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干净地强制 Log4j RollingFileAppender 在午夜后不久滚动？

发布于 2024-09-30 12:32:05 字数 122 浏览 0 评论 0原文

Log4j RollingFileAppender 的正常行为是在第一条日志消息发生在不同的一天时滚动，但有些人会因为每个日期的空日志文件而感到温暖和模糊，即使什么也没有发生。有没有办法强制它在午夜之后滚动而不向日志写入虚拟消息？

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肥爪爪 2024-10-07 12:32:05

我非常仔细地查看了这段代码 - 简单的答案是“不”。翻转作为 Appender 上 doAppend() 流程的一部分被触发 - 触发它的唯一方法是记录一些内容。

你可以用 cron 来伪造这个：只需让 cron 脚本在明天 11:58 点触摸文件即可。这将为您提供您正在寻找的空日志文件行为。

下面是实现翻转功能的代码：

void rollOver() throws IOException {

    /* Compute filename, but only if datePattern is specified */
    if (datePattern == null) {
      errorHandler.error("Missing DatePattern option in rollOver().");
      return;
    }

    String datedFilename = fileName+sdf.format(now);
    // It is too early to roll over because we are still within the
    // bounds of the current interval. Rollover will occur once the
    // next interval is reached.
    if (scheduledFilename.equals(datedFilename)) {
      return;
    }

    // close current file, and rename it to datedFilename
    this.closeFile();

    File target  = new File(scheduledFilename);
    if (target.exists()) {
      target.delete();
    }

    File file = new File(fileName);
    boolean result = file.renameTo(target);
    if(result) {
      LogLog.debug(fileName +" -> "+ scheduledFilename);
    } else {
      LogLog.error("Failed to rename ["+fileName+"] to ["+scheduledFilename+"].");
    }

    try {
      // This will also close the file. This is OK since multiple
      // close operations are safe.
      this.setFile(fileName, false, this.bufferedIO, this.bufferSize);
    }
    catch(IOException e) {
      errorHandler.error("setFile("+fileName+", false) call failed.");
    }
    scheduledFilename = datedFilename;
  }

I've looked at this code very closely - the simple answer is 'no'. The rollover is triggered as part of the doAppend() flow on the Appender - the only way to trigger it is to log something.

You could fake this with cron: just have a cron script touch the file for tomorrow at like 11:58. That will get you the empty logfile behavior you're looking for.

Here's the code that implements the rollover function:

void rollOver() throws IOException {

    /* Compute filename, but only if datePattern is specified */
    if (datePattern == null) {
      errorHandler.error("Missing DatePattern option in rollOver().");
      return;
    }

    String datedFilename = fileName+sdf.format(now);
    // It is too early to roll over because we are still within the
    // bounds of the current interval. Rollover will occur once the
    // next interval is reached.
    if (scheduledFilename.equals(datedFilename)) {
      return;
    }

    // close current file, and rename it to datedFilename
    this.closeFile();

    File target  = new File(scheduledFilename);
    if (target.exists()) {
      target.delete();
    }

    File file = new File(fileName);
    boolean result = file.renameTo(target);
    if(result) {
      LogLog.debug(fileName +" -> "+ scheduledFilename);
    } else {
      LogLog.error("Failed to rename ["+fileName+"] to ["+scheduledFilename+"].");
    }

    try {
      // This will also close the file. This is OK since multiple
      // close operations are safe.
      this.setFile(fileName, false, this.bufferedIO, this.bufferSize);
    }
    catch(IOException e) {
      errorHandler.error("setFile("+fileName+", false) call failed.");
    }
    scheduledFilename = datedFilename;
  }

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