feat(cloudwatch): add methods for lazy addition of graph metrics

packages/@aws-cdk/aws-cloudwatch/README.md

@@ -251,6 +251,8 @@ dashboard.addWidgets(new GraphWidget({
 }));
 ```
 
+Using the methods `addLeftMetric()` and `addRightMetric()` you can add metrics to a graph widget later on.
+
 Graph widgets can also display annotations attached to the left or the right y-axis.
 
 ```ts

packages/@aws-cdk/aws-cloudwatch/lib/graph.ts

@@ -219,11 +219,35 @@ export interface GraphWidgetProps extends MetricWidgetProps {
  * A dashboard widget that displays metrics
  */
 export class GraphWidget extends ConcreteWidget {
+
  private readonly props: GraphWidgetProps;
 
+ private readonly leftMetrics: IMetric[];
+ private readonly rightMetrics: IMetric[];
+
  constructor(props: GraphWidgetProps) {
  super(props.width || 6, props.height || 6);
  this.props = props;
+ this.leftMetrics = props.left ?? [];
+ this.rightMetrics = props.right ?? [];
+ }
+
+ /**
+ * Add another metric to the left Y axis of the GraphWidget
+ *
+ * @param metric the metric to add
+ */
+ public addLeftMetric(metric: IMetric) {
+ this.leftMetrics.push(metric);
+ }
+
+ /**
+ * Add another metric to the right Y axis of the GraphWidget
+ *
+ * @param metric the metric to add
+ */
+ public addRightMetric(metric: IMetric) {
+ this.rightMetrics.push(metric);
  }
 
  public toJson(): any[] {
@@ -232,7 +256,7 @@ export class GraphWidget extends ConcreteWidget {
  ...(this.props.rightAnnotations || []).map(mapAnnotation('right')),
  ];
 
- const metrics = allMetricsGraphJson(this.props.left || [], this.props.right || []);
+ const metrics = allMetricsGraphJson(this.leftMetrics, this.rightMetrics);
  return [{
  type: 'metric',
  width: this.width,

packages/@aws-cdk/aws-cloudwatch/test/test.graphs.ts

@@ -61,6 +61,35 @@ export = {
  test.done();
  },
 
+ 'add metrics to graphs on either axis lazily'(test: Test) {
+ // WHEN
+ const stack = new Stack();
+ const widget = new GraphWidget({
+ title: 'My fancy graph',
+ });
+ widget.addLeftMetric(new Metric({ namespace: 'CDK', metricName: 'Test' }));
+ widget.addRightMetric(new Metric({ namespace: 'CDK', metricName: 'Tast' }));
+
+ // THEN
+ test.deepEqual(stack.resolve(widget.toJson()), [{
+ type: 'metric',
+ width: 6,
+ height: 6,
+ properties: {
+ view: 'timeSeries',
+ title: 'My fancy graph',
+ region: { Ref: 'AWS::Region' },
+ metrics: [
+ ['CDK', 'Test'],
+ ['CDK', 'Tast', { yAxis: 'right' }],
+ ],
+ yAxis: {},
+ },
+ }]);
+
+ test.done();
+ },
+
  'label and color are respected in constructor'(test: Test) {
  // WHEN
  const stack = new Stack();