Creating Terraform module for AWS VPC creation

What is terraform module ?

A module can be any folder with a main.tf file in it, yes, that is the only required file for a module to be usable, but the recommendation is that you also put a README.md file with a description of the module if it’s intended to be used by people if it’s a sub-module it’s not necessary, also you will need a file called variables.tf and other outputs.tf of course if it’s a big module that cannot be split into sub-modules you can split those files for convenience or readability, variables should have descriptions so the tooling can show you what are they for, you can read more about the basics for a module here.

Setup terraform (Amazon Linux)

Get the latest release version.

TERRAFORM_VER=`curl -s https://api.github.com/repos/hashicorp/terraform/releases/latest |  grep tag_name | cut -d: -f2 | tr -d \"\,\v | awk '{$1=$1};1'`

To download the latest release of Terraform on Amazon Linux 2, run the command:

wget https://releases.hashicorp.com/terraform/${TERRAFORM_VER}/terraform_${TERRAFORM_VER}_linux_amd64.zip

Extract the file.

sudo yum -y install unzip
unzip terraform_${TERRAFORM_VER}_linux_amd64.zip

Move the binary file to the /usr/local/bin directory:

sudo mv terraform /usr/local/bin/

My Project

I have created a module which launches Elasticache which includes the following resources:

• AWS ELASTICACHE CLUSTER
• AWS ELASTICACHE GLOBAL REPLICATION GROUP
• AWS ELASTICACHE PARAMETER GROUP
• AWS ELASTICACHE REPLICATION GROUP
• AWS ELASTICACHE SECURITY GROUP
• AWS ELASTICACHE SUBNET GROUP
• AWS ELASTICACHE USER
• AWS ELASTICACHE USER GROUP

Let’s start with the main.tf that will call our module, It contains some required variables which is already defined in source path. Whatever resources you want to create you just need to set it’s value as true then also pass the required parameters for it from source path of module.

module "elasticache-example" {                 
  source                           = "github.com/vinodhakumara2681997/elasticache-module?ref=v0.1"
 
  name                             = "elasticache"
  cluster_create                   =  false 
  global_replication_group_create  =  false
  parameter_group_create           =  false
  replication_group_create         =  false
  security_group_create            =  false
  subnet_group_create              =  false
  user_create                      =  false
  user_group_create                =  false
  
}

Of course, you should always define your variables in a separate file that contains all the values defined in the source URL.

variable.tf

# PARAMETERS
# These variables have defaults, but may be overridden.

variable "elasticache_enabled" {
  description = "Enabling Elasticache service"
  type        = bool
  default     = true
}

variable "cluster_create" {
  description = ""
  type        = bool
  default     = false
}

variable "global_replication_group_create" {
  description = ""
  type        = bool
  default     = false
}

variable "parameter_group_create" {
  description = ""
  type        = bool
  default     = false
}

variable "replication_group_create" {
  description = ""
  type        = bool
  default     = false
}

variable "security_group_create" {
  description = ""
  type        = bool
  default     = false
}

variable "subnet_group_create" {
  description = ""
  type        = bool
  default     = false
}

variable "user_create" {
  description = ""
  type        = bool
  default     = false
}

variable "user_group_create" {
  description = ""
  type        = bool
  default     = false
}

#  AWS ELASTICACHE CLUSTER 
variable "cluster_cluster_id" {
  description  = "(Required) Group identifier. ElastiCache converts this name to lowercase. Changing this value will re-create the resource."
  type         = string    
  default      = null
}
 
variable "cluster_engine" {
  description  = " (Required) unless replication_group_id is provided) Name of the cache engine to be used for this cache cluster. Valid values are memcached or redis."
  type         = string
  default      = null
}

variable "cluster_node_type" {
  description  = "(Required unless replication_group_id is provided) The instance class used. See AWS documentation for information on supported node types for Redis and guidance on selecting node types for Redis."
  type         = string 
  default      = null
}

variable "cluster_num_cache_nodes" {
  description  = "(Required unless replication_group_id is provided) The initial number of cache nodes that the cache cluster will have. For Redis, this value must be 1. For Memcached, this value must be between 1 and 40."
  type         = number
  default      = null
}

variable "cluster_parameter_group_name" {
  description  = "(Required unless replication_group_id is provided) The name of the parameter group to associate with this cache cluster."
  type         = string
  default      = null
}

variable "cluster_port" {
  description  = ""
  type         = number     
  default      = null
}

variable "cluster_apply_immediately" {
  description  = " (Optional) Whether any database modifications are applied immediately, or during the next maintenance window. Default is false."
  type         = bool
  default      = null
}

variable "cluster_availability_zone" {
  description  = " (Optional) Availability Zone for the cache cluster. If you want to create cache nodes in multi-az, use preferred_availability_zones instead. Default: System chosen Availability Zone. Changing this value will re-create the resource."
  type         = string
  default      = null
}

variable "cluster_az_mode" {
  description  = "(Optional, Memcached only) Whether the nodes in this Memcached node group are created in a single Availability Zone or created across multiple Availability Zones in the cluster's region"
  type         = string
  default      = null
}

variable "cluster_engine_version" {
  description  = "(Optional) Version number of the cache engine to be used."
  type         = number
  default      = null
}

variable "cluster_final_snapshot_identifier" {
  description  = "(Optional, Redis only) Name of your final cluster snapshot. If omitted, no final snapshot will be made."
  type         = string
  default      = null
}

variable "cluster_maintenance_window" {
  description  = "(Optional) Specifies the weekly time range for when maintenance on the cache cluster is performed. The format is ddd:hh24:mi-ddd:hh24:mi"
  type         = any
  default      = null
}

variable "cluster_notification_topic_arn" {
  description  = "(Optional) ARN of an SNS topic to send ElastiCache notifications to."
  type         = string
  default      = null
}

variable "cluster_preferred_availability_zones" {
  description  = "(Optional, Memcached only) List of the Availability Zones in which cache nodes are created."
  type         = list(string)
  default      = []
}

variable "cluster_replication_group_id" {
  description  = "(Optional) ID of the replication group to which this cluster should belong. "
  type         = string
  default      = null
}

variable "cluster_security_group_ids" {
  description  = " (Optional, VPC only) One or more VPC security groups associated with the cache cluster"
  type         = list(string)
  default      = null
}

variable "cluster_security_group_names" {
  description  = "(Optional, EC2 Classic only) List of security group names to associate with this cache cluster."
  type         = list(string)
  default      = []
}

variable "cluster_snapshot_arns" {
  description  = "(Optional, Redis only) Single-element string list containing an Amazon Resource Name (ARN) of a Redis RDB snapshot file stored in Amazon S3."
  type         = list(string)
  default      = null
}

variable "cluster_snapshot_name" {
  description  = "(Optional, Redis only) Name of a snapshot from which to restore data into the new node group. Changing snapshot_name forces a new resource."
  type         = string
  default      = null
}

variable "cluster_snapshot_retention_limit" {
  description  = "(Optional, Redis only) Number of days for which ElastiCache will retain automatic cache cluster snapshots before deleting them. "
  type         = number
  default      = null
}

variable "cluster_snapshot_window" {
  description  = "(Optional, Redis only) Daily time range (in UTC) during which ElastiCache will begin taking a daily snapshot of your cache cluster."
  type         = any
  default      = null
}

variable "cluster_subnet_group_name" {
  description  = "(Optional, VPC only) Name of the subnet group to be used for the cache cluster"
  type         = string
  default      = null
}

#  AWS ELASTICACHE GLOBAL REPLICATION GROUP 

variable "global_replication_group_global_replication_group_id_suffix" {
  description  = "(Required) The suffix name of a Global Datastore."
  type         = string
  default      = null
}

variable "global_replication_group_primary_replication_group_id" {
  description  = "(Required) The ID of the primary cluster that accepts writes and will replicate updates to the secondary cluster."
  type         = string
  default      = null
}

variable "global_replication_group_global_replication_group_description" {
  description  = "(Optional) A user-created description for the global replication group."
  type         = string
  default      = null
}

#  AWS ELASTICACHE PARAMETER GROUP  
variable "parameter_group_name" {
  description  = "(Required) The name of the ElastiCache parameter group."
  type         = string
  default      = null
}

variable "parameter_group_family" {
  description  = "(Required) The family of the ElastiCache parameter group."
  type         = string
  default      = null
}

variable "parameter_group_description" {
  description  = "(Optional) The description of the ElastiCache parameter group."
  type         = string
  default      = null
}

variable "parameter_group" {
  description  = "(Optional) A list of ElastiCache parameters to apply."
  type = list(object({
    parameter_group_name = string
    parameter_group_value = string
    }))
  default      = []
}

#  AWS ELASTICACHE REPLICATION GROUP  

variable "replication_group_automatic_failover_enabled" {
  description  = " (Optional) Specifies whether a read-only replica will be automatically promoted to read/write primary if the existing primary fails. If enabled, number_cache_clusters must be greater than 1"
  type         = bool
  default      = null
}

variable "replication_group_availability_zones" {
  description  = "(Optional) A list of EC2 availability zones in which the replication group's cache clusters will be created. The order of the availability zones in the list is not important."
  type         = list(string)
  default      = null
}

variable "replication_group_replication_group_id" {
  description  = "(Required) The replication group identifier. This parameter is stored as a lowercase string."
  type         = string
  default      =  null
}

variable "replication_group_replication_group_description" {
  description  = "(Required) A user-created description for the replication group."
  type         = string
  default      = null
}

variable "replication_group_node_type" {
  description  = "(Optional) The instance class to be used."
  type         = string
  default      = null
}

variable "replication_group_number_cache_clusters" {
  description  = "(Optional) The number of cache clusters (primary and replicas) this replication group will have."
  type         = number
  default      = null
}

variable "replication_group_parameter_group_name" {
  description  = "(Optional) The name of the parameter group to associate with this replication group"
  type         = string
  default      = null
}

variable "replication_group_port" {
  description  = "(Optional) The port number on which each of the cache nodes will accept connections"
  type         = number
  default      = null
}

variable "replication_group_apply_immediately" {
  description  = "(Optional) Specifies whether any modifications are applied immediately, or during the next maintenance window."
  type         = bool
  default      = null
}

variable "replication_group_at_rest_encryption_enabled" {
  description  = "(Optional) Whether to enable encryption at rest."
  type         = bool
  default      = null
}

variable "replication_group_auth_token" {
  description  = " (Optional) The password used to access a password protected server."
  type         = string
  default      = null
}

variable "replication_group_auto_minor_version_upgrade" {
  description  = "(Optional) Specifies whether a minor engine upgrades will be applied automatically to the underlying Cache Cluster instances during the maintenance window"
  type         = bool
  default      = null
}

variable "cluster_mode_replicas_per_node_group" {
  description  = " (Required) Number of replica nodes in each node group. Valid values are 0 to 5."
  type         = number
  default      = null
}

variable "cluster_mode_num_node_groups" {
  description  = "(Optional) Number of node groups (shards) for this Redis replication group. "
  type         = number
  default      = null
}

variable "replication_group_data_tiering_enabled" {
  description  = "(Optional) Enables data tiering. Data tiering is only supported for replication groups using the r6gd node type. "
  type         = bool
  default      = null
}

variable "replication_group_engine" {
  description  = "(Optional) The name of the cache engine to be used for the clusters in this replication group"
  type         = string
  default      = null
}

variable "replication_group_engine_version" {
  description  = " (Optional) The version number of the cache engine to be used for the cache clusters in this replication group"
  type         = string
  default      = null
}

variable "replication_group_final_snapshot_identifier" {
  description  = "(Optional) The name of your final node group (shard) snapshot."
  type         = string
  default      = null
}

variable "replication_group_global_replication_group_id" {
  description  = " (Optional) The ID of the global replication group to which this replication group should belong."
  type         = string
  default      = null
}

variable "replication_group_kms_key_id" {
  description  = "(Optional) The ARN of the key that you wish to use if encrypting at rest."
  type         = string
  default      = null
}
variable "replication_group_maintenance_window" {
  description  = "(Optional) Specifies the weekly time range for when maintenance on the cache cluster is performed"
  type         = any
  default      = null
}

variable "replication_group_multi_az_enabled" {
  description  = "(Optional) Specifies whether to enable Multi-AZ Support for the replication group"
  type         = bool
  default      = null
}

variable "replication_group_notification_topic_arn" {
  description  = "(Optional) An Amazon Resource Name (ARN) of an SNS topic to send ElastiCache notifications to"
  type         = string
  default      = null
}

variable "replication_group_security_group_ids" {
  description  = "(Optional) One or more Amazon VPC security groups associated with this replication group. Use this parameter only when you are creating a replication group in an Amazon Virtual Private Cloud"
  type         = list(string)
  default      = null
}

variable "replication_group_security_group_names" {
  description  = " (Optional) A list of cache security group names to associate with this replication group."
  type         = list(string)
  default      = null
}

variable "replication_group_snapshot_arns" {
  description  = "(Optional) A list of Amazon Resource Names (ARNs) that identify Redis RDB snapshot files stored in Amazon S3. "
  type         = list(string)
  default      = []
}

variable "replication_group_snapshot_name" {
  description  = "(Optional) The name of a snapshot from which to restore data into the new node group"
  type         = string
  default      = null
}
variable "replication_group_snapshot_retention_limit" {
  description  = "(Optional, Redis only) The number of days for which ElastiCache will retain automatic cache cluster snapshots before deleting them"
  type         = number
  default      = null
}

variable "replication_group_snapshot_window" {
  description  = "(Optional, Redis only) The daily time range (in UTC) during which ElastiCache will begin taking a daily snapshot of your cache cluster. "
  type         = any
  default      = null
}

variable "replication_group_subnet_group_name" {
  description  = "(Optional) The name of the cache subnet group to be used for the replication group."
  type         = string
  default      = null
}

variable "replication_group_transit_encryption_enabled" {
  description  = "(Optional) Whether to enable encryption in transit."
  type         = bool
  default      = null
}

#  AWS ELASTICACHE SECURITY GROUP 

variable "security_group_name" {
  description  = "(Required) Name for the cache security group. This value is stored as a lowercase string."
  type         = string
  default      =  null
}

variable "security_group_security_group_names" {
  description  = "(Required) List of EC2 security group names to be authorized for ingress to the cache security group"
  type         = list(string)
  default      = []
}

variable "security_group_description" {
  description  = " (Optional) description for the cache security group. Defaults to."
  type         = string
  default      = null
}

#  AWS ELASTICACHE SUBNET GROUP  

variable "subnet_group_name" {
  description  = " (Required) Name for the cache subnet group. Elasticache converts this name to lowercase."
  type         = string
  default      = null
}

variable "subnet_group_subnet_ids" {
  description  = "(Required) List of VPC Subnet IDs for the cache subnet group"
  type         = list(string)
  default      = []
}

variable "subnet_group_description" {
  description  = "(Optional) Description for the cache subnet group. "
  type         = string
  default      = null
}

#  AWS ELASTICACHE USER 

variable "user_user_id" {
  description  = "(Required) The ID of the user."
  type         = string
  default      = null
}

variable "user_user_name" {
  description  = "(Required) The username of the user."
  type         = string
  default      = null
}

variable "user_access_string" {
  description  = " (Required) Access permissions string used for this user."
  type         = any
  default      = null
}

variable "user_engine" {
  description  = "(Required) The current supported value is REDIS."
  type         = string
  default      = "REDIS"
}

variable "user_passwords" {
  description  = " (Optional) Passwords used for this user. You can create up to two passwords for each user."
  type         = list(string)
  default      = null
}

variable "user_no_password_required" {
  description  = "(Optional) Indicates a password is not required for this user."
  type         = any
  default      = null
}

#  AWS ELASTICACHE USER GROUP  
variable "user_group_engine" {
  description  = "(Required) The current supported value is REDIS."
  type         = string
  default      = "REDIS"
}

variable "user_group_user_group_id" {
  description  = "(Required) The ID of the user group."
  type         = string
  default      = null
}

variable "user_group_user_ids" {
  description  = "(Optional) The list of user IDs that belong to the user group."
  type         = list(string)
  default      = []
}