Invoking an existing Lambda Function using AWSCustomResource

[houdinisparks]

I am trying to invoke an existing lambda function using AWSCustomResource with the code below:

  const existingLambda = cdk.aws_lambda.Function.fromFunctionName(
    stack,
    `TriggerExistingLambda`,
    'existing-function-name'
  );
  return new cdk.custom_resources.AwsCustomResource(stack, 'TriggerExistingLambdaCustomResource', {
    policy: cdk.custom_resources.AwsCustomResourcePolicy.fromStatements([
      new cdk.aws_iam.PolicyStatement({
        actions: ['lambda:InvokeFunction'],
        effect: cdk.aws_iam.Effect.ALLOW,
        resources: [existingLambda.functionArn],
      }),
    ]),

   // I presume AWS will generate another lambda internall to execute the onCreate API call?
    onCreate: {
      service: 'Lambda',
      action: 'invoke',
      parameters: {
        FunctionName: existingLambda.functionName,
        InvocationType: 'RequestResponse',
        Payload: 'some-payload',
      },
      physicalResourceId: cdk.custom_resources.PhysicalResourceId.of(`${resourceName}LambdaPhysicalResourceId`),
    },
    installLatestAwsSdk: false,
  });

Here is the generated cloudformation manifest.yml

  LambdaTriggerSetupRDSIAMEE3AB6F1:
    Type: Custom::AWS
    Properties:
      ServiceToken:
        Fn::GetAtt:
          - AWS679f53fac002430cb0da5b7982bd22872D164C4C
          - Arn
       Create: ....

  AWS679f53fac002430cb0da5b7982bd22872D164C4C:
    Type: AWS::Lambda::Function
    Properties:
      Code:
        S3Bucket: cdk-hnb659fds-assets-020653668000-ap-southeast-1
        S3Key: d62cd506a0f4ef6a29d7a97e2a02d80bc8248142ce428543cfbf0d84b3c116a2.zip
      Role:
        Fn::GetAtt:
          - AWS679f53fac002430cb0da5b7982bd2287ServiceRoleC1EA0FF2
          - Arn
      Handler: index.handler
      Runtime: nodejs18.x
      Timeout: 900
    DependsOn:
      - AWS679f53fac002430cb0da5b7982bd2287ServiceRoleC1EA0FF2
    Metadata:
      aws:cdk:path: Stack/AWS679f53fac002430cb0da5b7982bd2287/Resource
      aws:asset:path: asset.d62cd506a0f4ef6a29d7a97e2a02d80bc8248142ce428543cfbf0d84b3c116a2
      aws:asset:is-bundled: false
      aws:asset:property: Code

The error: For resource AWS679f53fac002430cb0da5b7982bd22872D164C4C, I am facing Resource handler returned message: "Error occurred while GetObject. S3 Error Code: NoSuchKey. S3 Error Message: The specified key does not exist. for the lambda function that I presume will be internally generated by AWS when using AWSCustomResource to make the AWS API call to invoke the existing lambda.

and when I checked the S3 console, S3Key: d62cd506a0f4ef6a29d7a97e2a02d80bc8248142ce428543cfbf0d84b3c116a2.zip does not exist in the bucket. I thought cdk bootstrap should help me create the internal lambda but I guess im wrong.

Am I understanding AWSCustomResource wrongly? I presumed the CDK should handle the onCreate event handling to call the lambda:Invoke action for me.

fyi: I am also using AWS's copilot cdk overrides for this.

[houdinisparks]

I've found the reason why:

I am using AWS's copilot to deploy. copilot runs cdk synth internally to generate the cloudformation templates, and then deploys the cloudformation template. It does not upload the assets that generated with cdk synth to the cdk S3 bucket. To resolve this, I separately use a cdk-assets publish --path <some-copilot-path>/cdk.out/Stack.assets.json to upload the assets first to S3 before deploying.

Script for copilot deployments:

export $SERVICE_NAME=<name>
copilot svc package --name $SERVICE_NAME --env dev
cdk-assets publish --path /copilot/$SERVICE_NAME/overrides/cdk.out/Stack.assets.json
copilot svc deploy --name $SERVICE_NAME --env dev