Exposing purge stored metrics function

Author: Alan Churley

packages/metrics/package.json

@@ -54,6 +54,5 @@
     "url": "https://github.com/awslabs/aws-lambda-powertools-typescript/issues"
   },
   "dependencies": {
-    "lodash": "^4.17.21"
   }
 }

packages/metrics/src/Metrics.ts

@@ -95,6 +95,12 @@ class Metrics implements MetricsInterface {
     };
   }
 
+  public purgeStoredMetrics(): void {
+    const target = this.serializeMetrics();
+    console.log(JSON.stringify(target));
+    this.storedMetrics = {};
+  }
+
   public serializeMetrics(): EmfOutput {
     const metricDefinitions = Object.values(this.storedMetrics).map((metricDefinition) => ({
       Name: metricDefinition.name,
@@ -177,12 +183,6 @@ class Metrics implements MetricsInterface {
     return <EnvironmentVariablesService> this.envVarsService;
   }
 
-  private purgeStoredMetrics(): void {
-    const target = this.serializeMetrics();
-    console.log(JSON.stringify(target));
-    this.storedMetrics = {};
-  }
-
   private setCustomConfigService(customConfigService?: ConfigServiceInterface): void {
     this.customConfigService = customConfigService? customConfigService : undefined;
   }

packages/metrics/src/MetricsInterface.ts

@@ -2,15 +2,16 @@ import { Metrics } from './Metrics';
 import { MetricUnit, EmfOutput, HandlerMethodDecorator, Dimensions, DecoratorOptions } from '../types';
 
 interface MetricsInterface {
-  addMetric(name: string, unit:MetricUnit, value:number): void
-  clearMetrics(): void
-  logMetrics(options?: DecoratorOptions): HandlerMethodDecorator
   addDimension(name: string, value: string): void
   addDimensions(dimensions: {[key: string]: string}): void
   addMetadata(key: string, value: string): void
-  clearMetadata(): void
+  addMetric(name: string, unit:MetricUnit, value:number): void
   clearDimensions(): void
+  clearMetadata(): void
+  clearMetrics(): void
   clearDefaultDimensions(): void
+  logMetrics(options?: DecoratorOptions): HandlerMethodDecorator
+  purgeStoredMetrics(): void
   serializeMetrics(): EmfOutput
   setDefaultDimensions(dimensions: Dimensions): void
   singleMetric(): Metrics

packages/metrics/tests/unit/Metrics.test.ts

@@ -377,6 +377,28 @@ describe('Class: Metrics', () => {
 
       new LambdaFunction().handler(dummyEvent, dummyContext, () => console.log('Lambda invoked!'));
     });
+
+    test('Purge Stored Metrics should log and clear', () => {
+      const metrics = new Metrics({ namespace: 'test' });
+      const extraCount = 10;
+      class LambdaFunction implements LambdaInterface {
+        @metrics.logMetrics()
+        // eslint-disable-next-line @typescript-eslint/ban-ts-comment
+        // @ts-ignore
+        public handler<TEvent, TResult>(_event: TEvent, _context: Context, _callback: Callback<TResult>): void | Promise<TResult> {
+          metrics.addMetric(`test_name_1`, MetricUnits.Count, 1);
+          metrics.purgeStoredMetrics();
+        }
+      }
+
+      new LambdaFunction().handler(dummyEvent, dummyContext, () => console.log('Lambda invoked!'));
+      const loggedData = [ JSON.parse(consoleSpy.mock.calls[0][0]), JSON.parse(consoleSpy.mock.calls[1][0]) ];
+
+      expect(console.log).toBeCalledTimes(2);
+      expect(loggedData[0]._aws.CloudWatchMetrics[0].Metrics.length).toBe(1);
+      expect(loggedData[1]._aws.CloudWatchMetrics[0].Metrics.length).toBe(0);
+    });
+
   });
 
   describe('Feature: Custom Config Service', () => {