Implementation:Apache Kafka Kafka Run Class Exec

Knowledge Sources	Apache Kafka
Domains	Operations, Server_Administration
Last Updated	2026-02-09 12:00 GMT

Overview

Concrete tool for launching a Kafka JVM process with assembled options provided by kafka-run-class.sh.

Description

The process launch section of kafka-run-class.sh is the terminal command that starts the actual JVM process. It combines all JVM options (heap, performance, GC logging, JMX, Log4j, custom) with the classpath and the target main class. In daemon mode, it uses nohup with output redirected to a console log. In native mode, it executes a pre-compiled binary directly.

Usage

This is the final section of kafka-run-class.sh and is not invoked directly. The execution mode is controlled by the -daemon flag passed by the calling script.

Code Reference

Source Location

• Repository: Apache Kafka
• File: bin/kafka-run-class.sh
• Lines: L345-354

Signature

# Foreground execution:
exec "$JAVA" $KAFKA_HEAP_OPTS $KAFKA_JVM_PERFORMANCE_OPTS \
  $KAFKA_GC_LOG_OPTS $KAFKA_JMX_OPTS $KAFKA_LOG4J_CMD_OPTS \
  -cp "$CLASSPATH" $KAFKA_OPTS "$@"

# Daemon execution:
nohup "$JAVA" $KAFKA_HEAP_OPTS $KAFKA_JVM_PERFORMANCE_OPTS \
  $KAFKA_GC_LOG_OPTS $KAFKA_JMX_OPTS $KAFKA_LOG4J_CMD_OPTS \
  -cp "$CLASSPATH" $KAFKA_OPTS "$@" > "$CONSOLE_OUTPUT_FILE" 2>&1 < /dev/null &

# Native execution:
exec "$base_dir"/kafka.Kafka "$@"

Import

# Invoked automatically by kafka-run-class.sh
# Controlled by -daemon flag and KAFKA_MODE=native

I/O Contract

Inputs

Name	Type	Required	Description
JAVA	env	Yes	Path to Java binary
CLASSPATH	env	Yes	Assembled classpath from previous step
All KAFKA_*_OPTS	env	Yes	Assembled JVM options from previous step
DAEMON_MODE	flag	No	If set, use nohup for background execution
KAFKA_MODE	env	No	If "native", use pre-compiled binary
$@	args	Yes	Main class name and its arguments

Outputs

Name	Type	Description
JVM process	process	Running Kafka JVM (foreground or daemon)
Console output	file	In daemon mode, written to $CONSOLE_OUTPUT_FILE

Usage Examples

Standard Foreground Launch

# Via kafka-server-start.sh (foreground)
bin/kafka-server-start.sh config/server.properties
# Internally executes: exec java -Xmx1G -Xms1G ... -cp "$CLASSPATH" kafka.Kafka config/server.properties

Daemon Launch

# Via kafka-server-start.sh with -daemon flag
bin/kafka-server-start.sh -daemon config/server.properties
# Internally executes: nohup java ... kafka.Kafka config/server.properties > console.log 2>&1 &

Related Pages

Implements Principle

• Principle:Apache_Kafka_Process_Launch
• Environment:Apache_Kafka_JVM_Runtime_Environment