Cloudwatch metrics are accumulating on every Send() call, but should be Reset

[feliksik]

On a call to cloudwatch.Send(), the state of the counter is not reset.
That means the value is always increasing.

This doesn't make sense to me, as Cloudwatch accumulates the values for you. It seems like we are basically implementing a counter with a Gauge-like behavior now.

Can we agree this is a bug?

[feliksik]

See PR #591 for a failing test case.

[feliksik]

I'm also not sure how the Histogram values are supposed to be reset.

Furthermore, note that if we move the test to teststat.TestCounter(), more (but not all) services fail. The still-succesful tests show which implementations use Reset().Walk().

$ go test ./metrics/...
ok  	github.com/go-kit/kit/metrics	0.253s
--- FAIL: TestCounter (0.00s)
	cloudwatch_test.go:81: Using counter second time: want 4641.000000, have 5978.000000
FAIL
FAIL	github.com/go-kit/kit/metrics/cloudwatch	0.086s
?   	github.com/go-kit/kit/metrics/discard	[no test files]
ok  	github.com/go-kit/kit/metrics/dogstatsd	0.761s
--- FAIL: TestCounter (0.00s)
	expvar_test.go:14: Using counter second time: want 4641.000000, have 5978.000000
FAIL
FAIL	github.com/go-kit/kit/metrics/expvar	0.077s
--- FAIL: TestCounter (0.00s)
	generic_test.go:25: Using counter second time: want 4641.000000, have 5978.000000
FAIL
FAIL	github.com/go-kit/kit/metrics/generic	0.680s
ok  	github.com/go-kit/kit/metrics/graphite	0.051s
ok  	github.com/go-kit/kit/metrics/influx	0.122s
ok  	github.com/go-kit/kit/metrics/internal/lv	0.002s
?   	github.com/go-kit/kit/metrics/internal/ratemap	[no test files]
ok  	github.com/go-kit/kit/metrics/multi	0.012s
--- FAIL: TestCounter (0.00s)
	pcp_test.go:26: Using counter second time: want 4641.000000, have 5978.000000
FAIL
FAIL	github.com/go-kit/kit/metrics/pcp	1.606s
--- FAIL: TestCounter (0.00s)
	prometheus_test.go:47: Using counter second time: want 4641.000000, have 5978.000000
--- FAIL: TestHistogram (0.02s)
	prometheus_test.go:186: Bucket 425: want 16, have 10 (37.5%)
FAIL
FAIL	github.com/go-kit/kit/metrics/prometheus	0.069s
?   	github.com/go-kit/kit/metrics/provider	[no test files]
ok  	github.com/go-kit/kit/metrics/statsd	0.176s
?   	github.com/go-kit/kit/metrics/teststat	[no test files]

[peterbourgon]

Histograms don't need to be reset.

[peterbourgon]

This is closed now, I think! :)