GitHub user zentol opened a pull request:

    https://github.com/apache/flink/pull/3106

    [FLINK-????] FIx inconsistent numBytesIn/Out metrics

    This PR fixes _some_ jira issue (i can't find the correct issue ID right 
now since JIRA is being stupid) regarding inconsistent numBytesIn/Out metrics.
    
    Given 2 subsequent tasks A->B the numBytesOut count of A was lower than the 
numBytesIn(Local/Remote) count of B by a huge margin, although they should be 
(nearly) identical.
    
    The problem is that A was counting how much bytes the serialized records 
were using, whereas B was counting how large the ```Buffer```s were that it 
received. A ```Buffer``` contains the following data:
    ```
    |size_of_R1|R1|size_of_R2|R2|...
    ```
    where as R1/R2 are serialized records and the sizes denote the serialized 
length of their respective record.
    
    So, while A was adding ```sizeOf(R1)```, B was adding sizeOf(size_of_R1) + 
sizeOf(R1).
    
    A was simply not accounting for the added bytes that size_of_RX were using, 
which is what this PR is fixing by adding ```4``` after the serialization of 
each record.
    
    cc @uce 

You can merge this pull request into a Git repository by running:

    $ git pull https://github.com/zentol/flink _metrics_incon

Alternatively you can review and apply these changes as the patch at:

    https://github.com/apache/flink/pull/3106.patch

To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:

    This closes #3106
    
----
commit 5300a35ac6ee8815d07a739c9b370ae475f0d9a0
Author: zentol <ches...@apache.org>
Date:   2017-01-12T13:59:22Z

    [FLINK-????] FIx inconsistent numBytesIn/Out metrics

----


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