性能优化之异步日志
Posted Dreamer who
tags:
篇首语:本文由小常识网(cha138.com)小编为大家整理,主要介绍了性能优化之异步日志相关的知识,希望对你有一定的参考价值。
你听说过打印日志能把系统拖垮的情况吗。
所以项目中一般打印日志会使用异步AsyncAppender打印日志。
那么使用了AsyncAppender,会不会性能就好了,就不会阻塞业务流程了,会不会丢失日志呢,我们来看一下logback的实现。
先看下官方文档的介绍,AsyncAppender 会把处理的事件缓存到一个阻塞队列,默认情况下达到队列容量的80%的时候,会丢弃TRACE, DEBUG and INFO级别的事件,
根据默认配置neverBlock=false,队列也会发生阻塞,所以设置true,虽然完全是非阻塞但会丢失日志,特别是error级别的日志。
我们看下源码如何实现的。
public class AsyncAppender extends AsyncAppenderBase<ILoggingEvent>
boolean includeCallerData = false;
/**
* Events of level TRACE, DEBUG and INFO are deemed to be discardable.
* @param event
* @return true if the event is of level TRACE, DEBUG or INFO false otherwise.
*/
protected boolean isDiscardable(ILoggingEvent event)
Level level = event.getLevel();
return level.toInt() <= Level.INFO_INT;
protected void preprocess(ILoggingEvent eventObject)
eventObject.prepareForDeferredProcessing();
if (includeCallerData)
eventObject.getCallerData();
public boolean isIncludeCallerData()
return includeCallerData;
public void setIncludeCallerData(boolean includeCallerData)
this.includeCallerData = includeCallerData;
根据实现:
protected boolean isDiscardable(ILoggingEvent event)
Level level = event.getLevel();
return level.toInt() <= Level.INFO_INT;
public static final int OFF_INT = Integer.MAX_VALUE;
public static final int ERROR_INT = 40000;
public static final int WARN_INT = 30000;
public static final int INFO_INT = 20000;
public static final int DEBUG_INT = 10000;
public static final int TRACE_INT = 5000;
public static final int ALL_INT = Integer.MIN_VALUE;
TRACE, DEBUG and INFO级别的事件,在容量默认到达80%的时候会丢弃。
事件放入阻塞队列的时候即调用put方法时会判断容量及是否可以丢弃条件的判断,如下:
@Override
protected void append(E eventObject)
if (isQueueBelowDiscardingThreshold() && isDiscardable(eventObject))
return;
preprocess(eventObject);
put(eventObject);
private boolean isQueueBelowDiscardingThreshold()
return (blockingQueue.remainingCapacity() < discardingThreshold);
private void put(E eventObject)
if (neverBlock)
blockingQueue.offer(eventObject);
else
putUninterruptibly(eventObject);
private void putUninterruptibly(E eventObject)
boolean interrupted = false;
try
while (true)
try
blockingQueue.put(eventObject);
break;
catch (InterruptedException e)
interrupted = true;
finally
if (interrupted)
Thread.currentThread().interrupt();
当事件真正放入队列,是调用阻塞方法put,还是非阻塞方法offer,是由neverBlock配置决定的,默认false,会阻塞,所以为了性能,我们可以设置为true,也会丢弃日志。
真正处理队列事件的线程是默无闻的后台(Daemon)消费线程,
Worker worker = new Worker();
worker.setDaemon(true);
worker.setName("AsyncAppender-Worker-" + getName());
// make sure this instance is marked as "started" before staring the worker Thread
super.start();
worker.start()
事件的最终归宿AppenderAttachableImpl<E> aa。
class Worker extends Thread
public void run()
AsyncAppenderBase<E> parent = AsyncAppenderBase.this;
AppenderAttachableImpl<E> aai = parent.aai;
// loop while the parent is started
while (parent.isStarted())
try
E e = parent.blockingQueue.take();
aai.appendLoopOnAppenders(e);
catch (InterruptedException ie)
break;
addInfo("Worker thread will flush remaining events before exiting. ");
for (E e : parent.blockingQueue)
aai.appendLoopOnAppenders(e);
parent.blockingQueue.remove(e);
aai.detachAndStopAllAppenders();
异步打印日志是否非阻塞,是否会丢弃日志,是完全可以配置的,如果可以丢弃,依据日志的报警系统就不太准了,只能靠打点系统在系统内部aop的方式或其他方式打点上报了。
以上是关于性能优化之异步日志的主要内容,如果未能解决你的问题,请参考以下文章