logback-kafka

Logback appenders for logging data to Apache Kafka

Maven Dependency

To use logback-kafka in your project add to following to your pom.xml:

<dependency>
    <groupId>com.github.ptgoetz</groupId>
    <artifactId>logback-kafka</artifactId>
    <version>0.1.0</version>
</dependency>

Configuration

To configure your application to log to kafka, add an appender entry in your logback configuration file, and specify a zookeeper host string, and kafka topic name to log to.

<?xml version="1.0" encoding="UTF-8" ?>
<configuration>
    <appender name="KAFKA"
        class="com.github.ptgoetz.logback.kafka.KafkaAppender">
        <topic>mytopic</topic>
        <zookeeperHost>localhost:2181</zookeeperHost>
    </appender>
    <root level="debug">
        <appender-ref ref="KAFKA" />
    </root>
</configuration>

Overriding Default Behavior

By default, the Kafka appender will simply write the received log message to the kafka queue. You can override this behavior by specifying a custom formatter class:

<?xml version="1.0" encoding="UTF-8" ?>
<configuration>
    <appender name="KAFKA"
        class="com.github.ptgoetz.logback.kafka.KafkaAppender">
        <topic>foo</topic>
        <zookeeperHost>localhost:2181</zookeeperHost>
        <!-- specify a custom formatter -->
        <formatter class="com.github.ptgoetz.logback.kafka.formatter.JsonFormatter">
            <!-- 
            Whether we expect the log message to be JSON encoded or not.
            If set to "false", the log message will be treated as a string, 
            and wrapped in quotes. Otherwise it will be treated as a parseable
            JSON object.
            -->
            <expectJson>true</expectJson>
        </formatter>
    </appender>
    <root level="debug">
        <appender-ref ref="KAFKA" />
    </root>
</configuration>

Formatters simply need to implement the com.github.ptgoetz.logback.kafka.formatter.Formatter interface:

package com.github.ptgoetz.logback.kafka.formatter;

import ch.qos.logback.classic.spi.ILoggingEvent;

public interface Formatter {
    String format(ILoggingEvent event);
}

You can find the ch.qos.logback.classic.spi.ILoggingEvent javadoc here.