Bug: Override of default dimension with new value results into wrong CloudWatch dimension output

[Jimmy89]

Expected Behaviour

If I set a default dimension, e.g. type with the value meeting, and then set through singleMetric with the same dimension name set to another value, the output to CloudWatch contains twice the dimension type. This is incorrect in my understanding.

Current Behaviour

Code snippet

import {Metrics, MetricUnits} from "@aws-lambda-powertools/metrics";

const metrics = new Metrics({
    namespace: 'testing',
    serviceName: 'serviceA',
});

export const handler = (event, handler) => {
  metrics.setDefaultDimensions({ type: "meeting" });
  const singleMetric = metrics.singleMetric();
  singleMetric.addDimension("type", "a");
  singleMetric.addMetric("hello", MetricUnits.Count, 1);
  metrics.publishStoredMetrics();
};

Output:

{"_aws":{"Timestamp":1698769257078,"CloudWatchMetrics":[{"Namespace":"testing","Dimensions":[["service","type","type"]],"Metrics":[{"Name":"hello","Unit":"Count"}]}]},"service":"serviceA","type":"a","hello":1}

The Dimensions field contains type twice, which should be once in my understanding.

Steps to Reproduce

Run code snippet below and watch output.

Possible Solution

When writing the dimension you could use new Set to ensure the array does not contain duplicates.

Powertools for AWS Lambda (TypeScript) version

latest

AWS Lambda function runtime

18.x

Packaging format used

npm

Execution logs

No response

[boring-cyborg]

Thanks for opening your first issue here! We'll come back to you as soon as we can.
In the meantime, check out the #typescript channel on our Powertools for AWS Lambda Discord: Invite link

[dreamorosi]

Hi @Jimmy89 thank you for taking the time to report the issue.

I was able to reproduce the bug and indeed the dimension gets duplicated.

I have created a sample minimal example which can be found in this repo: https://github.com/dreamorosi/repro-1773

I will add this to our backlog so we can fix it.

[github-actions]

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[github-actions]

This is now released under v1.14.2 version!