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From "Zhe Zhang (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-7859) Erasure Coding: Persist erasure coding policies in NameNode
Date Wed, 10 Aug 2016 23:41:22 GMT

    [ https://issues.apache.org/jira/browse/HDFS-7859?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15416209#comment-15416209
] 

Zhe Zhang commented on HDFS-7859:
---------------------------------

Thanks [~xinwei] much for the work. I think we should prioritize this since it's a pretty
important blocker. I'm reviewing the patch and I think it looks good overall, will post a
full review shortly. Looks like it's quite similar to how {{CacheManager}} persists state.
There are several minor issues worth fixing:
# {{required uint32 numPolicies =1;}} needs a space
# {{if(!activePoliciesByName.containsKey(ecPolicyName))}} needs a space after if
# {{ecPolicyName + " is already exists.")}} should remove "is"
# {{private void addInternal}} sounds like "addErasureCodingPolicyInternal" is better? Or
just merge it into {{addErasureCodingPolicy}}? It's a small method anyway.

More importantly, I'd like to discuss an operational issue. What if an admin adds a policy
by mistake? Right now the policy cannot be removed or overwritten by a correct policy with
the same name. I think we should add a {{removeErasureCodingPolicy}} operation; and I'm OK
if that's done in a follow-on JIRA. But pinging [~drankye] [~andrew.wang] [~jingzhao] for
more opinions.

> Erasure Coding: Persist erasure coding policies in NameNode
> -----------------------------------------------------------
>
>                 Key: HDFS-7859
>                 URL: https://issues.apache.org/jira/browse/HDFS-7859
>             Project: Hadoop HDFS
>          Issue Type: Sub-task
>            Reporter: Kai Zheng
>            Assignee: Xinwei Qin 
>              Labels: BB2015-05-TBR, hdfs-ec-3.0-must-do
>         Attachments: HDFS-7859-HDFS-7285.002.patch, HDFS-7859-HDFS-7285.002.patch, HDFS-7859-HDFS-7285.003.patch,
HDFS-7859.001.patch, HDFS-7859.002.patch, HDFS-7859.004.patch, HDFS-7859.005.patch
>
>
> In meetup discussion with [~zhz] and [~jingzhao], it's suggested that we persist EC schemas
in NameNode centrally and reliably, so that EC zones can reference them by name efficiently.



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