Merge branch 'feat/metrics-middleware' of github.com:awslabs/aws-lambda-powertools-typescript into feat/metrics-middleware

Author: saragerion

docs/core/metrics.md

@@ -145,7 +145,7 @@ See examples below:
     import { Context } from 'aws-lambda';
     import middy from '@middy/core';
 
-    const metrics = new Metrics({namespace:"serverlessAirline", service:"orders"});
+    const metrics = new Metrics({ namespace: 'serverlessAirline', service: 'orders' });
 
     const lambdaHandler = async (event: any, context: Context) => {
         metrics.addMetric('successfulBooking', MetricUnits.Count, 1);
@@ -205,7 +205,7 @@ If you do not the middleware or decorator, you have to flush your metrics manual
     If metrics are provided, and any of the following criteria are not met, a **`RangeError`** exception will be raised:
 
     * Maximum of 9 dimensions
-    * Namespace is set, and no more than one
+    * Namespace is set only once (or none)
     * Metric units must be [supported by CloudWatch](https://docs.aws.amazon.com/AmazonCloudWatch/latest/APIReference/API_MetricDatum.html)
 
 
@@ -219,7 +219,7 @@ See below an example of how to automatically flush metrics with the Middy-compat
     import { Context } from 'aws-lambda';
     import middy from '@middy/core';
 
-    const metrics = new Metrics({namespace:"exampleApplication", service:"exampleService"});
+    const metrics = new Metrics({ namespace: 'exampleApplication' , service: 'exampleService' });
 
     const lambdaHandler = async (event: any, context: Context) => {
         metrics.addMetric('bookingConfirmation', MetricUnits.Count, 1);
@@ -360,7 +360,7 @@ You can optionally capture cold start metrics with the `logMetrics` middleware o
     import { Context } from 'aws-lambda';
     import middy from '@middy/core';
 
-    const metrics = new Metrics({namespace:"serverlessAirline", service:"orders"});
+    const metrics = new Metrics({namespace: 'serverlessAirline', service: 'orders' });
 
     const lambdaHandler = async (event: any, context: Context) => {
         metrics.addMetric('successfulBooking', MetricUnits.Count, 1);
@@ -377,7 +377,7 @@ You can optionally capture cold start metrics with the `logMetrics` middleware o
     import { Context, Callback } from 'aws-lambda'; 
     import middy from '@middy/core';
 
-    const metrics = new Metrics({namespace:"serverlessAirline", service:"orders"});
+    const metrics = new Metrics({namespace: 'serverlessAirline', service: 'orders' });
 
     export class MyFunction {
 

packages/metrics/examples/decorator/default-dimensions.ts

@@ -21,6 +21,7 @@ class Lambda implements LambdaInterface {
     metrics.addDimension('environment', 'dev');
     metrics.addDimension('application', 'hello-world-dev');
     metrics.addMetric('test-metric', MetricUnits.Count, 10);
+    // You can override the default dimensions by clearing the existing metrics first. Note that the cleared metric will be dropped, it will NOT be published to CloudWatch 
     const metricsObject = metrics.serializeMetrics();
     metrics.clearMetrics();
     metrics.clearDimensions();

packages/metrics/examples/decorator/empty-metrics.ts

@@ -15,7 +15,8 @@ const metrics = new Metrics();
 
 class Lambda implements LambdaInterface {
 
-  @metrics.logMetrics({ raiseOnEmptyMetrics: true })
+    // Be default, we will not throw any error if there is no metrics. Use this property to override and throw an exception
+    @metrics.logMetrics({ raiseOnEmptyMetrics: true })
   public handler<TEvent, TResult>(_event: TEvent, _context: Context, _callback: Callback<TResult>): void | Promise<TResult> {
     // Notice that no metrics are added
     // Since the raiseOnEmptyMetrics parameter is set to true, the Powertool throw an Error

packages/metrics/examples/decorator/manual-flushing.ts

@@ -16,7 +16,7 @@ const lambdaHandler: Handler = async () => {
 
   metrics.addMetric('test-metric', MetricUnits.Count, 10);
   metrics.purgeStoredMetrics();
-  //Metrics will be logged and cleared
+  //Metrics will be published and cleared
 
   return {
     foo: 'bar'