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From "Wei-Chiu Chuang (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-11623) Move system erasure coding policies into hadoop-hdfs-client
Date Fri, 07 Apr 2017 06:56:41 GMT

    [ https://issues.apache.org/jira/browse/HDFS-11623?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15960373#comment-15960373
] 

Wei-Chiu Chuang commented on HDFS-11623:
----------------------------------------

Overall looks good to me. I just want to point out a few things for discussion.

# After this change, ErasureCodingPolicyManager becomes a little redundancy. It is only useful
for {{DistributedFileSystem#setErasureCodingPolicy()}} and {{DistributedFileSystem#getErasureCodingPolicies()}}.
That is to say, if the system has a file with ec policy A, but later the system disables the
ec policy A, that file is still fine. It's just that no more new files can be created with
ec policy A.

My editor told me the following code:
{code}
  private static final List<ErasureCodingPolicy> SYS_POLICIES =
      Collections.unmodifiableList(Arrays.asList(
          new ErasureCodingPolicy[]{
              SYS_POLICY1, SYS_POLICY2, SYS_POLICY3, SYS_POLICY4,
              SYS_POLICY5}));
{code}
can be simplified to
{code}
  private static final List<ErasureCodingPolicy> SYS_POLICIES =
      Collections.unmodifiableList(Arrays.asList(
          SYS_POLICY1, SYS_POLICY2, SYS_POLICY3, SYS_POLICY4, SYS_POLICY5));
{code}

By the way, I found a critical issue that I will post later.

> Move system erasure coding policies into hadoop-hdfs-client
> -----------------------------------------------------------
>
>                 Key: HDFS-11623
>                 URL: https://issues.apache.org/jira/browse/HDFS-11623
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>          Components: erasure-coding
>    Affects Versions: 3.0.0-alpha2
>            Reporter: Andrew Wang
>            Assignee: Andrew Wang
>         Attachments: HDFS-11623.001.patch, HDFS-11623.002.patch, HDFS-11623.003.patch,
HDFS-11623.004.patch
>
>
> This is a precursor to HDFS-11565. We need to move the set of system defined EC policies
out of the NameNode's ECPolicyManager into the hdfs-client module so it can be referenced
by the client.



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