feat: implement labelset

packages/opentelemetry-core/src/metrics/NoopMeter.ts

@@ -59,6 +59,10 @@ export class NoopMeter implements Meter {
   createGauge(name: string, options?: MetricOptions): Metric<GaugeHandle> {
     return NOOP_GAUGE_METRIC;
   }
+
+  labels(labels: LabelSet): LabelSet {
+    return NOOP_METER;
+  }
 }
 
 export class NoopMetric<T> implements Metric<T> {
@@ -71,7 +75,7 @@ export class NoopMetric<T> implements Metric<T> {
    * Returns a Handle associated with specified LabelSet.
    * It is recommended to keep a reference to the Handle instead of always
    * calling this method for every operations.
-   * @param labels the LabelSet used to associate with this metric handle.
+   * @param labels the canonicalized LabelSet used to associate with this metric handle.
    */
   getHandle(labels: LabelSet): T {
     return this._handle;
@@ -86,7 +90,7 @@ export class NoopMetric<T> implements Metric<T> {
 
   /**
    * Removes the Handle from the metric, if it is present.
-   * @param labels the LabelSet used to associate with this metric handle.
+   * @param labels the canonicalized LabelSet used to associate with this metric handle.
    */
   removeHandle(labels: LabelSet): void {
     // @todo: implement this method
@@ -139,3 +143,5 @@ export const NOOP_MEASURE_HANDLE = new NoopMeasureHandle();
 export const NOOP_MEASURE_METRIC = new NoopMetric<MeasureHandle>(
   NOOP_MEASURE_HANDLE
 );
+
+export const NOOP_METER = {} as LabelSet;

packages/opentelemetry-metrics/src/Meter.ts

@@ -93,4 +93,17 @@ export class Meter implements types.Meter {
     };
     return new GaugeMetric(name, opt);
   }
+
+  /**
+   * Provide a pre-computed re-useable LabelSet by
+   * converting the unordered LabelSet into a canonicalized 
+   * set of lables, useful for pre-aggregation.
+   * @param labels user provided unordered LabelSet.
+   */
+  labels(labels: types.LabelSet): types.LabelSet {
+    return Object.keys(labels).sort().reduce((result, key) => {
+      result[key] = labels[key];
+      return result;
+    }, {} as types.LabelSet);
+  }
 }

packages/opentelemetry-metrics/src/Metric.ts

@@ -36,7 +36,7 @@ export abstract class Metric<T> implements types.Metric<T> {
    * Returns a Handle associated with specified LabelSet.
    * It is recommended to keep a reference to the Handle instead of always
    * calling this method for each operation.
-   * @param labels the LabelSet used to associate with this metric handle.
+   * @param labels the canonicalized LabelSet used to associate with this metric handle.
    */
   getHandle(labels: types.LabelSet): T {
     const hash = hashLabelValues(Object.values(labels));
@@ -58,7 +58,7 @@ export abstract class Metric<T> implements types.Metric<T> {
 
   /**
    * Removes the Handle from the metric, if it is present.
-   * @param labels the LabelSet used to associate with this metric handle.
+   * @param labels the canonicalized LabelSet used to associate with this metric handle.
    */
   removeHandle(labels: types.LabelSet): void {
     this._handles.delete(hashLabelValues(Object.values(labels)));

packages/opentelemetry-metrics/src/Utils.ts

@@ -23,5 +23,5 @@ const COMMA_SEPARATOR = ',';
  * @returns The hashed label values string.
  */
 export function hashLabelValues(labelValues: string[]): string {
-  return labelValues.sort().join(COMMA_SEPARATOR);
+  return labelValues.join(COMMA_SEPARATOR);
 }

packages/opentelemetry-metrics/src/export/types.ts

@@ -61,6 +61,8 @@ export interface MetricDescriptor {
   readonly unit: string;
   /** MetricDescriptor type */
   readonly type: MetricDescriptorType;
+  /** The label keys associated with the metric descriptor. */
+  readonly labelKeys: string[];
   /** The label set associated with the metric descriptor. */
   readonly labels: LabelSet;
 }

packages/opentelemetry-metrics/src/types.ts

@@ -28,6 +28,9 @@ export interface MetricOptions {
   /** The unit of the Metric values. */
   unit: string;
 
+  /** The list of label keys for the Metric. */
+  labelKeys: string[];
+
   /** The map of constant labels for the Metric. */
   constantLabels?: Map<string, string>;
 
@@ -60,4 +63,5 @@ export const DEFAULT_METRIC_OPTIONS = {
   disabled: false,
   description: '',
   unit: '1',
+  labelKeys: [],
 };

packages/opentelemetry-metrics/test/Meter.test.ts

@@ -21,16 +21,28 @@ import { NoopLogger } from '@opentelemetry/core';
 
 describe('Meter', () => {
   let meter: Meter;
-  const key = 'key';
-  const labels: types.LabelSet = { [key]: 'value' };
+  const keya = 'keya';
+  const keyb = 'keyb';
+  let labels: types.LabelSet = { [keyb]: 'value2', [keya]: 'value1' };
   const hrTime: types.HrTime = [22, 400000000];
 
   beforeEach(() => {
     meter = new Meter({
       logger: new NoopLogger(),
     });
+    labels = meter.labels(labels);
   });
 
+  describe('#meter', () => {
+    it('should re-order labels to a canonicalized set', () => {
+      const orderedLabels: types.LabelSet = {
+        [keya]: 'value1',
+        [keyb]: 'value2'
+      }
+      assert.deepEqual(labels, orderedLabels);
+    });
+  });  
+
   describe('#counter', () => {
     it('should create a counter', () => {
       const counter = meter.createCounter('name');
@@ -124,7 +136,7 @@ describe('Meter', () => {
 
       it('should not fail when removing non existing handle', () => {
         const counter = meter.createCounter('name');
-        counter.removeHandle([]);
+        counter.removeHandle({});
       });
 
       it('should clear all handles', () => {
@@ -227,7 +239,7 @@ describe('Meter', () => {
 
       it('should not fail when removing non existing handle', () => {
         const gauge = meter.createGauge('name');
-        gauge.removeHandle([]);
+        gauge.removeHandle({});
       });
 
       it('should clear all handles', () => {

packages/opentelemetry-types/src/metrics/Meter.ts

@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-import { Metric, MetricOptions } from './Metric';
+import { Metric, MetricOptions, LabelSet } from './Metric';
 import { CounterHandle, GaugeHandle, MeasureHandle } from './Handle';
 
 /**
@@ -58,4 +58,12 @@ export interface Meter {
    * @param [options] the metric options.
    */
   createGauge(name: string, options?: MetricOptions): Metric<GaugeHandle>;
+
+  /**
+   * Provide a pre-computed re-useable LabelSet by
+   * converting the unordered LabelSet into a canonicalized 
+   * set of lables, useful for pre-aggregation.
+   * @param labels user provided unordered LabelSet.
+   */
+  labels(labels: LabelSet): LabelSet;
 }

packages/opentelemetry-types/src/metrics/Metric.ts

@@ -58,7 +58,7 @@ export interface Metric<T> {
    * Returns a Handle associated with specified LabelSet.
    * It is recommended to keep a reference to the Handle instead of always
    * calling this method for every operations.
-   * @param labels the LabelSet used to associate with this metric handle.
+   * @param labels the canonicalized LabelSet used to associate with this metric handle.
    */
   getHandle(labels: LabelSet): T;
 
@@ -69,7 +69,7 @@ export interface Metric<T> {
 
   /**
    * Removes the Handle from the metric, if it is present.
-   * @param labels the LabelSet used to associate with this metric handle.
+   * @param labels the canonicalized LabelSet used to associate with this metric handle.
    */
   removeHandle(labels: LabelSet): void;
 
@@ -84,4 +84,4 @@ export interface Metric<T> {
   setCallback(fn: () => void): void;
 }
 
-export interface LabelSet {}
+export type LabelSet = Record<string, string>;