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From "Surendra Singh Lilhore (JIRA)" <j...@apache.org>
Subject [jira] [Comment Edited] (HDFS-13522) Support observer node from Router-Based Federation
Date Fri, 03 May 2019 10:24:00 GMT

    [ https://issues.apache.org/jira/browse/HDFS-13522?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16832414#comment-16832414
] 

Surendra Singh Lilhore edited comment on HDFS-13522 at 5/3/19 10:23 AM:
------------------------------------------------------------------------

Thanks [~csun] and [~crh]
{quote}Separation of read vs write queuing in routers to begin with to fundamental continue
maintaining a fast lane access for read calls. This work should create foundations to help
to eventually separate read vs write per nameservice thus helping solve HDFS-14090.
{quote}
This can be done by implementing new queue same as {{FairCallQueue}}. New queue implementation
can create two internal queue for read and write calls.
{quote} Honor existing client configurations around whether or not to access Observer NN
for certain use cases. For ex: a client can currently continue using ConfiguredFailOverProxy
without connecting to Observer. If a client maintains such preference, routers should honor
it and connect to Active Namenode for read calls as well.
{quote}
 In case of router federation client will not use {{clientStateId}}. This we can use to check
if client wants to read from observer or active. If the {{clientStateId}} is {{Long.MIN_VALUE}}
then will send read to observer otherwise send to active.


was (Author: surendrasingh):
Thanks [~csun] and [~crh]
{quote}Separation of read vs write queuing in routers to begin with to fundamental continue
maintaining a fast lane access for read calls. This work should create foundations to help
to eventually separate read vs write per nameservice thus helping solve HDFS-14090.
{quote}
This can be done by implementing new queue same as {{FairCallQueue}}. New queue implementation
can create two internal queue for read and write calls.
{quote} Honor existing client configurations around whether or not to access Observer NN
for certain use cases. For ex: a client can currently continue using ConfiguredFailOverProxy
without connecting to Observer. If a client maintains such preference, routers should honor
it and connect to Active Namenode for read calls as well.
{quote}
 In case of router federation client will not use c{{lientStateId}}. This we can use to check
if client wants to read from observer or active. If the clientStateId is {{Long.MIN_VALUE}}
then will send read to observer otherwise send to active.

> Support observer node from Router-Based Federation
> --------------------------------------------------
>
>                 Key: HDFS-13522
>                 URL: https://issues.apache.org/jira/browse/HDFS-13522
>             Project: Hadoop HDFS
>          Issue Type: Sub-task
>          Components: federation, namenode
>            Reporter: Erik Krogen
>            Assignee: Chao Sun
>            Priority: Major
>         Attachments: HDFS-13522.001.patch, Router+Observer RPC clogging.png
>
>
> Changes will need to occur to the router to support the new observer node.
> One such change will be to make the router understand the observer state, e.g. {{FederationNamenodeServiceState}}.



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