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Date: Wed, 6 May 2009 16:00:31 -0700 (PDT)
From: "Raghu Angadi (JIRA)" <jira@apache.org>
To: core-dev@hadoop.apache.org
Subject: [jira] Commented: (HADOOP-5015) Separate block/replica management
 code from FSNamesystem
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    [ https://issues.apache.org/jira/browse/HADOOP-5015?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12706649#action_12706649 ] 

Raghu Angadi commented on HADOOP-5015:
--------------------------------------

> To make code review simpler, I have also retained the structure of the code moved from FSNamesystem.java as it is in BlockManager.java.

There are a lot of formatting changes the break existing patches HDFS : 
e.g. segment (Ideally it should have been a clean cut-n-paste) :

{noformat}
     synchronized (neededReplications) {
-      out.println("Metasave: Blocks waiting for replication: " +
-                  neededReplications.size());
+      out.println("Metasave: Blocks waiting for replication: "
+          + neededReplications.size());
       for (Block block : neededReplications) {
-        List<DatanodeDescriptor> containingNodes =
-                                          new ArrayList<DatanodeDescriptor>();
+        List<DatanodeDescriptor> containingNodes = new ArrayList<DatanodeDescriptor>();
         NumberReplicas numReplicas = new NumberReplicas();
         // source node returned is not used
         chooseSourceDatanode(block, containingNodes, numReplicas);
-        int usableReplicas = numReplicas.liveReplicas() +
-                             numReplicas.decommissionedReplicas();
+        int usableReplicas = numReplicas.liveReplicas()
+            + numReplicas.decommissionedReplicas();
         // l: == live:, d: == decommissioned c: == corrupt e: == excess
-        out.print(block + " (replicas:" +
-                  " l: " + numReplicas.liveReplicas() +
-                  " d: " + numReplicas.decommissionedReplicas() +
-                  " c: " + numReplicas.corruptReplicas() +
-                  " e: " + numReplicas.excessReplicas() +
-                  ((usableReplicas > 0)? "" : " MISSING") + ")");
+        out.print(block + " (replicas:" + " l: " + numReplicas.liveReplicas()
+            + " d: " + numReplicas.decommissionedReplicas() + " c: "
+            + numReplicas.corruptReplicas() + " e: "
+            + numReplicas.excessReplicas()
+            + ((usableReplicas > 0) ? "" : " MISSING") + ")");
 
-        for (Iterator<DatanodeDescriptor> jt = blocksMap.nodeIterator(block);
-             jt.hasNext();) {
+        for (Iterator<DatanodeDescriptor> jt = blocksMap.nodeIterator(block); jt
+            .hasNext();) {
           DatanodeDescriptor node = jt.next();
           out.print(" " + node + " : ");
         }
         out.println("");
{noformat}

Without such changes, it would have been much simpler to port the patches (just by changing the file name in patch file.


> Separate block/replica management code from FSNamesystem
> --------------------------------------------------------
>
>                 Key: HADOOP-5015
>                 URL: https://issues.apache.org/jira/browse/HADOOP-5015
>             Project: Hadoop Core
>          Issue Type: Improvement
>          Components: dfs
>            Reporter: Hairong Kuang
>            Assignee: Suresh Srinivas
>             Fix For: 0.21.0
>
>         Attachments: blkmanager.patch, blkmanager.patch
>
>
> Currently FSNamesystem contains a big amount of code that manages blocks and replicas. The code scatters in FSNamesystem and it is hard to read and maintain. It would be nice to move the code to a separate class called, for example, BlockManager. 

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