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From "Nathan Roberts (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HDFS-7645) Rolling upgrade is restoring blocks from trash multiple times
Date Tue, 20 Jan 2015 21:12:34 GMT
Nathan Roberts created HDFS-7645:
------------------------------------

             Summary: Rolling upgrade is restoring blocks from trash multiple times
                 Key: HDFS-7645
                 URL: https://issues.apache.org/jira/browse/HDFS-7645
             Project: Hadoop HDFS
          Issue Type: Bug
          Components: datanode
    Affects Versions: 2.6.0
            Reporter: Nathan Roberts


When performing an HDFS rolling upgrade, the trash directory is getting restored twice when
under normal circumstances it shouldn't need to be restored at all. iiuc, the only time these
blocks should be restored is if we need to rollback a rolling upgrade. 

On a busy cluster, this can cause significant and unnecessary block churn both on the datanodes,
and more importantly in the namenode.

The two times this happens are:
1) restart of DN onto new software
{code}
  private void doTransition(DataNode datanode, StorageDirectory sd,
      NamespaceInfo nsInfo, StartupOption startOpt) throws IOException {
    if (startOpt == StartupOption.ROLLBACK && sd.getPreviousDir().exists()) {
      Preconditions.checkState(!getTrashRootDir(sd).exists(),
          sd.getPreviousDir() + " and " + getTrashRootDir(sd) + " should not " +
          " both be present.");
      doRollback(sd, nsInfo); // rollback if applicable
    } else {
      // Restore all the files in the trash. The restored files are retained
      // during rolling upgrade rollback. They are deleted during rolling
      // upgrade downgrade.
      int restored = restoreBlockFilesFromTrash(getTrashRootDir(sd));
      LOG.info("Restored " + restored + " block files from trash.");
    }
{code}

2) When heartbeat response no longer indicates a rollingupgrade is in progress
{code}
  /**
   * Signal the current rolling upgrade status as indicated by the NN.
   * @param inProgress true if a rolling upgrade is in progress
   */
  void signalRollingUpgrade(boolean inProgress) throws IOException {
    String bpid = getBlockPoolId();
    if (inProgress) {
      dn.getFSDataset().enableTrash(bpid);
      dn.getFSDataset().setRollingUpgradeMarker(bpid);
    } else {
      dn.getFSDataset().restoreTrash(bpid);
      dn.getFSDataset().clearRollingUpgradeMarker(bpid);
    }
  }
{code}

HDFS-6800 and HDFS-6981 were modifying this behavior making it not completely clear whether
this is somehow intentional. 



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