CloudWatch + Lambda + Discord로 CPU 알림 만들기

Parameters:
  DiscordWebhookUrl:
    Type: String
    NoEcho: true
    Description: Discord Webhook URL

  InstanceId:
    Type: String
    Description: EC2 instance ID to monitor

  DiscordMentionRoleId:
    Type: String
    Description: Discord role ID to mention

  CpuThreshold:
    Type: Number
    Default: 80
    Description: CPU utilization threshold (%)

  EvaluationPeriods:
    Type: Number
    Default: 3
    Description: Number of consecutive breaches

  Period:
    Type: Number
    Default: 300
    Description: Evaluation period in seconds

CpuAlarm:
  Type: AWS::CloudWatch::Alarm
  Properties:
    AlarmName: ████-ec2-cpu-high
    Namespace: AWS/EC2
    MetricName: CPUUtilization
    Statistic: Average
    Period: !Ref Period
    EvaluationPeriods: !Ref EvaluationPeriods
    Threshold: !Ref CpuThreshold
    ComparisonOperator: GreaterThanThreshold
    Dimensions:
      - Name: InstanceId
        Value: !Ref InstanceId
    AlarmActions:
      - !Ref AlarmSnsTopic
    OKActions:
      - !Ref AlarmSnsTopic
    TreatMissingData: missing

ServerHealthAlarmFunction:
  Type: AWS::Serverless::Function
  Properties:
    FunctionName: ████-server-health-alarm
    Handler: index.handler
    Runtime: nodejs22.x
    Timeout: 30
    CodeUri: src/
    Environment:
      Variables:
        DISCORD_WEBHOOK_URL: !Ref DiscordWebhookUrl
        DISCORD_MENTION_ROLE_ID: !Ref DiscordMentionRoleId
    Events:
      SnsEvent:
        Type: SNS
        Properties:
          Topic: !Ref AlarmSnsTopic
  Metadata:
    BuildMethod: esbuild
    BuildProperties:
      Minify: true
      Target: es2022
      EntryPoints:
        - index.ts

import { SNSEvent } from "aws-lambda";

interface CloudWatchAlarmMessage {
  AlarmName: string;
  NewStateValue: string;
  NewStateReason: string;
  Region: string;
  StateChangeTime: string;
  Trigger: {
    MetricName: string;
    Namespace: string;
    Threshold: number;
    Period: number;
    Dimensions: { name: string; value: string }[];
  };
}

export const handler = async (event: SNSEvent): Promise<void> => {
  for (const record of event.Records) {
    const message: CloudWatchAlarmMessage = JSON.parse(record.Sns.Message);

    const { AlarmName, NewStateValue, NewStateReason, Region, StateChangeTime, Trigger } = message;

    const instanceId =
      Trigger.Dimensions?.find(({ name }) => name === "InstanceId")?.value ?? "N/A";

    const emoji =
      NewStateValue === "ALARM" ? "🔴" : NewStateValue === "OK" ? "🟢" : "🟡";

    const content = [
      `## ${emoji} CloudWatch 경보: ${NewStateValue}`,
      `<@&${DISCORD_MENTION_ROLE_ID}>`,
      `**경보 이름**: ${AlarmName}`,
      `**시각**: ${new Date(StateChangeTime).toLocaleString("ko-KR", { timeZone: "Asia/Seoul" })}`,
      `**리전**: ${Region}`,
      `**인스턴스**: \`${instanceId}\``,
      `**메트릭**: ${Trigger.Namespace} / ${Trigger.MetricName}`,
      `**임계값**: ${Trigger.Threshold}% (측정 주기: ${Trigger.Period}초)`,
      "",
      `**상세**: ${NewStateReason}`,
    ]
      .join("\n")
      .slice(0, 2000);

    await fetch(DISCORD_WEBHOOK_URL, {
      method: "POST",
      headers: { "Content-Type": "application/json" },
      body: JSON.stringify({ content }),
    });
  }
};