Make Stats singleton (globalStats), separate registerView from createView (#291)

* Make Stats singleton (globalStats), separate registerView from createView

* fix tests

* remove type annotation and redundant comment

Author: mayurkale22

CHANGELOG.md

@@ -10,9 +10,31 @@ All notable changes to this project will be documented in this file.
 - Add ignoreIncomingPaths and ignoreOutgoingUrls support to the http and https tracing instrumentations.
 - Add ```opencensus-resource-util``` to auto detect AWS, GCE and Kubernetes(K8S) monitored resource, based on the environment where the application is running.
 
- **Contains API breaking changes for trace implementations**
+ **This release has multiple breaking changes. Please test your code accordingly after upgrading.**
 
 - Modify `Logger` interface: `level` made optional, `silly` removed.
+- The ```new Stats()``` has been deprecated on Stats class. The global singleton ```globalStats``` object should be used instead. Also, ```registerView()``` is separated out from ```createView()```.
+
+##### Old code
+```js
+const { Stats } = require("@opencensus/core");
+const stats = new Stats();
+
+// Create and register the view
+stats.createView(...);
+```
+
+##### New code
+```js
+// Get the global singleton stats object
+const { globalStats } = require("@opencensus/core");
+
+// Create the view
+const view = globalStats.createView(...);
+
+// register the view
+globalStats.registerView(view);
+```
 
 ## 0.0.8 - 2018-12-14
  **Contains API breaking changes for stats/metrics implementations**

packages/opencensus-core/src/index.ts

@@ -66,7 +66,6 @@ export * from './exporters/console-exporter';
 // STATS CLASSES
 
 // classes
-export * from './stats/stats';
 export * from './stats/view';
 export * from './stats/recorder';
 export * from './stats/bucket-boundaries';
@@ -94,3 +93,10 @@ export * from './metrics/metric-registry';
 // GAUGES CLASSES
 export * from './metrics/gauges/derived-gauge';
 export * from './metrics/gauges/gauge';
+
+
+// Stats singleton instance
+import {BaseStats} from './stats/stats';
+import {Stats} from './stats/types';
+const globalStats: Stats = BaseStats.instance;
+export {globalStats};

packages/opencensus-core/src/stats/metric-producer.ts

@@ -17,7 +17,7 @@
 import {BaseMetricProducer} from '../metrics/export/base-metric-producer';
 import {Metric} from '../metrics/export/types';
 
-import {Stats} from './stats';
+import {Stats} from './types';
 
 /**
  * A MetricProducer producer that can be registered for exporting using

packages/opencensus-core/src/stats/stats.ts

@@ -18,17 +18,21 @@ import * as defaultLogger from '../common/console-logger';
 import * as loggerTypes from '../common/types';
 import {StatsEventListener} from '../exporters/types';
 import {Metric} from '../metrics/export/types';
+import {Metrics} from '../metrics/metrics';
 
-import {AggregationType, Measure, Measurement, MeasureType, MeasureUnit, View} from './types';
+import {MetricProducerForStats} from './metric-producer';
+import {AggregationType, Measure, Measurement, MeasureType, MeasureUnit, Stats, View} from './types';
 import {BaseView} from './view';
 
-export class Stats {
+export class BaseStats implements Stats {
   /** A list of Stats exporters */
   private statsEventListeners: StatsEventListener[] = [];
   /** A map of Measures (name) to their corresponding Views */
   private registeredViews: {[key: string]: View[]} = {};
   /** An object to log information to */
   private logger: loggerTypes.Logger;
+  /** Singleton instance */
+  private static singletonInstance: BaseStats;
 
   /**
    * Creates stats
@@ -37,21 +41,22 @@ export class Stats {
   constructor(logger = defaultLogger) {
     this.logger = logger.logger();
 
-    // TODO (mayurkale): Decide how to inject MetricProducerForStats.
-    // It should be something like below, but looks like not the right place.
-
     // Create a new MetricProducerForStats and register it to
     // MetricProducerManager when Stats is initialized.
-    // const metricProducer: MetricProducer = new MetricProducerForStats(this);
-    // Metrics.getMetricProducerManager().add(metricProducer);
+    const metricProducer = new MetricProducerForStats(this);
+    Metrics.getMetricProducerManager().add(metricProducer);
+  }
+
+  /** Gets the stats instance. */
+  static get instance(): Stats {
+    return this.singletonInstance || (this.singletonInstance = new this());
   }
 
   /**
-   * Registers a view to listen to new measurements in its measure. Prefer using
-   * the method createView() that creates an already registered view.
+   * Registers a view to listen to new measurements in its measure.
    * @param view The view to be registered
    */
-  registerView(view: View) {
+  registerView(view: View): void {
     if (this.registeredViews[view.measure.name]) {
       this.registeredViews[view.measure.name].push(view);
     } else {
@@ -67,7 +72,7 @@ export class Stats {
   }
 
   /**
-   * Creates and registers a view.
+   * Creates a view.
    * @param name The view name
    * @param measure The view measure
    * @param aggregation The view aggregation type
@@ -82,15 +87,14 @@ export class Stats {
       bucketBoundaries?: number[]): View {
     const view = new BaseView(
         name, measure, aggregation, tagKeys, description, bucketBoundaries);
-    this.registerView(view);
     return view;
   }
 
   /**
    * Registers an exporter to send stats data to a service.
    * @param exporter An stats exporter
    */
-  registerExporter(exporter: StatsEventListener) {
+  registerExporter(exporter: StatsEventListener): void {
     this.statsEventListeners.push(exporter);
 
     for (const measureName of Object.keys(this.registeredViews)) {
@@ -153,7 +157,7 @@ export class Stats {
    * Updates all views with the new measurements.
    * @param measurements A list of measurements to record
    */
-  record(...measurements: Measurement[]) {
+  record(...measurements: Measurement[]): void {
     if (this.hasNegativeValue(measurements)) {
       this.logger.warn(`Dropping measurments ${measurements}, value to record
           must be non-negative.`);
@@ -176,4 +180,12 @@ export class Stats {
       }
     }
   }
+
+  /**
+   * Remove all registered Views and exporters from the stats.
+   */
+  clear(): void {
+    this.registeredViews = {};
+    this.statsEventListeners = [];
+  }
 }

packages/opencensus-core/src/stats/types.ts

@@ -14,8 +14,76 @@
  * limitations under the License.
  */
 
+import {StatsEventListener} from '../exporters/types';
 import {Metric} from '../metrics/export/types';
 
+/** Main interface for stats. */
+export interface Stats {
+  /**
+   * Creates a view.
+   * @param name The view name
+   * @param measure The view measure
+   * @param aggregation The view aggregation type
+   * @param tagKeys The view columns (tag keys)
+   * @param description The view description
+   * @param bucketBoundaries The view bucket boundaries for a distribution
+   * aggregation type
+   */
+  createView(
+      name: string, measure: Measure, aggregation: AggregationType,
+      tagKeys: string[], description: string,
+      bucketBoundaries?: number[]): View;
+
+  /**
+   * Registers a view to listen to new measurements in its measure.
+   * @param view The view to be registered
+   */
+  registerView(view: View): void;
+
+  /**
+   * Creates a measure of type Double.
+   * @param name The measure name
+   * @param unit The measure unit
+   * @param description The measure description
+   */
+  createMeasureDouble(name: string, unit: MeasureUnit, description?: string):
+      Measure;
+
+  /**
+   * Creates a measure of type Int64. Values must be integers up to
+   * Number.MAX_SAFE_INTERGER.
+   * @param name The measure name
+   * @param unit The measure unit
+   * @param description The measure description
+   */
+  createMeasureInt64(name: string, unit: MeasureUnit, description?: string):
+      Measure;
+
+  /**
+   * Updates all views with the new measurements.
+   * @param measurements A list of measurements to record
+   */
+  record(...measurements: Measurement[]): void;
+
+  /**
+   * Remove all registered Views and exporters from the stats.
+   */
+  clear(): void;
+
+  /**
+   * Gets a collection of produced Metric`s to be exported.
+   * @returns {Metric[]} List of metrics
+   */
+  getMetrics(): Metric[];
+
+  /**
+   * Registers an exporter to send stats data to a service.
+   * @param exporter An stats exporter
+   */
+  registerExporter(exporter: StatsEventListener): void;
+}
+
+
 /** Tags are maps of names -> values */
 export interface Tags {
   [key: string]: string;

packages/opencensus-core/test/test-metric-producer.ts

@@ -15,21 +15,21 @@
  */
 
 import * as assert from 'assert';
-import {AggregationType, Measurement, MeasureUnit, Stats, Tags, View} from '../src';
+
+import {AggregationType, globalStats, Measurement, MeasureUnit, Tags, View} from '../src';
 import {LabelKey, LabelValue, MetricDescriptorType} from '../src/metrics/export/types';
 import {MetricProducerForStats} from '../src/stats/metric-producer';
 
 describe('Metric producer for stats', () => {
-  const stats = new Stats();
-  const metricProducerForStats = new MetricProducerForStats(stats);
+  const metricProducerForStats = new MetricProducerForStats(globalStats);
 
   // constants for view name
   const viewName1 = 'test/view/name1';
   const viewName2 = 'test/view/name2';
   const viewName3 = 'test/view/name2';
   const description = 'test description';
 
-  const measureDouble = stats.createMeasureDouble(
+  const measureDouble = globalStats.createMeasureDouble(
       'opencensus.io/test/double', MeasureUnit.UNIT, 'Measure Double');
   const tags: Tags = {testKey1: 'testValue1', testKey2: 'testValue2'};
   const labelKeys: LabelKey[] = [
@@ -72,9 +72,10 @@ describe('Metric producer for stats', () => {
   };
 
   it('should add sum stats', () => {
-    const view: View = stats.createView(
+    const view: View = globalStats.createView(
         viewName1, measureDouble, AggregationType.SUM, Object.keys(tags),
         description);
+    globalStats.registerView(view);
     view.recordMeasurement(measurement1);
 
     const metrics = metricProducerForStats.getMetrics();
@@ -92,9 +93,10 @@ describe('Metric producer for stats', () => {
 
   it('should add count stats',
      () => {
-       const view: View = stats.createView(
+       const view: View = globalStats.createView(
            viewName2, measureDouble, AggregationType.COUNT, Object.keys(tags),
            description);
+       globalStats.registerView(view);
        view.recordMeasurement(measurement1);
 
        let metrics = metricProducerForStats.getMetrics();
@@ -122,9 +124,10 @@ describe('Metric producer for stats', () => {
      });
 
   it('should add lastValue stats', () => {
-    const view: View = stats.createView(
+    const view: View = globalStats.createView(
         viewName3, measureDouble, AggregationType.LAST_VALUE, Object.keys(tags),
         description);
+    globalStats.registerView(view);
     view.recordMeasurement(measurement1);
     view.recordMeasurement(measurement2);
 
@@ -153,9 +156,10 @@ describe('Metric producer for stats', () => {
     const measurementValues = [1.1, 2.3, 3.2, 4.3, 5.2];
     const buckets = [2, 4, 6];
 
-    const view: View = stats.createView(
+    const view: View = globalStats.createView(
         viewName3, measureDouble, AggregationType.DISTRIBUTION,
         Object.keys(tags), description, buckets);
+    globalStats.registerView(view);
     for (const value of measurementValues) {
       const measurement: Measurement = {measure: measureDouble, value, tags};
       view.recordMeasurement(measurement);