feat(worker): Custom Metrics

[mjameswh]

What was changed

• Add support for custom metrics. Fixes [Feature Request] Add support for custom metrics #1229.

Example usage:

From a workflow

import * as wf from `@temporalio/workflow`;

async function myWorkflow() {
  const myHistogramMetric = wf.metricMeter.createHistogram(
    'my-custom-histogram',
    'int', // or 'float'
    'ms', // Units (optional)
    'description' // (optional)
  );

  myHistogramMetric.record(50);
  myHistogramMetric.record(50, { tag1: 'tag-value' });
}

From an activity

import * as act from `@temporalio/activity`

const myCounterMetric = metricMeter.createCounter('activity-counter');

async function myActivity() {
  const myCounterMetric.add(1);
}

[Sushisource]

Looks really clean & thorough. I didn't do an incredibly close analysis, but overall it looks great and the tests have excellent coverage.

[Sushisource]

Why not put withTags on Metric?

[mjameswh]

What would be the return type of that function if defined on the parent class? Unfortunately, TS doesn't have anything like the Self type.