Add Optional `elasticache_subnet_group` (#34)

* [issue-30] Optional elasticache_subnet_group ID

Add optional variable for the Elasticache subnet group ID so we can 
create the replication group in an already existing subnet group.

* Update main.tf
Co-Authored-By: aknysh <aknysh@users.noreply.github.com>

* Update variables.tf
Co-Authored-By: aknysh <aknysh@users.noreply.github.com>

* Update variables.tf
Co-Authored-By: aknysh <aknysh@users.noreply.github.com>

* Update main.tf
Co-Authored-By: aknysh <aknysh@users.noreply.github.com>

* Address comments, update LICENSE, update descriptions, update `README`

* Update example

* Update README

.travis.yml

@@ -9,8 +9,8 @@ install:
   - make init
 
 script:
-  - make terraform:install
-  - make terraform:get-plugins
-  - make terraform:get-modules
-  - make terraform:lint
-  - make terraform:validate
+  - make terraform/install
+  - make terraform/get-plugins
+  - make terraform/get-modules
+  - make terraform/lint
+  - make terraform/validate

LICENSE

@@ -187,7 +187,7 @@
       same "printed page" as the copyright notice for easier
       identification within third-party archives.
 
-   Copyright 2017 Cloud Posse, LLC
+   Copyright 2017-2019 Cloud Posse, LLC
 
    Licensed under the Apache License, Version 2.0 (the "License");
    you may not use this file except in compliance with the License.

README.md

@@ -42,7 +42,11 @@ We literally have [*hundreds of terraform modules*][terraform_modules] that are
 
 ## Usage
 
-Include this repository as a module in your existing terraform code:
+
+**IMPORTANT:** The `master` branch is used in `source` just as an example. In your code, do not pin to `master` because there may be breaking changes between releases.
+Instead pin to the release tag (e.g. `?ref=tags/x.y.z`) of one of our [latest releases](https://github.com/cloudposse/terraform-aws-elasticache-redis/releases).
+
+
 
 ```hcl
 // Generate a random string for auth token, no special chars
@@ -113,6 +117,7 @@ Available targets:
 | availability_zones | Availability zone ids | list | `<list>` | no |
 | cluster_size | Count of nodes in cluster | string | `1` | no |
 | delimiter | Delimiter between `name`, `namespace`, `stage` and `attributes` | string | `-` | no |
+| elasticache_subnet_group_name | Subnet group name for the ElastiCache instance | string | `` | no |
 | enabled | Set to false to prevent the module from creating any resources | string | `true` | no |
 | engine_version | Redis engine version | string | `4.0.10` | no |
 | family | Redis family | string | `redis4.0` | no |
@@ -127,10 +132,10 @@ Available targets:
 | replication_group_id | Replication group ID with the following constraints:  A name must contain from 1 to 20 alphanumeric characters or hyphens.   The first character must be a letter.   A name cannot end with a hyphen or contain two consecutive hyphens. | string | `` | no |
 | security_groups | AWS security group ids | list | `<list>` | no |
 | stage | Stage | string | `default` | no |
-| subnets | AWS subnet ids | list | `<list>` | no |
+| subnets | AWS subnet IDs | list | `<list>` | no |
 | tags | Additional tags (_e.g._ map("BusinessUnit","ABC") | map | `<map>` | no |
 | transit_encryption_enabled | Enable TLS | string | `true` | no |
-| vpc_id | AWS VPC id | string | `REQUIRED` | no |
+| vpc_id | AWS VPC id | string | - | yes |
 | zone_id | Route53 DNS Zone id | string | `` | no |
 
 ## Outputs
@@ -138,9 +143,9 @@ Available targets:
 | Name | Description |
 |------|-------------|
 | host | Redis host |
-| id | Redis cluster id |
+| id | Redis cluster ID |
 | port | Redis port |
-| security_group_id | Security group id |
+| security_group_id | Security group ID |
 
 
 
@@ -207,7 +212,7 @@ In general, PRs are welcome. We follow the typical "fork-and-pull" Git workflow.
 
 ## Copyright
 
-Copyright © 2017-2018 [Cloud Posse, LLC](https://cpco.io/copyright)
+Copyright © 2017-2019 [Cloud Posse, LLC](https://cpco.io/copyright)
 
 
 

README.yaml

----
-#
-# This is the canonical configuration for the `README.md`
-# Run `make readme` to rebuild the `README.md`
-#
-
-# Name of this project
-name: terraform-aws-elasticache-redis
-
-# Tags of this project
-tags:
-  - aws
-  - terraform
-  - terraform-modules
-  - databases
-  - redis
-  - elasticache
-  - cache
-
-# Categories of this project
-categories:
-  - terraform-modules/databases
-
-# Logo for this project
-#logo: docs/logo.png
-
-# License of this project
-license: "APACHE2"
-
-# Canonical GitHub repo
-github_repo: cloudposse/terraform-aws-elasticache-redis
-
-# Badges to display
-badges:
-  - name: "Build Status"
-    image: "https://travis-ci.org/cloudposse/terraform-aws-elasticache-redis.svg?branch=master"
-    url: "https://travis-ci.org/cloudposse/terraform-aws-elasticache-redis"
-  - name: "Latest Release"
-    image: "https://img.shields.io/github/release/cloudposse/terraform-aws-elasticache-redis.svg"
-    url: "https://github.com/cloudposse/terraform-aws-elastic-beanstalk-environment/releases/latest"
-  - name: "Slack Community"
-    image: "https://slack.cloudposse.com/badge.svg"
-    url: "https://slack.cloudposse.com"
-
-# Short description of this project
-description: |-
-  Terraform module to provision an [`ElastiCache`](https://aws.amazon.com/elasticache/) Redis Cluster
-
-# How to use this project
-usage: |-
-  Include this repository as a module in your existing terraform code:
-
-  ```hcl
-  // Generate a random string for auth token, no special chars
-  resource "random_string" "auth_token" {
-    length = 64
-    special = false
-  }
-
-  module "example_redis" {
-    source          = "git::https://github.com/cloudposse/terraform-aws-elasticache-redis.git?ref=master"
-    namespace       = "general"
-    name            = "redis"
-    stage           = "prod"
-    zone_id         = "${var.route53_zone_id}"
-    security_groups = ["${var.security_group_id}"]
-
-    auth_token                   = "${random_string.auth_token.result}"
-    vpc_id                       = "${var.vpc_id}"
-    subnets                      = "${var.private_subnets}"
-    maintenance_window           = "wed:03:00-wed:04:00"
-    cluster_size                 = "2"
-    instance_type                = "cache.t2.micro"
-    engine_version               = "4.0.10"
-    alarm_cpu_threshold_percent  = "${var.cache_alarm_cpu_threshold_percent}"
-    alarm_memory_threshold_bytes = "${var.cache_alarm_memory_threshold_bytes}"
-    apply_immediately            = "true"
-    availability_zones           = "${var.availability_zones}"
-
-    automatic_failover = "false"
-  }
-
-  output "auth_token" {
-    value = "${random_string.auth_token.result}"
-  }
-  ```
-
-examples: |-
-  Review the [complete example](examples/simple) to see how to use this module.
-
-include:
-  - "docs/targets.md"
-  - "docs/terraform.md"
-
-# Contributors to this project
-contributors:
-  - name: "Erik Osterman"
-    github: "osterman"
-  - name: "Igor Rodionov"
-    github: "goruha"
-  - name: "Andriy Knysh"
-    github: "aknysh"
-  - name: "Daren Desjardins"
-    github: "darend"
-  - name: "Max Moon"
-    github: "MoonMoon1919"
-  - name: "Christopher Riley"
-    github: "christopherriley"
+---
+#
+# This is the canonical configuration for the `README.md`
+# Run `make readme` to rebuild the `README.md`
+#
+
+# Name of this project
+name: terraform-aws-elasticache-redis
+
+# Tags of this project
+tags:
+  - aws
+  - terraform
+  - terraform-modules
+  - databases
+  - redis
+  - elasticache
+  - cache
+
+# Categories of this project
+categories:
+  - terraform-modules/databases
+
+# Logo for this project
+#logo: docs/logo.png
+
+# License of this project
+license: "APACHE2"
+
+# Canonical GitHub repo
+github_repo: cloudposse/terraform-aws-elasticache-redis
+
+# Badges to display
+badges:
+  - name: "Build Status"
+    image: "https://travis-ci.org/cloudposse/terraform-aws-elasticache-redis.svg?branch=master"
+    url: "https://travis-ci.org/cloudposse/terraform-aws-elasticache-redis"
+  - name: "Latest Release"
+    image: "https://img.shields.io/github/release/cloudposse/terraform-aws-elasticache-redis.svg"
+    url: "https://github.com/cloudposse/terraform-aws-elastic-beanstalk-environment/releases/latest"
+  - name: "Slack Community"
+    image: "https://slack.cloudposse.com/badge.svg"
+    url: "https://slack.cloudposse.com"
+
+# Short description of this project
+description: |-
+  Terraform module to provision an [`ElastiCache`](https://aws.amazon.com/elasticache/) Redis Cluster
+
+# How to use this project
+usage: |-
+
+  ```hcl
+  // Generate a random string for auth token, no special chars
+  resource "random_string" "auth_token" {
+    length = 64
+    special = false
+  }
+
+  module "example_redis" {
+    source          = "git::https://github.com/cloudposse/terraform-aws-elasticache-redis.git?ref=master"
+    namespace       = "general"
+    name            = "redis"
+    stage           = "prod"
+    zone_id         = "${var.route53_zone_id}"
+    security_groups = ["${var.security_group_id}"]
+
+    auth_token                   = "${random_string.auth_token.result}"
+    vpc_id                       = "${var.vpc_id}"
+    subnets                      = "${var.private_subnets}"
+    maintenance_window           = "wed:03:00-wed:04:00"
+    cluster_size                 = "2"
+    instance_type                = "cache.t2.micro"
+    engine_version               = "4.0.10"
+    alarm_cpu_threshold_percent  = "${var.cache_alarm_cpu_threshold_percent}"
+    alarm_memory_threshold_bytes = "${var.cache_alarm_memory_threshold_bytes}"
+    apply_immediately            = "true"
+    availability_zones           = "${var.availability_zones}"
+
+    automatic_failover = "false"
+  }
+
+  output "auth_token" {
+    value = "${random_string.auth_token.result}"
+  }
+  ```
+
+examples: |-
+  Review the [complete example](examples/simple) to see how to use this module.
+
+include:
+  - "docs/targets.md"
+  - "docs/terraform.md"
+
+# Contributors to this project
+contributors:
+  - name: "Erik Osterman"
+    github: "osterman"
+  - name: "Igor Rodionov"
+    github: "goruha"
+  - name: "Andriy Knysh"
+    github: "aknysh"
+  - name: "Daren Desjardins"
+    github: "darend"
+  - name: "Max Moon"
+    github: "MoonMoon1919"
+  - name: "Christopher Riley"
+    github: "christopherriley"

docs/terraform.md

@@ -13,6 +13,7 @@
 | availability_zones | Availability zone ids | list | `<list>` | no |
 | cluster_size | Count of nodes in cluster | string | `1` | no |
 | delimiter | Delimiter between `name`, `namespace`, `stage` and `attributes` | string | `-` | no |
+| elasticache_subnet_group_name | Subnet group name for the ElastiCache instance | string | `` | no |
 | enabled | Set to false to prevent the module from creating any resources | string | `true` | no |
 | engine_version | Redis engine version | string | `4.0.10` | no |
 | family | Redis family | string | `redis4.0` | no |
@@ -27,10 +28,10 @@
 | replication_group_id | Replication group ID with the following constraints:  A name must contain from 1 to 20 alphanumeric characters or hyphens.   The first character must be a letter.   A name cannot end with a hyphen or contain two consecutive hyphens. | string | `` | no |
 | security_groups | AWS security group ids | list | `<list>` | no |
 | stage | Stage | string | `default` | no |
-| subnets | AWS subnet ids | list | `<list>` | no |
+| subnets | AWS subnet IDs | list | `<list>` | no |
 | tags | Additional tags (_e.g._ map("BusinessUnit","ABC") | map | `<map>` | no |
 | transit_encryption_enabled | Enable TLS | string | `true` | no |
-| vpc_id | AWS VPC id | string | `REQUIRED` | no |
+| vpc_id | AWS VPC id | string | - | yes |
 | zone_id | Route53 DNS Zone id | string | `` | no |
 
 ## Outputs
@@ -38,7 +39,7 @@
 | Name | Description |
 |------|-------------|
 | host | Redis host |
-| id | Redis cluster id |
+| id | Redis cluster ID |
 | port | Redis port |
-| security_group_id | Security group id |
+| security_group_id | Security group ID |
 

examples/simple/terraform.tfvars

 namespace = "eg"
+
 name = "redis"
+
 stage = "testing"
+
 zone_id = "Z3SO0TKDDQ0RGG"
+
 region = "us-west-2"
+
 availability_zones = ["us-west-2a", "us-west-2b"]

main.tf

@@ -35,8 +35,12 @@ resource "aws_security_group" "default" {
   tags = "${module.label.tags}"
 }
 
+locals {
+  elasticache_subnet_group_name = "${var.elasticache_subnet_group_name != "" ? var.elasticache_subnet_group_name : join("", aws_elasticache_subnet_group.default.*.name) }"
+}
+
 resource "aws_elasticache_subnet_group" "default" {
-  count      = "${var.enabled == "true" ? 1 : 0}"
+  count      = "${var.enabled == "true" && var.elasticache_subnet_group_name == "" && length(var.subnets) > 0 ? 1 : 0}"
   name       = "${module.label.id}"
   subnet_ids = ["${var.subnets}"]
 }
@@ -60,7 +64,7 @@ resource "aws_elasticache_replication_group" "default" {
   parameter_group_name          = "${aws_elasticache_parameter_group.default.name}"
   availability_zones            = ["${slice(var.availability_zones, 0, var.cluster_size)}"]
   automatic_failover_enabled    = "${var.automatic_failover}"
-  subnet_group_name             = "${aws_elasticache_subnet_group.default.name}"
+  subnet_group_name             = "${local.elasticache_subnet_group_name}"
   security_group_ids            = ["${aws_security_group.default.id}"]
   maintenance_window            = "${var.maintenance_window}"
   notification_topic_arn        = "${var.notification_topic_arn}"
@@ -119,7 +123,7 @@ resource "aws_cloudwatch_metric_alarm" "cache_memory" {
 }
 
 module "dns" {
-  source    = "git::https://github.com/cloudposse/terraform-aws-route53-cluster-hostname.git?ref=tags/0.2.1"
+  source    = "git::https://github.com/cloudposse/terraform-aws-route53-cluster-hostname.git?ref=tags/0.2.6"
   enabled   = "${var.enabled == "true" && length(var.zone_id) > 0 ? "true" : "false"}"
   namespace = "${var.namespace}"
   name      = "${var.name}"

output.tf

 output "id" {
   value       = "${join("", aws_elasticache_replication_group.default.*.id)}"
-  description = "Redis cluster id"
+  description = "Redis cluster ID"
 }
 
 output "security_group_id" {
   value       = "${join("", aws_security_group.default.*.id)}"
-  description = "Security group id"
+  description = "Security group ID"
 }
 
 output "port" {

variables.tf

@@ -25,16 +25,21 @@ variable "security_groups" {
 }
 
 variable "vpc_id" {
-  default     = "REQUIRED"
   description = "AWS VPC id"
 }
 
 variable "subnets" {
   type        = "list"
-  description = "AWS subnet ids"
+  description = "AWS subnet IDs"
   default     = []
 }
 
+variable "elasticache_subnet_group_name" {
+  type        = "string"
+  description = "Subnet group name for the ElastiCache instance"
+  default     = ""
+}
+
 variable "maintenance_window" {
   default     = "wed:03:00-wed:04:00"
   description = "Maintenance window"