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https://issues.apache.org/jira/browse/HBASE-28934?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Wellington Chevreuil resolved HBASE-28934.
------------------------------------------
    Resolution: Fixed

Merged into master, branch-3 and branch-2. Thanks for the contribution, 
[~janardhan.hungund] !

> The HFile Reader creation should not be blocked due to waits for cache 
> initialisation.
> --------------------------------------------------------------------------------------
>
>                 Key: HBASE-28934
>                 URL: https://issues.apache.org/jira/browse/HBASE-28934
>             Project: HBase
>          Issue Type: Bug
>          Components: BucketCache
>    Affects Versions: 3.0.0-beta-1, 2.7.0
>            Reporter: Janardhan Hungund
>            Assignee: Janardhan Hungund
>            Priority: Major
>              Labels: pull-request-available
>             Fix For: 3.0.0, 2.7.0
>
>
> When persistent bucket cache is enabled, bucket cache needs to read and load 
> the persistent cache file contents during region server starting time. This 
> cache initialisation is currently asynchronous. The server restart completes 
> after spawning a thread to initialise the cache.
> When the subsequent HFile readers are created, the current implementation is 
> such that the constructor of the hfile (HFilePreadReader) waits until the 
> cache is initialised. Due to this wait, all client requests to these regions 
> would fail during the whole cache initialisation period, as these regions are 
> not yet online.
> The correct way to handle this is that, the constructors of HFile readers 
> should not wait for cache initialisation. Only the prefetch threads should 
> wait for the cache initialisation.
> Subsequently, any client requests should be served by accessing the 
> underlying file system if the cache is not yet initialised, and a cache miss 
> should be computed in the cache stats.
> Thanks,
> Janardhan



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