还在用 Log4j ？快用 Log4j2，性能太猛了！ / 开普饭

环境

jdk：1.7.0_79

cpu：i5-4570@3.20GHz 4核

eclipse：3.7

操作系统：win7

准备

1.log4j:1.7.21

org.slf4jslf4j-log4j121.7.21

log4j.xml

<?xml version="1.0" encoding="UTF-8"?>

2.logback:1.1.7

ch.qos.logbacklogback-classic1.1.7

logback.xml

%d{HH:mm:ss.SSS} [%thread] %-5level %logger{36} - %msg%ntestFile.logtrue[%t] - %m%n0

3.log4j2:2.6.2

org.apache.logging.log4jlog4j-core2.6.2org.apache.logging.log4jlog4j-slf4j-impl2.6.2com.lmaxdisruptor3.3.4

log4j2.xml

<?xml version="1.0" encoding="UTF-8"?>[%t] - %m%n

测试

准备50条线程同时记录1000000条数据，然后统计时间，详细代码如下：

import java.util.concurrent.CountDownLatch;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public class App {
    private static Logger log = LoggerFactory.getLogger(App.class);

    public static void main(String[] args) throws InterruptedException {
        int messageSize = 1000000;
        int threadSize = 50;
        final int everySize = messageSize / threadSize;

        final CountDownLatch cdl = new CountDownLatch(threadSize);
        long startTime = System.currentTimeMillis();
        for (int ts = 0; ts < threadSize; ts++) {
            new Thread(new Runnable() {

                @Override
                public void run() {
                    for (int es = 0; es < everySize; es++) {
                        log.info("======info");
                    }
                    cdl.countDown();
                }
            }).start();
        }

        cdl.await();
        long endTime = System.currentTimeMillis();
        System.out.println("log4j1:messageSize = " + messageSize
                + ",threadSize = " + threadSize + ",costTime = "
                + (endTime - startTime) + "ms");
    }
}

log4j1和logback的同步和异步分别修改为对应的appender就行了

log4j2的异步方式提供了2中模式：

1.全局开启

设置Log4jContextSelector系统属性为：
org.apache.logging.log4j.core.async.AsyncLoggerContextSelector

System.setProperty("Log4jContextSelector", "org.apache.logging.log4j.core.async.AsyncLoggerContextSelector");

2.混合同步异步模式

不需要设置Log4jContextSelector，但是需要使用AsyncLogger标签

更多详细参考官方文档：http://logging.apache.org/log4j/2.x/manual/async.html#AllAsync

结果
分别测试完以后统计成表格如下：

log4j2的异步模式表现了绝对的性能优势，优势主要得益于Disruptor框架的使用

LMAX Disruptor technology. Asynchronous Loggers internally use the Disruptor, a lock-free inter-thread communication library, instead of queues, resulting in higher throughput and lower latency.

一个无锁的线程间通信库代替了原来的队列

http://ifeve.com/disruptor/

来源：https://my.oschina.net/OutOfMemory/blog/789267

还在用 Log4j ？快用 Log4j2，性能太猛了！

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