handlers.py 文件源码

def emit(self, record):
        """
        Emit a record.

        First check if the underlying file has changed, and if it
        has, close the old stream and reopen the file to get the
        current stream.
        """
        # Reduce the chance of race conditions by stat'ing by path only
        # once and then fstat'ing our new fd if we opened a new log stream.
        # See issue #14632: Thanks to John Mulligan for the problem report
        # and patch.
        try:
            # stat the file by path, checking for existence
            sres = os.stat(self.baseFilename)
        except OSError as err:
            if err.errno == errno.ENOENT:
                sres = None
            else:
                raise
        # compare file system stat with that of our stream file handle
        if not sres or sres[ST_DEV] != self.dev or sres[ST_INO] != self.ino:
            if self.stream is not None:
                # we have an open file handle, clean it up
                self.stream.flush()
                self.stream.close()
                self.stream = None  # See Issue #21742: _open () might fail.
                # open a new file handle and get new stat info from that fd
                self.stream = self._open()
                self._statstream()
        logging.FileHandler.emit(self, record)