> On Jul 22, 2016, at 5:47 PM, Zheng, Kai <kai.zh...@intel.com> wrote:
> 
> For the leveldb thing, wouldn't we have an alternative option in Java for the 
> platforms where leveldb isn't supported yet due to whatever reasons. IMO, 
> native library would be best to be used for optimization and production for 
> performance. For development and pure Java platform, by default pure Java 
> approach should still be provided and used. That is to say, if no Hadoop 
> native is used, all the functionalities should still work and not break. 

        Yes and no.  I can certainly understand some high-end features being 
tied to native libraries, simply because system programming with Java is like 
being a touch typist with your nose.  

        That said, absolutely key functionality should definitely work. Take a 
look at the last Linux/ppc64le report that was emailed to these very lists a 
few days ago [1]:

        
https://builds.apache.org/job/hadoop-qbt-trunk-java8-linux-ppc/30/artifact/out/console-report.html

        Almost all of those YARN failures are due to MiniYARN trying to 
initiate leveldb as part of the service startup but can't because the embedded 
shared library is the wrong hardware architecture. Rather than catch the 
exception and do something else, the code just blows up in a very dramatic 
fashion. That should translate into YARN is completely busted and unusable 
without doing some very weird workarounds.

        To get us back on topic:  the class path isolation work absolutely 
cannot make this situation worse.  We either need to make sure end users can 
replace/modify Hadoop's dependencies if they require native lirbaries or work 
harder on making multiplatform stuff better supported.  The nightly PowerPC 
builds should help tremendously towards this goal. [2]

1 - While I greatly appreciate the OpenPOWER Foundation getting the ASF access 
to these boxes -- Mesos and Hadoop are both actively using them -- It'd be 
great if they were more reliable so we could get a report every day of the 
week. :(

2 - At some point, I'll set up a manually triggered precommit job to test 
patches.  But until both boxes are online and available on a consistent basis, 
it just isn't worth the effort.
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