Public API for getting metrics that have been set

[springmeyer]

I have a usecase where I want to get access to one or all the metrics that have been set with putMetric before sending a response back to the user. Specifically I'm planning on putting some of the metric values into server timing headers so that I can tie clientside behavior back to serverside metrics.

I'm found that while there is not a public getMetric method I can get access to previously set metrics by inspecting the data here

My question is whether this is an okay, somewhat stable method to use? Or if this is exclusively private/internal data that I should not be touching? If the latter, is there interest in adding formal getMetric or getProperty methods?

[jaredcnance]

Any non-public members are subject to changes without changing major versions so while I don’t have any plans to change them, I wouldn’t recommend depending on internal/private members because you can’t rely on semver to identify breaking changes.

Would access to the current metrics context suffice? Seems this would be the only blocker.

aws-embedded-metrics-node/src/logger/MetricsLogger.ts

Line 28 in 730bbae

private context: MetricsContext;

[springmeyer]

Thanks for the thoughts!

Would access to the current metrics context suffice? Seems this would be the only blocker.

Yes, that is working right now. I'm currently getting access like:

context.metrics.forEach( (value, key) => {
      console.log(value,key);
    })

which dumps metrics I've added (in earlier code) like:

MetricValues { values: [ 1 ], unit: 'None' } 'RequestCount'
MetricValues { values: [ 314.675 ], unit: 'Milliseconds' } 'ResponseTime'

So, if that seems reasonable to you and unlikely to break, I'm 👍 on doing this. But I figured I'd ask before assuming.

[jaredcnance]

The metrics are public on the context, so that is a safe bet. I think we just need to add public access to the context on the logger and export MetricsContext: https://github.com/awslabs/aws-embedded-metrics-node/blob/master/src/index.ts