Disable Kafka metricsets based on Jolokia

[jsoriano]

What does this PR do?

Kafka metricsets based on Jolokia require a different configuration to
the native metricsets. Disable the Jolokia ones by default, if someone
wants to use them, they need to explicitly enable and configure them.
Reference configuration contains information about this.

At the moment there is no way we can provide default metricsets in the
same module that need different hosts configurations.

In any case consumer and producer metricsets are intended to monitor
Java consumers and producers, while the rest of metricsets are intended
to monitor Kafka brokers. So there is little chance that all of them are going
to be enabled in the same configuration.

Why is it important?

To avoid errors with default configuration.

Checklist

• My code follows the style guidelines of this project
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have made corresponding change to the default configuration files
• I have added tests that prove my fix is effective or that my feature works
• I have added an entry in CHANGELOG.next.asciidoc or CHANGELOG-developer.next.asciidoc.

Related issues

• Errors seen in this discuss topic: https://discuss.elastic.co/t/kafka-monitoring-in-kubernetes/247527/3

Use cases

Using the kafka module, without specifying defaults, should provide a working configuration.

Logs

Errors like these ones appear when using default configuration:

Error fetching data for metricset kafka.broker: error making http request: Post "http://pipeline-kafka:9092/jolokia/%3FignoreErrors=true&canonicalNaming=false": read tcp 10.5.7.136:34466->172.20.79.178:9092: read: connection reset by peer
Error fetching data for metricset kafka.producer: error making http request: Post "http://pipeline-kafka:9092/jolokia/%3FignoreErrors=true&canonicalNaming=false": read tcp 10.5.7.136:34470->172.20.79.178:9092: read: connection reset by peer

Metricbeat tries to request jolokia metrics from the Kafka endpoint.

[elasticmachine]

Pinging @elastic/integrations-services (Team:Services)

[elasticmachine]

💚 Build Succeeded

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Build stats

• Build Cause: [Pull request #20989 updated]

• Start Time: 2020-09-04T14:49:34.801+0000

• Duration: 67 min 1 sec

Test stats 🧪

Test	Results
Failed	0
Passed	3192
Skipped	693
Total	3885

[andresrc]

Will users that are using the module see a change in configuration when upgrading? I.e, can they get the module disabled?

[jsoriano]

Will users that are using the module see a change in configuration when upgrading? I.e, can they get the module disabled?

Users using the default configuration will see the jolokia metricsets disabled. For most of the cases this will mean less errors in logs, but no functionality loss.

The only case where I think this change may break something is if someone is using the kafka module, with default metricsets, to query a jolokia endpoint. In this case they will continue seeing errors querying the kafka broker, and they will lose the jolokia metrics. But I think this is a corner case.

Also, the jolokia metricsets are on beta, so I think it is ok if we do the change at this point, even when having the chance of breaking some cases.

I am removing the backport to 7.9, we have had it like this since 7.5, it is probably ok to wait till 7.10 to fix it.