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https://issues.apache.org/jira/browse/HDFS-7866?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14494050#comment-14494050
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Kai Zheng commented on HDFS-7866:
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Thanks [~vinayrpet] for the further thoughts.
bq.Following changes not required.
I agree, better to remove the duplication.
bq.reloadPredefined() should be called on initialization.
I have an offline discussion with Vinay about this. Let me summarize the
discussion below. Please correct me if anything incorrect.
Originally {{ec-schemas.xml}} was thought of as an input method for admin to
define their schemas because it's not easy to specify schema parameters well in
command line if we allow that by providing a command. Therefore it's expected
to trigger a reload command after manually editing the schema file. To avoid
bad situation when have an immature schema file, the automatic loading of the
file isn't expected.
Vinay has different thoughts, and suggests that we have system defined schemas
as defined in the current ec-schema.xml, which are fixed and not allowed to
change. Additionally, we also allow site specific schemas, which can be defined
in site specific xml file. The system defined xml file should be loaded
automatically. The site specific xml file needs admin to trigger the loading
once it's changed.
I agree with the thoughts above. To simplify a little bit, we can have the
system schemas defined just in Java codes, as storage policies do, not using
any xml file; and rename the existing ec-schema.xml file to
ec-schema-template.xml, so a deployment can have its own site specific xml file
like {{ec-schema-site.xml}}, for admin to define their own schemas. Loading
this file will need admin to trigger a reload command, not automatically.
Would anyone have more thoughts? Thanks!
> Erasure coding: NameNode manages EC schemas
> -------------------------------------------
>
> Key: HDFS-7866
> URL: https://issues.apache.org/jira/browse/HDFS-7866
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Reporter: Kai Zheng
> Assignee: Kai Zheng
> Attachments: HDFS-7866-v1.patch, HDFS-7866-v2.patch,
> HDFS-7866-v3.patch
>
>
> This is to extend NameNode to load, list and sync predefine EC schemas in
> authorized and controlled approach. The provided facilities will be used to
> implement DFSAdmin commands so admin can list available EC schemas, then
> could choose some of them for target EC zones.
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