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https://issues.apache.org/jira/browse/HDFS-13923?focusedWorklogId=713526&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-713526
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ASF GitHub Bot logged work on HDFS-13923:
-----------------------------------------

                Author: ASF GitHub Bot
            Created on: 24/Jan/22 07:14
            Start Date: 24/Jan/22 07:14
    Worklog Time Spent: 10m 
      Work Description: tomscut commented on pull request #3912:
URL: https://github.com/apache/hadoop/pull/3912#issuecomment-1019787146


   > Based on discussion in 
[HDFS-13923](https://issues.apache.org/jira/browse/HDFS-13923), we don't think 
need to Add a configuration to turn on/off observer reads.
   > 
   > So I suggest removing the `TODO comment` that are not needed.
   
   Hi @ayushtkn , I am sorry that I did not explain the reason in the PR 
description.
   
   Based on discussion in 
[HDFS-13923](https://issues.apache.org/jira/browse/HDFS-13923), we don't think 
need to Add a configuration to turn on/off observer reads. So I suggest 
removing the `TODO comment` that are not needed. 
   
   I don't know if it is appropriate to change the title of the original ISSUE, 
this PR is just a suggestion.
   
   
   


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Issue Time Tracking
-------------------

    Worklog Id:     (was: 713526)
    Time Spent: 40m  (was: 0.5h)

> Add a configuration to turn on/off observer reads
> -------------------------------------------------
>
>                 Key: HDFS-13923
>                 URL: https://issues.apache.org/jira/browse/HDFS-13923
>             Project: Hadoop HDFS
>          Issue Type: Sub-task
>            Reporter: Chao Sun
>            Assignee: Shweta
>            Priority: Major
>              Labels: pull-request-available
>          Time Spent: 40m
>  Remaining Estimate: 0h
>
> In some situations having a config to turn on/off observer reads dynamically 
> may be useful. For instance, some applications may be sensitive for data 
> freshness and want to always reach directly to active NN. In a more complex 
> scenario, services such as Presto may want to apply observer reads for 
> different types of queries. In this case, simply change 
> {{dfs.client.failover.proxy.provider.<nameservice>}} may not be enough, since 
> with FileSystem cache (which is usually turned on) will ignore the change and 
> still use the same FileSystem object.
> Here I'm proposing to add a flag in {{HdfsClientConfigKeys}}, such as 
> {{dfs.client.observer.reads.enabled}}, that can be used to dynamically turn 
> on/off observer reads. The FileSystem cache key should also take account of 
> this flag in its {{hashCode}} and {{equals}} impl, so that different 
> FileSystem objects will be used depending on the flag.
>  
> cc [~shv], [~xkrogen], [~vagarychen], [~zero45] for discussion.



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