Re: profiling hdfs write path

[Radim Kolar]

If you're just going to insult us, please stay away. We don't need
your help unless you're going to be constructive.

Good units tests will catch code modifications like:

from:
    long getLastByteOffsetBlock() {
      return lastByteOffsetInBlock;
    }

to

from:
    long getLastByteOffsetBlock() {
      return lastByteOffsetInBlock-1;
  }

I did 10 of such changes and about 60% were undetected.