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https://issues.apache.org/jira/browse/HDFS-12427?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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James Clampffer updated HDFS-12427:
-----------------------------------
    Resolution: Fixed
        Status: Resolved  (was: Patch Available)

Committed the 001 patch that [~mtracy] reviewed to HDFS-8707.  The later 
patches were just there to poke the CI system.

Still trying to sort out the CI issues with HDFS-12640 so I prior to committing 
I checked docker runs locally and ran stress tests on a few large clusters that 
were hitting the issue as well as valgrind tests and everything looked good.

> libhdfs++: Prevent Requests from holding dangling pointer to RpcEngine
> ----------------------------------------------------------------------
>
>                 Key: HDFS-12427
>                 URL: https://issues.apache.org/jira/browse/HDFS-12427
>             Project: Hadoop HDFS
>          Issue Type: Sub-task
>          Components: hdfs-client
>            Reporter: James Clampffer
>            Assignee: James Clampffer
>            Priority: Critical
>         Attachments: HDFS-12427.HDFS-8707.000.patch, 
> HDFS-12427.HDFS-8707.001.patch, HDFS-12427.HDFS-8707.002.patch, 
> HDFS-12427.HDFS-8707.003.patch, HDFS-12427.HDFS-8707.004.patch
>
>
> The lifetime of Request objects is tied to the worker thread(s) in the async 
> event loop.  In the current code there's nothing that prevents a request from 
> outliving the RpcEngine (bound to FileSystem) while it's waiting for IO.  If 
> the Request, or a task that makes a new request, outlives the RpcEngine it 
> attempts to dereference a dangling pointer and either crashes or continues to 
> run with bad data.
> Proposed fix is to reference count the RpcEngine via shared_ptr so that 
> Requests can hold a weak_ptr to it.  When a request or RpcConnection 
> attempting to make a request needs something from the RpcEngine like a call 
> id number it can promote the weak_ptr to a shared_ptr.  If it's unable to 
> promote because the RpcEngine has been destroyed the Request's handler can be 
> invoked with an appropriate error message.  A weak_ptr must be used rather 
> than a shared_ptr to avoid reference cycles.



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