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Copilot
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New: [AEA-6520] - SnsAlarm (#708)
## Summary - ✨ New Feature ### Details Share SnsAlarm construct from PfP for use in PSU --------- Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
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‎package-lock.json‎

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‎packages/cdkConstructs/src/constructs/SnsAlarm.ts‎

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import {Duration} from "aws-cdk-lib"
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import {Construct} from "constructs"
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import {
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Alarm,
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ComparisonOperator,
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CreateAlarmOptions,
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Metric,
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MetricStatConfig,
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TreatMissingData,
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Unit
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} from "aws-cdk-lib/aws-cloudwatch"
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import {SnsAction} from "aws-cdk-lib/aws-cloudwatch-actions"
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import {ITopic} from "aws-cdk-lib/aws-sns"
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/**
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* Alarm definition for SnsAlarm with defaults applied by the construct.
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*/
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export interface SnsAlarmDefinition
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extends Omit<CreateAlarmOptions, "threshold" | "evaluationPeriods"> {
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/**
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* The value against which the specified statistic is compared.
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*
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* @default 1
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*/
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readonly threshold?: number
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/**
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* The number of periods over which data is compared to the specified threshold.
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*
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* @default 1
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*/
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readonly evaluationPeriods?: number
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}
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/**
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* Metric stat configuration for SnsAlarm with defaults applied by the construct.
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*/
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export interface SnsMetricStatConfig extends Omit<MetricStatConfig, "period" | "statistic"> {
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/**
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* How many seconds to aggregate over.
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*
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* @default Duration.minutes(1)
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*/
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readonly period?: Duration
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/**
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* Aggregation function to use.
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*
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* @default "Sum"
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*/
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readonly statistic?: string
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}
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const toDimensionsMap = (
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dimensions: MetricStatConfig["dimensions"]
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): {[dimensionName: string]: string} | undefined => {
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if (!dimensions || dimensions.length === 0) {
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return undefined
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}
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const dimensionMap: {[dimensionName: string]: string} = {}
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dimensions.forEach((dimension) => {
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dimensionMap[dimension.name] = String(dimension.value)
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})
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return dimensionMap
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}
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/**
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* Constructs a concrete CloudWatch Metric from a MetricStatConfig.
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* @see {@link import("aws-cdk-lib/aws-cloudwatch").MetricConfig} for alternate concrete metric configs.
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*/
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export const metricFromStatConfig = (
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metricStatConfig: MetricStatConfig
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): Metric =>
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new Metric({
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namespace: metricStatConfig.namespace,
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metricName: metricStatConfig.metricName,
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dimensionsMap: toDimensionsMap(metricStatConfig.dimensions),
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statistic: metricStatConfig.statistic,
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period: metricStatConfig.period,
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unit: metricStatConfig.unitFilter,
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account: metricStatConfig.accountOverride ?? metricStatConfig.account,
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region: metricStatConfig.regionOverride ?? metricStatConfig.region
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})
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/**
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* Configuration for creating a CloudWatch metric alarm with SNS publication construct.
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*/
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export interface SnsAlarmProps {
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/** Prefix used in the generated CloudWatch alarm name. */
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readonly stackName: string
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/** Enables alarm actions when true, disabling notifications when false. */
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readonly enableAlerts: boolean
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/** CloudWatch metric and threshold settings for the alarm. */
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readonly alarmDefinition: SnsAlarmDefinition
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/** Defines the metric configuration to be monitored by the alarm. */
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readonly metricStatConfig: SnsMetricStatConfig
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/** SNS topic that receives alarm, OK, and insufficient data notifications. Common example is for Slack alerts. */
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readonly snsTopic: ITopic
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}
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/**
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* Creates a single CloudWatch alarm and wires all alarm state changes to an SNS topic.
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*/
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export class SnsAlarm extends Construct {
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public readonly alarm: Alarm
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/**
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* Creates a CloudWatch alarm and publishes alarm state changes to the provided SNS topic.
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*
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* @param props Alarm configuration including metric settings, threshold settings, and notification topic.
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* @example
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* new SnsAlarm(this, 'MyApiErrorAlarm', {
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* stackName: 'pfp-prod',
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* enableAlerts: true,
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* alarmDefinition: {
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* alarmDescription: 'API errors detected',
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* threshold: 1
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* },
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* metricStatConfig: {
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* namespace: 'LambdaLogFilterMetrics',
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* metricName: 'ErrorCount'
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* },
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* snsTopic: slackAlertTopic
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* })
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*/
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public constructor(scope: Construct, id: string, props: SnsAlarmProps) {
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super(scope, id)
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const generatedAlarmName = props.alarmDefinition.alarmName ?? id
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const {
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threshold,
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evaluationPeriods,
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comparisonOperator,
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treatMissingData,
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...supportedAlarmDefinitionProps
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} = props.alarmDefinition
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const alarm = new Alarm(this, `${generatedAlarmName}Alarm`, {
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...supportedAlarmDefinitionProps,
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alarmName: `${props.stackName}-${generatedAlarmName}`,
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metric: metricFromStatConfig({
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...props.metricStatConfig,
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unitFilter: props.metricStatConfig.unitFilter ?? Unit.COUNT,
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statistic: props.metricStatConfig.statistic ?? "Sum",
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period: props.metricStatConfig.period ?? Duration.minutes(1)
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}),
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threshold: threshold ?? 1,
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evaluationPeriods: evaluationPeriods ?? 1,
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comparisonOperator: comparisonOperator ?? ComparisonOperator.GREATER_THAN_OR_EQUAL_TO_THRESHOLD,
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treatMissingData: treatMissingData ?? TreatMissingData.NOT_BREACHING,
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actionsEnabled: props.enableAlerts
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})
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const snsAction = new SnsAction(props.snsTopic)
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alarm.addAlarmAction(snsAction)
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alarm.addOkAction(snsAction)
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alarm.addInsufficientDataAction(snsAction)
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this.alarm = alarm
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}
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}

‎packages/cdkConstructs/src/index.ts‎

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export * from "./constructs/RestApiGateway/LambdaEndpoint.js"
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export * from "./constructs/RestApiGateway/StateMachineEndpoint.js"
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export * from "./constructs/PythonLambdaFunction.js"
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export * from "./constructs/SnsAlarm.js"
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export * from "./constructs/SsmParametersConstruct.js"
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export * from "./apps/createApp.js"
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export * from "./config/index.js"

‎packages/cdkConstructs/tests/constructs/SnsAlarm.test.ts‎

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import {App, Duration, Stack} from "aws-cdk-lib"
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import {Template} from "aws-cdk-lib/assertions"
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import {ComparisonOperator, Unit} from "aws-cdk-lib/aws-cloudwatch"
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import {Topic} from "aws-cdk-lib/aws-sns"
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import {describe, expect, it} from "vitest"
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import {SnsAlarm} from "../../src/constructs/SnsAlarm"
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const importedSlackTopicArn = "arn:aws:sns:eu-west-2:111111111111:SlackAlertsTopic"
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describe("SnsAlarm construct", () => {
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it("applies sane defaults for simple alarm definitions", () => {
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const app = new App()
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const stack = new Stack(app, "TestStack")
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const slackAlertTopic = Topic.fromTopicArn(stack, "SlackAlertsTopic", importedSlackTopicArn)
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const metricAlarm = new SnsAlarm(stack, "SimpleMetricAlarm", {
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stackName: "pfp-test-stack",
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enableAlerts: true,
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alarmDefinition: {
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alarmName: "MySimpleAlarm",
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alarmDescription: "An alarm for any breach (threshold 1) in a single period"
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},
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metricStatConfig: {
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namespace: "LambdaLogFilterMetrics",
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metricName: "ErrorCount"
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},
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snsTopic: slackAlertTopic
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})
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expect(metricAlarm.alarm).toBeDefined()
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const template = Template.fromStack(stack)
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template.resourceCountIs("AWS::SNS::Topic", 0)
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template.hasResourceProperties("AWS::CloudWatch::Alarm", {
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AlarmName: "pfp-test-stack-MySimpleAlarm",
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Namespace: "LambdaLogFilterMetrics",
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MetricName: "ErrorCount",
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Threshold: 1,
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ComparisonOperator: "GreaterThanOrEqualToThreshold",
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Unit: "Count",
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Statistic: "Sum",
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Period: 60,
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EvaluationPeriods: 1,
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TreatMissingData: "notBreaching",
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AlarmDescription: "An alarm for any breach (threshold 1) in a single period",
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AlarmActions: [importedSlackTopicArn],
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OKActions: [importedSlackTopicArn],
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InsufficientDataActions: [importedSlackTopicArn],
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ActionsEnabled: true
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})
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})
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it("allows overriding threshold, comparison operator, unit and dimensions", () => {
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const app = new App()
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const stack = new Stack(app, "OverrideStack")
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const slackAlertTopic = Topic.fromTopicArn(stack, "SlackAlertsTopic", importedSlackTopicArn)
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const metricAlarm = new SnsAlarm(stack, "OverrideMetricAlarm", {
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stackName: "pfp-test-stack",
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enableAlerts: false,
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alarmDefinition: {
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alarmName: "MyOverrideAlarm",
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alarmDescription: "Override alarm",
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threshold: 250,
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comparisonOperator: ComparisonOperator.GREATER_THAN_THRESHOLD,
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evaluationPeriods: 3,
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datapointsToAlarm: 2
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},
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metricStatConfig: {
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namespace: "CustomNamespace",
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metricName: "Latency",
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unitFilter: Unit.MILLISECONDS,
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dimensions: [
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{
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name: "FunctionName",
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value: "my-function"
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}
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],
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period: Duration.minutes(1),
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statistic: "Sum"
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},
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snsTopic: slackAlertTopic
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})
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expect(metricAlarm.alarm).toBeDefined()
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const template = Template.fromStack(stack)
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template.hasResourceProperties("AWS::CloudWatch::Alarm", {
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AlarmName: "pfp-test-stack-MyOverrideAlarm",
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Namespace: "CustomNamespace",
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MetricName: "Latency",
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Threshold: 250,
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ComparisonOperator: "GreaterThanThreshold",
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DatapointsToAlarm: 2,
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Unit: "Milliseconds",
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Dimensions: [
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{
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Name: "FunctionName",
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Value: "my-function"
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}
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],
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AlarmDescription: "Override alarm",
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AlarmActions: [importedSlackTopicArn],
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OKActions: [importedSlackTopicArn],
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InsufficientDataActions: [importedSlackTopicArn],
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ActionsEnabled: false
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})
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})
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})

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