Converting AWS CloudWatch Metrics Insight query to CDK Metric - amazon-cloudwatch

Question

I am modifying the sample at https://github.com/cdk-patterns/serverless/tree/main/the-eventbridge-etl/typescript as I want to add a dashboard widget to my CloudFormation Stack that shows the Fargate vCPU usage. I have been able to upgrade the app to use CDK v2, and deployment/functionality has been confirmed. However, I cannot get the vCPU widget in the dashboard to show any data.
If I configure the widget manually, from within AWS CloudWatch's Source field, the query looks as follows:
{
"metrics": [
[ { "expression": "SELECT COUNT(ResourceCount) FROM SCHEMA(\"AWS/Usage\", Class,Resource,Service,Type) WHERE Service = 'Fargate' AND Resource = 'vCPU'", "label": "Query1", "id": "q1" } ],
[ "AWS/Usage", "ResourceCount", "Service", "Fargate", "Type", "Resource", { "id": "m1" } ]
],
"view": "timeSeries",
"title": "ExtractECSJob",
"region": "us-west-2",
"timezone": "Local",
"stat": "Sum",
"period": 300
}
However, when I attempt to use CDK, with the following TypeScript code:
const extractECSWidget = new GraphWidget({
title: "ExtractECSJob",
left: [
new Metric({
namespace: "AWS/Usage",
metricName: "ResourceCount",
statistic: "Sum",
period: Duration.seconds(300),
dimensionsMap: {
"Service": "Fargate",
"Type": "Resource",
"Resource": "vCPU"
}
})
]
});
This does not translate to the above, and no information is shown in this widget. The new source looks as follows:
{
"view": "timeSeries",
"title": "ExtractECSJob",
"region": "us-west-2",
"metrics": [
[ "AWS/Usage", "ResourceCount", "Resource", "vCPU", "Service", "Fargate", "Type", "Resource", { "stat": "Sum" } ]
],
"period": 300
}
How do I map the above metrics source definition to the CDK source construct?
I tried using MathExpression but with the following:
let metrics = new MathExpression({
expression: "SELECT COUNT('metricName') FROM SCHEMA('\"AWS/Usage\"', 'Class','Resource','Service','Type') WHERE Service = 'Fargate' AND Resource = 'vCPU'",
usingMetrics: {}
})
const extractECSWidget = new GraphWidget({
title: "ExtractECSJob",
left: [
metrics
]
});
I get the warning during cdk diff:
[Warning at /EventbridgeEtlStack/EventBridgeETLDashboard] Math expression 'SELECT COUNT(metricName) FROM SCHEMA($namespace, Class,Resource,Service,Type) WHERE Service = 'Fargate' AND Resource = 'vCPU'' references unknown identifiers: metricName, namespace, lass, esource, ervice, ype, ervice, argate, esource, vCPU. Please add them to the 'usingMetrics' map.
What should I put in the usingMetrics map? Any help is appreciated.

Answer 1

Thanks to AWS Support I was able to have this fixed. The updated code looks like the following:
let metrics = new MathExpression({
expression: "SELECT COUNT(ResourceCount) FROM SCHEMA(\"AWS/Usage\", Class,Resource,Service,Type) WHERE Service = 'Fargate' AND Resource = 'vCPU'",
usingMetrics: {},
label: "Query1"
})
let metric2 = new Metric({
namespace: "AWS/Usage",
metricName: "ResourceCount",
period: cdk.Duration.seconds(300),
dimensionsMap: {
"Service": "Fargate",
"Type": "Resource",
}
})
const extractECSWidget = new GraphWidget({
title: "ExtractECSJobTest",
left: [metrics, metric2],
region: "us-west-2",
statistic: "Sum",
width: 24
});
dashboardStack.addWidgets(
extractECSWidget
);
When running cdk deploy, I still get the same warning (about unknown identifiers being referenced) but the widget is functioning as expected.

Answer 2

This feature has not been supported by CDK yet. I've opened the issue https://github.com/aws/aws-cdk/issues/22844
I faced the same issue while creating an alarm based on a metric based on a query. I found the workaround with level 1 construct CfnAlarm
Maybe same kind of workaround exists for Widget.