use Cascading 2.6.1 and cascading-jdbc 2.6.0

[fs111]

Cascading 2.6.x adds amongst various bugfixes a new set of annotations that can be used to send additional user defined information to a DocumentService like driven. Since it is backwards compatible, updating will not cause any issue.

In case you want to review the changes in Cascading 2.6 before merging, see here: https://github.com/Cascading/cascading/blob/2.6/CHANGES.txt

[fs111]

The build fails with internal sbt problems. I did not touch any of those things.

[johnynek]

We'll merge this after we run our internal integration tests. Pretty conservative on bumping external dependencies. We'll try to get to this soon.

PS: Is there any reason to force this here? What if cascading is provided dependency and users pick their own version. Shouldn't we chose the lowest version we need (i.e. the features we use inside scalding proper) that is compatible with the latest version?

[fs111]

I agree that being conservative can be a good thing. I'd argue that 2.6 is a pretty conservative release in itself. The big thing from our point of view are the annotations and the FlowDescriptor, which make driven a lot more useful for cascading and scalding users.

It looks to me that scalding users will not update the cascading underneath, unless you guys do it. That means they will not get the new features/bug fixes unless it is in scalding proper. Also, we do not backport bug-fixes from 2.6 to 2.5, since 2.6 is backwards compatible, so following along in the 2.x line with proper testing seems like the right thing to do to me. Remember that we run the salding tests internally with new versions of cascading continously as well, to make sure, things don't go wrong.

[fs111]

@johnynek any update on this?