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https://issues.apache.org/jira/browse/HDFS-14090?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16897621#comment-16897621
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CR Hota commented on HDFS-14090:
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[~aajisaka] [~elgoiri] [~fengnanli] [~linyiqun] [~hexiaoqiao] Thanks for the
previous reviews. Took care of most the comments in 009.patch. Below are 3
things that is still not changed.
# I could not remove the log line from assignHandlersToNameservices before
exception is thrown, since there is no other way to test how the assignment
fails when the instance is created. Mainly to test the root cause and error
message.
# Did not add assertJ apis, the dependencies need to be added in pom and
various places changed. I suggest lets introduce AssertJ api in a separate Jira
for easier review. Will create one.
# concurrent permits won't have any default value. Users are expected to
specify the values based on load of the clusters. Default value assigned is
actually a division of all threads with sum of all nameservices + 1 during run
time.
> RBF: Improved isolation for downstream name nodes.
> --------------------------------------------------
>
> Key: HDFS-14090
> URL: https://issues.apache.org/jira/browse/HDFS-14090
> Project: Hadoop HDFS
> Issue Type: Sub-task
> 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, 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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