Cloudformation error when deploying serverless.yml - amazon-web-services

Question

I am following a serverless tutorial and I am trying to send a notification every time an image is uploaded to the s3 bucket. I've created a sendUploadNotifications function under functions and instead of adding an event to the function I've set up the "NotificationsConfiguration" under the AttachmentsBucket, as well as created a new sendUploadNotificationsPermission Resource under resources.
But when I deploy the app I get the following error when I try to deploy my serverless app:
Error: The CloudFormation template is invalid: Template error: instance of Fn::GetAtt references undefined resource sendUploadNotificationsLambdaFunction
The Error seems to stem from the way that I am referencing the FunctionName under the sendUploadNotificationsPermission resource.
I've tried different ways of referencing the function name, but to no avail. I still get the same error.
My serverless.yml file
service: serverless-udagram2
frameworkVersion: '2'
provider:
name: aws
runtime: nodejs12.x
lambdaHashingVersion: 20201221
stage: ${opt:stage, 'dev'}
region: ${opt:region, 'ap-southeast-1'}
environment:
GROUPS_TABLE: groups-${self:provider.stage}
IMAGES_TABLE: images-${self:provider.stage}
IMAGE_ID_INDEX: ImageIdIndex
IMAGES_S3_BUCKET: branded-serverless-udagram-images-${self:provider.stage}
SIGNED_URL_EXPIRATION: 300
iamRoleStatements:
- Effect: Allow
Action:
- dynamodb:Scan
- dynamodb:PutItem
- dynamodb:GetItem
- dynamodb:Query
Resource: arn:aws:dynamodb:${self:provider.region}:*:table/${self:provider.environment.GROUPS_TABLE}
- Effect: Allow
Action:
- dynamodb:PutItem
- dynamodb:Query
Resource: arn:aws:dynamodb:${self:provider.region}:*:table/${self:provider.environment.IMAGES_TABLE}
- Effect: Allow
Action:
- dynamodb:Query
- dynamodb:PutItem
Resource: arn:aws:dynamodb:${self:provider.region}:*:table/${self:provider.environment.IMAGES_TABLE}/index/${self:provider.environment.IMAGE_ID_INDEX}
- Effect: Allow
Action:
- s3:PutObject
- s3:GetObject
Resource: arn:aws:s3:::${self:provider.environment.IMAGES_S3_BUCKET}/*
functions:
getGroups:
handler: src/lambda/http/getGroups.handler
events:
- http:
path: groups
method: get
cors: true
createGroup:
handler: src/lambda/http/createGroup.handler
events:
- http:
path: groups
method: post
cors: true
request:
schema:
application/json: ${file(models/create-group-request.json)}
getImages:
handler: src/lambda/http/getImages.handler
events:
- http:
path: groups/{groupId}/images
method: get
cors: true
getImage:
handler: src/lambda/http/getImage.handler
events:
- http:
path: images/{imageId}
method: get
cors: true
createImage:
handler: src/lambda/http/createImage.handler
events:
- http:
path: groups/{groupId}/images
method: post
cors: true
request:
schema:
application/json: ${file(models/create-image-request.json)}
sendUploadNotifications:
handler: src/lambda/s3/sendNotifications.handler
resources:
Resources:
# API gateway validates the request in accordance with json schemas that are identified in the function section under schema
RequestBodyValidator:
Type: AWS::ApiGateway::RequestValidator
Properties:
Name: 'request-body-validator'
RestApiId:
Ref: ApiGatewayRestApi
ValidateRequestBody: true
ValidateRequestParameters: true
GroupsDynamoDBTable:
Type: AWS::DynamoDB::Table
Properties:
AttributeDefinitions:
- AttributeName: id
AttributeType: S
KeySchema:
- AttributeName: id
KeyType: HASH
BillingMode: PAY_PER_REQUEST
TableName: ${self:provider.environment.GROUPS_TABLE}
ImagesDynamoDBTable:
Type: AWS::DynamoDB::Table
Properties:
AttributeDefinitions:
- AttributeName: groupId
AttributeType: S
- AttributeName: timestamp
AttributeType: S
- AttributeName: imageId
AttributeType: S
KeySchema:
- AttributeName: groupId
KeyType: HASH #partition key
- AttributeName: timestamp
KeyType: RANGE #sort key
GlobalSecondaryIndexes:
- IndexName: ${self:provider.environment.IMAGE_ID_INDEX}
KeySchema:
- AttributeName: imageId
KeyType: HASH
Projection:
ProjectionType: ALL
BillingMode: PAY_PER_REQUEST
TableName: ${self:provider.environment.IMAGES_TABLE}
# Bucket for file uploads
AttachmentsBucket:
Type: AWS::S3::Bucket
Properties:
BucketName: ${self:provider.environment.IMAGES_S3_BUCKET}
NotificationConfiguration: # Sends notification when image has been uploaded
LambdaConfigurations: #
- Event: s3:ObjectCreated:*
Function: !GetAtt sendUploadNotificationsLambdaFunction.Arn
CorsConfiguration:
CorsRules:
-
AllowedOrigins:
- "*"
AllowedHeaders:
- "*"
AllowedMethods:
- 'GET'
- 'PUT'
- 'POST'
- 'DELETE'
- 'HEAD'
MaxAge: 3000
sendUploadNotificationsPermission:
Type: AWS::Lambda::Permission
Properties:
FunctionName: !GetAtt sendUploadNotificationsLambdaFunction.Arn
Action: lambda:InvokeFunction
Principal: s3.amazonaws.com
SourceAccount: !Ref AWS::AccountId #!Ref
SourceArn: arn:aws:s3:::${self:provider.environment.IMAGES_S3_BUCKET}
BucketPolicy:
Type: AWS::S3::BucketPolicy
Properties:
PolicyDocument:
Id: MyPolicy
Version: "2012-10-17"
Statement:
- Sid: PublicReadForGetBucketObjects
Effect: Allow
Principal: '*'
Action: 's3:GetObject'
Resource: 'arn:aws:s3:::${self:provider.environment.IMAGES_S3_BUCKET}/*'
Bucket:
Ref: AttachmentsBucket
I've tried changing the name of the function in both the sendUploadNotificationsPermission and the AttachmentsBucket by appending LamdaFunction to the end of the function name, but still getting the same error.
Any help with this error would be appreciated.

Answer 1

You are trying to reference something which doesn't exist in the template at in the CloudFormation section Resource.
sendUploadNotificationsLambdaFunction
In case you want to reference any of the function you have defined named
sendUploadNotifications
you need to construct the ARN inside the Resources section.
To generate Logical ID for CloudFormation, the plugin transform the specified name in serverless.yml based on the following scheme.
Transform a leading character into uppercase
Transform - into Dash
Transform _ into Underscore
SendUploadNotificationsLambdaFunction in your case.
There are now two ways:
You reference this inside Resource section of the template:
sendUploadNotificationsPermission:
Type: AWS::Lambda::Permission
Properties:
FunctionName: !GetAtt SendUploadNotificationsLambdaFunction.Arn
Action: lambda:InvokeFunction
Principal: s3.amazonaws.com
SourceAccount: !Ref AWS::AccountId #!Ref
SourceArn: arn:aws:s3:::${self:provider.environment.IMAGES_S3_BUCKET}
You construct the ARN using Fn::Join.
sendUploadNotificationsPermission:
Type: AWS::Lambda::Permission
Properties:
FunctionName: !Join [":", ['arn:aws:lambda', !Ref 'AWS::Region', !Ref AWS::AccountId, '${self:service}-${self:provider.stage}-sendUploadNotifications']]
Action: lambda:InvokeFunction
Principal: s3.amazonaws.com
SourceAccount: !Ref AWS::AccountId #!Ref
SourceArn: arn:aws:s3:::${self:provider.environment.IMAGES_S3_BUCKET}

Answer 2

Solved it. The 'references undefined resource error' was caused by the fact that after the serverless.yml file compiles it capitalizes the function name.
sendUploadNotifications becomes SendUploadNotificationsLambdaFunction
changed:
FunctionName: !Ref sendUploadNotificationsLambdaFunction
to:
FunctionName: !Ref SendUploadNotificationsLambdaFunction
It now deploys without an issue.