METRON-2155 Cache Maven in Travis CI Builds

[nickwallen]

This PR attempts to resolve the recent spat of failed Travis CI builds. These builds seem to fail when attempting to download Maven from the Apache Mirrors.

This PR attempts to cache Maven so it does not need to be repeatedly downloaded from the Apache Mirrors. This would mitigate the issue if there are transient problems with Travis connectivity to the Apache Mirrors or if the Apache Mirrors themselves are having sporadic outages.

Note: This is a replacement for #1442. For some reason, Travis has refused to run a CI build for the additional commits that I have made on the original branch.

Pull Request Checklist

• Is there a JIRA ticket associated with this PR? If not one needs to be created at Metron Jira.
• Does your PR title start with METRON-XXXX where XXXX is the JIRA number you are trying to resolve? Pay particular attention to the hyphen "-" character.
• Has your PR been rebased against the latest commit within the target branch (typically master)?

[nickwallen]

I still cannot determine why Travis will not pick-up and run this PR. It did the same for #1442. I have tried closing and reopening, creating a new PR, event creating a new branch and Travis still refuses to run this. Let me know if anyone has ideas.

[ottobackwards]

Do you have your own travis? did it build there. That is strange, although the last build did fail in metron for the storm pr

[nickwallen]

Up to a certain commit, it was running in my own PR. It does not run on the last commit for some reason, even in my own personal account.

[ottobackwards]

maybe the yaml is invalid now?
what if you revert the last change or something?

[nickwallen]

@ottobackwards That is it! Good thinking! I thought at least it would launch a job and fail, but no. Thanks, now I have something to work with.

[ottobackwards]

https://support.travis-ci.com/hc/en-us/articles/115002904174-Validating-travis-yml-files
future reference

[ottobackwards]

feels like we should have some kind of step for doing that stuff when modifying, but we don't change it often do we?

[nickwallen]

FYI - I've triggered the CI build on this quite a few times now and at times have cleared the Travis cache associated with the build. On rare occasions some of the jobs fail with this error. No idea why... yet.

The command "[[ -d $M2_HOME ]] || wget -nc -q 
https://archive.apache.org/dist/maven/maven-3/3.3.9/binaries/apache-maven-3.3.9-bin.zip" 
failed and exited with 8 during .

https://travis-ci.org/apache/metron/jobs/547316532

[ottobackwards]

8 is a server error, which doesn't seem to get logged here. I wonder if we can

• try a newer version of maven
• script this operation to retry or something

[nickwallen]

I added back the retry logic from #1433. I have retried the build a few times and have yet to see a failure.

[ottobackwards]

+1