Add support for AggregatedHistogram metrics to the AWS CloudWatch Sink

[mkwan-amzn]

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Use Cases

The end goal is for the AWS CloudWatch sink to support sending AggregatedHistogram MetricValue types to CloudWatch. An example such metric is http_client_rtt_seconds, which right now when attempting to send through the CloudWatch Sink is dropped, with no error messages or logging to reveal why.

Attempted Solutions

I have not attempted to solve this. It may be possible by attempting to restructure the emitted metric in a transform step but I'm not sure and have not tested it.

Proposal

We need to add support for that MetricValue type here:

vector/src/sinks/aws_cloudwatch_metrics/mod.rs

Lines 271 to 308 in 3d7f06d

	match event.value() {
	MetricValue::Counter { value } => Some(
	MetricDatum::builder()
	.metric_name(metric_name)
	.value(*value)
	.set_timestamp(timestamp)
	.set_dimensions(dimensions)
	.build(),
	),
	MetricValue::Distribution {
	samples,
	statistic: _,
	} => Some(
	MetricDatum::builder()
	.metric_name(metric_name)
	.set_values(Some(samples.iter().map(|s| s.value).collect()))
	.set_counts(Some(samples.iter().map(|s| s.rate as f64).collect()))
	.set_timestamp(timestamp)
	.set_dimensions(dimensions)
	.build(),
	),
	MetricValue::Set { values } => Some(
	MetricDatum::builder()
	.metric_name(metric_name)
	.value(values.len() as f64)
	.set_timestamp(timestamp)
	.set_dimensions(dimensions)
	.build(),
	),
	MetricValue::Gauge { value } => Some(
	MetricDatum::builder()
	.metric_name(metric_name)
	.value(*value)
	.set_timestamp(timestamp)
	.set_dimensions(dimensions)
	.build(),
	),
	_ => None,

Stealing from @jszwedko as we discussed here: #21851

It should probably log a warning or something when dropping those metrics. I agree it should support them; probably by converting each bucket into a separate counter.

References

This was discussed here: #21851

Version

0.37.1