[docs] Document new Central configuration support

[bmorelli25]

Summary

Central configuration will be enabled for all dynamic parameters in 7.7. These new parameters need to be documented somewhere.

Currently

Currently, we document supported parameters in the Kibana reference. This makes sense, as prior to this update, all Agents supported the same few configurations. With more configurations coming online, this might not make sense for 7.7.

Solution

We should make a note of supported configuration options in each Agent reference. There are a few ways we could do this...

Custom badge

A custom badge would be very easy to scan for. This could help supported parameters stand out, and would link to more information on the feature. As a quick example, I created this badge and added it to the first two configurations in the Python reference:

or...

Unfortunately, these badges have to be inline, and we're very limited in terms of how asciidoctor displays something like this.

Just another paragraph

Doesn't pop as much, but maybe it doesn't need to.

Related issues

• Official name of the feature APM Agent central configuration, per Agent remote configuration #76 (comment).
• Agent support: Enable Remote Config for all dynamic parameters. #213 (comment)
• Discussion: Enable Remote Config for all dynamic parameters. #213

Related PRs

• Removes config list from the Kibana reference: docs: Update APM central config documentation kibana#61893.

[bmorelli25]

The Java Agent documents dynamic parameters: https://www.elastic.co/guide/en/apm/agent/java/master/configuration.html#configuration-dynamic. Perhaps this is a better route to go?

cc @felixbarny since you seem to be leading the Central configuration charge

[felixbarny]

The downside of tagging options explicitly with Central configuration ✔️ is that there might be other configuration sources, like configuration files, that allow options to be reloaded. That's why we mark them with Dynamic true:

However, Dynamic=true does not really pop out as nice as the badge does and "dynamic" sounds a bit vague. Maybe we could have a badge for Reloadable option ✔️ that also acts as a link to the section explaining what dynamic/reloadable options are and which configuration sources support reloading:

[bmorelli25]

I'm shying away from "reloadable" as it's not a real word. Elasticsearch also uses dynamic, which I think is descriptive enough.

[bmorelli25]

All agents have PRs opened.