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https://issues.apache.org/jira/browse/HDFS-12682?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16210220#comment-16210220
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Xiao Chen commented on HDFS-12682:
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Looking at the history of HDFS-11565, I understand this is done to save the
redundant object constructions in NN.
I'm thinking we should keep the same for the NN, but construct every time for
the client.
Don't think this overhead will matter for a downstream long-running dfsclient
that calls {{DFS#getAllErasureCodingPolicies}} repeatedly, since there will be
numerous other objects created during the RPC. There will also be the headache
to update these objects without the FSN lock.
Would this be okay with the intent of HDFS-11565, [~andrew.wang]?
> ECAdmin -listPolicies will always show policy state as DISABLED
> ---------------------------------------------------------------
>
> Key: HDFS-12682
> URL: https://issues.apache.org/jira/browse/HDFS-12682
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: erasure-coding
> Reporter: Xiao Chen
> Assignee: Xiao Chen
> Labels: hdfs-ec-3.0-must-do
>
> On a real cluster, {{hdfs ec -listPolicies}} will always show policy state as
> DISABLED.
> {noformat}
> [hdfs@nightly6x-1 root]$ hdfs ec -listPolicies
> Erasure Coding Policies:
> ErasureCodingPolicy=[Name=RS-10-4-1024k, Schema=[ECSchema=[Codec=rs,
> numDataUnits=10, numParityUnits=4]], CellSize=1048576, Id=5, State=DISABLED]
> ErasureCodingPolicy=[Name=RS-3-2-1024k, Schema=[ECSchema=[Codec=rs,
> numDataUnits=3, numParityUnits=2]], CellSize=1048576, Id=2, State=DISABLED]
> ErasureCodingPolicy=[Name=RS-6-3-1024k, Schema=[ECSchema=[Codec=rs,
> numDataUnits=6, numParityUnits=3]], CellSize=1048576, Id=1, State=DISABLED]
> ErasureCodingPolicy=[Name=RS-LEGACY-6-3-1024k,
> Schema=[ECSchema=[Codec=rs-legacy, numDataUnits=6, numParityUnits=3]],
> CellSize=1048576, Id=3, State=DISABLED]
> ErasureCodingPolicy=[Name=XOR-2-1-1024k, Schema=[ECSchema=[Codec=xor,
> numDataUnits=2, numParityUnits=1]], CellSize=1048576, Id=4, State=DISABLED]
> [hdfs@nightly6x-1 root]$ hdfs ec -getPolicy -path /ecec
> XOR-2-1-1024k
> {noformat}
> This is because when [deserializing
> protobuf|https://github.com/apache/hadoop/blob/branch-3.0.0-beta1/hadoop-hdfs-project/hadoop-hdfs-client/src/main/java/org/apache/hadoop/hdfs/protocolPB/PBHelperClient.java#L2942],
> the static instance of [SystemErasureCodingPolicies
> class|https://github.com/apache/hadoop/blob/branch-3.0.0-beta1/hadoop-hdfs-project/hadoop-hdfs-client/src/main/java/org/apache/hadoop/hdfs/protocol/SystemErasureCodingPolicies.java#L101]
> is first checked, and always returns the cached policy objects, which are
> created by default with state=DISABLED.
> All the existing unit tests pass, because that static instance that the
> client (e.g. ECAdmin) reads in unit test is updated by NN. :)
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