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https://issues.apache.org/jira/browse/HDFS-14090?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17230344#comment-17230344
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Fengnan Li commented on HDFS-14090:
-----------------------------------
Thanks for the review [~linyiqun] and here is the late response.
1. the isolated concurrent is for the case where renew lease doesn't stop due
to connection leak. We have seen this production and YARN added some fix to it.
Interestingly, the bug was fixed by you in
[HDFS-10549|https://issues.apache.org/jira/browse/HDFS-10549] . If we remove
concurrent, these calls would consume the permit for other calls quickly and
soon the whole cluster will be swamped with renew lease.
I will address 2 in a following patch and leave 3 as a follow-up JIRA when more
production data is collected.
> RBF: Improved isolation for downstream name nodes. {Static}
> -----------------------------------------------------------
>
> Key: HDFS-14090
> URL: https://issues.apache.org/jira/browse/HDFS-14090
> Project: Hadoop HDFS
> Issue Type: New Feature
> Reporter: CR Hota
> Assignee: Fengnan Li
> Priority: Major
> Attachments: HDFS-14090-HDFS-13891.001.patch,
> HDFS-14090-HDFS-13891.002.patch, HDFS-14090-HDFS-13891.003.patch,
> HDFS-14090-HDFS-13891.004.patch, HDFS-14090-HDFS-13891.005.patch,
> HDFS-14090.006.patch, HDFS-14090.007.patch, HDFS-14090.008.patch,
> HDFS-14090.009.patch, HDFS-14090.010.patch, HDFS-14090.011.patch,
> HDFS-14090.012.patch, HDFS-14090.013.patch, HDFS-14090.014.patch,
> HDFS-14090.015.patch, HDFS-14090.016.patch, HDFS-14090.017.patch,
> HDFS-14090.018.patch, HDFS-14090.019.patch, HDFS-14090.020.patch,
> HDFS-14090.021.patch, HDFS-14090.022.patch, HDFS-14090.023.patch, RBF_
> Isolation design.pdf
>
>
> Router is a gateway to underlying name nodes. Gateway architectures, should
> help minimize impact of clients connecting to healthy clusters vs unhealthy
> clusters.
> For example - If there are 2 name nodes downstream, and one of them is
> heavily loaded with calls spiking rpc queue times, due to back pressure the
> same with start reflecting on the router. As a result of this, clients
> connecting to healthy/faster name nodes will also slow down as same rpc queue
> is maintained for all calls at the router layer. Essentially the same IPC
> thread pool is used by router to connect to all name nodes.
> Currently router uses one single rpc queue for all calls. Lets discuss how we
> can change the architecture and add some throttling logic for
> unhealthy/slow/overloaded name nodes.
> One way could be to read from current call queue, immediately identify
> downstream name node and maintain a separate queue for each underlying name
> node. Another simpler way is to maintain some sort of rate limiter configured
> for each name node and let routers drop/reject/send error requests after
> certain threshold.
> This won’t be a simple change as router’s ‘Server’ layer would need redesign
> and implementation. Currently this layer is the same as name node.
> Opening this ticket to discuss, design and implement this feature.
>
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