Breakdown graphs: introduce config option instead of special value for DISABLE_METRICS

[beniwohli]

Description of the issue

The current spec proposes to use a special value (span.self_time) for DISABLE_METRICS to disable collection of breakdown metrics. This introduces special cases into a mechanism that did not have any previous considerations for special casing, which can be problematic (in the case of the Python agent, it would require a substantial refactor of how DISABLE_METRICS currently works).

Instead, I propose to use a boolean config option BREAKDOWN_METRICS, with default to True. While this sadly adds to the proliferation of config options, I think it is preferable to overloading existing config options with special meaning.

What we are voting on

Should we add a new config option to disable/enable collection of breakdown metrics?

Vote

Agent	Yes	No	Indifferent	N/A	Link to agent issue
.NET					elastic/apm-agent-dotnet#227
Go					elastic/apm-agent-go#597
Java					elastic/apm-agent-java#743
Node.js
Python
Ruby
RUM

cc @elastic/apm-agent-devs

[felixbarny]

Note that even when BREAKDOWN_METRICS=false, the transaction.duration metric still has to be tracked.

[SergeyKleyman]

Note that even when BREAKDOWN_METRICS=false, the transaction.duration metric still has to be tracked.

@felixbarny Just to clarify - by "transaction.duration metric" you refer to duration property in transaction event object and not a dedicated sample in metricset event object, right?

[axw]

@SergeyKleyman there's a metricset for it, but it's a new thing introduced along with breakdown metrics. It's not needed for the .NET agent just yet. More here: https://docs.google.com/document/d/1-_LuC9zhmva0VvLgtI0KcHuLzNztPHbcM0ZdlcPUl64/edit#heading=h.cs6w4ad6jo6c

[SergeyKleyman]

@axw Thank you for clarification. A follow-up question: is there a way to disable "transaction.duration metric" as well?

[axw]

@SergeyKleyman You should be able to do that using DISABLE_METRICS.