Drop support for Elasticsearch 5.x

[danielmitterdorfer]

Elasticsearch 5.x is end of life since 2019-03-11. According to our
version policy in Rally we drop support two years after the end of life
date.

Relates #1107

[ebadyano]

Do we want to somehow prevent people running with esrally race --distribution-version=5.6.16?

[ebadyano]

A few more spots where we reference 5.0.0:

rally/esrally/mechanic/supplier.py

Line 141 in 7eaee22

raise exceptions.SystemSetupError("Could not determine version. Please specify the Elasticsearch distribution "

rally/esrally/resources/track-schema.json

Line 494 in 7eaee22

"description": "[Only for type == 'index']: Defines the name of the ingest node pipeline to use (only supported from Elasticsearch 5.0)."

rally/esrally/utils/versions.py

Line 74 in 7eaee22

class VersionVariants:

There are also a few references to 5.x and 5.0 in rally tracks README file and rally teams README

[danielmitterdorfer]

Thanks for your review @ebadyano. I've pushed 1a9b53c to address your feedback. Can you please have another look?

To your comments:

• I did not touch VersionVariants now because 5.x is only referenced in a source code comment and only serves as an example how that piece of code is supposed to work.
• I've removed the 5.x reference in the other places
• We could probably fail fast when people attempt to benchmark an unsupported version but I'm honestly not sure whether we should actively prohibit it. I see this as out of scope for this PR but we could discuss this in next week's sync. I've added it to the agenda.

[ebadyano]

Looks good, but i think I found a few more references:

rally/docs/pipelines.rst

Line 52 in 7eaee22

You should use this pipeline when you want to build and benchmark Elasticsearch from sources. This pipeline will only work from Elasticsearch 5.0 onwards because Elasticsearch switched from Maven to Gradle and Rally only supports one build tool in the interest of maintainability.

rally/docs/command_line_reference.rst

Line 550 in 7eaee22

If you actively develop Elasticsearch and want to benchmark a source build of Elasticsearch (which Rally will create for you), you can specify the git revision of Elasticsearch that you want to benchmark. But note that Rally uses and expects the Gradle Wrapper in the Elasticsearch repository (``./gradlew``) which effectively means that it will only support this for Elasticsearch 5.0 or better. The default value is ``current``.

rally/docs/recipes.rst

Line 87 in 7eaee22

3. Start the benchmark by invoking Rally as usual on the benchmark coordinator, for example: ``esrally race --track=pmc --distribution-version=5.0.0 --target-hosts=10.5.5.10:39200,10.5.5.11:39200``. Rally will derive from the ``--target-hosts`` parameter that it should provision the nodes ``10.5.5.10`` and ``10.5.5.11``.

rally/docs/track.rst

Line 658 in 7eaee22

* ``pipeline`` (optional): Defines the name of an (existing) ingest pipeline that should be used (only supported from Elasticsearch 5.0).

Also do we want to add anything in the migrate guide?

[ebadyano]

no need for another iteration after the 4 more spots i mentioned above. Thank you, LGTM!

[danielmitterdorfer]

Thanks for your review! I've removed the remaining references in 0359c64.