aws_cloudwatch: Stat helper does not support lower bounds, or fixed values.

[everett1992]

Describe the feature

There are valid statistics that cannot be created with the Stats helper

• Range stats with open upper limits, TM(%1:) Trimmed Mean, excluding the lowest 1 percent
• Range stats with fixed values, TM(1:2) Trimmed Mean excluding values less than 1 or greater than 2.

https://docs.aws.amazon.com/AmazonCloudWatch/latest/monitoring/Statistics-definitions.html

Use Case

Defining stats such as PR(1:), TC(1:2), TC(1:), TC(1%:)

Proposed Solution

I don't think mixing percent and fixed values is allowed, so I recommend an interface like this

TC({abovePercent: 10})                   // TC(10%:)
TC({abovePrecent: 10, belowPercent: 90}) // TC(10%:90%)
TC({belowPercent: 90})                   // TC(:90%)
TC({above: 10})                          // TC(10:)
TC({above: 10, below: 90})               // TC(10:90)
TC({below: 90})                          // TC(:90)

Which can be implemented as function overloads

function TC(lower: number, upper?: number)
function TC(range: PercentRange)
function TC(range: FixedRange)

Other options

• a fixed function on the stat to switch to fixed mode
• allow undefined for the lower bound, which mean unbounded.

TC.fixed(10, 90)
TC.fixed(undefined, 90)

• Allow Infinity as unbounded

TC(10, Infinity)
TC(-Infinity, 90)

Other Information

No response

Acknowledgements

• I may be able to implement this feature request
• This feature might incur a breaking change

CDK version used

2.133.0

Environment details (OS name and version, etc.)

NA

[tim-finnigan]

Thank you for the feature request!

[MrHen]

I just hit this issue. I needed to define three PR stats and I can't do two of them:

PR(:1000)
PR(1000:2000)
PR(2000:)

Only the middle scenario is supported.