差異處
這裏顯示兩個版本的差異處。
下次修改 | 前次修改 | ||
java:log4j:config_watchdog [2013/03/13 18:19] tony 建立 |
java:log4j:config_watchdog [2023/06/25 09:48] (目前版本) |
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行 2: | 行 2: | ||
====== FileWatchDog for Configuration ====== | ====== FileWatchDog for Configuration ====== | ||
===== Problem ===== | ===== Problem ===== | ||
- | 在軟體開發與debug的時候, | + | 在軟體開發與debug的時候,為了幫助了解程式做到什麼地方、發生問題在哪或狀態如何,會使用log去記錄重要的執行過程。但每次修改完log4j property file為了讓它生效,會重新啟動應用程式讓它reload,但這樣不是很煩嗎?為了解決這樣問題,我們可以透過Log4J提供的PropertyWatchdog去polling property file是否有做過修改。如以下程式碼,透過PropertyConfigurator的configureAndWatch就可以了,預設是60秒check一次。 |
+ | <code java> | ||
+ | org.apache.log4j.PropertyConfigurator.configureAndWatch(aLogPropertyFilePath); | ||
+ | </code> | ||
+ | 但如果你是使用1.2版本或之前的,可能會遇到和我一樣的情況。在我將package名稱如以下更動後(增加.internal),就收到了**log4j:ERROR Attempted to append to closed appender named**的訊息,還狂跳不停。這是怎麼一回事? | ||
+ | <code> | ||
+ | log4j.additivity.org.tonylin.facebook=false | ||
+ | log4j.logger.org.tonylin.facebook=INFO, CONSOLE, LOGFILE | ||
+ | -> | ||
+ | log4j.additivity.org.tonylin.facebook.internal=false | ||
+ | log4j.logger.org.tonylin.facebook.internal=INFO, CONSOLE, LOGFILE | ||
+ | </code> | ||
===== How to resolve? ===== | ===== How to resolve? ===== | ||
+ | 我先告訴大家我最後的解法,細部內容待我最後說明,有興趣的再繼續看。一看訊息就可以猜應該是狀態不正常造成的,在trace code後發現原先在每次檔案有改變後,也僅做了下面的動作。 | ||
+ | <code> | ||
+ | new PropertyConfigurator().doConfigure(filename, LogManager.getLoggerRepository()) | ||
+ | </code> | ||
+ | 於是我直接寫了一個class去繼承Log4j既有的FileWatchdog,並於發生改變時,重新reset configuration,這個問題就這樣解決了。 | ||
+ | <code java> | ||
+ | public class Log4jPropertyWatcher extends FileWatchdog { | ||
+ | |||
+ | private static Logger mLogger = LoggerFactory.getLogger(Log4jPropertyWatcher.class); | ||
+ | private static long mDefaultInterval = 1000l; | ||
+ | |||
+ | Log4jPropertyWatcher(String filename){ | ||
+ | super(filename); | ||
+ | } | ||
+ | |||
+ | @Override | ||
+ | protected void doOnChange() { | ||
+ | mLogger.debug("Log4j config is changed."); | ||
+ | LogManager.getLoggerRepository().resetConfiguration(); | ||
+ | new PropertyConfigurator().doConfigure(filename, LogManager.getLoggerRepository()); | ||
+ | } | ||
+ | |||
+ | public static void configureAndWatch(String filename){ | ||
+ | Log4jPropertyWatcher fileWatcher = new Log4jPropertyWatcher(filename); | ||
+ | fileWatcher.setDelay(mDefaultInterval); | ||
+ | fileWatcher.start(); | ||
+ | } | ||
+ | |||
+ | public static void setWatchInterval(long aInterval){ | ||
+ | mDefaultInterval = aInterval; | ||
+ | } | ||
+ | } | ||
+ | </code>h | ||
+ | 那Root Cuase呢? 錯誤訊息是由AppenderSkeleton丟出的,原因是它發現Appender已經被close了。close也許是關閉檔案或串流等等動作,這由根據Append實做決定,但重點是的確被某人給關閉了。 | ||
+ | <code java> | ||
+ | public synchronized void doAppend(LoggingEvent event) | ||
+ | { | ||
+ | if (this.closed) { | ||
+ | LogLog.error("Attempted to append to closed appender named [" + this.name + "]."); | ||
+ | return; | ||
+ | } | ||
+ | </code> | ||
+ | 於是重頭開始trace PropertyConfigurator,在parseCategory中發現它會透過logger的removeAllAppenders,將可能原有的Appender都close掉,且它每一個Appender都是相同的instance。這會造成什麼問題? 因為Log4j在做config的時候,會根據你所設定的package去加入Appender。如果你移除了某些package,又或者像是Problem中增加package的child而不保留原本的。**原先的package並沒有被Log4j回收或清除**,它在執行log時,會使用原本設定在它身上的Appender,跟著就死翹翹啦!\\ | ||
===== Reference ===== | ===== Reference ===== | ||
* [[http://blog.csdn.net/bxyz1203/article/details/7645185|log4j:ERROR Attempted to append to closed appender named的問題]] | * [[http://blog.csdn.net/bxyz1203/article/details/7645185|log4j:ERROR Attempted to append to closed appender named的問題]] | ||
* [[http://aofengblog.blog.163.com/blog/static/631702120114295537239/|Log4j的架構]] | * [[http://aofengblog.blog.163.com/blog/static/631702120114295537239/|Log4j的架構]] | ||
+ | * [[https://issues.apache.org/bugzilla/show_bug.cgi?id=17531|PropertyConfigurator.configureAndWatch() Bug]] | ||
===== ===== | ===== ===== |