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本文主要研究一下rocketmq的DailyRollingFileAppender
DailyRollingFileAppender
org/apache/rocketmq/logging/inner/LoggingBuilder.java
public static class DailyRollingFileAppender extends FileAppender { static final int TOP_OF_TROUBLE = -1; static final int TOP_OF_MINUTE = 0; static final int TOP_OF_HOUR = 1; static final int HALF_DAY = 2; static final int TOP_OF_DAY = 3; static final int TOP_OF_WEEK = 4; static final int TOP_OF_MONTH = 5; /** * The date pattern. By default, the pattern is set to * "'.'yyyy-MM-dd" meaning daily rollover. */ private String datePattern = "'.'yyyy-MM-dd"; private String scheduledFilename; private long nextCheck = System.currentTimeMillis() - 1; Date now = new Date(); SimpleDateFormat sdf; RollingCalendar rc = new RollingCalendar(); final TimeZone gmtTimeZone = TimeZone.getTimeZone("GMT"); public void setDatePattern(String pattern) { datePattern = pattern; } public String getDatePattern() { return datePattern; } public void activateOptions() { super.activateOptions(); if (datePattern != null && fileName != null) { now.setTime(System.currentTimeMillis()); sdf = new SimpleDateFormat(datePattern); int type = computeCheckPeriod(); printPeriodicity(type); rc.setType(type); File file = new File(fileName); scheduledFilename = fileName + sdf.format(new Date(file.lastModified())); } else { SysLogger.error("Either File or DatePattern options are not set for appender [" + name + "]."); } } void printPeriodicity(int type) { switch (type) { case TOP_OF_MINUTE: SysLogger.debug("Appender [" + name + "] to be rolled every minute."); break; case TOP_OF_HOUR: SysLogger.debug("Appender [" + name + "] to be rolled on top of every hour."); break; case HALF_DAY: SysLogger.debug("Appender [" + name + "] to be rolled at midday and midnight."); break; case TOP_OF_DAY: SysLogger.debug("Appender [" + name + "] to be rolled at midnight."); break; case TOP_OF_WEEK: SysLogger.debug("Appender [" + name + "] to be rolled at start of week."); break; case TOP_OF_MONTH: SysLogger.debug("Appender [" + name + "] to be rolled at start of every month."); break; default: SysLogger.warn("Unknown periodicity for appender [" + name + "]."); } } int computeCheckPeriod() { RollingCalendar rollingCalendar = new RollingCalendar(gmtTimeZone, Locale.getDefault()); // set sate to 1970-01-01 00:00:00 GMT Date epoch = new Date(0); if (datePattern != null) { for (int i = TOP_OF_MINUTE; i <= TOP_OF_MONTH; i++) { SimpleDateFormat simpleDateFormat = new SimpleDateFormat(datePattern); simpleDateFormat.setTimeZone(gmtTimeZone); String r0 = simpleDateFormat.format(epoch); rollingCalendar.setType(i); Date next = new Date(rollingCalendar.getNextCheckMillis(epoch)); String r1 = simpleDateFormat.format(next); if (r0 != null && r1 != null && !r0.equals(r1)) { return i; } } } return TOP_OF_TROUBLE; } void rollOver() throws IOException { if (datePattern == null) { handleError("Missing DatePattern option in rollOver()."); return; } String datedFilename = fileName + sdf.format(now); if (scheduledFilename.equals(datedFilename)) { return; } this.closeFile(); File target = new File(scheduledFilename); if (target.exists() && !target.delete()) { SysLogger.error("Failed to delete [" + scheduledFilename + "]."); } File file = new File(fileName); boolean result = file.renameTo(target); if (result) { SysLogger.debug(fileName + " -> " + scheduledFilename); } else { SysLogger.error("Failed to rename [" + fileName + "] to [" + scheduledFilename + "]."); } try { this.setFile(fileName, true, this.bufferedIO, this.bufferSize); } catch (IOException e) { handleError("setFile(" + fileName + ", true) call failed."); } scheduledFilename = datedFilename; } protected void subAppend(LoggingEvent event) { long n = System.currentTimeMillis(); if (n >= nextCheck) { now.setTime(n); nextCheck = rc.getNextCheckMillis(now); try { rollOver(); } catch (IOException ioe) { if (ioe instanceof InterruptedIOException) { Thread.currentThread().interrupt(); } SysLogger.error("rollOver() failed.", ioe); } } super.subAppend(event); } }复制代码 - 这里重写了subAppend方法，先检查当前时间是否大于nextCheck值，大于则更新nextCheck值，然后进行rollOver操作，最后在调用父类的subAppend方法
- rollOver方法先检查datedFilename是否等于scheduledFilename，如果不等则进行重命名操作，然后调用FileAppender的setFile操作，最后更新scheduledFilename值
小结
- rocketmq的DailyRollingFileAppender的实现是重写subAppend，每次subAppend之前先检查是否需要重命名文件，如果需要则调用rollOver方法
- rollOver方法主要是将文件名重名为scheduledFilename，datePattern的格式为.yyyy-MM-dd