[
https://issues.apache.org/jira/browse/HDFS-5776?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13878382#comment-13878382
]
Liang Xie commented on HDFS-5776:
---------------------------------
About naming, personally i'd like to keep "hedged" unchanged, it's not a big
issue if HBASE-10070 use another naming, just my thought:)
About increased RPC, sure, it's just a tradeoff, we all know that:) i can give
a metric result against diff timeout setting, probably put into HBASE-7509
bq. doing the 3rd requests with larger timeout does not buy a lot
Current patch just picks only one secondary dn, thats means there're no more
than two requests under normal situation.
BTW, is it possible let it go into HADOOP-2.4 if all comments are done ? i saw
[~andrew.wang]'s post from mail list that there's a plan to release 2.4 in the
end of this month, right ?
If this patch could go in, then we can work immediately at HBASE-7509 with
bumping the according dependency version to 2.4, otherwise we need to kick off
once it goes into 2.5+, maybe need several weeks ?
> 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-v3.txt, HDFS-5776-v4.txt,
> HDFS-5776-v5.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.
--
This message was sent by Atlassian JIRA
(v6.1.5#6160)
