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https://issues.apache.org/jira/browse/HDFS-5776?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13875161#comment-13875161
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stack commented on HDFS-5776:
-----------------------------
[~xieliang007]
Nit: The 'return null' necessary in below given it Void return type:
+ public Void call() throws IOException {
+ pReadFile(fileSys, file);
+ return null;
+ }
We should rename these methods given this is not 'quorum' reading:
{code}
testQuorumPreadDFSBasic
{code}
... and here testMaxOutQuorumPool
And this variable name needs changing? numQuorumPoolThreads... and here
DFS_DFSCLIENT_QUORUM_READ_THREADPOOL_SIZE
... more review to come (have to head out)
> Support 'hedged' reads in DFSClient
> -----------------------------------
>
> Key: HDFS-5776
> URL: https://issues.apache.org/jira/browse/HDFS-5776
> Project: Hadoop HDFS
> Issue Type: Improvement
> Components: hdfs-client
> Affects Versions: 3.0.0
> Reporter: Liang Xie
> Assignee: Liang Xie
> Attachments: HDFS-5776-v2.txt, HDFS-5776.txt
>
>
> This is a placeholder of hdfs related stuff backport from
> https://issues.apache.org/jira/browse/HBASE-7509
> The quorum read ability should be helpful especially to optimize read outliers
> we can utilize "dfs.dfsclient.quorum.read.threshold.millis" &
> "dfs.dfsclient.quorum.read.threadpool.size" to enable/disable the hedged read
> ability from client side(e.g. HBase), and by using DFSQuorumReadMetrics, we
> could export the interested metric valus into client system(e.g. HBase's
> regionserver metric).
> The core logic is in pread code path, we decide to goto the original
> fetchBlockByteRange or the new introduced fetchBlockByteRangeSpeculative per
> the above config items.
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