聊聊logback的TimeBasedRollingPolicy

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本文主要研究一下logback的TimeBasedRollingPolicy

TimeBasedRollingPolicy

public class TimeBasedRollingPolicy<E> extends RollingPolicyBase implements TriggeringPolicy<E> {static final String FNP_NOT_SET = "The FileNamePattern option must be set before using TimeBasedRollingPolicy. ";// WCS: without compression suffixFileNamePattern fileNamePatternWithoutCompSuffix;private Compressor compressor;private RenameUtil renameUtil = new RenameUtil();Future<?> compressionFuture;Future<?> cleanUpFuture;private int maxHistory = UNBOUNDED_HISTORY;protected FileSize totalSizeCap = new FileSize(UNBOUNDED_TOTAL_SIZE_CAP);private ArchiveRemover archiveRemover;TimeBasedFileNamingAndTriggeringPolicy<E> timeBasedFileNamingAndTriggeringPolicy;boolean cleanHistoryOnStart = false;//......
}    

TimeBasedRollingPolicy继承了RollingPolicyBase，它定义了maxHistory、cleanHistoryOnStart、timeBasedFileNamingAndTriggeringPolicy等属性

start

    public void start() {// set the LR for our utility objectrenameUtil.setContext(this.context);// find out period from the filename patternif (fileNamePatternStr != null) {fileNamePattern = new FileNamePattern(fileNamePatternStr, this.context);determineCompressionMode();} else {addWarn(FNP_NOT_SET);addWarn(CoreConstants.SEE_FNP_NOT_SET);throw new IllegalStateException(FNP_NOT_SET + CoreConstants.SEE_FNP_NOT_SET);}compressor = new Compressor(compressionMode);compressor.setContext(context);// wcs : without compression suffixfileNamePatternWithoutCompSuffix = new FileNamePattern(Compressor.computeFileNameStrWithoutCompSuffix(fileNamePatternStr, compressionMode), this.context);addInfo("Will use the pattern " + fileNamePatternWithoutCompSuffix + " for the active file");if (compressionMode == CompressionMode.ZIP) {String zipEntryFileNamePatternStr = transformFileNamePattern2ZipEntry(fileNamePatternStr);zipEntryFileNamePattern = new FileNamePattern(zipEntryFileNamePatternStr, context);}if (timeBasedFileNamingAndTriggeringPolicy == null) {timeBasedFileNamingAndTriggeringPolicy = new DefaultTimeBasedFileNamingAndTriggeringPolicy<>();}timeBasedFileNamingAndTriggeringPolicy.setContext(context);timeBasedFileNamingAndTriggeringPolicy.setTimeBasedRollingPolicy(this);timeBasedFileNamingAndTriggeringPolicy.start();if (!timeBasedFileNamingAndTriggeringPolicy.isStarted()) {addWarn("Subcomponent did not start. TimeBasedRollingPolicy will not start.");return;}// the maxHistory property is given to TimeBasedRollingPolicy instead of to// the TimeBasedFileNamingAndTriggeringPolicy. This makes it more convenient// for the user at the cost of inconsistency here.if (maxHistory != UNBOUNDED_HISTORY) {archiveRemover = timeBasedFileNamingAndTriggeringPolicy.getArchiveRemover();archiveRemover.setMaxHistory(maxHistory);archiveRemover.setTotalSizeCap(totalSizeCap.getSize());if (cleanHistoryOnStart) {addInfo("Cleaning on start up");Instant now = Instant.ofEpochMilli(timeBasedFileNamingAndTriggeringPolicy.getCurrentTime());cleanUpFuture = archiveRemover.cleanAsynchronously(now);}} else if (!isUnboundedTotalSizeCap()) {addWarn("'maxHistory' is not set, ignoring 'totalSizeCap' option with value [" + totalSizeCap + "]");}super.start();}

start方法根据fileNamePatternStr创建FileNamePattern，根据compressionMode创建Compressor，对于zip压缩的创建zipEntryFileNamePattern，另外默认设置了DefaultTimeBasedFileNamingAndTriggeringPolicy，然后执行其start，对于maxHistory不为0的，则设置archiveRemover

stop

   public void stop() {if (!isStarted())return;waitForAsynchronousJobToStop(compressionFuture, "compression");waitForAsynchronousJobToStop(cleanUpFuture, "clean-up");super.stop();}private void waitForAsynchronousJobToStop(Future<?> aFuture, String jobDescription) {if (aFuture != null) {try {aFuture.get(CoreConstants.SECONDS_TO_WAIT_FOR_COMPRESSION_JOBS, TimeUnit.SECONDS);} catch (TimeoutException e) {addError("Timeout while waiting for " + jobDescription + " job to finish", e);} catch (Exception e) {addError("Unexpected exception while waiting for " + jobDescription + " job to finish", e);}}}    

stop方法执行waitForAsynchronousJobToStop，主要是等待compressionFuture及cleanUpFuture

rollover

    public void rollover() throws RolloverFailure {// when rollover is called the elapsed period's file has// been already closed. This is a working assumption of this method.String elapsedPeriodsFileName = timeBasedFileNamingAndTriggeringPolicy.getElapsedPeriodsFileName();String elapsedPeriodStem = FileFilterUtil.afterLastSlash(elapsedPeriodsFileName);if (compressionMode == CompressionMode.NONE) {if (getParentsRawFileProperty() != null) {renameUtil.rename(getParentsRawFileProperty(), elapsedPeriodsFileName);} // else { nothing to do if CompressionMode == NONE and parentsRawFileProperty ==// null }} else {if (getParentsRawFileProperty() == null) {compressionFuture = compressor.asyncCompress(elapsedPeriodsFileName, elapsedPeriodsFileName,elapsedPeriodStem);} else {compressionFuture = renameRawAndAsyncCompress(elapsedPeriodsFileName, elapsedPeriodStem);}}if (archiveRemover != null) {Instant now = Instant.ofEpochMilli(timeBasedFileNamingAndTriggeringPolicy.getCurrentTime());this.cleanUpFuture = archiveRemover.cleanAsynchronously(now);}}

rollover方法通过timeBasedFileNamingAndTriggeringPolicy获取elapsedPeriodsFileName，然后将当前文件重命名为elapsedPeriodsFileName，对于archiveRemover不为null的则执行cleanAsynchronously

ArchiveRemover

ch/qos/logback/core/rolling/helper/ArchiveRemover.java

public interface ArchiveRemover extends ContextAware {void clean(Instant instant);void setMaxHistory(int maxHistory);void setTotalSizeCap(long totalSizeCap);Future<?> cleanAsynchronously(Instant now);
}

ArchiveRemover定义了clean、setMaxHistory、setTotalSizeCap、cleanAsynchronously方法

TimeBasedArchiveRemover

ch/qos/logback/core/rolling/helper/TimeBasedArchiveRemover.java

public class TimeBasedArchiveRemover extends ContextAwareBase implements ArchiveRemover {static protected final long UNINITIALIZED = -1;// aim for 32 days, except in case of hourly rollover, see// MAX_VALUE_FOR_INACTIVITY_PERIODSstatic protected final long INACTIVITY_TOLERANCE_IN_MILLIS = 32L * (long) CoreConstants.MILLIS_IN_ONE_DAY;static final int MAX_VALUE_FOR_INACTIVITY_PERIODS = 14 * 24; // 14 days in case of hourly rolloverfinal FileNamePattern fileNamePattern;final RollingCalendar rc;private int maxHistory = CoreConstants.UNBOUNDED_HISTORY;private long totalSizeCap = CoreConstants.UNBOUNDED_TOTAL_SIZE_CAP;final boolean parentClean;long lastHeartBeat = UNINITIALIZED;public TimeBasedArchiveRemover(FileNamePattern fileNamePattern, RollingCalendar rc) {this.fileNamePattern = fileNamePattern;this.rc = rc;this.parentClean = computeParentCleaningFlag(fileNamePattern);}//......
}    

TimeBasedArchiveRemover定义了fileNamePattern、rollingCalendar、maxHistory、totalSizeCap属性

clean

    public void clean(Instant now) {long nowInMillis = now.toEpochMilli();// for a live appender periodsElapsed is expected to be 1int periodsElapsed = computeElapsedPeriodsSinceLastClean(nowInMillis);lastHeartBeat = nowInMillis;if (periodsElapsed > 1) {addInfo("Multiple periods, i.e. " + periodsElapsed+ " periods, seem to have elapsed. This is expected at application start.");}for (int i = 0; i < periodsElapsed; i++) {int offset = getPeriodOffsetForDeletionTarget() - i;Instant instantOfPeriodToClean = rc.getEndOfNextNthPeriod(now, offset);cleanPeriod(instantOfPeriodToClean);}}public void cleanPeriod(Instant instantOfPeriodToClean) {File[] matchingFileArray = getFilesInPeriod(instantOfPeriodToClean);for (File f : matchingFileArray) {addInfo("deleting " + f);f.delete();}if (parentClean && matchingFileArray.length > 0) {File parentDir = getParentDir(matchingFileArray[0]);removeFolderIfEmpty(parentDir);}}    

clean方法主要是计算periodsElapsed，然后通过rollingCalendar获取instantOfPeriodToClean，再执行cleanPeriod方法；cleanPeriod方法则通过getFilesInPeriod获取对应的文件，然后挨个执行delete，最后再判断下parentDir是否为空，为空则删除

cleanAsynchronously

    public Future<?> cleanAsynchronously(Instant now) {ArhiveRemoverRunnable runnable = new ArhiveRemoverRunnable(now);ExecutorService executorService = context.getExecutorService();Future<?> future = executorService.submit(runnable);return future;}public class ArhiveRemoverRunnable implements Runnable {Instant now;ArhiveRemoverRunnable(Instant now) {this.now = now;}@Overridepublic void run() {clean(now);if (totalSizeCap != UNBOUNDED_TOTAL_SIZE_CAP && totalSizeCap > 0) {capTotalSize(now);}}}    

cleanAsynchronously主要是创建ArhiveRemoverRunnable，然后提交到context的executorService；ArhiveRemoverRunnable实现了Runnable接口，其run方法执行clean，对于totalSizeCap大于0的执行capTotalSize

小结

TimeBasedRollingPolicy包含了RollingPolicy及TriggeringPolicy，其rollover方法主要是委托给timeBasedFileNamingAndTriggeringPolicy获取elapsedPeriodsFileName然后去rename，对于maxHistory不是无限制的设置timeBasedFileNamingAndTriggeringPolicy的archiveRemover的maxHistory及totalSizeCap，执行其cleanAsynchronously方法；其isTriggeringEvent方法也是委托给了timeBasedFileNamingAndTriggeringPolicy。