feat(alarm): Make AlarmNamingStrategy customizable (#316)

Making the AlarmNamingStrategy configurable. My team wants to add the disambiguator to the alarm dedupe string. This requires custom logic for generating the deduplication string, which is why we want to be able to override this class's functionality.

_By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license_

Author: Mitchell-Cook

API.md

@@ -19,6 +19,7 @@ import {
   IAlarmAnnotationStrategy,
 } from "./IAlarmAnnotationStrategy";
 import { IAlarmDedupeStringProcessor } from "./IAlarmDedupeStringProcessor";
+import { IAlarmNamingStrategy } from "./IAlarmNamingStrategy";
 import { noopAction } from "./NoopAlarmActionStrategy";
 import {
   MetricFactoryDefaults,
@@ -403,6 +404,13 @@ export interface AlarmFactoryDefaults {
    */
   readonly dedupeStringProcessor?: IAlarmDedupeStringProcessor;
 
+  /**
+   * Custom strategy to name alarms
+   *
+   * @default - default behaviour (no change)
+   */
+  readonly alarmNamingStrategy?: IAlarmNamingStrategy;
+
   /**
    * Number of breaches required to transition into an ALARM state.
    *
@@ -460,17 +468,19 @@ export class AlarmFactory {
   protected readonly alarmScope: Construct;
   protected readonly globalAlarmDefaults: AlarmFactoryDefaults;
   protected readonly globalMetricDefaults: MetricFactoryDefaults;
-  protected readonly alarmNamingStrategy: AlarmNamingStrategy;
+  protected readonly alarmNamingStrategy: IAlarmNamingStrategy;
 
   constructor(alarmScope: Construct, props: AlarmFactoryProps) {
     this.alarmScope = alarmScope;
     this.globalAlarmDefaults = props.globalAlarmDefaults;
     this.globalMetricDefaults = props.globalMetricDefaults;
-    this.alarmNamingStrategy = new AlarmNamingStrategy(
-      props.globalAlarmDefaults.alarmNamePrefix,
-      props.localAlarmNamePrefix,
-      props.globalAlarmDefaults.dedupeStringProcessor
-    );
+    this.alarmNamingStrategy =
+      props.globalAlarmDefaults.alarmNamingStrategy ??
+      new AlarmNamingStrategy(
+        props.globalAlarmDefaults.alarmNamePrefix,
+        props.localAlarmNamePrefix,
+        props.globalAlarmDefaults.dedupeStringProcessor
+      );
   }
 
   addAlarm(

lib/common/alarm/AlarmFactory.ts

@@ -2,19 +2,12 @@ import {
   DoNotModifyDedupeString,
   IAlarmDedupeStringProcessor,
 } from "./IAlarmDedupeStringProcessor";
+import { AlarmNamingInput, IAlarmNamingStrategy } from "./IAlarmNamingStrategy";
 
 const AlarmNamePartSeparator = "-";
 const AlarmLabelPartSeparator = " ";
 
-export interface AlarmNamingInput {
-  readonly alarmNameSuffix: string;
-  readonly alarmNameOverride?: string;
-  readonly alarmDedupeStringSuffix?: string;
-  readonly dedupeStringOverride?: string;
-  readonly disambiguator?: string;
-}
-
-export class AlarmNamingStrategy {
+export class AlarmNamingStrategy implements IAlarmNamingStrategy {
   protected readonly globalPrefix: string;
   protected readonly localPrefix: string;
   protected readonly dedupeStringStrategy: IAlarmDedupeStringProcessor;

lib/common/alarm/AlarmNamingStrategy.ts

@@ -0,0 +1,31 @@
+export interface AlarmNamingInput {
+  readonly alarmNameSuffix: string;
+  readonly alarmNameOverride?: string;
+  readonly alarmDedupeStringSuffix?: string;
+  readonly dedupeStringOverride?: string;
+  readonly disambiguator?: string;
+}
+
+/**
+ * Strategy used to name alarms, their widgets, and their dedupe strings.
+ */
+export interface IAlarmNamingStrategy {
+  /**
+   * How to generate the name of an alarm.
+   *
+   * @param props AlarmNamingInput
+   */
+  getName(props: AlarmNamingInput): string;
+
+  /**
+   * How to generate the label for the alarm displayed on a widget.
+   *
+   * @param props AlarmNamingInput
+   */
+  getWidgetLabel(props: AlarmNamingInput): string;
+
+  /**
+   * How to generate the deduplication string for an alarm.
+   */
+  getDedupeString(props: AlarmNamingInput): string | undefined;
+}

lib/common/alarm/IAlarmNamingStrategy.ts

@@ -4,6 +4,7 @@ export * from "./CustomAlarmThreshold";
 export * from "./IAlarmActionStrategy";
 export * from "./IAlarmAnnotationStrategy";
 export * from "./IAlarmDedupeStringProcessor";
+export * from "./IAlarmNamingStrategy";
 export * from "./MultipleAlarmActionStrategy";
 export * from "./NoopAlarmActionStrategy";
 export * from "./OpsItemAlarmActionStrategy";

lib/common/alarm/index.ts

@@ -14,7 +14,9 @@ import {
   AddAlarmProps,
   AlarmFactory,
   AlarmFactoryDefaults,
+  AlarmNamingInput,
   CompositeAlarmOperator,
+  IAlarmNamingStrategy,
   MetricFactoryDefaults,
   multipleActions,
   noopAction,
@@ -409,3 +411,33 @@ test("addAlarm: disambigatorAction takes precedence over default action", () =>
 
   expect(alarm.action).toStrictEqual(snsAction);
 });
+
+test("addAlarm: custom alarm naming strategy", () => {
+  const alarmName = "alarmName";
+  const alarmLabel = "alarmLabel";
+  const alarmDedupe = "alarmDedupe";
+  const disambiguator = "Critical";
+  const stack = new Stack();
+  const customNamingStrategy: IAlarmNamingStrategy = {
+    getName: (props: AlarmNamingInput) => `${alarmName}-${props.disambiguator}`,
+    getWidgetLabel: (props: AlarmNamingInput) =>
+      `${alarmLabel}-${props.disambiguator}`,
+    getDedupeString: (props: AlarmNamingInput) =>
+      `${alarmDedupe}-${props.disambiguator}`,
+  };
+  const factory = new AlarmFactory(stack, {
+    globalMetricDefaults,
+    globalAlarmDefaults: {
+      ...globalAlarmDefaultsWithDisambiguator,
+      alarmNamingStrategy: customNamingStrategy,
+    },
+    localAlarmNamePrefix: "prefix",
+  });
+  const alarm = factory.addAlarm(metric, {
+    ...props,
+    disambiguator,
+  });
+  expect(alarm.alarmName).toBe(`${alarmName}-${disambiguator}`);
+  expect(alarm.alarmLabel).toBe(`${alarmLabel}-${disambiguator}`);
+  expect(alarm.dedupeString).toBe(`${alarmDedupe}-${disambiguator}`);
+});