feat(api-metrics): remove observable types

experimental/packages/opentelemetry-api-metrics/src/NoopMeter.ts

@@ -20,13 +20,9 @@ import {
   Attributes,
   Counter,
   Histogram,
-  ObservableGauge,
   UpDownCounter,
-  ObservableBase,
-  ObservableCounter,
-  ObservableUpDownCounter,
+  ObservableCallback,
 } from './types/Metric';
-import { ObservableResult } from './types/ObservableResult';
 
 /**
  * NoopMeter is a noop implementation of the {@link Meter} interface. It reuses
@@ -70,11 +66,9 @@ export class NoopMeter implements Meter {
    */
   createObservableGauge(
     _name: string,
-    _callback: (observableResult: ObservableResult) => void,
+    _callback: ObservableCallback,
     _options?: MetricOptions,
-  ): ObservableGauge {
-    return NOOP_OBSERVABLE_GAUGE_METRIC;
-  }
+  ): void {}
 
   /**
    * Returns a constant noop observable counter.
@@ -84,11 +78,9 @@ export class NoopMeter implements Meter {
    */
   createObservableCounter(
     _name: string,
-    _callback: (observableResult: ObservableResult) => void,
+    _callback: ObservableCallback,
     _options?: MetricOptions,
-  ): ObservableCounter {
-    return NOOP_OBSERVABLE_COUNTER_METRIC;
-  }
+  ): void {}
 
   /**
    * Returns a constant noop up down observable counter.
@@ -98,11 +90,9 @@ export class NoopMeter implements Meter {
    */
   createObservableUpDownCounter(
     _name: string,
-    _callback: (observableResult: ObservableResult) => void,
+    _callback: ObservableCallback,
     _options?: MetricOptions,
-  ): ObservableUpDownCounter {
-    return NOOP_OBSERVABLE_UP_DOWN_COUNTER_METRIC;
-  }
+  ): void {}
 }
 
 export class NoopMetric {}
@@ -119,16 +109,9 @@ export class NoopHistogramMetric extends NoopMetric implements Histogram {
   record(_value: number, _attributes: Attributes): void {}
 }
 
-export class NoopObservableBaseMetric extends NoopMetric implements ObservableBase {}
-
 export const NOOP_METER = new NoopMeter();
 
 // Synchronous instruments
 export const NOOP_COUNTER_METRIC = new NoopCounterMetric();
 export const NOOP_HISTOGRAM_METRIC = new NoopHistogramMetric();
 export const NOOP_UP_DOWN_COUNTER_METRIC = new NoopUpDownCounterMetric();
-
-// Asynchronous instruments
-export const NOOP_OBSERVABLE_COUNTER_METRIC = new NoopObservableBaseMetric();
-export const NOOP_OBSERVABLE_GAUGE_METRIC = new NoopObservableBaseMetric();
-export const NOOP_OBSERVABLE_UP_DOWN_COUNTER_METRIC = new NoopObservableBaseMetric();

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

@@ -18,15 +18,12 @@ import { CounterOptions, HistogramOptions, UpDownCounterOptions } from '..';
 import {
   Counter,
   Histogram,
-  ObservableCounter,
+  ObservableCallback,
   ObservableCounterOptions,
-  ObservableGauge,
   ObservableGaugeOptions,
-  ObservableUpDownCounter,
   ObservableUpDownCounterOptions,
   UpDownCounter,
 } from './Metric';
-import { ObservableResult } from './ObservableResult';
 
 /**
  * An interface describes additional metadata of a meter.
@@ -89,9 +86,9 @@ export interface Meter {
    */
   createObservableGauge(
     name: string,
-    callback: (observableResult: ObservableResult) => void,
+    callback: ObservableCallback,
     options?: ObservableGaugeOptions
-  ): ObservableGauge;
+  ): void;
 
   /**
    * Creates a new `ObservableCounter` metric.
@@ -101,9 +98,9 @@ export interface Meter {
    */
   createObservableCounter(
     name: string,
-    callback: (observableResult: ObservableResult) => void,
+    callback: ObservableCallback,
     options?: ObservableCounterOptions
-  ): ObservableCounter;
+  ): void;
 
   /**
    * Creates a new `ObservableUpDownCounter` metric.
@@ -113,7 +110,7 @@ export interface Meter {
    */
   createObservableUpDownCounter(
     name: string,
-    callback: (observableResult: ObservableResult) => void,
+    callback: ObservableCallback,
     options?: ObservableUpDownCounterOptions
-  ): ObservableUpDownCounter;
+  ): void;
 }

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

@@ -15,6 +15,7 @@
  */
 
 import { Context } from '@opentelemetry/api';
+import { ObservableResult } from './ObservableResult';
 
 /**
  * Options needed for metric creation
@@ -88,21 +89,12 @@ export interface Histogram {
   record(value: number, attributes?: Attributes, context?: Context): void;
 }
 
-// ObservableBase has to be an Object but for now there is no field or method
-// declared.
-/** Base interface for the Observable metrics. */
-export type ObservableBase = Record<never, never>;
-
-/** Base interface for the ObservableGauge metrics. */
-export type ObservableGauge = ObservableBase;
-
-/** Base interface for the ObservableUpDownCounter metrics. */
-export type ObservableUpDownCounter = ObservableBase;
-
-/** Base interface for the ObservableCounter metrics. */
-export type ObservableCounter = ObservableBase;
-
 /**
  * key-value pairs passed by the user.
  */
 export type Attributes = { [key: string]: string };
+
+/**
+ * The observable callback for Observable instruments.
+ */
+export type ObservableCallback = (observableResult: ObservableResult) => void | Promise<void>;

experimental/packages/opentelemetry-sdk-metrics-base/src/Meter.ts

@@ -61,25 +61,25 @@ export class Meter implements metrics.Meter {
 
   createObservableGauge(
     _name: string,
-    _callback: (observableResult: metrics.ObservableResult) => void,
+    _callback: metrics.ObservableCallback,
     _options?: metrics.ObservableGaugeOptions,
-  ): metrics.ObservableGauge {
+  ): void {
     throw new Error('Method not implemented.');
   }
 
   createObservableCounter(
     _name: string,
-    _callback: (observableResult: metrics.ObservableResult) => void,
+    _callback: metrics.ObservableCallback,
     _options?: metrics.ObservableCounterOptions,
-  ): metrics.ObservableCounter {
+  ): void {
     throw new Error('Method not implemented.');
   }
 
   createObservableUpDownCounter(
     _name: string,
-    _callback: (observableResult: metrics.ObservableResult) => void,
+    _callback: metrics.ObservableCallback,
     _options?: metrics.ObservableUpDownCounterOptions,
-  ): metrics.ObservableUpDownCounter {
+  ): void {
     throw new Error('Method not implemented.');
   }