MathExpression in Cloudwatch graphs are fixed to a 5min period

[alexmv]

When serializing the JSON of MathExpression objects, only the expression is output. If the MathExpression has a period other than 5min (due to being derived, say, from 1m metrics), it gets (incorrectly) rendered with 5min intervals -- because the default period at the graph level is 5min, and the serialized MathExpression doesn't specify one.

Reproduction Steps

from aws_cdk import aws_cloudwatch, aws_elasticloadbalancingv2, core


class Example(core.Construct):
    def __init__(
        self,
        scope: core.Construct,
        id: str,
        target_group: aws_elasticloadbalancingv2.ApplicationTargetGroup,
    ) -> None:
        super().__init__(scope, id)

        metric = aws_cloudwatch.MathExpression(
            expression=f"FILL(something,0)",
            using_metrics={
                "something": target_group.metric_healthy_host_count(
                    statistic="average", period=core.Duration.minutes(1),
                )
            },
            period=core.Duration.minutes(1),
        )

        dashboard = aws_cloudwatch.Dashboard(self, "dashboard")
        dashboard.add_widgets(aws_cloudwatch.GraphWidget(left=[metric], width=24))

(Note 5-min intervals on the datapoints)

Error Log

N/A

Environment

• CLI Version: 1.17.13
• Framework Version: 1.31.0
• OS: OS X 10.14.6
• Language: Python 3.8.0

Other

---

This is 🐛 Bug Report

[rix0rrr]

Works as intended. Specify the intended duration on the MathExpression, not on its compound metrics.

[alexmv]

The fifth line from the end specifies the desired period, as part of the MathExpression. Can you be more specific where else the period should be supplied?

[alexmv]

Works as intended. Specify the intended duration on the MathExpression, not on its compound metrics.

I believe that's what the code I showed does:

        metric = aws_cloudwatch.MathExpression(
            # ...
            period=core.Duration.minutes(1),
        )

If you meant something else, please clarify.

[alexmv]

@rix0rrr: Am I misunderstanding your comment, or was this issue closed in error?

[zhy2002]

This problem still exists as of CDK 1.85.0

[bentonkribbs]

Looks like this issue has been fixed: #13078