[jira] [Resolved] (ACCUMULO-3508) Zoocache utilizes course grained locking causing unnecessary synchronization in many tserver ops

["Eric Newton (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/ACCUMULO-3508?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Eric Newton resolved ACCUMULO-3508.
-----------------------------------
    Resolution: Fixed

Patch applied on [~phrocker]'s behalf.

> Zoocache utilizes course grained locking causing unnecessary synchronization in many tserver ops
> ------------------------------------------------------------------------------------------------
>
>                 Key: ACCUMULO-3508
>                 URL: https://issues.apache.org/jira/browse/ACCUMULO-3508
>             Project: Accumulo
>          Issue Type: Sub-task
>          Components: fate
>    Affects Versions: 1.6.0
>            Reporter: marco polo
>            Assignee: marco polo
>            Priority: Minor
>             Fix For: 1.8.0
>
>          Time Spent: 10m
>  Remaining Estimate: 0h
>
> Through jstacking I have observed busy tablet server threads waiting for the Zoocache to be updated or even read. Profiling via yourkit indicates potential deadlocks when threads wait for a long period of time ( in my case my waits were 10+s ) when many scans were running against my instance.
> My patch, which is forthcoming, removes synchronization and utilizes a reentrant read/write lock (RERWL) to synchronize the maps. My initial design utilized concurrent hash maps, but the design of existence becomes simpler and changes fewer by using the RERWL. 



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