Jackson version upgrade: default from 2.4.2 to 2.7.4 (latest stable)

[cowtowncoder]

Fix for [FLINK-3855] -- upgrade default Jackson version from 2.4.2 to 2.5.5 (last 2.5 patch); remove unnecessary explicit version ref, and upgrade ES client to latest patch for minor version it refers.

[aljoscha]

@fhueske jackson-databind is only used in the Table API to render the explain output. We should be good to update to latest there as well, right?

[fhueske]

Yes, I hope so.

[aljoscha]

@cowtowncoder do you see a reason for not upgrading all the way to 2.7?

[cowtowncoder]

@aljoscha @fhueske Nothing special, just thought I'd start with smallest step, given that this is my first contribution here.
But given that 2.7.4 is out now, I agree that going right there does make most sense and should be safe.
It also looks like most usage is via Tree API (JsonNodes), some streaming; most changes are typically in databinding and very few compatibility issues occur outside databinding. So to me upgrade seems safe either way. And since Elastic-client already uses 2.7 that would allow unification of versions as well.

[smarthi]

ElasticSearch 2.x requires jackson >= 2.6.2, hence the Elastic 2.x connector jackson version is set at 2.7.x. Locally, I changed the Jackson version to be 2.7.x in the parent pom and didn't see any issues or tests failures. I think its safe to change the jackson.version to 2.7.4 in parent pom. If so, please remove the <jackson.version> in ElasticSearch2/pom.xml

[cowtowncoder]

@smarthi Updated as suggested.

[aljoscha]

The build now fails consistently for the wikipedia connector? Could you push another dummy commit to rerun travis tests. Let's see if it goes away.

[smarthi]

The IRC Wikimedia channel is timing out and hence the reason for Wiki test failures, nothing to do with this PR.

LGTM IMO

[aljoscha]

I'm running a last local test and then merging this. Thanks for the work! 😃

[fhueske]

Merging