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https://issues.apache.org/jira/browse/HDFS-9390?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15531219#comment-15531219
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Lei (Eddy) Xu commented on HDFS-9390:
-------------------------------------
Hi, [~mingma] Thanks so much for posting this patch.
It looks good to me overall. Some small nits:
In {{HeartbeatManager.java#heartbeatCheck()}}:
{code}
try {
dm.removeDeadDatanode(dead, !dead.isMaintenance());
}
{code}
If we change it to the following code, we can undo most of the
{{DatanodeManager.java}} changes, of which the motivation of these changes are
not clear to me in the first sight.
{code}
if (!dead.isMaintenance()) {
dm.removeDeadDatanode(dead);
}
{code}
Can you elaborate a little bit more about the following code?
{code}
} else if (blockManager.getMinReplicationToBeInMaintenance() == 0) {
LOG.info("MinReplicationToBeInMaintenance is set to zero. " + node +
" is put in maintenance state" + " immediately.");
node.setInMaintenance();
} else {
stats.subtract(node);
node.startMaintenance();
stats.add(node);
}
{code}
Why it does not re-calculate {{stats}} when {{minReplicationToBeInMaintanence
== 0}}?
In {{DecommissionManager#startmaintance()}}
{code}
// hbManager.startDecommission will set dead node to decommissioned.
{code}
Is the comment correct in the context?
One related question is that, why {{startMaintenance()}} and
{{stopMaintenance()}} are in {{DecommissionManager}}.
In {{NumberReplicas.java}}, you might want consider rename {{int
maintenance()}} to {{int maintenanceReplicas}}, so is
{{liveEnteringMaintence()}}.
Thanks.
> Block management for maintenance states
> ---------------------------------------
>
> Key: HDFS-9390
> URL: https://issues.apache.org/jira/browse/HDFS-9390
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Reporter: Ming Ma
> Assignee: Ming Ma
> Attachments: HDFS-9390-2.patch, HDFS-9390.patch
>
>
> When a node is transitioned to/stay in/transitioned out of maintenance state,
> we need to make sure blocks w.r.t. that nodes are properly handled.
> * When nodes are put into maintenance, it will first go to
> ENTERING_MAINTENANCE, and make sure blocks are minimally replicated before
> the nodes are transitioned to IN_MAINTENANCE.
> * Do not replica blocks when nodes are in maintenance states. Maintenance
> replica will remain in BlockMaps and thus is still considered valid from
> block replication point of view. In other words, putting a node to
> “maintenance” mode won’t trigger BlockManager to replicate its blocks.
> * Do not invalidate replicas on node under maintenance. After any file's
> replication factor is reduced, NN needs to invalidate some replicas. It
> should exclude nodes under maintenance in the handling.
> * Do not put IN_MAINTENANCE replicas in LocatedBlock for read operation.
> * Do not allocate any new block on nodes under maintenance.
> * Have Balancer exclude nodes under maintenance.
> * Exclude nodes under maintenance for DN cache.
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