Automate EC2 instance start/stop

.gitignore

@@ -9,4 +9,5 @@
 .terraform/
 *.tfstate
 *.tfstate*
+*.lock.hcl
 secret.tfvars

data.tf

@@ -21,3 +21,94 @@ data "aws_ami" "this" {
 
   most_recent = true
 }
+
+data "aws_iam_policy_document" "lambda" {
+  version = "2012-10-17"
+
+  statement {
+    effect = "Allow"
+
+    principals {
+      type = "Service"
+
+      identifiers = [
+        "lambda.amazonaws.com",
+      ]
+    }
+
+    actions = [
+      "sts:AssumeRole",
+    ]
+  }
+}
+
+data "aws_iam_policy_document" "instance" {
+  version = "2012-10-17"
+
+  statement {
+    effect = "Allow"
+
+    resources = [
+      "*",
+    ]
+
+    actions = [
+      "ec2:Start*",
+      "ec2:Stop*",
+    ]
+  }
+}
+
+data "aws_iam_policy_document" "cloudwatch" {
+  version = "2012-10-17"
+
+  statement {
+    effect = "Allow"
+
+    resources = [
+      "arn:aws:logs:*:*:*",
+    ]
+
+    actions = [
+      "logs:CreateLogGroup",
+      "logs:CreateLogStream",
+      "logs:PutLogEvents",
+    ]
+  }
+}
+
+data "archive_file" "start_instance" {
+  type                    = "zip"
+  output_path             = "${path.module}/start_instance.zip"
+  source_content_filename = "${path.module}/start_instance.js"
+  source_content          = <<EOF
+const AWS = require('aws-sdk');
+const ec2 = new AWS.EC2({
+  region: '${var.aws_region}',
+});
+
+exports.handler = async (event, context, callback) => await ec2.startInstances({
+  InstanceIds: [
+    '${aws_instance.this.id}',
+  ],
+}).promise();
+  EOF
+}
+
+data "archive_file" "stop_instance" {
+  type                    = "zip"
+  output_path             = "${path.module}/stop_instance.zip"
+  source_content_filename = "${path.module}/stop_instance.js"
+  source_content          = <<EOF
+const AWS = require('aws-sdk');
+const ec2 = new AWS.EC2({
+  region: '${var.aws_region}',
+});
+
+exports.handler = async (event, context, callback) => await ec2.stopInstances({
+  InstanceIds: [
+    '${aws_instance.this.id}',
+  ],
+}).promise();
+  EOF
+}

main.tf

@@ -140,6 +140,136 @@ resource "aws_instance" "this" {
   }
 }
 
+resource "aws_iam_role" "lambda" {
+  name               = "tailscale"
+  assume_role_policy = data.aws_iam_policy_document.lambda.json
+}
+
+resource "aws_iam_policy" "lambda" {
+  name   = "tailscale-lambda"
+  path   = "/"
+  policy = data.aws_iam_policy_document.instance.json
+}
+
+resource "aws_iam_policy" "cloudwatch" {
+  name   = "tailscale-cloudwatch"
+  path   = "/"
+  policy = data.aws_iam_policy_document.cloudwatch.json
+}
+
+resource "aws_iam_role_policy_attachment" "lambda" {
+  role       = aws_iam_role.lambda.name
+  policy_arn = aws_iam_policy.lambda.arn
+}
+
+resource "aws_iam_role_policy_attachment" "cloudwatch" {
+  role       = aws_iam_role.lambda.name
+  policy_arn = aws_iam_policy.cloudwatch.arn
+}
+
+resource "aws_cloudwatch_log_group" "start_instance" {
+  name              = "/aws/lambda/${var.server_hostname}-${var.aws_region}-start-instance"
+  retention_in_days = var.log_retention
+}
+
+resource "aws_cloudwatch_log_group" "stop_instance" {
+  name              = "/aws/lambda/${var.server_hostname}-${var.aws_region}-stop-instance"
+  retention_in_days = var.log_retention
+}
+
+resource "aws_cloudwatch_event_rule" "start_instance" {
+  name                = "${var.server_hostname}-${var.aws_region}-start-instance"
+  schedule_expression = var.server_start_expression
+}
+
+resource "aws_cloudwatch_event_rule" "stop_instance" {
+  name                = "${var.server_hostname}-${var.aws_region}-stop-instance"
+  schedule_expression = var.server_stop_expression
+}
+
+resource "aws_s3_bucket" "this" {
+  bucket        = "${var.server_hostname}-${var.aws_region}"
+  force_destroy = true
+}
+
+resource "aws_s3_object" "start_instance" {
+  bucket = aws_s3_bucket.this.id
+  key    = "start_instance.zip"
+  source = data.archive_file.start_instance.output_path
+}
+
+resource "aws_s3_object" "stop_instance" {
+  bucket = aws_s3_bucket.this.id
+  key    = "stop_instance.zip"
+  source = data.archive_file.stop_instance.output_path
+}
+
+resource "aws_lambda_function" "start_instance" {
+  function_name = "${var.server_hostname}-${var.aws_region}-start-instance"
+  role          = aws_iam_role.lambda.arn
+  s3_bucket     = aws_s3_bucket.this.id
+  s3_key        = aws_s3_object.start_instance.id
+  handler       = "start_instance.handler"
+  runtime       = "nodejs16.x"
+  memory_size   = 128
+  timeout       = 60
+
+  architectures = [
+    "arm64",
+  ]
+
+  depends_on = [
+    aws_cloudwatch_log_group.start_instance,
+  ]
+}
+
+resource "aws_lambda_function" "stop_instance" {
+  function_name = "${var.server_hostname}-${var.aws_region}-stop-instance"
+  role          = aws_iam_role.lambda.arn
+  s3_bucket     = aws_s3_bucket.this.id
+  s3_key        = aws_s3_object.stop_instance.id
+  handler       = "stop_instance.handler"
+  runtime       = "nodejs16.x"
+  memory_size   = 128
+  timeout       = 60
+
+  architectures = [
+    "arm64",
+  ]
+
+  depends_on = [
+    aws_cloudwatch_log_group.stop_instance,
+  ]
+}
+
+resource "aws_cloudwatch_event_target" "start_instance" {
+  rule      = aws_cloudwatch_event_rule.start_instance.name
+  target_id = aws_cloudwatch_event_rule.start_instance.name
+  arn       = aws_lambda_function.start_instance.arn
+}
+
+resource "aws_cloudwatch_event_target" "stop_instance" {
+  rule      = aws_cloudwatch_event_rule.stop_instance.name
+  target_id = aws_cloudwatch_event_rule.stop_instance.name
+  arn       = aws_lambda_function.stop_instance.arn
+}
+
+resource "aws_lambda_permission" "start_instance" {
+  statement_id  = "AllowExecutionFromCloudWatch"
+  principal     = "events.amazonaws.com"
+  action        = "lambda:InvokeFunction"
+  function_name = aws_lambda_function.start_instance.function_name
+  source_arn    = aws_cloudwatch_event_rule.start_instance.arn
+}
+
+resource "aws_lambda_permission" "stop_instance" {
+  statement_id  = "AllowExecutionFromCloudWatch"
+  principal     = "events.amazonaws.com"
+  action        = "lambda:InvokeFunction"
+  function_name = aws_lambda_function.stop_instance.function_name
+  source_arn    = aws_cloudwatch_event_rule.stop_instance.arn
+}
+
 resource "tailscale_tailnet_key" "this" {
   reusable      = true
   preauthorized = true

variables.tf

@@ -50,6 +50,24 @@ variable "server_hostname" {
   default     = "vpn"
 }
 
+variable "server_start_expression" {
+  description = "Server start schedule expression"
+  type        = string
+  default     = "cron(0 10 * * ? *)"
+}
+
+variable "server_stop_expression" {
+  description = "Server stop schedule expression"
+  type        = string
+  default     = "cron(0 1 * * ? *)"
+}
+
+variable "log_retention" {
+  description = "CloudWatch log retention"
+  type        = number
+  default     = 14
+}
+
 variable "tailscale_api_key" {
   description = "Tailscale API access token"
   type        = string