Journal.java 文件源码

/**
 * @return the current state of the given segment, or null if the
 * segment does not exist.
 */
@VisibleForTesting
SegmentStateProto getSegmentInfo(long segmentTxId)
    throws IOException {
  EditLogFile elf = fjm.getLogFile(segmentTxId);
  if (elf == null) {
    return null;
  }
  if (elf.isInProgress()) {
    elf.scanLog();
  }
  if (elf.getLastTxId() == HdfsConstants.INVALID_TXID) {
    LOG.info("Edit log file " + elf + " appears to be empty. " +
        "Moving it aside...");
    elf.moveAsideEmptyFile();
    return null;
  }
  SegmentStateProto ret = SegmentStateProto.newBuilder()
      .setStartTxId(segmentTxId)
      .setEndTxId(elf.getLastTxId())
      .setIsInProgress(elf.isInProgress())
      .build();
  LOG.info("getSegmentInfo(" + segmentTxId + "): " + elf + " -> " +
      TextFormat.shortDebugString(ret));
  return ret;
}