Circular dependency in AWS lambda function - amazon-web-services

Question

The following is the template.yaml for the lambda function. I'm trying to add permissions to access the status database. However, it needs the database to exist and vice versa, and so I get a circular dependency error with DynamoDBIamPolicy. How can I resolve this?
AWSTemplateFormatVersion: '2010-09-09'
Transform: 'AWS::Serverless-2016-10-31'
Description: An AWS Serverless Specification template describing your function.
Resources:
friendTeachers:
Type: 'AWS::Serverless::Function'
Properties:
Handler: friendTeachers/index.handler
Runtime: nodejs6.10
Description: ''
MemorySize: 128
Timeout: 15
status:
Type: 'AWS::DynamoDB::Table'
Properties:
TableName: status
AttributeDefinitions:
- AttributeName: screenName
AttributeType: S
KeySchema:
- AttributeName: screenName
KeyType: HASH
ProvisionedThroughput:
ReadCapacityUnits: 1
WriteCapacityUnits: 1
# A policy is a resource that states one or more permssions. It lists actions, resources and effects.
DynamoDBIamPolicy:
Type: 'AWS::IAM::Policy'
DependsOn: status
Properties:
PolicyName: lambda-dynamodb
PolicyDocument:
Version: '2012-10-17'
Statement:
- Effect: Allow
Action:
- dynamodb:DescribeTable
- dynamodb:Query
- dynamodb:Scan
- dynamodb:GetItem
- dynamodb:PutItem
- dynamodb:UpdateItem
- dynamodb:DeleteItem
- dynamodb:batchWriteItem
Resource: arn:aws:dynamodb:*:*:table/status
Roles:
- Ref: IamRoleLambdaExecution

Answer 1

You are missing a role where you specify that the lambda service can AssumeRole. The role needs to have a policy associated that specifies the operations that can be done in the DynamoDb table. Find below an example that shows what you are trying to accomplish:
---
AWSTemplateFormatVersion: '2010-09-09'
Transform: 'AWS::Serverless-2016-10-31'
Description: An AWS Serverless Specification template describing your function.
Resources:
friendTeachersFunction:
Type: AWS::Lambda::Function
Properties:
Code:
S3Bucket:
Ref: LambdaCodeBucket
S3Key:
Ref: LambdaCodePath
Handler: friendTeachers/index.handler
Runtime: "nodejs6.10"
Description: ''
MemorySize: 128
Timeout: 15
Role:
Fn::GetAtt:
- friendTeachersExecutionRole
- Arn
friendTeachersExecutionRole:
Type: AWS::IAM::Role
Properties:
AssumeRolePolicyDocument:
Version: '2012-10-17'
Statement:
- Effect: Allow
Principal:
Service:
- lambda.amazonaws.com
Action:
- sts:AssumeRole
Policies:
- PolicyName: UseDBPolicy
PolicyDocument:
Version: '2012-10-17'
Statement:
- Effect: Allow
Action:
- dynamodb:DescribeTable
- dynamodb:Query
- dynamodb:Scan
- dynamodb:GetItem
- dynamodb:PutItem
- dynamodb:UpdateItem
- dynamodb:DeleteItem
- dynamodb:batchWriteItem
Resource: arn:aws:dynamodb:*:*:table/status
APIDynamoDBTable:
Type: AWS::DynamoDB::Table
Properties:
TableName: status
AttributeDefinitions:
- AttributeName: screenName
AttributeType: S
KeySchema:
- AttributeName: screenName
KeyType: HASH
ProvisionedThroughput:
ReadCapacityUnits: 1
WriteCapacityUnits: 1
Note that Code.S3Bucket and Code.S3Key are defined as parameters. When you create the stack in AWS Console you can specify the path there.