cloudwatch: CDK detects false-positive missing identifiers on metric expressions

[garciparedes]

Describe the bug

I have a metric expression defined as SUM(METRICS("prefix")) where some of my metrics contains the "prefix" string.

When I synthetize the CDK, I started getting warning like this:

[Warning at $SECRET Math expression 'SUM(METRICS("prefix"))' references unknown identifiers: prefix. Please add them to the 'usingMetrics' map. [ack: CloudWatch:Math:UnknownIdentifier]

However, those are false-positives and should be skipped in the following line:

aws-cdk/packages/aws-cdk-lib/aws-cloudwatch/lib/metric.ts

Line 710 in 6df9bfe

if (!this.expression.toUpperCase().match('\\s*INSIGHT_RULE_METRIC|SELECT|SEARCH|METRICS\\s.*') && missingIdentifiers.length > 0) {

Regression Issue

• Select this option if this issue appears to be a regression.

Last Known Working CDK Version

No response

Expected Behavior

Given that the METRICS operation accept part identifier names, it should not produce any warnings.

Current Behavior

It produces warnings.

Reproduction Steps

Partially define a identifier in a SUM(METRICS("partial")) expression.

Possible Solution

Update regular expression to properly handle the keywords that skip the warning:

'\\b(INSIGHT_RULE_METRIC|SELECT|SEARCH|METRICS)\\b'

Additional Information/Context

No response

CDK CLI Version

2.173.4

Framework Version

No response

Node.js Version

18

OS

OS X

Language

TypeScript

Language Version

No response

Other information

No response

[ashishdhingra]

Looking at the documentation for METRICS() function at Using math expressions with CloudWatch metrics, it mentions that:

---

You can use the METRICS() function with a string to return only the graphed metrics that contain that string in their Id field. For example, the expression SUM(METRICS("errors")) returns a time series that is the sum of the values of all the graphed metrics that have ‘errors’ in their Id field. You can also use SUM([METRICS(“4xx”), METRICS(“5xx”)]) to match multiple strings.

---

So the check at

aws-cdk/packages/aws-cdk-lib/aws-cloudwatch/lib/metric.ts

Line 710 in 6df9bfe

if (!this.expression.toUpperCase().match('\\s*INSIGHT_RULE_METRIC|SELECT|SEARCH|METRICS\\s.*') && missingIdentifiers.length > 0) {

appears to be incorrect.

[garciparedes]

Yeah, seems like there is a set of functions that can be used in the CloudWatch Metric expressions where partial identifiers are supported.

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If you need help, please open a new issue that references this one.