version: "3"

services:
    kafka:
        image: apache/kafka:latest
        container_name: kafka-python-conn
        ports:
            - "127.0.0.1:9092:9092" # localhost interface,host:container
        environment:
            # who am I in the cluster
            KAFKA_NODE_ID: 1 # node identifier in cluster
            KAFKA_PROCESS_ROLES: broker,controller # Combined broker + controller (KRaft mode, no Zookeeper)
            # how to vote in the cluster, service name at line 4
            KAFKA_CONTROLLER_QUORUM_VOTERS: 1@kafka:9093 # Controller nodes for quorum (node_id@host:port)

            # Listener configuration
            # what interfaces and ports on the container layer ( not host )
            # PLAINTEXT and CONTROLLER are listener names, can be anything as long as
            # referenced the correct ones after
            KAFKA_LISTENERS: PLAINTEXT://:9092,CONTROLLER://:9093 # Ports Kafka listens on internally
            # outside container layer ( host )
            KAFKA_ADVERTISED_LISTENERS: PLAINTEXT://localhost:9092 # Address advertised to clients
            KAFKA_LISTENER_SECURITY_PROTOCOL_MAP: CONTROLLER:PLAINTEXT,PLAINTEXT:PLAINTEXT # encryption settings for listeners
            KAFKA_CONTROLLER_LISTENER_NAMES: CONTROLLER # listener name for controller communication

            KAFKA_LOG_DIRS: /var/lib/kafka/data # Directory for message data storage

            # when running locally you NEED this else consumer can't read via group
            # as by default it wants 3 replicas for these internal topics and errors out
            KAFKA_OFFSETS_TOPIC_REPLICATION_FACTOR: 1 # replication factor for offsets topic
            KAFKA_TRANSACTION_STATE_LOG_REPLICATION_FACTOR: 1 # replication factor for transaction log
            KAFKA_TRANSACTION_STATE_LOG_MIN_ISR: 1 # how many replicas must acknowledge a write
        volumes:
            - ./kafka-data:/var/lib/kafka/data # Persist data across container restarts