如何在AWS Lambda中获取CDK创建的Step Functions状态机ARN？

你遇到的${Token[TOKEN.xxx]}是CDK在合成阶段的占位符，此时真实ARN还未生成，手动写入.env文件的方法行不通，推荐以下两种靠谱的解决方案：

1. 通过Lambda环境变量直接传递（最常用） #

CDK支持直接将状态机ARN作为环境变量注入Lambda，部署阶段会自动替换为真实的ARN值，无需手动处理。

CDK栈代码示例： #

import * as cdk from 'aws-cdk-lib';
import * as sfn from 'aws-cdk-lib/aws-stepfunctions';
import * as lambda from 'aws-cdk-lib/aws-lambda-nodejs';

export class MyStack extends cdk.Stack {
  constructor(scope: cdk.App, id: string, props?: cdk.StackProps) {
    super(scope, id, props);

    // 创建Step Functions状态机
    const myStateMachine = new sfn.StateMachine(this, 'MyStateMachine', {
      // 替换为你的状态机定义
      definition: sfn.Chain.start(new sfn.Pass(this, 'StartPass'))
    });

    // 创建Lambda函数，注入状态机ARN到环境变量
    const myLambda = new lambda.NodejsFunction(this, 'MyLambda', {
      entry: './lambda/index.ts',
      environment: {
        // 直接引用状态机的ARN属性
        STATE_MACHINE_ARN: myStateMachine.stateMachineArn
      }
    });

    // 给Lambda添加调用StartExecution的权限
    myStateMachine.grantStartExecution(myLambda);
  }
}

Lambda代码示例（index.ts）： #

import { SFNClient, StartExecutionCommand } from "@aws-sdk/client-sfn";

const sfnClient = new SFNClient({});

export const handler = async () => {
  // 从环境变量读取真实ARN
  const stateMachineArn = process.env.STATE_MACHINE_ARN;
  
  if (!stateMachineArn) {
    throw new Error('STATE_MACHINE_ARN环境变量未设置');
  }

  const command = new StartExecutionCommand({
    stateMachineArn,
    // 按需添加输入等其他参数
    input: JSON.stringify({ key: 'value' })
  });

  await sfnClient.send(command);
  return { statusCode: 200, body: '状态机执行已启动' };
};

2. 存入SSM参数存储（跨栈/多场景共享时用） #

如果需要在多个Lambda或跨栈场景中共享状态机ARN，可以将ARN存入AWS Systems Manager参数存储，再让Lambda读取该参数。

CDK栈代码示例： #

import * as ssm from 'aws-cdk-lib/aws-ssm';
import * as iam from 'aws-cdk-lib/aws-iam';

// ... 前面的状态机创建代码不变

// 将状态机ARN存入SSM参数
new ssm.StringParameter(this, 'StateMachineArnParam', {
  parameterName: '/my-app/step-functions/state-machine-arn',
  stringValue: myStateMachine.stateMachineArn
});

// 给Lambda添加读取SSM参数的权限
myLambda.addToRolePolicy(new iam.PolicyStatement({
  actions: ['ssm:GetParameter'],
  resources: [ssm.StringParameter.fromStringParameterName(this, 'ParamArn', '/my-app/step-functions/state-machine-arn').parameterArn]
}));

Lambda代码示例： #

import { SSMClient, GetParameterCommand } from "@aws-sdk/client-ssm";
import { SFNClient, StartExecutionCommand } from "@aws-sdk/client-sfn";

const ssmClient = new SSMClient({});
const sfnClient = new SFNClient({});

export const handler = async () => {
  // 从SSM读取ARN
  const paramCommand = new GetParameterCommand({
    Name: '/my-app/step-functions/state-machine-arn'
  });
  const paramResult = await ssmClient.send(paramCommand);
  const stateMachineArn = paramResult.Parameter?.Value;

  if (!stateMachineArn) {
    throw new Error('未从SSM获取到状态机ARN');
  }

  // 启动状态机执行
  const executionCommand = new StartExecutionCommand({
    stateMachineArn,
    input: JSON.stringify({ key: 'value' })
  });
  await sfnClient.send(executionCommand);
  
  return { statusCode: 200, body: '状态机执行已启动' };
};

注意：不要用本地文件写入的方式传递ARN，CDK在合成阶段无法获取真实资源标识符，只会生成占位Token，只有部署阶段才会替换为真实值。

内容的提问来源于stack exchange，提问作者hello planet