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Apache Kafka

Build Status Lint Code Base Ansible Lint Molecule

Ansible role to install and configure Apache Kafka 2.8.0

Apache Kafka is a distributed event streaming platform using publish-subscribe topics. Applications and streaming components can produce and consume messages by subscribing to these topics. Kafka is extremely fast, handling megabytes of reads and writes per second from thousands of clients. Messages are persisted and replicated to prevent data loss. Data streams are partitioned and can be elastically scaled with no downtime.

Supported Platforms

  • RedHat 6
  • RedHat 7
  • RedHat 8
  • Debian 10.x
  • Ubuntu 18.04.x
  • Ubuntu 20.04.x

Requirements

The below Apache ZooKeeper role from Ansible Galaxy can be used if one is needed.

ansible-galaxy install sleighzy.zookeeper

Ansible 2.9.16 or 2.10.4 are the minimum required versions to workaround an issue with certain kernels that have broken the systemd status check. The error message "Service is in unknown state" will be output when attempting to start the service via the Ansible role and the task will fail. The service will start as expected if the systemctl start command is run on the physical host. See ansible/ansible#71528 for more information.

Role Variables

Variable Default
kafka_download_base_url http://www-eu.apache.org/dist/kafka
kafka_version 2.8.0
kafka_scala_version 2.13
kafka_create_user_group true
kafka_user kafka
kafka_group kafka
kafka_root_dir /opt
kafka_dir {{ kafka_root_dir }}/kafka
kafka_start yes
kafka_restart yes
kafka_log_dir /var/log/kafka
kafka_broker_id 0
kafka_java_heap -Xms1G -Xmx1G
kafka_background_threads 10
kafka_listener_protocol PLAINTEXT
kafka_listener_hostname localhost
kafka_listener_port 9092
kafka_num_network_threads 3
kafka_num_io_threads 8
kafka_num_replica_fetchers 1
kafka_socket_send_buffer_bytes 102400
kafka_socket_receive_buffer_bytes 102400
kafka_socket_request_max_bytes 104857600
kafka_replica_socket_receive_buffer_bytes 65536
kafka_data_log_dirs /var/lib/kafka/logs
kafka_num_partitions 1
kafka_num_recovery_threads_per_data_dir 1
kafka_log_cleaner_threads 1
kafka_offsets_topic_replication_factor 1
kafka_transaction_state_log_replication_factor 1
kafka_transaction_state_log_min_isr 1
kafka_log_retention_hours 168
kafka_log_segment_bytes 1073741824
kafka_log_retention_check_interval_ms 300000
kafka_auto_create_topics_enable false
kafka_delete_topic_enable true
kafka_default_replication_factor 1
kafka_group_initial_rebalance_delay_ms 0
kafka_zookeeper_connect localhost:2181
kafka_zookeeper_connection_timeout 6000
kafka_bootstrap_servers localhost:9092
kafka_consumer_group_id kafka-consumer-group

Starting and Stopping Kafka services using systemd

  • The Kafka service can be started via: systemctl start kafka
  • The Kafka service can be stopped via: systemctl stop kafka

Starting and Stopping Kafka services using initd

  • The Kafka service can be started via: service kafka start
  • The Kafka service can be stopped via: service kafka stop

Default Properties

Property Value
ZooKeeper connection localhost:2181
Kafka bootstrap servers localhost:9092
Kafka consumer group Id kafka-consumer-group
Kafka broker id 0
Number of partitions 1
Data log file retention period 168 hours
Enable auto topic creation false
Enable topic deletion true

Ports

Port Description
9092 Kafka listener port

Directories and Files

Directory / File
Kafka installation directory (symlink to installed version) /opt/kafka
Kafka configuration directory (symlink to /opt/kafka/config) /etc/kafka
Directory to store data files /var/lib/kafka/logs
Directory to store logs files /var/log/kafka
Kafka service /usr/lib/systemd/system/kafka.service

Example Playbook

Add the below to a playbook to run those role against hosts belonging to the kafka-nodes group.

- hosts: kafka-nodes
  roles:
    - sleighzy.kafka

Linting

Linting should be done using ansible-lint.

pip3 install ansible-lint --user

Testing

This module uses the [Ansible Molecule] testing framework. This test suite creates a Kafka and ZooKeeper cluster consisting of three nodes running within Docker containers. Each container runs a different OS to test the supported platforms for this Ansible role.

As per the Molecule Installation guide this should be done using a virtual environment. The commands below will create a Python virtual environment and install Molecule including the Docker driver.

$ python3 -m venv molecule-venv
$ source molecule-venv/bin/activate
(molecule-venv) $ python3 -m pip install molecule-docker "molecule[docker,lint]"

Run playbook and tests. Linting errors need to be corrected before Molecule will execute any tests. This will run all tests and then destroy the Docker containers.

molecule test

The below command can be used to run the playbook without the tests. This can be run multiple times when making changes to the role, and ensuring that operations are idempotent.

molecule converge

The below commands can be used to just run the tests without tearing everything down. The command molecule verify can be repeated for each test run.

molecule create
molecule converge
molecule verify

Tear down Molecule tests and Docker containers.

molecule destroy

License

MIT license