Add PullController

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

@@ -21,7 +21,7 @@ import { Resource } from '@opentelemetry/resources';
 import { BatchObserver } from './BatchObserver';
 import { BaseBoundInstrument } from './BoundInstrument';
 import { CounterMetric } from './CounterMetric';
-import { PushController } from './export/Controller';
+import { PushController, Controller, PullController } from './export/Controller';
 import { NoopExporter } from './export/NoopExporter';
 import { Processor, UngroupedProcessor } from './export/Processor';
 import { Metric } from './Metric';
@@ -31,6 +31,7 @@ import { UpDownCounterMetric } from './UpDownCounterMetric';
 import { UpDownSumObserverMetric } from './UpDownSumObserverMetric';
 import { ValueObserverMetric } from './ValueObserverMetric';
 import { ValueRecorderMetric } from './ValueRecorderMetric';
+import { MetricExporter } from './export/types';
 // eslint-disable-next-line @typescript-eslint/no-var-requires
 const merge = require('lodash.merge');
 
@@ -43,7 +44,7 @@ export class Meter implements api.Meter {
   private readonly _processor: Processor;
   private readonly _resource: Resource;
   private readonly _instrumentationLibrary: InstrumentationLibrary;
-  private readonly _controller: PushController;
+  private readonly _controller: Controller;
   private _isShutdown = false;
   private _shuttingDownPromise: Promise<void> = Promise.resolve();
 
@@ -59,10 +60,17 @@ export class Meter implements api.Meter {
     this._resource =
       mergedConfig.resource || Resource.empty();
     this._instrumentationLibrary = instrumentationLibrary;
-    // start the push controller
-    const exporter = mergedConfig.exporter || new NoopExporter();
-    const interval = mergedConfig.interval;
-    this._controller = new PushController(this, exporter, interval);
+    const exporter: MetricExporter = mergedConfig.exporter || new NoopExporter();
+
+    // start the pull or push controller, depending on if the exporter defines the optional function registerPullController
+    if(typeof exporter.registerPullController === 'function') {
+      const pullController = new PullController(this, exporter);
+      this._controller = pullController;
+      exporter.registerPullController(pullController);
+    } else {
+      const interval = mergedConfig.interval;
+      this._controller = new PushController(this, exporter, interval);
+    }
   }
 
   /**

experimental/packages/opentelemetry-sdk-metrics-base/src/export/Controller.ts

@@ -26,7 +26,7 @@ const DEFAULT_EXPORT_INTERVAL = 60_000;
 
 export class Controller {}
 
-/** Controller organizes a periodic push of metric data. */
+/** PushController organizes a periodic push of metric data. */
 export class PushController extends Controller {
   private _timer: NodeJS.Timeout;
 
@@ -67,3 +67,35 @@ export class PushController extends Controller {
     });
   }
 }
+
+/** PullController pulls metric data whenever the exporter requests it. */
+export class PullController extends Controller {
+  constructor(
+    private readonly _meter: Meter,
+    private readonly _exporter: MetricExporter,
+  ) {
+    super();
+  }
+
+  shutdown(): Promise<void> {
+    return this._collect();
+  }
+
+  public async _collect(): Promise<void> {
+    await this._meter.collect();
+    return new Promise(resolve => {
+      this._exporter.export(
+        this._meter.getProcessor().checkPointSet(),
+        result => {
+          if (result.code !== ExportResultCode.SUCCESS) {
+            globalErrorHandler(
+              result.error ??
+                new Error('PullController: export failed in _collect')
+            );
+          }
+          resolve();
+        }
+      );
+    });
+  }
+}

experimental/packages/opentelemetry-sdk-metrics-base/src/export/types.ts

@@ -22,6 +22,7 @@ import {
 } from '@opentelemetry/api-metrics';
 import { ExportResult, InstrumentationLibrary } from '@opentelemetry/core';
 import { Resource } from '@opentelemetry/resources';
+import { PullController } from './Controller';
 
 /** The kind of metric. */
 export enum MetricKind {
@@ -104,6 +105,11 @@ export interface MetricExporter {
     resultCallback: (result: ExportResult) => void
   ): void;
 
+  /** Registers a {@Link PullController}. If this function is defined, the MetricsExporter will use a {@Link PullController} instead of a {@Link PushController} */
+  registerPullController?(
+    pullController: PullController
+  ): void;
+
   /** Stops the exporter. */
   shutdown(): Promise<void>;
 }