fix: improve docker compose

01-broken-setup/docker-compose.yaml

@@ -1,21 +1,27 @@
-version: "3" # Docker Compose format version
+version: "3"
 
 services:
     kafka:
         image: apache/kafka:latest
         container_name: kafka-crash-test
         ports:
-            - "9092:9092" # host:container
+            - "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
-            KAFKA_CONTROLLER_LISTENER_NAMES: CONTROLLER # Listener for controller communication
+            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
         volumes: