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https://issues.apache.org/jira/browse/HDFS-13873?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16715942#comment-16715942
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Konstantin Shvachko commented on HDFS-13873:
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I simplest solution would be to assume that Observer can consume 10,000
transactions per second. This is fairly conservative based on my experience
with NNTHroughputBenchmark. The client wait time for the result is defined by
{{ipc.client.connection.maxidletime}}. So the server should reject requests if
{code}
client.LastSeenId - observer.LastWrittenId > 10000 * maxidletime * 0.8
{code}
Otherwise there will be nobody to respond to. Here 0.8 is a multiplier intended
to allow the server to deliver the response to the client.
> ObserverNode should reject read requests when it is too far behind.
> -------------------------------------------------------------------
>
> Key: HDFS-13873
> URL: https://issues.apache.org/jira/browse/HDFS-13873
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Components: hdfs-client, namenode
> Affects Versions: HDFS-12943
> Reporter: Konstantin Shvachko
> Assignee: Chao Sun
> Priority: Major
>
> Add a server-side threshold for ObserverNode to reject read requests when it
> is too far behind.
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