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From "Harsh J (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-1120) Make DataNode's block-to-device placement policy pluggable
Date Wed, 08 Feb 2012 22:50:59 GMT

    [ https://issues.apache.org/jira/browse/HDFS-1120?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13204079#comment-13204079
] 

Harsh J commented on HDFS-1120:
-------------------------------

Nicholas,

Thanks for linking back!

Do we really need per-method audience levels in interfaces?

This one added in:
{code}
+@InterfaceAudience.Public
+@InterfaceStability.Evolving
+public interface BlockVolumeChoosingPolicy {
{code}

While I see the changes in your patch as just one backwards-incompatible change:
{code}
Index: hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/BlockVolumeChoosingPolicy.java
===================================================================
--- hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/BlockVolumeChoosingPolicy.java
(revision 1241740)
+++ hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/BlockVolumeChoosingPolicy.java
(working copy)
@@ -22,7 +22,7 @@
 
 import org.apache.hadoop.classification.InterfaceAudience;
 import org.apache.hadoop.classification.InterfaceStability;
-import org.apache.hadoop.hdfs.server.datanode.FSDataset.FSVolume;
+import org.apache.hadoop.hdfs.server.datanode.FSDatasetInterface.FSVolumeInterface;
 
 /**************************************************
  * BlockVolumeChoosingPolicy allows a DataNode to
@@ -46,7 +46,7 @@
    * @return the chosen volume to store the block.
    * @throws IOException when disks are unavailable or are full.
    */
-  public FSVolume chooseVolume(List<FSVolume> volumes, long blockSize)
+  public FSVolumeInterface chooseVolume(List<FSVolumeInterface> volumes, long blockSize)
     throws IOException;
{code}

So am not sure what you meant by InterfaceAudience.Private comment above?
                
> Make DataNode's block-to-device placement policy pluggable
> ----------------------------------------------------------
>
>                 Key: HDFS-1120
>                 URL: https://issues.apache.org/jira/browse/HDFS-1120
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>          Components: data-node
>            Reporter: Jeff Hammerbacher
>            Assignee: Harsh J
>             Fix For: 0.23.0
>
>         Attachments: HDFS-1120.r1.diff, HDFS-1120.r2.diff, HDFS-1120.r3.diff, HDFS-1120.r4.diff
>
>
> As discussed on the mailing list, as the number of disk drives per server increases,
it would be useful to allow the DataNode's policy for new block placement to grow in sophistication
from the current round-robin strategy.

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