Joep Rottinghuis commented on YARN-4053:

Now that I'm looking at it again in detail with [~vrushalic] the perf impact is 
probably not quite as bad. I thought for a moment that the iteration had to 
happen for each cell, but it is needed for each column only.

I agree with your point that we should keep it generic and be future proof. If 
we have the converter, then we should just use it. However, in 
FlowScanner.compareCellValues (line 357) you're assuming a long and just 
blindly cast to long. If this happens to be a GenericObjectMapper then that 
will fail.

Perhaps we should do the following: make converter extend comparable and also 
add a method to sum two (or more) byte values in a vararg style. For the long 
implementation that should simply be a regular sum, for the generic object 
mapper it may be a string append, or whatever makes sense. Then we're future 
proof when another style of conversion and summing and comparison can happen 
safely right?

Would that make sense?

> Change the way metric values are stored in HBase Storage
> --------------------------------------------------------
>                 Key: YARN-4053
>                 URL: https://issues.apache.org/jira/browse/YARN-4053
>             Project: Hadoop YARN
>          Issue Type: Sub-task
>          Components: timelineserver
>    Affects Versions: YARN-2928
>            Reporter: Varun Saxena
>            Assignee: Varun Saxena
>              Labels: yarn-2928-1st-milestone
>         Attachments: YARN-4053-YARN-2928.01.patch, 
> YARN-4053-YARN-2928.02.patch, YARN-4053-feature-YARN-2928.03.patch
> Currently HBase implementation uses GenericObjectMapper to convert and store 
> values in backend HBase storage. This converts everything into a string 
> representation(ASCII/UTF-8 encoded byte array).
> While this is fine in most cases, it does not quite serve our use case for 
> metrics. 
> So we need to decide how are we going to encode and decode metric values and 
> store them in HBase.

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