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https://issues.apache.org/jira/browse/HBASE-23744?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17025408#comment-17025408
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Xu Cang commented on HBASE-23744:
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The idea you showed in PR makes sense to me.
Just wondering, is there another way to properly "temporarily prevent writes on
cluster" such as disabling PRC handling ?
Setting the callqueue.length to 0 is a bit subtle to indicate the fact we want
to disable writes. If we do so, could you please add a one sentence comment
in FastPathBalancedQueueRpcExecutor class? thanks.
[~gjacoby]
> FastPathBalancedQueueRpcExecutor should enforce queue length of 0
> -----------------------------------------------------------------
>
> Key: HBASE-23744
> URL: https://issues.apache.org/jira/browse/HBASE-23744
> Project: HBase
> Issue Type: Bug
> Reporter: Geoffrey Jacoby
> Assignee: Geoffrey Jacoby
> Priority: Minor
>
> FastPathBalancedQueueRpcExecutor allows RPC requests to skip the RPC queue
> and get worked by an available handler under certain circumstances.
> Relatedly, the hbase.ipc.server.max.callqueue.length parameter can be set to
> 0, including dynamically. This can be useful to temporarily prevent writes on
> a cluster.
> When this is the case the executor is supposed to block all dispatching.
> However, the FastPathBalancedQueueRpcExecutor will still dispatch the request
> if one of the "fast path" handlers is available on its stack. This both isn't
> the desired effect, and also makes
> TestSimpleRpcScheduler.testSoftAndHardQueueLimits unstable when it checks the
> queue length 0 behavior.
> A simple fix is just to check max queue length > 0 before
> FastPathBalancedQueueRpcExecutor pops the fast handler off the stack.
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