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https://issues.apache.org/jira/browse/HDFS-7645?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14598582#comment-14598582
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Andrew Wang commented on HDFS-7645:
-----------------------------------
Hey Vinay,
It might be okay to sneak in this incompat change, I doubt there are many users
of this API. It's also possible to write an "after" check will work with both
old and new NNs to check for finalization:
{code}
// before
if (ruinfo == null)
// after
if (ruinfo == null || ruinfo.isFinalized())
{code}
One related change we could also make is adding boolean isStarted and
isFinalized to the JMX output, since that way callers won't have to do a "!= 0"
check. Essentially all the normal benefits of a getter. I just filed HDFS-8656
to do this.
In hindsight it would have been nice to always return an RUInfo so the check
could just be {{if (ruinfo.isFinalized)}}. The need for null checking is a bit
ugly.
> 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: Improvement
> Components: datanode
> Affects Versions: 2.6.0
> Reporter: Nathan Roberts
> Assignee: Keisuke Ogiwara
> Fix For: 2.8.0
>
> Attachments: HDFS-7645.01.patch, HDFS-7645.02.patch,
> HDFS-7645.03.patch, HDFS-7645.04.patch, HDFS-7645.05.patch,
> HDFS-7645.06.patch, HDFS-7645.07.patch
>
>
> 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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