hadoop-hdfs-issues mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From "stack (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-5776) Support 'hedged' reads in DFSClient
Date Fri, 24 Jan 2014 06:06:38 GMT

    [ https://issues.apache.org/jira/browse/HDFS-5776?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13880746#comment-13880746
] 

stack commented on HDFS-5776:
-----------------------------

bq. An alternative way to do this is to have an "Allow-Hedged-Reads" configuration, and if
it is set to true, we load the number of thread pool and the threshold time. We will provide
an isHedgedReadsEnabled method but we will not provide enable/disable methods.

The reviews are great.  On the above,  while I can see putting the on/off switch as a DN config.,
we should allow setting at least the config on when to start the hedge read per DFSCient instance.

bq.  This means that we do need to put this in a static, for now, or else FileContext users
will be constantly destroying and creating thread-pools.

Thanks Colin.  Makes sense.







> 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-v6.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)

Mime
View raw message