feat(instrumentation): added synchronous gauge to SDK

Author: clintonb

packages/sdk-metrics/src/InstrumentDescriptor.ts

@@ -23,6 +23,7 @@ import { equalsCaseInsensitive } from './utils';
  */
 export enum InstrumentType {
   COUNTER = 'COUNTER',
+  GAUGE = 'GAUGE',
   HISTOGRAM = 'HISTOGRAM',
   UP_DOWN_COUNTER = 'UP_DOWN_COUNTER',
   OBSERVABLE_COUNTER = 'OBSERVABLE_COUNTER',

packages/sdk-metrics/src/Instruments.ts

@@ -22,6 +22,7 @@ import {
   ValueType,
   UpDownCounter,
   Counter,
+  Gauge,
   Histogram,
   Observable,
   ObservableCallback,
@@ -110,6 +111,18 @@ export class CounterInstrument extends SyncInstrument implements Counter {
   }
 }
 
+/**
+ * The class implements {@link Gauge} interface.
+ */
+export class GaugeInstrument extends SyncInstrument implements Gauge {
+  /**
+   * Records a measurement.
+   */
+  record(value: number, attributes?: MetricAttributes, ctx?: Context): void {
+    this._record(value, attributes, ctx);
+  }
+}
+
 /**
  * The class implements {@link Histogram} interface.
  */

packages/sdk-metrics/src/Meter.ts

@@ -25,13 +25,16 @@ import {
   ObservableUpDownCounter,
   BatchObservableCallback,
   Observable,
+  Attributes,
+  Gauge,
 } from '@opentelemetry/api';
 import {
   createInstrumentDescriptor,
   InstrumentType,
 } from './InstrumentDescriptor';
 import {
   CounterInstrument,
+  GaugeInstrument,
   HistogramInstrument,
   ObservableCounterInstrument,
   ObservableGaugeInstrument,
@@ -46,6 +49,22 @@ import { MeterSharedState } from './state/MeterSharedState';
 export class Meter implements IMeter {
   constructor(private _meterSharedState: MeterSharedState) {}
 
+  /**
+   * Create a {@link Gauge} instrument.
+   */
+  createGauge<AttributesTypes extends Attributes = Attributes>(
+    name: string,
+    options?: MetricOptions
+  ): Gauge<AttributesTypes> {
+    const descriptor = createInstrumentDescriptor(
+      name,
+      InstrumentType.GAUGE,
+      options
+    );
+    const storage = this._meterSharedState.registerMetricStorage(descriptor);
+    return new GaugeInstrument(storage, descriptor);
+  }
+
   /**
    * Create a {@link Histogram} instrument.
    */

packages/sdk-metrics/src/aggregator/ExponentialHistogram.ts

@@ -580,6 +580,7 @@ export class ExponentialHistogramAggregator
 
         // determine if instrument allows negative values.
         const allowsNegativeValues =
+          descriptor.type === InstrumentType.GAUGE ||
           descriptor.type === InstrumentType.UP_DOWN_COUNTER ||
           descriptor.type === InstrumentType.OBSERVABLE_GAUGE ||
           descriptor.type === InstrumentType.OBSERVABLE_UP_DOWN_COUNTER;

packages/sdk-metrics/src/aggregator/Histogram.ts

@@ -231,6 +231,7 @@ export class HistogramAggregator implements Aggregator<HistogramAccumulation> {
 
         // determine if instrument allows negative values.
         const allowsNegativeValues =
+          descriptor.type === InstrumentType.GAUGE ||
           descriptor.type === InstrumentType.UP_DOWN_COUNTER ||
           descriptor.type === InstrumentType.OBSERVABLE_GAUGE ||
           descriptor.type === InstrumentType.OBSERVABLE_UP_DOWN_COUNTER;

packages/sdk-metrics/src/view/Aggregation.ts

@@ -182,6 +182,7 @@ export class DefaultAggregation extends Aggregation {
       case InstrumentType.OBSERVABLE_UP_DOWN_COUNTER: {
         return SUM_AGGREGATION;
       }
+      case InstrumentType.GAUGE:
       case InstrumentType.OBSERVABLE_GAUGE: {
         return LAST_VALUE_AGGREGATION;
       }

packages/sdk-metrics/test/export/ConsoleMetricExporter.test.ts

@@ -160,6 +160,7 @@ describe('ConsoleMetricExporter', () => {
         switch (instrumentType) {
           case InstrumentType.COUNTER:
           case InstrumentType.OBSERVABLE_COUNTER:
+          case InstrumentType.GAUGE:
           case InstrumentType.HISTOGRAM:
           case InstrumentType.OBSERVABLE_GAUGE:
             return AggregationTemporality.DELTA;

packages/sdk-metrics/test/export/utils.ts

@@ -29,6 +29,7 @@ const instrumentTypes = [
   InstrumentType.UP_DOWN_COUNTER,
   InstrumentType.OBSERVABLE_UP_DOWN_COUNTER,
   InstrumentType.HISTOGRAM,
+  InstrumentType.GAUGE,
   InstrumentType.OBSERVABLE_GAUGE,
 ];