On Apr 24, 2015, at 5:53 AM, Yongjun Zhang <yzh...@cloudera.com> wrote:
>
> Basically we are adding two additional lines to the report (as highlighted
> above).
>
> Theoretically if a tool parses existing fsck report and expects the
> 'Corrupt blocks" entry to be right after the "Average block replication"
> entry, then the change would fail the tool. But is this really a concern?
>
> I guess this is not really a concern, so I don't think this change is
> incompatible. but would anyone please comment?
>
If it changes the output of a CLI command, it's an incompatible change:
http://hadoop.apache.org/docs/r2.7.0/hadoop-project-dist/hadoop-common/Compatibility.html#Command_Line_Interface_CLI
Other changes to fsck have been punted to 3.x for the *exact same
reason*. In other cases, committers have violated these rules in branch-2 (not
just to fsck, but to all sorts of other command line bits, even removing
command options!) to the point that our compatibility guarantees are pretty
much useless. It's open season on nuking the ecosystem. :(
People not following the compat rules is one of the reasons I started
building my own changes and release notes, because we have too many committers
either accidentally committing incompatible changes or just outright lying
about them. (… and, as much as I hate to say it, the HDFS project is easily
the biggest offender.)
