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https://issues.apache.org/jira/browse/HDFS-9044?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14954827#comment-14954827
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Vinayakumar B commented on HDFS-9044:
-------------------------------------
Hi [~andreina], thanks for the patch,
Patch looks almost good.
Here are few minor comments,
1. Below lines from
{{BlockPlacementPolicyWithNodeGroup#chooseFavouredNodes(..)}} could be just
replaced with {{super.chooseFavouredNodes(..)}}
{code}+ for (int i = 0; i < favoredNodes.size() && results.size() <
numOfReplicas;
+ i++) {
+ DatanodeDescriptor favoredNode = favoredNodes.get(i);
+ // Choose a single node which is local to favoredNode.
+ // 'results' is updated within chooseLocalNode
+ DatanodeStorageInfo target = null;
+ try {
+ target =
+ chooseLocalStorage(favoredNode, favoriteAndExcludedNodes,
+ blocksize, maxNodesPerRack, results, avoidStaleNodes,
+ storageTypes, false);
+ } catch (NotEnoughReplicasException e) {
+ // catch Exception and continue with other favored nodes
+ continue;
+ }
+ if (target == null) {
+ LOG.warn("Could not find a target for file " + src
+ + " with favored node " + favoredNode);
+ continue;
+ }
+ favoriteAndExcludedNodes.add(target.getDatanodeDescriptor());
+ }{code}
2. {{checkFavoredNodePartOfTarget(..)}} could be renamed to {{isNodeChosen(..)}}
3. {{clusterMapNodeGroup.getNodeGroup(favoredNode.getNetworkLocation())}} can
be extracted to a variable {{scope}} for better readability
4. I think its better to update javadoc for
{{BlockPlacementPolicyWithNodeGroup#chooseLocalStorage(..)}} by mentioning,
fallback to nodegroup/rack will happen if flag
{{fallbackToNodeGroupAndLocalRack}} is set.
> Give Priority to FavouredNodes , before selecting nodes from FavouredNode's
> Node Group
> --------------------------------------------------------------------------------------
>
> Key: HDFS-9044
> URL: https://issues.apache.org/jira/browse/HDFS-9044
> Project: Hadoop HDFS
> Issue Type: Bug
> Reporter: J.Andreina
> Assignee: J.Andreina
> Attachments: HDFS-9044.1.patch, HDFS-9044.2.patch, HDFS-9044.3.patch,
> HDFS-9044.4.patch
>
>
> Passing Favored nodes intention is to place replica among the favored node
> Current behavior in Node group is
> If favored node is not available it goes to one among favored
> nodegroup.
> {noformat}
> Say for example:
> 1)I need 3 replicas and passed 5 favored nodes.
> 2)Out of 5 favored nodes 3 favored nodes are not good.
> 3)Then based on BlockPlacementPolicyWithNodeGroup out of 5 targets node
> returned , 3 will be random node from 3 bad FavoredNode's nodegroup.
> 4)Then there is a probability that all my 3 replicas are placed on
> Random node from FavoredNodes's nodegroup , instead of giving priority to 2
> favored nodes returned as target.
> {noformat}
> *Instead of returning 5 targets on 3rd step above , we can return 2 good
> favored nodes as target*
> *And remaining 1 needed replica can be chosen from Random node of bad
> FavoredNodes's nodegroup.*
> This will make sure that the FavoredNodes are given priority.
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