How-to setup a HA/DR database in AWS? [9 - Generate a random value]

In this part (and the last part of the serie), we will see how to generate a random value.

Really useful to generate unique names for a snapshot for example, you will see that there are multiple definitions available, depending on what you need.

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Random Id

resource "random_id" "rdm_id" {
  byte_length = 8
}

Declared as this, it will generate for you an 8 bytes long id which can be retrieve in :

• base64 : random_id.rdm_id.id => MDc3NDA2OGE5YTNhMjc5MQ==
• decimal digits : random_id.rdm_id.dec => 537061447926687633
• hexadecimal digits : random_id.rdm_id.hex => 0774068a9a3a2791

But it you are doing it like this, the random_id will always be the same!

So to be sure the value change when something append, you can use the keepers parameter.

With this, you can say "if the parameter X and Y change, so the random value must change too".

In this example the random value will change each time the arn of the global cluster example will change.

resource "random_id" "rdm_id" {
  byte_length = 8

  keepers = {
    first = aws_rds_global_cluster.example.arn
  }
}

And if you want this value to change each time the script is executed, use a timestamp :

resource "random_id" "rdm_id" {
  byte_length = 8

  keepers = {
    first = timestamp()
  }
}

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Other random possibilities

Following the same pattern, Terraform let you to generate random

• integer

resource "random_integer" "priority" {
  min = 1
  max = 50000
}

• password

resource "random_password" "password" {
  length           = 16
  special          = true
  override_special = "_%@"
}

• string

resource "random_string" "random" {
  length           = 16
  special          = true
  override_special = "/@£$"
}

• UUID

resource "random_uuid" "test" {
}

• A shuffled sublist

resource "random_shuffle" "az" {
  input        = ["us-west-1a", "us-west-1c", "us-west-1d", "us-west-1e"]
  result_count = 2
}

Here you will retrieve a sublist of the input list, with only 2 items.

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Links

• Terraform doc random_id : https://registry.terraform.io/providers/hashicorp/random/latest/docs/resources/id
• Terraform doc random_integer : https://registry.terraform.io/providers/hashicorp/random/latest/docs/resources/integer
• Terraform doc random_password : https://registry.terraform.io/providers/hashicorp/random/latest/docs/resources/password
• Terraform doc random_shuffle : https://registry.terraform.io/providers/hashicorp/random/latest/docs/resources/shuffle
• Terraform doc random_string : https://registry.terraform.io/providers/hashicorp/random/latest/docs/resources/string
• Terraform doc random_uuid : https://registry.terraform.io/providers/hashicorp/random/latest/docs/resources/uuid

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I hope it will help you and you liked this serie! 🍺

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Serie link

• 1 - Start : https://dev.to/adaendra/how-to-setup-a-hadr-database-in-aws-1-1ko7
• 2 - Definitions : https://dev.to/adaendra/how-to-setup-a-hadr-database-in-aws-2-definitions-93p
• 3 - Simple database : https://dev.to/adaendra/how-to-setup-a-hadr-database-in-aws-3-simple-database-a9o
• 4 - HA Database : https://dev.to/adaendra/how-to-setup-a-hadr-database-in-aws-4-ha-database-4kek
• 5 - DR database : https://dev.to/adaendra/how-to-setup-a-hadr-database-in-aws-5-dr-database-278b
• 6 - Create from snapshot : https://dev.to/adaendra/how-to-setup-a-hadr-database-in-aws-6-create-from-snapshot-2mbf
• 7 - Dynamic Terraform backend definition : https://dev.to/adaendra/how-to-setup-a-hadr-database-in-aws-7-dynamic-terraform-backend-definition-3aga
• 8 - Multiple instances in multiple regions : https://dev.to/adaendra/how-to-setup-a-hadr-database-in-aws-8-multiple-instances-in-multiple-regions-210d
• 9 - Generate a random value : https://dev.to/adaendra/how-to-setup-a-hadr-database-in-aws-9-generate-a-random-value-5g8a

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