Java Asynchronous logger with log4j2

We know performance is critical for any application and nobody wants the underlying logging framework to become a bottleneck. We want lower logging latency and higher throughput. Also we want to increased the logging performance.

In that case, The asynchronous logger in log4J2 does this by decoupling the logging overhead from the thread executing your code. Async logger is designed to optimize this area by replacing the blocking queue with disruptor . Disruptor is a Lock-free inter-thread communication library. So by using this its provide higher throughput and lower latency in Log4J2 logging.

Log4J2 supports JSON,XML and YAML in addition to properties file configuration . Here I use XML file for the configuration.

Add log4j Dependancy :

Add log4j Dependancy in pom.xml file:

<dependency>
    <groupId>org.apache.logging.log4j</groupId>
    <artifactId>log4j-bom</artifactId>
</dependency>

<dependency>
    <groupId>org.apache.logging.log4j</groupId>
    <artifactId>log4j-core</artifactId>
    <scope>runtime</scope>
</dependency>

Add disruptor Dependancy :

Add disruptor in pom.xml file

<dependency>
    <groupId>com.lmax</groupId>
    <artifactId>disruptor</artifactId>
    <version>3.4.4</version>
</dependency>

Configure log4j2.xml file for Log4J 2 async logger :

We will use XML to configure Log4J2 2 async logger. Now Create a log4j2.xml file in the project classpath.

1. Add basic configuration

Path : src/resources/log4j2.xml

<?xml version="1.0" encoding="UTF-8"?>
<Configuration status="DEBUG">
    <Appenders>
        <Console name="LogToConsole" target="SYSTEM_OUT">
            <PatternLayout pattern="%d{HH:mm:ss.SSS} [%t] %-5level %logger{36} - %msg%n"/>
        </Console>
    </Appenders>
    <Loggers>
        <Logger name="org.apache.logging.log4j.samples.async" level="debug">
            <AppenderRef ref="LogToConsole"/>
        </Logger>
        <Root level="error">
            <AppenderRef ref="LogToConsole"/>
        </Root>
    </Loggers>
</Configuration>

2. Now add RollingRandomAccessFile Sections into Appenders to configure the rolling log files

 <RollingRandomAccessFile name="LogToRollingRandomAccessFile" fileName="logs/app.log"
                                 filePattern="logs/$${date:yyyy-MM}/app-%d{MM-dd-yyyy}-%i.log">
    <PatternLayout>
        <Pattern>%d %p %c{1.} [%t] %m%n</Pattern>
    </PatternLayout>
    <Policies>
        <TimeBasedTriggeringPolicy/>
        <SizeBasedTriggeringPolicy size="3 MB"/>
    </Policies>
    <DefaultRolloverStrategy max="5"/>
</RollingRandomAccessFile>

3. Now add AsyncAppender Appender into the Loggers sections. So after the configuraiton, log4j2.xml file should be look like :

<Configuration status="DEBUG">
    <Appenders>
        <Console name="LogToConsole" target="SYSTEM_OUT">
            <PatternLayout pattern="%d{HH:mm:ss.SSS} [%t] %-5level %logger{36} - %msg%n"/>
        </Console>
        <RollingRandomAccessFile name="LogToRollingRandomAccessFile" fileName="logs/app.log"
                                 filePattern="logs/$${date:yyyy-MM}/app-%d{MM-dd-yyyy}-%i.log">
            <PatternLayout>
                <Pattern>%d %p %c{1.} [%t] %m%n</Pattern>
            </PatternLayout>
            <Policies>
                <TimeBasedTriggeringPolicy/>
                <SizeBasedTriggeringPolicy size="3 MB"/>
            </Policies>
            <DefaultRolloverStrategy max="5"/>
        </RollingRandomAccessFile>

    </Appenders>
    <Loggers>

        <!--  asynchronous loggers -->
       <AsyncLogger  name="org.apache.logging.log4j.samples.async" level="debug">
            <AppenderRef ref="LogToRollingRandomAccessFile"/>
        </AsyncLogger>
        <Root level="debug">
            <AppenderRef ref="LogToConsole"/>
        </Root>

    </Loggers>
</Configuration>

We can change the status to trace, debug, info, warn, and fatal to enable the internal Log4j events.

Configure Log4J2AsyncLogger.java Class :

Now create a logger class Log4J2AsyncLogger.java that uses the Log4J2 API to log the messages.

package org.apache.logging.log4j.async;

import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;

public class Log4J2AsyncLogger {

    private static final Logger logger = LogManager.getLogger(Log4J2AsyncLogger.class);

    public static void main(String[] args) {

        Log4J2AsyncLogger myLog = new Log4J2AsyncLogger();
        myLog.getLog("Log4j2 Log");

    }

    private void getLog(String param){

        logger.info("This is a info log");

        // Previously, need to check the log level log to increase performance
        logger.debug("This is debug log with param : {}", param);

        if(logger.isWarnEnabled()){
            logger.info("This is warn log with param : " + param);
        }

        // In Java 8, No need to check the log level, we can do this
        while (true) //for test rolling file
            logger.debug("Hello print {}", () -> getValue());
    }

    static String getValue() {
        return "Debug Log";
    }
}

Configure Log4J2AsyncLoggerException.java Class :

Create another logger class Log4J2AsyncLoggerException.java to create and check exceptions.

package org.apache.logging.log4j.async;

import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;

public class Log4J2AsyncLoggerException {

    private static final Logger logger = LogManager.getLogger(Log4J2AsyncLoggerException.class);

    public static void main(String[] args) {

        try {
            System.out.println(getException());
        } catch (IllegalArgumentException e) {
            logger.error("An error occurred.", e);
        }
    }

    static int getException() throws IllegalArgumentException {
        throw new IllegalArgumentException("Hello, Something Went Wrong. Exception Occured!!");
    }

}

To Enable all loggers to asynchronous, we need 2 things :

1. Need to be present disruptor in project class path.
2. Set system property log4j2.contextSelector=org.apache.logging.log4j.core.async.AsyncLoggerContextSelector

Asynchronous Loggers

Now Run the below commands :

It will build a jar log4j2-1.0.0.jar file under the target Location

$ mvn clean package

Run another commend with Log4j 2 configuration in debug status.

$ java -Dlog4j2.contextSelector=org.apache.logging.log4j.core.async.AsyncLoggerContextSelector -jar target/log4j2-1.0.0.jar

The Output should be l0ok like this in your terminal :

2022-02-21 16:55:31,637 main DEBUG Registering MBean org.apache.logging.log4j2:type=AsyncContext@464bee09
2022-02-21 16:55:32,638 main DEBUG Registering MBean org.apache.logging.log4j2:type=AsyncContext@464bee09,component=AsyncLoggerRingBuffer
2022-02-21 16:55:32,638 main DEBUG Registering MBean org.apache.logging.log4j2:type=AsyncContext@464bee09,component=StatusLogger
2022-02-21 16:55:32,638 main DEBUG Registering MBean org.apache.logging.log4j2:type=AsyncContext@464bee09,component=ContextSelector
2022-02-21 16:55:32,638 main DEBUG Registering MBean org.apache.logging.log4j2:type=AsyncContext@464bee09,component=Loggers,name=
2022-02-21 16:55:32,639 main DEBUG Registering MBean org.apache.logging.log4j2:type=AsyncContext@464bee09,component=Appenders,name=LogToConsole
2022-02-21 16:55:32,640 main DEBUG Registering MBean org.apache.logging.log4j2:type=AsyncContext@464bee09,component=Appenders,name=LogToRollingFile
//...
2022-02-21 16:55:33,020 pool-1-thread-1 DEBUG Stopped LoggerContext[name=AsyncContext@464bee09, org.apache.logging.log4j.core.async.AsyncLoggerContext@45fd9a4d] with status true

So we are done with configuring asynchronous logging in Log4j 2 using the Log4jContextSelector system property. You can optimize the performance of your Java by using The option for asynchronous in Log4J 2 tools.

For more detials you can check this link. https://logging.apache.org/log4j/2.x/manual/async.html