_brokers Number of brokers in the Kafka cluster Table 16.2. Topic metrics output Name Information kafka_topic_partitions Number of partitions for a topic kafka_topic_partition_current_offset Current topic partition offset for a broker kafka_topic_partition_oldest_offset Oldest topic partition offset for a broker kafka_topic_partition_in_sync_replica Number of in-sync replicas for a topic partition kafka_topic_partition_leader Leader broker ID of a topic partition kafka_topic_partition_leader_is_preferred Shows 1 if a topic partition is using the preferred broker kafka_topic_partition_replicas Number of replicas for this topic partition kafka_topic_partition_under_replicated_partition Shows 1 if a topic partition is under-replicated Table 16.3. Consumer group metrics output Name Information kafka_consumergroup_current_offset Current topic partition offset for a consumer group kafka_consumergroup_lag Current approximate lag for a consumer group at a topic partition 16.4. Running Kafka Exporter Kafka Exporter is provided with the download archive used for Installing AMQ Streams . You can run it to expose Prometheus metrics for presentation in a Grafana dashboard. Prerequisites AMQ Streams is installed on the host This procedure assumes you already have access to a Grafana user interface and Prometheus is deployed and added as a data source. Procedure Run the Kafka Exporter script using appropriate configuration parameter values. ./bin/kafka_exporter --kafka.server=< kafka-bootstrap-address >:9092 --kafka.version=2.8.0 --< my-other-parameters > The parameters require a double-hyphen convention, such as --kafka.server . Table 16.4. Kafka Exporter configuration parameters Option Description Default kafka.server Host/post address of the Kafka server. kafka:9092 kafka.version Kafka broker version. 1.0.0 group.filter A regular expression to specify the consumer groups to include in the metrics. .* (all) topic.filter A regular expression to specify the topics to include in the metrics. .* (all) sasl.< parameter > Parameters to enable and connect to the Kafka cluster using SASL/PLAIN authentication, with user name and password. false tls.< parameter > Parameters to enable connect to the Kafka cluster using TLS authentication, with optional certificate and key. false web.listen-address Port address to expose the metrics. :9308 web.telemetry-path Path for the exposed metrics. /metrics log.level Logging configuration, to log messages with a given severity (debug, info, warn, error, fatal) or above. info log.enable-sarama Boolean to enable Sarama logging, a Go client library used by the Kafka Exporter. false legacy.partitions Boolean to enable metrics to be fetched from inactive topic partitions as well as from active partitions. If you want Kafka Exporter to return metrics for inactive partitions, set to true . false You can use kafka_exporter --help for information on the properties. Configure Prometheus to monitor the Kafka Exporter metrics. For more information on configuring Prometheus, see the Prometheus documentation . Enable Grafana to present the Kafka Exporter metrics data exposed by Prometheus. For more information, see Presenting Kafka Exporter metrics in Grafana . 16.5. Presenting Kafka Exporter metrics in Grafana Using Kafka Exporter Prometheus metrics as a data source, you can create a dashboard of Grafana charts. For example, from the metrics you can create the following Grafana charts: Message in per second (from topics) Message in per minute (from topics) Lag by consumer group Messages consumed per minute (by consumer groups) When metrics data has been collected for some time, the Kafka Exporter charts are populated. Use the Grafana charts to analyze lag and to check if actions to reduce lag are having an impact on an affected consumer group. If, for example, Kafka brokers are adjusted to reduce lag, the dashboard will show the Lag by consumer group chart going down and the Messages consumed per minute chart going up. Additional resources Example dashboard for Kafka Exporter Grafana documentation
./bin/kafka_exporter --kafka.server=< kafka-bootstrap-address >:9092 --kafka.version=2.8.0 --< my-other-parameters >