BREAKING CHANGE: update module to include latest features and remove use of count for module count/for_each (#234)

Author: bryantbiggs

.github/workflows/pre-commit.yml

@@ -91,7 +91,7 @@ jobs:
       - name: Install pre-commit dependencies
         run: |
           pip install pre-commit
-          curl -Lo ./terraform-docs.tar.gz https://github.com/terraform-docs/terraform-docs/releases/download/v0.13.0/terraform-docs-v0.13.0-$(uname)-amd64.tar.gz && tar -xzf terraform-docs.tar.gz && chmod +x terraform-docs && sudo mv terraform-docs /usr/bin/
+          curl -Lo ./terraform-docs.tar.gz https://github.com/terraform-docs/terraform-docs/releases/download/v0.13.0/terraform-docs-v0.13.0-$(uname)-amd64.tar.gz && tar -xzf terraform-docs.tar.gz terraform-docs && chmod +x terraform-docs && sudo mv terraform-docs /usr/bin/
           curl -L "$(curl -s https://api.github.com/repos/terraform-linters/tflint/releases/latest | grep -o -E "https://.+?_linux_amd64.zip")" > tflint.zip && unzip tflint.zip && rm tflint.zip && sudo mv tflint /usr/bin/
       - name: Execute pre-commit
         # Run all pre-commit checks on max version supported

.pre-commit-config.yaml

@@ -21,6 +21,6 @@ repos:
           - '--args=--only=terraform_standard_module_structure'
           - '--args=--only=terraform_workspace_remote'
   - repo: git://github.com/pre-commit/pre-commit-hooks
-    rev: v3.4.0
+    rev: v4.0.1
     hooks:
       - id: check-merge-conflict

README.md

@@ -0,0 +1,123 @@
+# Upgrade from v2.x to v3.x
+
+If you have any questions regarding this upgrade process, please consult the `examples` directory:
+
+- [Complete](https://github.com/terraform-aws-modules/terraform-aws-ec2-instance/tree/master/examples/complete)
+- [Volume Attachment](https://github.com/terraform-aws-modules/terraform-aws-ec2-instance/tree/master/examples/volume-attachment)
+
+If you find a bug, please open an issue with supporting configuration to reproduce.
+
+## List of backwards incompatible changes
+
+- Terraform v0.13.1 is now minimum supported version to take advantage of `count` and `for_each` arguments at module level
+
+### Variable and output changes
+
+1. Removed variables:
+
+   - `instance_count`
+   - `subnet_ids` (only need to use `subnet_id` now)
+   - `private_ips` (only need to use `private_ip` now)
+   - `use_num_suffix`
+   - `num_suffix_format`
+
+2. Renamed variables:
+
+   - `tags` -> `tags_all`
+
+3. Removed outputs:
+
+   - `availability_zone`
+   - `placement_group`
+   - `key_name`
+   - `ipv6_addresses`
+   - `private_ip`
+   - `security_groups`
+   - `vpc_security_group_ids`
+   - `subnet_id`
+   - `credit_specification`
+   - `metadata_options`
+   - `root_block_device_volume_ids`
+   - `ebs_block_device_volume_ids`
+   - `volume_tags`
+   - `instance_count`
+
+4. Renamed outputs:
+
+   :info: All outputs used to be lists, and are now singular outputs due to the removal of `count`
+
+## Upgrade State Migrations
+
+### Before 2.x Example
+
+```hcl
+module "ec2_upgrade" {
+  source  = "terraform-aws-modules/ec2-instance/aws"
+  version = "2.21.0"
+
+  instance_count = 3
+
+  name                        = local.name
+  ami                         = data.aws_ami.amazon_linux.id
+  instance_type               = "c5.large"
+  subnet_ids                  = module.vpc.private_subnets
+  vpc_security_group_ids      = [module.security_group.security_group_id]
+  associate_public_ip_address = true
+
+  tags = local.tags
+}
+```
+
+### After 3.x Example
+
+```hcl
+locals {
+  num_suffix_format = "-%d"
+  multiple_instances = {
+    0 = {
+      num_suffix    = 1
+      instance_type = "c5.large"
+      subnet_id     = element(module.vpc.private_subnets, 0)
+    }
+    1 = {
+      num_suffix    = 2
+      instance_type = "c5.large"
+      subnet_id     = element(module.vpc.private_subnets, 1)
+    }
+    2 = {
+      num_suffix    = 3
+      instance_type = "c5.large"
+      subnet_id     = element(module.vpc.private_subnets, 2)
+    }
+  }
+}
+
+module "ec2_upgrade" {
+  source = "../../"
+
+  for_each = local.multiple_instances
+
+  name = format("%s${local.num_suffix_format}", local.name, each.value.num_suffix)
+
+  ami                         = data.aws_ami.amazon_linux.id
+  instance_type               = each.value.instance_type
+  subnet_id                   = each.value.subnet_id
+  vpc_security_group_ids      = [module.security_group.security_group_id]
+  associate_public_ip_address = true
+
+  tags = local.tags
+}
+```
+
+To migrate from the `v2.x` version to `v3.x` version example shown above, the following state move commands can be performed to maintain the current resources without modification:
+
+```bash
+terraform state mv 'module.ec2_upgrade.aws_instance.this[0]' 'module.ec2_upgrade["0"].aws_instance.this[0]'
+terraform state mv 'module.ec2_upgrade.aws_instance.this[1]' 'module.ec2_upgrade["1"].aws_instance.this[0]'
+terraform state mv 'module.ec2_upgrade.aws_instance.this[2]' 'module.ec2_upgrade["2"].aws_instance.this[0]'
+```
+
+:info: Notes
+
+- In the `v2.x` example we use `subnet_ids` which is an array of subnets. These are mapped to the respective instance based on their index location; therefore in the `v3.x` example we are doing a similar index lookup to map back to the existing subnet used for that instance. This would also be the case for `private_ips`
+- In the `v3.x` example we have shown how users can continue to use the same naming scheme that is currently in use by the `v2.x` module. By moving the `num_suffix_format` into the module name itself inside a format function, users can continue to customize the names generated in a similar manner as that of the `v2.x` module.