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https://issues.apache.org/jira/browse/HDFS-1332?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13033233#comment-13033233
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Ted Yu commented on HDFS-1332:
------------------------------
In this method:
{code}
private void chooseRandom(int numOfReplicas,
String nodes,
HashMap<Node, Node> excludedNodes,
long blocksize,
int maxNodesPerRack,
List<DatanodeDescriptor> results)
{code}
it is possible that numOfAvailableNodes is greater than numOfReplicas. Meaning,
if we see a bad target, NotEnoughReplicasException may not be thrown at the end
of the method.
Using LOG without creating map would report unnecessary alarm.
> When unable to place replicas, BlockPlacementPolicy should log reasons nodes
> were excluded
> ------------------------------------------------------------------------------------------
>
> Key: HDFS-1332
> URL: https://issues.apache.org/jira/browse/HDFS-1332
> Project: Hadoop HDFS
> Issue Type: Improvement
> Components: name-node
> Reporter: Todd Lipcon
> Assignee: Ted Yu
> Priority: Minor
> Labels: newbie
> Fix For: 0.23.0
>
> Attachments: HDFS-1332.patch
>
>
> Whenever the block placement policy determines that a node is not a "good
> target" it could add the reason for exclusion to a list, and then when we log
> "Not able to place enough replicas" we could say why each node was refused.
> This would help new users who are having issues on pseudo-distributed (eg
> because their data dir is on /tmp and /tmp is full). Right now it's very
> difficult to figure out the issue.
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