[jira] [Updated] (KUDU-717) Test that write-throttling is an effective RAM control in replicated tablets

["Mike Percy (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/KUDU-717?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Mike Percy updated KUDU-717:
----------------------------
    Parent: KUDU-808

> Test that write-throttling is an effective RAM control in replicated tablets
> ----------------------------------------------------------------------------
>
>                 Key: KUDU-717
>                 URL: https://issues.apache.org/jira/browse/KUDU-717
>             Project: Kudu
>          Issue Type: Sub-task
>          Components: consensus, tablet, test
>    Affects Versions: Private Beta
>            Reporter: Todd Lipcon
>            Assignee: Adar Dembo
>            Priority: Critical
>
> Currently, we have some rudimentary write-throttling when a server is under too much RAM pressure. KUDU-542 discusses making it a bit more effective, but we also need to make sure that it's effective in a replicated setup.
> For example:
> - we have three servers replicating a tablet.
> - one of the followers is IO-constrained (or has more load from other tablets) and thus can't flush as fast as the other two nodes. It starts to apply write-throttling in Apply()
> Does blocking Apply() end up producing enough backpressure to slow down the other tablets? My guess is not -- we probably just end up with a backlogged Apply threadpool work queue, so we have a ton of RAM being used up here instead of being used up in the MRS, and we'd still eventually OOM.



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