Index level metrics

[lukas-vlcek]

Adding esplugin integaration tests.
Bring indices level metrics back.

[lukas-vlcek]

@vvanholl PTAL

I need your review. I do not like creating massive PRs. The next feature I will contribute is #124 and it would be really great if this PR is already merged before I submit next one. We also need back-port these changes into older releases. So there is a lot of work to do...

Let me sum up what this PR brings:

1. Adoption of gradle esplugin. This simplifies ES plugin build automation, streamlines gradle build script (i.e plugin descriptor and Java security manager configuration) and enables implementation of REST API tests using Elasticsearch tools.

2. Added couple of basic REST API tests.

3. (Re-)Introducing index level metrics. I was also able to clean up the original code and drop some of the unnecessary ES plugin boilerplate code. I added complete coverage of all index level metrics into REST API tests. Although this sounds unnecessary I was able to spot and fix at least two minor issues in the metrics (one was typo in metric name, second was registration of metrics that were no longer available and reported).

In general I think it will be useful to add REST tests for every exposed metric. In the future I want to make sure that there is also Grafana dashboard available for each release version of this plugin. For this I want to be sure all the used metric names match.

[lukas-vlcek]

Just note: if you wan to run all tests use gradle clean check

[vvanholl]

As usual this is a very awesome contribution to my project :)
Thank you for your work !

Vincent.

By the way, from now CI will also done by Gitlab CI.

[lukas-vlcek]

By the way, from now CI will also done by Gitlab CI.

This is great news! I am trying to learn more about Gitlab CI ATM.
https://gitlab.com/vvanholl/elasticsearch-prometheus-exporter/

Does the CI start when PR is created? I created #132 but it does not seem to kickstart CI. Is there anything we can do about this?

Also it would be nice to add project badges to README.dm.

I was able to figure out build badge for the master branch:

https://gitlab.com/vvanholl/elasticsearch-prometheus-exporter/badges/master/build.svg

Though coverage badge does not seem to work for me:

https://gitlab.com/vvanholl/elasticsearch-prometheus-exporter/badges/master/coverage.svg

I need to dig deeper. Thoughts welcome.

[lukas-vlcek]

Hmm... is it possible that Gitlab-CI does not support easy pipeline start when new PR is created in GitHub? See https://stackoverflow.com/questions/43918324/trigger-jobs-in-gitlab-ci-on-merge-request

[vvanholl]

Unfortunately this is not yet implemented as well : https://gitlab.com/gitlab-org/gitlab-ce/issues/23902