修改Flume Log4j Appender

自定义Log4j Appender

要修改Flume Log4j Appender的实现，我们先了解一下Log4j Appender是如何自定义的。

自定义log4j appender需要继承log4j公共的基类：AppenderSkeleton

• 打印日志核心方法：abstract protected void append(LoggingEvent event);
• 初始化加载资源：public void activateOptions()，默认实现为空
• 释放资源：public void close()
• 是否需要按格式输出文本：public boolean requiresLayout()
• 正常情况下我们只需要覆盖append方法即可。然后就可以在log4j中使用了

Demo:

1. import org.apache.log4j.AppenderSkeleton;  
2. import org.apache.log4j.spi.LoggingEvent;  
3.   
4. public class HelloAppender extends AppenderSkeleton {  
5.   
6.     private String account ;  
7.       
8.     @Override  
9.     protected void append(LoggingEvent event) {  
10.         System.out.println("Hello, " + account + " : "+ event.getMessage());  
11.     }  
12.   
13.     @Override  
14.     public void close() {  
15.         // TODO Auto-generated method stub  
16.   
17.     }  
18.   
19.     @Override  
20.     public boolean requiresLayout() {  
21.         // TODO Auto-generated method stub  
22.         return false;  
23.     }  
24.   
25.     public String getAccount() {  
26.         return account;  
27.     }  
28.   
29.     public void setAccount(String account) {  
30.         this.account = account;  
31.     }  
32. }  

1. public static void main(String[] args) {  
2.     Log log = LogFactory.getLog("helloLog") ;  
3.     log.info("I am ready.") ;  
4. }  

log4j.properties 配置

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log4j.logger.helloLog=INFO, hello

log4j.appender.hello=HelloAppender
log4j.appender.hello.account=World

执行main函数，输出结果 Hello, World : I am ready.

修改FLume Log4j Appender

Event Header加入appname,hostname,logtype

由于hostname,logtype是固定不变的。所以直接写死在代码中。appname则用log4j.properties进行配置 – appname在log4j.properties中配置,添加：

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#应用程序名
log4j.appender.flume.Appname = 91pc

• 在Log4jAppender类中添加：

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private String appname;

public String getAppname() {
  return appname;
}

public void setAppname(String appname) {
  this.appname = appname;
}

• hostname,logtype在Log4jAppender类中添加

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//author:scy
try {
  hdrs.put("hostname", InetAddress.getLocalHost()+"");
} catch (UnknownHostException e1) {
      String msg = "Cant't get localhost IP";
      LogLog.error(msg);
      if (unsafeMode) {
        return;
      }
      throw new FlumeException(msg + " Exception follows.", e1);
}
//author:scy Need to alarm(>Info)
if(event.getLevel().toInt() > 20000){
  hdrs.put("logtype", "alarm");
}else{
  hdrs.put("logtype", "log4j");
}

Flume Log4j Appender添加log4j的异常详细信息

由于Flume Log4j Appender并没有将Log4j的错误异常栈详细信息封装到Event中，不利于我们的告警系统分析原因。 Log4jAppender.append()中添加如下：

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Event flumeEvent;
Object message = event.getMessage();
if (message instanceof GenericRecord) {
..
} else {
  hdrs.put(Log4jAvroHeaders.MESSAGE_ENCODING.toString(), "UTF8");
  //按照log4j.properties配置格式化日志
  String msg = layout != null ? layout.format(event) : message.toString();
        
  //author:edwardsbean
  if(layout.ignoresThrowable()) {
      String[] s = event.getThrowableStrRep();
      if (s != null) {
  int len = s.length;
  for(int i = 0; i < len; i++) {
      msg += s[i];
      msg += Layout.LINE_SEP;
  }
    }
  }
  
  flumeEvent = EventBuilder.withBody(msg, Charset.forName("UTF8"), hdrs);
}
try {
  rpcClient.append(flumeEvent);

日志接收端就可以接受到日志的详细信息：

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 [x] Received '2013-12-26 10:38:08 user log detail
 [nd-PC2600/192.168.253.126] FATAL [com.xx.test.Main] java.lang.Exception: error detail
  at com.xx.test.Main.main(Main.java:35)