remove Gauge instrument (open-telemetry#791)

* remove Gauge instrument

api/src/metrics/BoundInstrument.ts

@@ -26,15 +26,6 @@ export interface BoundCounter {
   add(value: number): void;
 }
 
-/** An Instrument for Gauge Metric. */
-export interface BoundGauge {
-  /**
-   * Sets the given value. Values can be negative.
-   * @param value the new value.
-   */
-  set(value: number): void;
-}
-
 /** Measure to report instantaneous measurement of a value. */
 export interface BoundMeasure {
   /**

api/src/metrics/Meter.ts

@@ -15,13 +15,13 @@
  */
 
 import { Metric, MetricOptions, Labels, LabelSet } from './Metric';
-import { BoundCounter, BoundGauge, BoundMeasure } from './BoundInstrument';
+import { BoundCounter, BoundMeasure } from './BoundInstrument';
 
 /**
  * An interface to allow the recording metrics.
  *
- * {@link Metric}s are used for recording pre-defined aggregation (`Gauge` and
- * `Counter`), or raw values (`Measure`) in which the aggregation and labels
+ * {@link Metric}s are used for recording pre-defined aggregation (`Counter`),
+ * or raw values (`Measure`) in which the aggregation and labels
  * for the exported metric are deferred.
  */
 export interface Meter {
@@ -41,16 +41,6 @@ export interface Meter {
    */
   createCounter(name: string, options?: MetricOptions): Metric<BoundCounter>;
 
-  /**
-   * Creates a new `gauge` metric. Generally, this kind of metric should be used
-   * when the metric cannot be expressed as a sum or because the measurement
-   * interval is arbitrary. Use this kind of metric when the measurement is not
-   * a quantity, and the sum and event count are not of interest.
-   * @param name the name of the metric.
-   * @param [options] the metric options.
-   */
-  createGauge(name: string, options?: MetricOptions): Metric<BoundGauge>;
-
   /**
    * Provide a pre-computed re-useable LabelSet by
    * converting the unordered labels into a canonicalized

api/src/metrics/NoopMeter.ts

@@ -16,7 +16,7 @@
 
 import { Meter } from './Meter';
 import { MetricOptions, Metric, Labels, LabelSet, MetricUtils } from './Metric';
-import { BoundMeasure, BoundCounter, BoundGauge } from './BoundInstrument';
+import { BoundMeasure, BoundCounter } from './BoundInstrument';
 import { DistributedContext } from '../distributed_context/DistributedContext';
 import { SpanContext } from '../trace/span_context';
 
@@ -45,15 +45,6 @@ export class NoopMeter implements Meter {
     return NOOP_COUNTER_METRIC;
   }
 
-  /**
-   * Returns a constant gauge metric.
-   * @param name the name of the metric.
-   * @param [options] the metric options.
-   */
-  createGauge(name: string, options?: MetricOptions): Metric<BoundGauge> {
-    return NOOP_GAUGE_METRIC;
-  }
-
   labels(labels: Labels): LabelSet {
     return NOOP_LABEL_SET;
   }
@@ -111,13 +102,6 @@ export class NoopCounterMetric extends NoopMetric<BoundCounter>
   }
 }
 
-export class NoopGaugeMetric extends NoopMetric<BoundGauge>
-  implements Pick<MetricUtils, 'set'> {
-  set(value: number, labelSet: LabelSet) {
-    this.bind(labelSet).set(value);
-  }
-}
-
 export class NoopMeasureMetric extends NoopMetric<BoundMeasure>
   implements Pick<MetricUtils, 'record'> {
   record(
@@ -142,12 +126,6 @@ export class NoopBoundCounter implements BoundCounter {
   }
 }
 
-export class NoopBoundGauge implements BoundGauge {
-  set(value: number): void {
-    return;
-  }
-}
-
 export class NoopBoundMeasure implements BoundMeasure {
   record(
     value: number,
@@ -159,10 +137,6 @@ export class NoopBoundMeasure implements BoundMeasure {
 }
 
 export const NOOP_METER = new NoopMeter();
-
-export const NOOP_BOUND_GAUGE = new NoopBoundGauge();
-export const NOOP_GAUGE_METRIC = new NoopGaugeMetric(NOOP_BOUND_GAUGE);
-
 export const NOOP_BOUND_COUNTER = new NoopBoundCounter();
 export const NOOP_COUNTER_METRIC = new NoopCounterMetric(NOOP_BOUND_COUNTER);
 

api/test/noop-implementations/noop-meter.test.ts

@@ -19,10 +19,8 @@ import {
   Labels,
   NoopMeterProvider,
   NOOP_BOUND_COUNTER,
-  NOOP_BOUND_GAUGE,
   NOOP_BOUND_MEASURE,
   NOOP_COUNTER_METRIC,
-  NOOP_GAUGE_METRIC,
   NOOP_MEASURE_METRIC,
 } from '../../src';
 
@@ -64,14 +62,6 @@ describe('NoopMeter', () => {
     assert.strictEqual(measure.getDefaultBound(), NOOP_BOUND_MEASURE);
     assert.strictEqual(measure.bind(labelSet), NOOP_BOUND_MEASURE);
 
-    const gauge = meter.createGauge('some-name');
-    gauge.getDefaultBound().set(1);
-
-    // ensure the correct noop const is returned
-    assert.strictEqual(gauge, NOOP_GAUGE_METRIC);
-    assert.strictEqual(gauge.getDefaultBound(), NOOP_BOUND_GAUGE);
-    assert.strictEqual(gauge.bind(labelSet), NOOP_BOUND_GAUGE);
-
     const options = {
       component: 'tests',
       description: 'the testing package',
@@ -81,7 +71,5 @@ describe('NoopMeter', () => {
     assert.strictEqual(measureWithOptions, NOOP_MEASURE_METRIC);
     const counterWithOptions = meter.createCounter('some-name', options);
     assert.strictEqual(counterWithOptions, NOOP_COUNTER_METRIC);
-    const gaugeWithOptions = meter.createGauge('some-name', options);
-    assert.strictEqual(gaugeWithOptions, NOOP_GAUGE_METRIC);
   });
 });