Part 3 - Create an RDS DB instance.

By Ben Outram / 2018-06-15

Create a new file rds.tf which we will add all of our RDS configuration to.

Create subnets in each availability zone for RDS, each with address blocks within the VPC:

resource "aws_subnet" "rds" {
  count                   = "${length(data.aws_availability_zones.available.names)}"
  vpc_id                  = "${aws_vpc.vpc.id}"
  cidr_block              = "10.0.${length(data.aws_availability_zones.available.names) + count.index}.0/24"
  map_public_ip_on_launch = true
  availability_zone       = "${element(data.aws_availability_zones.available.names, count.index)}"
  tags {
    Name = "rds-${element(data.aws_availability_zones.available.names, count.index)}"
  }
}

Create a subnet group with all of our RDS subnets. The group will be applied to the database instance:

resource "aws_db_subnet_group" "default" {
  name        = "${var.rds_instance_identifier}-subnet-group"
  description = "Terraform example RDS subnet group"
  subnet_ids  = ["${aws_subnet.rds.*.id}"]
}

Create a RDS security group in the VPC which our database will belong to:

resource "aws_security_group" "rds" {
  name        = "terraform_rds_security_group"
  description = "Terraform example RDS MySQL server"
  vpc_id      = "${aws_vpc.vpc.id}"
  # Keep the instance private by only allowing traffic from the web server.
  ingress {
    from_port       = 3306
    to_port         = 3306
    protocol        = "tcp"
    security_groups = ["${aws_security_group.default.id}"]
  }
  # Allow all outbound traffic.
  egress {
    from_port   = 0
    to_port     = 0
    protocol    = "-1"
    cidr_blocks = ["0.0.0.0/0"]
  }
  tags {
    Name = "terraform-example-rds-security-group"
  }
}

Create a RDS MySQL database instance in the VPC with our RDS subnet group and security group:

resource "aws_db_instance" "default" {
  identifier                = "${var.rds_instance_identifier}"
  allocated_storage         = 5
  engine                    = "mysql"
  engine_version            = "5.6.35"
  instance_class            = "db.t2.micro"
  name                      = "${var.database_name}"
  username                  = "${var.database_user}"
  password                  = "${var.database_password}"
  db_subnet_group_name      = "${aws_db_subnet_group.default.id}"
  vpc_security_group_ids    = ["${aws_security_group.rds.id}"]
  skip_final_snapshot       = true
  final_snapshot_identifier = "Ignore"
}

Manage the MySQL configuration by creating a parameter group:

resource "aws_db_parameter_group" "default" {
  name        = "${var.rds_instance_identifier}-param-group"
  description = "Terraform example parameter group for mysql5.6"
  family      = "mysql5.6"
  parameter {
    name  = "character_set_server"
    value = "utf8"
  }
  parameter {
    name  = "character_set_client"
    value = "utf8"
  }
}

Finally let's define new variables that we have introduced in configuration blocks during this section.

Add the following to variables.tf:

variable "rds_instance_identifier" {}
variable "database_name" {}
variable "database_password" {}
variable "database_user" {}

Assign the variable values in terraform.tfvars, excluding the password variable:

rds_instance_identifier = "terraform-mysql"
database_name = "terraform_test_db"
database_user = "terraform"

Assign the password variable in our user.tfvars file which should be ignored from version control. Give this property a random password. It will be the MySQL password for the Terraform user account used by the web application.

database_password = "some-random-password"

We can now try another plan:

$ terraform plan -var-file="user.tfvars"

Terraform will perform the following actions:

  + aws_db_instance.default
  + aws_db_parameter_group.default
  + aws_db_subnet_group.default
  + aws_security_group.rds
  + aws_subnet.rds[0]
  + aws_subnet.rds[1]
  + aws_subnet.rds[2]

Plan: 7 to add, 0 to change, 0 to destroy.

It's time to review the plan and apply our changes again before we move on!

$ terraform apply -var-file="user.tfvars"

Apply complete! Resources: 7 added, 0 changed, 0 destroyed.

You can find all the source code for this part of the lab here in GitHub.

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Part 2 - Create the VPC

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Part 4 - Create the application load balancer

Part 3 - Create an RDS DB instance.

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