logback TimeBasedRollingPolicy按天生成日志源码解析

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 suffix
    FileNamePattern 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;
    //......
}

public void start() {
        // set the LR for our utility object
        renameUtil.setContext(this.context);
        // find out period from the filename pattern
        if (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 suffix
        fileNamePatternWithoutCompSuffix = 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();
    }

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);
            }
        }
    }

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);
        }
    }

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

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_PERIODS
    static 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 rollover
    final 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);
    }
    //......
}

public void clean(Instant now) {
        long nowInMillis = now.toEpochMilli();
        // for a live appender periodsElapsed is expected to be 1
        int 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);
        }
    }

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;
        }
        @Override
        public void run() {
            clean(now);
            if (totalSizeCap != UNBOUNDED_TOTAL_SIZE_CAP && totalSizeCap > 0) {
                capTotalSize(now);
            }
        }
    }