signal信号捕捉

[置顶]signal信号捕捉       

        分类：            java初级2013-02-17 13:431074人阅读评论(0)收藏举报

Signal 顾名思义是信号的意思,为什么要用到这个东西了？

原因：由于现在在负责写网游的后台loginServer，里面写了不少配置文件，当我们的产品上线后，loginServer开启后这时配置文件的数据就被读取进去了，但是当我们想修改这些配置数据怎么办呢？不可能让把loginServer关掉吧! 假如在线几万了，你导致关闭服务弄的几千上万的用户进不去，你知道会损失多少用户，多少钱吗？还会被老板搞死的..

有两种方法：

1.Signal

2.通过协议发送一个消息过来，然后重新读取一下配置文件

如果朋友知道更好的办法的朋友也希望能分享一下，告诉下我..

由于博文标题是signal信号捕捉，第二种方法通过协议消息来重新读取配置数据，就不说了...

一、首先看下java中Signal枚举有哪些各代表什么含义：

USR1:用户自定义信号1
USR2:用户自定义信号2

推荐：用户自定义信号USR1和USR2,其他信号我同事说可能会隐患别的问题,最好不用.

TERM:终止信号

KILL:Kill信号

INT:键盘中断

HUP :终端挂起或者控制进程终止

BUS：总线错误

上面这5个出现的比较多，下面是其他的信号

ALRM:警告

CHLD：子进程结束信号

CONT:进程继续（曾被停止的进程）

FPE:浮点异常

ILL:非法指令

IO:某I/O操作现在可以进行了

IOT:IO捕获指令

PIPE:管道破裂: 写一个没有读端口的管道

PROF:Profiling定时器到

PWR:电源故障

QUIT:键盘的退出键被按下

SEGV:无效的内存引用

STKFLT:协处理器堆栈错误

STOP:终止进程
TRAP:跟踪/断点捕获

TSTP:控制终端（tty）上按下停止键

TTIN:后台进程企图从控制终端读

TTOU:后台进程企图从控制终端写

VTALRM: 实际时间报警时钟信号

WINCH:窗口大小改变

XCPU:超出设定的CPU时间限制

XFSZ:超出设定的文件大小限制

二、老样子上传我的demo

[java] view plaincopyprint?

1. <span style="font-size: 12px;">package com.back; 
2.  
3. import org.apache.commons.logging.Log; 
4. import org.apache.commons.logging.LogFactory; 
5. import org.apache.log4j.PropertyConfigurator; 
6.  
7. import sun.misc.Signal; 
8. import sun.misc.SignalHandler; 
9.  
10. /***
11. * java信号捕获处理demo
12. */ 
13. public class SignalHandlerExampleimplements SignalHandler { 
14.     static Log log=LogFactory.getLog(SignalHandlerExample.class); 
15.      
16.     private boolean Running =true; 
17.       
18.     public SignalHandlerExample() { 
19.          this.setupHandler(); 
20.      } 
21.       
22.     private void setupHandler() { 
23.          this.handleSignal("INT"); 
24.          this.handleSignal("TERM"); 
25.          this.handleSignal("HUP"); 
26.      } 
27.       
28.     public void handleSignal(final String signalName) { 
29.          try { 
30.              Signal.handle(new Signal(signalName),this); 
31.          } catch (IllegalArgumentException e) { 
32.              // 可能这个信号,并不支持这个平台或JVM作为目前配置 
33.              e.printStackTrace(); 
34.          } 
35.      } 
36.       
37.     /**
38.      * 捕获信号
39.      * @param signal The {@link sun.misc.Signal} that we received
40.      **/ 
41.      public synchronizedvoid handle(Signal signal) { 
42.          // we are only interested in catching the "TERM" signal 
43.          if ( signal.getName().equals("TERM") ) { 
44.              log.info(" TERM received " + signal.getName() ); 
45.              log.info("threadName" + Thread.currentThread().getName()); 
46.              System.exit(-1); 
47.          } else if ( signal.getName().equals("INT") ||signal.getName().equals("HUP") ) { 
48.              setRunningStatus( false ); 
49.              notifyAll(); //TODO - clarify if notify OR notifyall 
50.          } 
51.          log.info( signal.getName() + " " + signal.getNumber() ); 
52.          log.info( getRunningStatus()+"" ); 
53.      } 
54.       
55.     public void setRunningStatus(boolean Status ) { 
56.         this.Running = Status; 
57.     } 
58.       
59.     public boolean getRunningStatus() { 
60.         return Running; 
61.     } 
62.       
63.     /**
64.      * General "clean up" method which is called when we receive a TERM
65.      signal
66.      * This will likely be superseeded by specific cleanup code
67.      *
68.      **/ 
69.      public boolean cleanUp() { 
70.          // TODO - we need to decide what we are going to do one we trap a 
71.          //  TERMinate signal. 
72.          // We need to complete all our threads nicely. 
73.          log.info("Cleaning up!"); 
74.          return true; 
75.      } 
76.       
77.     public synchronizedvoid myWait() { 
78.          try{ 
79.              wait(); 
80.          }catch (InterruptedException e){ 
81.              log.info( "myWait WOKEN UP" + e ); 
82.          } 
83.     } 
84.       
85.     public staticvoid main(final String[] args) { 
86.         PropertyConfigurator.configure("./config/log4j.properties"); 
87.           
88.         SignalHandlerExample mySignalHandler = new SignalHandlerExample(); 
89.       
90.         while ( mySignalHandler.getRunningStatus() ) { 
91.             log.info("waiting"); 
92.             mySignalHandler.myWait(); 
93.             log.info("woken up"); 
94.         } 
95.     } 
96. } 
97. </span> 

package com.back;import org.apache.commons.logging.Log;import org.apache.commons.logging.LogFactory;import org.apache.log4j.PropertyConfigurator;import sun.misc.Signal;import sun.misc.SignalHandler;/**** java信号捕获处理demo*/public class SignalHandlerExample implements SignalHandler {static Log log=LogFactory.getLog(SignalHandlerExample.class);private boolean Running = true; public SignalHandlerExample() { this.setupHandler(); } private void setupHandler() { this.handleSignal("INT"); this.handleSignal("TERM"); this.handleSignal("HUP"); } public void handleSignal(final String signalName) { try { Signal.handle(new Signal(signalName), this); } catch (IllegalArgumentException e) { // 可能这个信号,并不支持这个平台或JVM作为目前配置 e.printStackTrace(); } } /** * 捕获信号 * @param signal The {@link sun.misc.Signal} that we received **/ public synchronized void handle(Signal signal) { // we are only interested in catching the "TERM" signal if ( signal.getName().equals("TERM") ) { log.info(" TERM received " + signal.getName() ); log.info("threadName" + Thread.currentThread().getName()); System.exit(-1); } else if ( signal.getName().equals("INT") ||signal.getName().equals("HUP") ) { setRunningStatus( false ); notifyAll(); //TODO - clarify if notify OR notifyall } log.info( signal.getName() + " " + signal.getNumber() ); log.info( getRunningStatus()+"" ); } public void setRunningStatus( boolean Status ) {this.Running = Status;} public boolean getRunningStatus() {return Running;} /** * General "clean up" method which is called when we receive a TERM signal * This will likely be superseeded by specific cleanup code * **/ public boolean cleanUp() { // TODO - we need to decide what we are going to do one we trap a // TERMinate signal. // We need to complete all our threads nicely. log.info("Cleaning up!"); return true; } public synchronized void myWait() { try{ wait(); }catch (InterruptedException e){ log.info( "myWait WOKEN UP" + e ); }} public static void main(final String[] args) {    PropertyConfigurator.configure("./config/log4j.properties"); SignalHandlerExample mySignalHandler = new SignalHandlerExample(); while ( mySignalHandler.getRunningStatus() ) {log.info("waiting");mySignalHandler.myWait();log.info("woken up");}}}

补充：sun.misc.Signal和SignalHandler引入不进来解决方法：

设置设计到了日志的打印，如果不知道请参看我java日志打印那篇文章

我们上次SignalTest.jar到linux服务器上运行如下：

1.Ctrl+C:

2.INT:kill -s INT 端口号

这个时候我们就可以利用这种方式来重读我们的配置文件了...

参看文章：

http://coding.derkeiler.com/Archive/Java/comp.lang.java.help/2006-10/msg00248.html

http://wangym.iteye.com/blog/733693

http://blog.chinaunix.net/uid-20441206-id-3138952.html

相关文章：

http://blog.csdn.net/qinghua9/article/details/5295934

http://www.csl.mtu.edu/cs4411.ck/www/NOTES/signal/install.html