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Posted to hdfs-issues@hadoop.apache.org by "Lisheng Sun (Jira)" <ji...@apache.org> on 2020/05/03 07:23:00 UTC
[jira] [Updated] (HDFS-14283) DFSInputStream to prefer cached
replica
[ https://issues.apache.org/jira/browse/HDFS-14283?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Lisheng Sun updated HDFS-14283:
-------------------------------
Attachment: HDFS-14283.006.patch
> DFSInputStream to prefer cached replica
> ---------------------------------------
>
> Key: HDFS-14283
> URL: https://issues.apache.org/jira/browse/HDFS-14283
> Project: Hadoop HDFS
> Issue Type: Improvement
> Affects Versions: 2.6.0
> Environment: HDFS Caching
> Reporter: Wei-Chiu Chuang
> Assignee: Lisheng Sun
> Priority: Major
> Attachments: HDFS-14283.001.patch, HDFS-14283.002.patch, HDFS-14283.003.patch, HDFS-14283.004.patch, HDFS-14283.005.patch, HDFS-14283.006.patch
>
>
> HDFS Caching offers performance benefits. However, currently NameNode does not treat cached replica with higher priority, so HDFS caching is only useful when cache replication = 3, that is to say, all replicas are cached in memory, so that a client doesn't randomly pick an uncached replica.
> HDFS-6846 proposed to let NameNode give higher priority to cached replica. Changing a logic in NameNode is always tricky so that didn't get much traction. Here I propose a different approach: let client (DFSInputStream) prefer cached replica.
> A {{LocatedBlock}} object already contains cached replica location so a client has the needed information. I think we can change {{DFSInputStream#getBestNodeDNAddrPair()}} for this purpose.
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