How do I define resources for iamrolestatements for multiple dynamodb tables in serverless framework?

Question

I want to use more than one dynamodb table in my serverless project. How do I properly define multiple resources in the iamrolestatements?

I have an example serverless.yml

service: serverless-expense-tracker
frameworkVersion: ">=1.1.0 <2.0.0"

provider:
  name: aws
  runtime: nodejs6.10
  environment:
    EXPENSES_TABLE: "${self:service}-${opt:stage, self:provider.stage}-expenses"
    BUDGETS_TABLE: "${self:service}-${opt:stage, self:provider.stage}-budgets"

  iamRoleStatements:
    - Effect: Allow
      Action:
        - dynamodb:Query
        - dynamodb:Scan
        - dynamodb:GetItem
        - dynamodb:PutItem
        - dynamodb:UpdateItem
        - dynamodb:DeleteItem
      Resource: "arn:aws:dynamodb:${opt:region, self:provider.region}:*:table/${self:provider.environment.EXPENSES_TABLE}"
      # what is the best way to add the other DB as a resource

functions:
  create:
    handler: expenseTracker/create.create
    events:
      - http:
          path: expenses
          method: post
          cors: true

  list:
    handler: expenseTracker/list.list
    events:
      - http:
          path: expenses
          method: get
          cors: true

  get:
    handler: expenseTracker/get.get
    events:
      - http:
          path: expenses/{id}
          method: get
          cors: true

  update:
    handler: expenseTracker/update.update
    events:
      - http:
          path: expenses/{id}
          method: put
          cors: true

  delete:
    handler: expenseTracker/delete.delete
    events:
      - http:
          path: expenses/{id}
          method: delete
          cors: true

resources:
  Resources:
    DynamoDbExpenses:
      Type: 'AWS::DynamoDB::Table'
      DeletionPolicy: Retain
      Properties:
        AttributeDefinitions:
          -
            AttributeName: id
            AttributeType: S
        KeySchema:
          -
            AttributeName: id
            KeyType: HASH
        ProvisionedThroughput:
          ReadCapacityUnits: 1
          WriteCapacityUnits: 1
        TableName: ${self:provider.environment.EXPENSES_TABLE}

    DynamoDbBudgets:
      Type: 'AWS::DynamoDB::Table'
      DeletionPolicy: Retain
      Properties:
        AttributeDefinitions:
          -
            AttributeName: id
            AttributeType: S
        KeySchema:
          -
            AttributeName: id
            KeyType: HASH
        ProvisionedThroughput:
          ReadCapacityUnits: 1
          WriteCapacityUnits: 1
        TableName: ${self:provider.environment.BUDGETS_TABLE}

You can see the area in question in the comments there.

Answer 1

I got it!

The key was just adding a list under the key - Resource, but I also learned that it's better to just use the logicalIDs you use when provisioning the tables. Full example to follow:

service: serverless-expense-tracker

frameworkVersion: ">=1.1.0 <2.0.0"

provider:
  name: aws
  runtime: nodejs6.10
  environment:
    EXPENSES_TABLE: { "Ref": "DynamoDbExpenses" } #DynamoDbExpenses is a logicalID also used when provisioning below
    BUDGETS_TABLE: { "Ref": "DynamoDbBudgets" }

  iamRoleStatements:
    - Effect: Allow
      Action:
        - dynamodb:DescribeTable
        - dynamodb:Query
        - dynamodb:Scan
        - dynamodb:GetItem
        - dynamodb:PutItem
        - dynamodb:UpdateItem
        - dynamodb:DeleteItem
      Resource:
        - { "Fn::GetAtt": ["DynamoDbExpenses", "Arn"] } #you will also see the logical IDs below where they are provisioned
        - { "Fn::GetAtt": ["DynamoDbBudgets", "Arn"] }
functions:
  create:
    handler: expenseTracker/create.create
    events:
      - http:
          path: expenses
          method: post
          cors: true

  createBudget:
    handler: expenseTracker/createBudget.createBudget
    events:
      - http:
          path: budgets
          method: post
          cors: true

  list:
    handler: expenseTracker/list.list
    events:
      - http:
          path: expenses
          method: get
          cors: true

  listBudgets:
    handler: expenseTracker/listBudgets.listBudgets
    events:
      - http:
          path: budgets
          method: get
          cors: true

  get:
    handler: expenseTracker/get.get
    events:
      - http:
          path: expenses/{id}
          method: get
          cors: true

  update:
    handler: expenseTracker/update.update
    events:
      - http:
          path: expenses/{id}
          method: put
          cors: true

  delete:
    handler: expenseTracker/delete.delete
    events:
      - http:
          path: expenses/{id}
          method: delete
          cors: true

resources:
  Resources:
    DynamoDbExpenses: #this is where the logicalID is defined
      Type: 'AWS::DynamoDB::Table'
      DeletionPolicy: Retain
      Properties:
        AttributeDefinitions:
          -
            AttributeName: id
            AttributeType: S
        KeySchema:
          -
            AttributeName: id
            KeyType: HASH
        ProvisionedThroughput:
          ReadCapacityUnits: 1
          WriteCapacityUnits: 1

    DynamoDbBudgets: #here too
      Type: 'AWS::DynamoDB::Table'
      DeletionPolicy: Retain
      Properties:
        AttributeDefinitions:
          -
            AttributeName: id
            AttributeType: S
        KeySchema:
          -
            AttributeName: id
            KeyType: HASH
        ProvisionedThroughput:
          ReadCapacityUnits: 1
          WriteCapacityUnits: 1

Answer 2

I'd like to put my updates since I spend time and learn a lot from this question. The currently accepted answer is not fully functioned.

What I added:

1) Make sure in your handler, there is an environment TABLE_NAME(or another name, you can adjust accordingly) as below, it is referring the lambda function's environment variables

  const params = {
    TableName: process.env.TABLE_NAME,
    Item: {
      ...
    }
  }

2) update serverless.yml to nominate table name to each function.

environment:
  TABLE_NAME: { "Ref": "DynamoDbExpenses" }

or

environment:
  TABLE_NAME: { "Ref": "DynamoDbBudgets" }

Depend on which table the function targets.

The full serverless.yml is updated here:

service: serverless-expense-tracker

frameworkVersion: ">=1.1.0 <2.0.0"

provider:
  name: aws
  runtime: nodejs6.10
  environment:
    EXPENSES_TABLE: { "Ref": "DynamoDbExpenses" } #DynamoDbExpenses is a logicalID also used when provisioning below
    BUDGETS_TABLE: { "Ref": "DynamoDbBudgets" }

  iamRoleStatements:
    - Effect: Allow
      Action:
        - dynamodb:DescribeTable
        - dynamodb:Query
        - dynamodb:Scan
        - dynamodb:GetItem
        - dynamodb:PutItem
        - dynamodb:UpdateItem
        - dynamodb:DeleteItem
      Resource:
        - { "Fn::GetAtt": ["DynamoDbExpenses", "Arn"] } #you will also see the logical IDs below where they are provisioned
        - { "Fn::GetAtt": ["DynamoDbBudgets", "Arn"] }
functions:
  create:
    handler: expenseTracker/create.create
    environment:
      TABLE_NAME: { "Ref": "DynamoDbExpenses" }
    events:
      - http:
          path: expenses
          method: post
          cors: true

  createBudget:
    handler: expenseTracker/createBudget.createBudget
    environment:
      TABLE_NAME: { "Ref": "DynamoDbBudgets" }
    events:
      - http:
          path: budgets
          method: post
          cors: true

  list:
    handler: expenseTracker/list.list
    environment:
      TABLE_NAME: { "Ref": "DynamoDbExpenses" }
    events:
      - http:
          path: expenses
          method: get
          cors: true

  listBudgets:
    handler: expenseTracker/listBudgets.listBudgets
    environment:
      TABLE_NAME: { "Ref": "DynamoDbBudgets" }
    events:
      - http:
          path: budgets
          method: get
          cors: true

  get:
    handler: expenseTracker/get.get
    environment:
      TABLE_NAME: { "Ref": "DynamoDbExpenses" }
    events:
      - http:
          path: expenses/{id}
          method: get
          cors: true

  update:
    handler: expenseTracker/update.update
    environment:
      TABLE_NAME: { "Ref": "DynamoDbExpenses" }
    events:
      - http:
          path: expenses/{id}
          method: put
          cors: true

  delete:
    handler: expenseTracker/delete.delete
    environment:
      TABLE_NAME: { "Ref": "DynamoDbExpenses" }
    events:
      - http:
          path: expenses/{id}
          method: delete
          cors: true

resources:
  Resources:
    DynamoDbExpenses: #this is where the logicalID is defined
      Type: 'AWS::DynamoDB::Table'
      DeletionPolicy: Retain
      Properties:
        AttributeDefinitions:
          -
            AttributeName: id
            AttributeType: S
        KeySchema:
          -
            AttributeName: id
            KeyType: HASH
        ProvisionedThroughput:
          ReadCapacityUnits: 1
          WriteCapacityUnits: 1
        TableName: ${self:service}-${opt:stage, self:provider.stage}-expenses

    DynamoDbBudgets: #here too
      Type: 'AWS::DynamoDB::Table'
      DeletionPolicy: Retain
      Properties:
        AttributeDefinitions:
          -
            AttributeName: id
            AttributeType: S
        KeySchema:
          -
            AttributeName: id
            KeyType: HASH
        ProvisionedThroughput:
          ReadCapacityUnits: 1
          WriteCapacityUnits: 1
        TableName: ${self:service}-${opt:stage, self:provider.stage}-budgets

Refer:

serverless environment variables