How to create Postgres DB with Public access using AWS CloudFormation

Question

for testing purposes, I need to create Postgres Database which will have Public access and will be available from anywhere. My current CloudFormation looks like this:

---
AWSTemplateFormatVersion: "2010-09-09"
Resources:
  VPC:
    Type: AWS::EC2::VPC
    Properties:
      CidrBlock: 10.0.0.0/16
      EnableDnsSupport: true
      EnableDnsHostnames: true

  InternetGateway:
    Type: AWS::EC2::InternetGateway

  VPCGatewayAttachment:
    Type: AWS::EC2::VPCGatewayAttachment
    Properties:
      VpcId: !Ref VPC
      InternetGatewayId: !Ref InternetGateway

  PublicSubnet1:
    Type: AWS::EC2::Subnet
    Properties:
      VpcId: !Ref VPC
      CidrBlock: 10.0.1.0/24
      MapPublicIpOnLaunch: true
      AvailabilityZone: eu-central-1a

  PublicSubnet2:
    Type: AWS::EC2::Subnet
    Properties:
      VpcId: !Ref VPC
      CidrBlock: 10.0.2.0/24
      MapPublicIpOnLaunch: true
      AvailabilityZone: eu-central-1b

  DBSubnetGroup:
    Type: AWS::RDS::DBSubnetGroup
    Properties:
      DBSubnetGroupDescription: Subnets for RDS database
      SubnetIds:
        - !Ref PublicSubnet1
        - !Ref PublicSubnet2

  SecurityGroup:
    Type: AWS::EC2::SecurityGroup
    Properties:
      GroupDescription: Allow all inbound traffic
      VpcId: !Ref VPC
      SecurityGroupIngress:
        - IpProtocol: tcp
          FromPort: 5432
          ToPort: 5432
          CidrIp: 0.0.0.0/0

  DBInstance:
    Type: AWS::RDS::DBInstance
    Properties:
      DBInstanceIdentifier: ourpostgres
      DBName: "database"
      AllocatedStorage: "5"
      DBInstanceClass: db.t3.micro
      Engine: postgres
      VPCSecurityGroups:
        - !Ref SecurityGroup
      DBSubnetGroupName: !Ref DBSubnetGroup
      PubliclyAccessible: true
      MasterUsername: myusername
      MasterUserPassword: mypassword

Outputs:
  DBInstanceEndpoint:
    Description: Endpoint to access the Postgres database
    Value: !GetAtt [DBInstance, Endpoint.Address]

After running this CloudFormation database instance starts successfully but I am still unable to login into the database from a local machine (using Sequel Pro as the viewer). I tried already set up VPC, Security Groups, Gateway and Su.nets but it still seems like I am missing something.

Can you help me to identify the issues in CloudFormation above?

Answer 1

The reason for your issue is that your su.nets are private .

While the CloudFormation template does create an Inte.net Gateway and attaches it to the VPC, the two su.nets are using the default Route Table , which does not contain a route to the Inte.net Gateway. Therefore, the su.nets are effectively private su.nets .

You would need to update the template to:

• Create a Route Table
• Route traffic for 0.0.0.0/0 to the Inte.net Gateway
• Associate the Route Table to both of the su.nets

As an example, here's some code that I grabbed from Building a VPC with CloudFormation - Part 1 :

  # Some route tables for our subnets:
  PublicRouteTable:
    Type: AWS::EC2::RouteTable
    Properties:
      VpcId: !Ref VPC
      Tags:
      - Key: Name
        Value: Public
  PublicRoute1:   # Public route table has direct routing to IGW:
    Type: AWS::EC2::Route
    DependsOn: AttachGateway
    Properties:
      RouteTableId: !Ref PublicRouteTable
      DestinationCidrBlock: 0.0.0.0/0
      GatewayId: !Ref InternetGateway  

You would need something similar to that.