StackdriverMeterRegistry should report Counters as CUMULATIVE not as GAUGE

[jayleenli]

Calling .counter() for a StackdriverMeterRegistry creates a GAUGE metric instead of CUMULATIVE metric.

This is basically a repost of a previously reported bug because that one is closed.
#2231

Environment

• Micrometer latest version (io.micrometer:micrometer-registry-stackdriver:latest.release)
• Stackdriver Micrometer registry
• macOS
• Java version: 15

To Reproduce
How to reproduce the bug:
Example:

    MeterRegistry registry = StackdriverMeterRegistry.builder(stackdriverConfig).build();
    Counter x = registry.counter("example_counter","example_key","20");
    someUserCaseIncrementingCounter(x);

Will create a gauge metric and not a cumulative one in Cloud Monitoring.

Expected behavior
Create a CUMULATIVE Metric instead of a Gauge Metric

Additional context
User @tmarszal has proposed changes to fix this bug.
tmarszal@9e6809f

[jonatan-ivanov]

We have a PR to fix this: #2232
I linked it to this issue.

[tmarszal]

Thanks a lot for creating this Issue, @jayleenli !

I see one thing to consider, I would like to get your thoughts on. What MetricKind should we use e.g. for Counters? @shakuzen mentioned in the PR that Step* variants of meters that are used for Stackdriver behave more like DELTA than CUMULATIVE - they reset value on every publish and I agree. Does it make sense to you to produce DELTA instead?

[tmarszal]

Ok, I think I answered my own question. It is not super obvious in Google Monitoring docs, but custom metrics are only allowed to have GAUGE and CUMULATIVE MetricKind. So we can't use DELTA.

https://cloud.google.com/monitoring/api/v3/kinds-and-types#kind-type-combos - in the DELTA column all of the allowed combinations have footnote saying it's not actually supported for custom metrics.

[shakuzen]

Just sharing that I found this discussion which resulted in this feature request being opened to support DELTA with custom metrics. Also of note is that a Stackdriver product manager suggested the approach with CUMULATIVE and timstamp resets as a workaround.