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https://issues.apache.org/jira/browse/HDFS-14090?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16919031#comment-16919031
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CR Hota commented on HDFS-14090:
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[~elgoiri] Thanks for the comments. Uploaded 011.patch
Have taken care of the nits except the below.
* I think we can make PermitAllocationException more specific (right now it
just takes whatever string). I think it would be nice to have the messages in
PermitAllocationException itself and we would just pass the number of handlers,
the min and the nsId as a parameter. This is already nice in
PermitLimitExceededException.
* StaticFairnessPolicyController#184 can fit in one line. Actually, this might
be better to have as a different exception (which can be a subclass of
PermitAllocationException).
PermitAllocationException can happen not just for misconfigured handlers but
also for misconfigured nameservices, hence deliberately kept it generic with a
String msg as param. Also dint create a subclass for permitallocation again
just to keep it simple in the beginning. I suggest we can always re-look at
refactoring these based on how dynamic allocation work shapes up.
> 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: CR Hota
> 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, 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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