Qua*_*nic 6 java logging log4j thread-safety
(这是在SLES11,Java 7,Tomcat 6,log4j-1.2.16)
我们使用log4j将不同的东西写入不同的日志文件.我继承了这段代码,所以无论好坏,一般结构都会暂时停留.
记录器将创建两个日志文件:main.log和stats.log.通过单独的调用将两个记录器记录到某个统计信息(您将在下面看到),并将大量其他内容记录到主日志中.
所以通过我们的代码你会看到类似的东西Log.logMain(someMessageToLog);.在我们的代码中的一个地方(由多个线程执行)有以下内容:
String statsMessage = createStatsMessage();
Log.logMain(statsMessage);
Log.logStats(statsMessage);
主记录器main的名称是,统计记录器的名称stats.问题是,有时在负载很重的情况下,我们会看到main.log其中包含字符串stats INFO的行.所有内容main.log应该只包含在内,main INFO因为这是记录到该文件的唯一记录器,而且我们在某些行中看到混合输出.这似乎是线程安全问题,但log4j文档说log4j是线程安全的.这是我的意思的一个例子:
2012-03-21 16:01:34,7742012-03-21 16:01:34,774| | stats main INFO [INFO http-8080-18]: [message redacted].
2012-03-21 16:01:36,380| main 2012-03-21 16:01:36,380| INFO [stats INFO http-8080-15]: [message redacted].
2012-03-21 16:01:37,465| main INFO 2012-03-21 16:01:37,465 [| stats http-8080-1]: [message redacted].
这是Log类(被剥离以仅显示有问题的记录器 - 其中实际上有一堆其他记录器,所有设置都与这些类似):
import org.apache.log4j.*;
import java.io.IOException;
final public class Log
{
private static final String LOG_IDENTIFIER_MAINLOG = "main";
private static final String LOG_IDENTIFIER_STATSLOG = "stats";
private static final String MAIN_FILENAME = "/var/log/app_main.log";
private static final String STATS_FILENAME = "/var/log/app_stats.log";
private static final int BACKUP_INDEX = 40;
private static final String BACKUP_SIZE = "10MB";
private static final PatternLayout COMMON_LAYOUT =
new PatternLayout("%d| %c %-6p [%t]: %m.%n");
private static Logger mainLogger;
private static Logger statsLogger;
public static void init() {
init(MAIN_FILENAME, STATS_FILENAME);
}
public static void init(String mainLogFilename,
String statsLogFilename) {
mainLogger = initializeMainLogger(mainLogFilename);
statsLogger = initializeStatsLogger(statsLogFilename);
}
public static void logMain(String message) {
if (mainLogger != null) {
mainLogger.info(message);
}
}
public static void logStats(String message) {
if (statsLogger != null) {
statsLogger.info(message);
}
}
private static Logger getLogger(String loggerIdentifier) {
Logger logger = Logger.getLogger(loggerIdentifier);
logger.setAdditivity(false);
return logger;
}
private static boolean addFileAppender(Logger logger,
String logFilename,
int maxBackupIndex,
String maxSize) {
try {
RollingFileAppender appender =
new RollingFileAppender(COMMON_LAYOUT, logFilename);
appender.setMaxBackupIndex(maxBackupIndex);
appender.setMaxFileSize(maxSize);
logger.addAppender(appender);
}
catch (IOException ex) {
ex.printStackTrace();
return false;
}
return true;
}
private static Logger initializeMainLogger(String filename) {
Logger logger = getLogger(LOG_IDENTIFIER_MAINLOG);
addFileAppender(logger, filename, BACKUP_INDEX, BACKUP_SIZE);
logger.setLevel(Level.INFO);
return logger;
}
private static Logger initializeStatsLogger(String filename) {
Logger logger = getLogger(LOG_IDENTIFIER_STATSLOG);
addFileAppender(logger, filename, BACKUP_INDEX, BACKUP_SIZE);
logger.setLevel(Level.INFO);
return logger;
}
}
更新:
这是一个小程序(至少对我而言)将重现上述Log类的问题:
final public class Stress
{
public static void main(String[] args) throws Exception {
if (args.length != 2) {
Log.init();
}
else {
Log.init(args[0], args[1]);
}
for (;;) {
// I know Executors are preferred, but this
// is a quick & dirty test program
Thread t = new Thread(new TestLogging());
t.start();
}
}
private static final class TestLogging implements Runnable
{
private static int counter = 0;
@Override
public void run() {
String msg = new StringBuilder("Count is: ")
.append(counter++).toString();
Log.logMain(msg);
Log.logStats(msg);
try {
Thread.sleep(1);
}
catch (InterruptedException e) {
Log.logMain(e.getMessage());
}
}
}
}
以及日志中的一些示例输出:
$ grep stats main.log
2012-03-23 15:30:35,919| stats 2012-03-23 15:30:35,919| main INFO INFO [ [Thread-313037]: Thread-313036]: Count is: 312987.
2012-03-23 15:30:35,929| stats INFO [Thread-313100]: Count is: 313050.
2012-03-23 15:30:35,937| stats INFO [Thread-313168]: Count is: 313112.
2012-03-23 15:30:35,945| stats INFO [Thread-313240]: Count is: 313190.
2012-03-23 15:30:35,946| stats INFO [Thread-313251]: Count is: 313201.
2012-03-23 15:30:35,949| stats INFO [2012-03-23 15:30:35,949| main INFO Thread-313281]: Count is: 313231.
2012-03-23 15:30:35,954| stats INFO [Thread-313331]: Count is: 313281.
2012-03-23 15:30:35,956| 2012-03-23 15:30:35,956stats | main INFOINFO [ [Thread-313356]: Count is: 313306.
2012-03-23 15:30:35,9562012-03-23 15:30:35,956| main | INFO stats [INFOThread-313359]: Count is: 313309.
2012-03-23 15:30:35,962| stats INFO 2012-03-23 15:30:35,962| main INFO [Thread-313388]: [Count is: 313338.
和
$ grep main stats.log
2012-03-23 15:30:35,913| 2012-03-23 15:30:35,913| main INFO [Thread-312998]: Count is: 312948.
2012-03-23 15:30:35,915| main INFO [Thread-313014]: Count is: 312964.
2012-03-23 15:30:35,919| stats 2012-03-23 15:30:35,919| main INFO INFO [ [Thread-313037]: Thread-313036]: Count is: 312987.
2012-03-23 15:30:35,931| main INFO [Thread-313116]: Count is: 313066.
2012-03-23 15:30:35,947| main INFO [2012-03-23 15:30:35,947Thread-313264]: | Count is: 313214.
2012-03-23 15:30:35,949| stats INFO [2012-03-23 15:30:35,949| main INFO Thread-313281]: Count is: 313231.
2012-03-23 15:30:35,956| 2012-03-23 15:30:35,956stats | main INFOINFO [ [Thread-313356]: Count is: 313306.
2012-03-23 15:30:35,9562012-03-23 15:30:35,956| main | INFO stats [INFOThread-313359]: Count is: 313309.
2012-03-23 15:30:35,962| stats INFO 2012-03-23 15:30:35,962| main INFO [Thread-313388]: [Count is: 313338.
值得一提的是,在一个145516行的main.log文件中,"统计数据"出现了2452次.所以它并不罕见,但它不是一直都在发生(当然这个测试非常极端).
Chr*_*ite 11
http://logging.apache.org/log4j/1.2/apidocs/org/apache/log4j/PatternLayout.html
你在两个appender之间共享PatternLayout,根据上面的API链接:
已知此代码具有同步和org.apache.log4j.EnhancedPatternLayout中不存在的其他问题.应优先使用EnhancedPatternLayout而不是PatternLayout.EnhancedPatternLayout分布在log4j extras伴侣中.
因此,为每个appender创建一个新的PatternLayout
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