On-Call Kafka Quick Check

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On any of Kafka cluster nodes runs following commands.

Topic

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# list topics created
./bin/kafka-topics.sh \
--bootstrap-server localhost:9092 \
--list

# display:
# number of partitions of this topic
# relica factor
# overridden configs
# in-sync replicas
./bin/kafka-topics.sh \
--bootstrap-server localhost:9092 \
--topic <topic name> \
--describe
# the output for example:
# "Isr" is a status, it shows which replica is in-sync, the below means all replicas are good
# Configs field shows the override settings of default
Topic: apple	PartitionCount: 3	ReplicationFactor: 3	Configs: cleanup.policy=delete,segment.bytes=536870912,retention.ms=172800000,retention.bytes=2000000000
	Topic: apple	Partition: 0	Leader: 28	Replicas: 28,29,27	Isr: 28,29,27
	Topic: apple	Partition: 1	Leader: 29	Replicas: 29,27,28	Isr: 29,27,28
	Topic: apple	Partition: 2	Leader: 27	Replicas: 27,28,29	Isr: 27,28,29

# only show overridden config
./bin/kafka-topics.sh \
--bootstrap-server localhost:9092 \
--topics-with-overrides \
--topic <topic name> \
--describe
# or using kafka-config
./bin/kafka-configs.sh \
--zookeeper <zookeeper>:2181 \
--entity-type topics \
--entity-name <topic name> \
--describe

# add or update topic config
./bin/kafka-configs.sh \
--zookeeper <zookeeper>:2181 \
--entity-type topics \
--entity-name <topic name> \
--alter \
--add-config 'max.message.bytes=16777216'

# remove topic overrides
./bin/kafka-configs.sh \
--zookeeper <zookeeper>:2181 \
--entity-type topics \
--entity-name <topic name> \
--alter \
--delete-config 'max.message.bytes'

# list all consumer groups of a topic
# no direct command

Consumer Group

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# list consumer groups
./bin/kafka-consumer-groups.sh  \
--bootstrap-server localhost:9092 \
--list 

# check partition/offset/lag messages in each consumer group/topic
# also see topics consumed by the group

# Consumer lag indicates the lag between Kafka producers and consumers. If the rate of
# production of data far exceeds the rate at which it is getting consumed, consumer
# groups will exhibit lag.
# From column name:
# LAG = LOG-END-OFFSET - CURRENT-OFFSET
# CLIENT-ID: xxx-0-0: means consumer 0 and its worker thread 0
./bin/kafka-consumer-groups.sh \
--bootstrap-server localhost:9092 \
--group <consumer group name> \
--describe

# read last one message in topic of consumer group
# note that one topic can be consumed by different consumer group
# each has separate consumer offset
./bin/kafka-console-consumer.sh \
--bootstrap-server localhost:9092 \
--topic <topic name> \
--group <consumer group name> \
--max-messages 1

Partition

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# increase partition number
# partition number can only grow up
./bin/kafka-topics.sh \
--bootstrap-server localhost:9092 \
--topic <topic name> \
--partitions <new partition number> \
--alter

Delete Messages

If there is bad data in message that stucks the consumer, we can delete them from the specified partition:

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./bin/kafka-delete-records.sh \
--bootstrap-server localhost:9092 \
--offset-json-file deletion.json
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{
  "partitions": [
    {
      "topic": "<topic name>",
			// partition number, such as 0
      "partition": 0,
			// offset, delete all message from the beginning of partition till this
			// offset(excluded).
			// The offset specified is one higher than the problematic offset reported
			// in the log
      "offset": 149615102
    }
  ],
	// check ./bin/kafka-delete-records.sh --help to see the version
  "version": 1
}

Note that if all messages need deleting from the topic, then specify in the JSON an offset of -1.

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