一、asyncLogger和asyncRootLogger的异同
在使用log4j2异步日志配置时,可以使用asyncLogger和asyncRootLogger两个配置项来实现异步日志记录。两者的主要区别在于asyncRootLogger会记录所有的日志事件,而asyncLogger仅记录指定了级别的日志事件。asyncRootLogger的默认级别为ERROR,而asyncLogger的默认级别为DEBUG。
示例代码:
<Configuration status="debug" name="AsyncAppenders"> <Appenders> <Async name="Async"> <AppenderRef ref="SomeAppender"/> </Async> </Appenders> <Loggers> <AsyncLogger name="com.foo.Bar" level="debug" includeLocation="true"> <AppenderRef ref="Async"/> </AsyncLogger> <AsyncRoot level="error"> <AppenderRef ref="Async"/> </AsyncRoot> </Loggers> </Configuration>
二、异步日志队列的配置
在log4j2异步日志配置中,可以通过配置异步日志队列来实现更好的性能。包括BlockingQueue、LinkedBlockingQueue和ArrayBlockingQueue在内的多种队列实现都被支持。BlockingQueue可以无限制地添加新的元素,LinkedBlockingQueue限制队列大小为Integer.MAX_VALUE,而ArrayBlockingQueue则需要指定队列的大小。
示例代码:
<Configuration status="debug" name="AsyncAppenders"> <Appenders> <Async name="Async"> <AppenderRef ref="SomeAppender"/> <BlockingQueueFactory> <ArrayBlockingQueue> <capacity>1000</capacity> </ArrayBlockingQueue> </BlockingQueueFactory> </Async> </Appenders> <Loggers> <AsyncLogger name="com.foo.Bar" level="debug" includeLocation="true"> <AppenderRef ref="Async"/> <BlockingQueueFactory> <LinkedBlockingQueue/> </BlockingQueueFactory> </AsyncLogger> </Loggers> </Configuration>
三、异步日志并发线程数的配置
在log4j2异步日志配置中,可以通过配置异步日志的并发线程数来控制日志的处理速度。可以指定最小、最大、以及线程池名称等参数。如果不指定最大线程数值,默认为2147483647。
示例代码:
<Configuration status="debug" name="AsyncAppenders"> <Appenders> <Async name="Async"> <AppenderRef ref="SomeAppender"/> <BlockingQueueFactory> <ArrayBlockingQueue> <capacity>1000</capacity> </ArrayBlockingQueue> </BlockingQueueFactory> <AsyncQueueFullPolicy> <DiscardPolicy/> </AsyncQueueFullPolicy> <AsyncLoggerConfig> <ContextStackFactory> <ThreadContextStackFactory/> </ContextStackFactory> <ThreadName>AsyncLoggerConfig</ThreadName> <Level>info</Level> <Properties> <Property name="vendor">Apache</Property> <Property name="product">MyApp</Property> </Properties> </AsyncLoggerConfig> <disruptor> <WaitStrategy>BlockingWait</WaitStrategy> <RingBufferSize>262144</RingBufferSize> <ClaimStrategy>SingleThreaded</ClaimStrategy> <BufferSize>32768</BufferSize> </disruptor> <ThreadProperties> <Property name="ThreadPriority">5</Property> </ThreadProperties> <executor> <ThreadFactory> <name>MyThread</name> <priority>1</priority> </ThreadFactory> <core>1</core> <max>4</max> <keepAliveMillis>1000</keepAliveMillis> <shutdownTimeout>5000</shutdownTimeout> <BlockingQueueFactory> <LinkedBlockingQueue/> </BlockingQueueFactory> </executor> </Async> </Appenders> <Loggers> <AsyncRoot level="error"> <AppenderRef ref="Async"/> </AsyncRoot> </Loggers> </Configuration>
四、异步日志的discard_policy属性
在使用log4j2异步日志配置时,可以通过discard_policy属性来控制队列满时的行为。默认情况下,队列满时会阻塞,然后等待空闲状态。用户可以通过discard_policy属性,选择在队列满时直接抛弃最早的一条日志,或者抛弃最新的一条日志。
示例代码:
<Async name="async"> ... <AsyncQueueFullPolicy> <DiscardPolicy/> </AsyncQueueFullPolicy> ... </Async>
五、异步日志的性能测试
下面是异步日志的性能测试代码。可以通过测试代码来验证使用异步日志配置后的性能优化效果。
package com.jeff.example; import org.apache.logging.log4j.LogManager; import org.apache.logging.log4j.Logger; import org.apache.logging.log4j.ThreadContext; public class AsyncLoggerPerformanceTest { public static void main(String[] args) { Runnable task = new Runnable() { @Override public void run() { Logger logger = LogManager.getLogger("async"); int count = 0; while (count++ < 100000) { logger.info("count: " + count); } } }; Thread t1 = new Thread(task); Thread t2 = new Thread(task); t1.start(); t2.start(); } }