A serverless.yml file configuring a AWS ElastiCache redis instance that is accessible by all AWS Lambda functions deployed by this serverless function.

serverless.yml

service: my-service

provider:
  name: aws
  runtime: nodejs8.10
  stage: ${opt:stage, 'dev'}
  environment:
    REDIS_HOST:
      "Fn::GetAtt": [ElasticCacheCluster, RedisEndpoint.Address]
functions:
  trigger:
    handler: src/serverless.trigger
    vpc:
      securityGroupIds:
        - "Fn::GetAtt": ServerlessSecurityGroup.GroupId
      subnetIds:
        - Ref: PrivateSubnetA
    events:
      - http: POST /trigger
  status:
    handler: src/serverless.getStatus
    vpc:
      securityGroupIds:
        - "Fn::GetAtt": ServerlessSecurityGroup.GroupId
      subnetIds:
        - Ref: PrivateSubnetA
    events:
      - http: GET /status
  transform:
    handler: src/serverless.transform
    vpc:
      securityGroupIds:
        - "Fn::GetAtt": ServerlessSecurityGroup.GroupId
      subnetIds:
        - Ref: PrivateSubnetA
resources:
  Resources:
    VPC:
      Type: AWS::EC2::VPC
      Properties:
        CidrBlock: "10.0.0.0/16"
    IP:
      Type: AWS::EC2::EIP
      Properties:
        Domain: vpc
    InternetGateway:
      Type: AWS::EC2::InternetGateway
    VPCGatewayAttachment:
      Type: AWS::EC2::VPCGatewayAttachment
      Properties:
        VpcId:
          Ref: VPC
        InternetGatewayId:
          Ref: InternetGateway
    NatGateway:
      Type: AWS::EC2::NatGateway
      Properties:
        AllocationId:
          Fn::GetAtt:
            - IP
            - AllocationId
        SubnetId:
          Ref: PublicSubnetA
    PrivateSubnetA:
      DependsOn: VPC
      Type: AWS::EC2::Subnet
      Properties:
        VpcId:
          Ref: VPC
        AvailabilityZone: ${self:provider.region}a
        CidrBlock: "10.0.1.0/24"
    PublicSubnetA:
      DependsOn: VPC
      Type: AWS::EC2::Subnet
      Properties:
        VpcId:
          Ref: VPC
        AvailabilityZone: ${self:provider.region}a
        CidrBlock: "10.0.2.0/24"
    PrivateRouteTable:
      Type: AWS::EC2::RouteTable
      Properties:
        VpcId:
          Ref: VPC
    PrivateRoute:
      Type: AWS::EC2::Route
      Properties:
        RouteTableId:
          Ref: PrivateRouteTable
        DestinationCidrBlock: 0.0.0.0/0
        NatGatewayId:
          Ref: NatGateway
    PublicRouteTable:
      Type: AWS::EC2::RouteTable
      Properties:
        VpcId:
          Ref: VPC
    PublicRoute:
      Type: AWS::EC2::Route
      Properties:
        RouteTableId:
          Ref: PublicRouteTable
        DestinationCidrBlock: 0.0.0.0/0
        GatewayId:
          Ref: InternetGateway
    SubnetRouteTableAssociationLambdaPrivateA:
      Type: AWS::EC2::SubnetRouteTableAssociation
      Properties:
        SubnetId:
          Ref: PrivateSubnetA
        RouteTableId:
          Ref: PrivateRouteTable
    SubnetRouteTableAssociationLambdaPublicA:
      Type: AWS::EC2::SubnetRouteTableAssociation
      Properties:
        SubnetId:
          Ref: PublicSubnetA
        RouteTableId:
          Ref: PublicRouteTable
    ServerlessSecurityGroup:
      DependsOn: VPC
      Type: AWS::EC2::SecurityGroup
      Properties:
        GroupDescription: SecurityGroup for Serverless Functions
        VpcId:
          Ref: VPC
    ServerlessStorageSecurityGroup:
      DependsOn: VPC
      Type: AWS::EC2::SecurityGroup
      Properties:
        GroupDescription: Ingress for Redis Cluster
        VpcId:
          Ref: VPC
        SecurityGroupIngress:
        - IpProtocol: tcp
          FromPort: '6379'
          ToPort: '6379'
          SourceSecurityGroupId:
            Ref: ServerlessSecurityGroup
    ServerlessCacheSubnetGroup:
      Type: AWS::ElastiCache::SubnetGroup
      Properties:
        Description: "Cache Subnet Group"
        SubnetIds:
        - Ref: PrivateSubnetA
    ElasticCacheCluster:
      DependsOn: ServerlessStorageSecurityGroup
      Type: AWS::ElastiCache::CacheCluster
      Properties:
        AutoMinorVersionUpgrade: true
        Engine: redis
        CacheNodeType: ${self:custom.config.CACHE_INSTANCE_SIZE}
        NumCacheNodes: 1
        VpcSecurityGroupIds:
        - "Fn::GetAtt": ServerlessStorageSecurityGroup.GroupId
        CacheSubnetGroupName:
          Ref: ServerlessCacheSubnetGroup

custom:
  config:
    CACHE_INSTANCE_SIZE: cache.t2.micro

Thanks for share this ☺

Getting tis warning
Warning: Invalid configuration encountered
at 'functions.trigger.vpc.securityGroupIds.0.Fn::GetAtt': must NOT have fewer than 2 items
at 'functions.status.vpc.securityGroupIds.0.Fn::GetAtt': must NOT have fewer than 2 items
at 'functions.transform.vpc.securityGroupIds.0.Fn::GetAtt': must NOT have fewer than 2 items

@dheerdotk I had the same issue. Perhaps the serverless.yml syntax has changed this this was posted. I was able to get it to work by updating all the instances where Fn::GetAtt is being called with a string to calling them with an array. For example:

"Fn::GetAtt": ServerlessSecurityGroup.GroupId

should be changed to

Fn::GetAtt: [ServerlessSecurityGroup, GroupId]