Feature/fargate

MIGRATION_EC2_TO_FARGATE.md

@@ -0,0 +1,79 @@
+# EC2 to Fargate Migration Guide
+
+## Configuration Changes
+
+### 1. ECS Cluster (`ecs-cluster/terragrunt.hcl`)
+```hcl
+# Disable EC2 instances
+ecs_cluster_instances_desired       = 0
+ecs_cluster_instances_autoscale_max = 0
+# Optional: Enable ECS Exec logging
+ecs_cluster_logging = true
+```
+
+### 2. Load Balancer (`load-balancer/terragrunt.hcl`)
+
+⚠️ **Warning**: This change will break existing EC2 services using bridge mode on the same target group.
+
+```hcl
+# Required: Fargate uses awsvpc network mode
+load_balancer_listener_ip_target = true
+```
+
+### 3. ECS Service (`service-app/terragrunt.hcl`)
+```hcl
+ecs_service_fargate         = true
+ecs_service_fargate_spot    = false  # Set true for 70% cost savings (tasks may be interrupted)
+
+# Required: Specify CPU and memory (see valid combinations below)
+ecs_service_cpu             = 256
+ecs_service_memory          = 512
+
+# Optional: Auto-scaling
+ecs_service_desired_count           = 2
+ecs_use_fargate_scaling             = true
+ecs_fargate_min_capacity            = 2
+ecs_fargate_max_capacity             = 10
+ecs_fargate_cpu_target_value         = 70
+ecs_fargate_memory_target_value      = 85
+```
+
+## Migration Steps
+
+1. Update cluster:
+   ```bash
+   cd ecs-cluster
+   terragrunt apply
+   ```
+
+2. Recreate service (causes brief downtime):
+   ```bash
+   cd ../service-app
+   terragrunt taint module.ecs-service.aws_ecs_service.service
+   terragrunt apply
+   ```
+
+**Note**: Tainting is required because ECS services cannot change launch type in-place.
+
+## Valid CPU/Memory Combinations
+
+| CPU | Memory (MB) |
+|-----|-------------|
+| 256 | 512, 1024, 2048 |
+| 512 | 1024, 2048, 3072, 4096 |
+| 1024 | 2048-8192 (1GB increments) |
+| 2048 | 4096-16384 (1GB increments) |
+| 4096 | 8192-30720 (1GB increments) |
+
+## Troubleshooting
+
+**Invalid CPU or memory value**
+- Check your CPU/memory combination against the table above
+
+**Target group health check failing**
+- Ensure `load_balancer_listener_ip_target = true`
+- Verify security groups allow traffic from load balancer
+
+**Tasks not starting**
+- Check CloudWatch logs: `/ecs/<cluster-name>/exec`
+- Verify subnet has internet access (NAT gateway or public IP)

README.md

@@ -1,8 +1,18 @@
 # terraform-aws-ecs-cluster for terraform >= 0.12
 
-This module configures ECS-cluster consisting of number of ec2 instances. It supports spot ec2 instances, which might be
-cost effective for a development environment that allows some downtime.
+This module creates an ECS cluster supporting EC2 instances, Fargate, and Fargate Spot capacity providers.
 
 ## Required variables
 
-Only `cluster_name` is required to be set.
+Only `cluster_name` is required.
+
+## Enabling Fargate
+
+The cluster registers FARGATE, FARGATE_SPOT, and EC2 capacity providers. To use Fargate exclusively, set EC2 instances to 0:
+
+```hcl
+ecs_cluster_instances_desired       = 0
+ecs_cluster_instances_autoscale_max = 0
+```
+
+Services can then use Fargate by setting `ecs_service_fargate = true`. See `MIGRATION_EC2_TO_FARGATE.md` for migration steps.

main.tf

@@ -140,21 +140,75 @@ resource "aws_ecs_capacity_provider" "autoscale" {
 
 resource "aws_ecs_cluster" "main" {
   name = var.cluster_name
+
+  dynamic "configuration" {
+    for_each = var.cluster_logging ? [1] : []
+
+    content {
+      execute_command_configuration {
+        logging = "OVERRIDE"
+
+        log_configuration {
+          cloud_watch_log_group_name = aws_cloudwatch_log_group.ecs_exec_logs[0].name
+        }
+      }
+    }
+  }
+}
+
+resource "aws_cloudwatch_log_group" "ecs_exec_logs" {
+  count             = var.cluster_logging ? 1 : 0
+  name              = "/ecs/${var.cluster_name}/exec"
+  retention_in_days = var.cluster_log_retention_days
 }
 
 resource "aws_ecs_cluster_capacity_providers" "providers" {
   cluster_name = aws_ecs_cluster.main.name
 
-  capacity_providers = compact([
+  capacity_providers = distinct(compact([
     var.instances_autoscale_max > 0 && var.instances_desired == 0 ? aws_ecs_capacity_provider.autoscale[0].name : "",
     "FARGATE",
     "FARGATE_SPOT",
-  ])
+  ]))
+
 
-  default_capacity_provider_strategy {
-    base              = 1
-    weight            = 100
-    capacity_provider = var.instances_autoscale_max > 0 && var.instances_desired == 0 ? aws_ecs_capacity_provider.autoscale[0].name : "FARGATE"
+  dynamic "default_capacity_provider_strategy" {
+    for_each = var.cluster_strategy_type == "default" ? [1] : []
+    content {
+      base              = 1
+      weight            = 100
+      capacity_provider = var.instances_autoscale_max > 0 && var.instances_desired == 0 ? aws_ecs_capacity_provider.autoscale[0].name : "FARGATE"
+    }
   }
-}
 
+  dynamic "default_capacity_provider_strategy" {
+    for_each = var.cluster_strategy_type == "fargate" ? [1] : []
+    content {
+      base              = 0
+      weight            = 1
+      capacity_provider = "FARGATE"
+    }
+  }
+
+  dynamic "default_capacity_provider_strategy" {
+    for_each = var.cluster_strategy_type == "fargate_spot" ? [1] : []
+    content {
+      base              = 0
+      weight            = 1
+      capacity_provider = "FARGATE_SPOT"
+    }
+  }
+
+  dynamic "default_capacity_provider_strategy" {
+    for_each = var.cluster_strategy_type == "fargate_spot_with_fallback" ? [
+      { base = 1, weight = 0, provider = "FARGATE" },
+      { base = 0, weight = 1, provider = "FARGATE_SPOT" }
+    ] : []
+    content {
+      base              = default_capacity_provider_strategy.value.base
+      weight            = default_capacity_provider_strategy.value.weight
+      capacity_provider = default_capacity_provider_strategy.value.provider
+    }
+  }
+
+}

variables.tf

@@ -109,8 +109,36 @@ variable "vpc_name" {
   default     = ""
 }
 
+variable "cluster_logging" {
+  description = "Enable logging for ECS cluster. Set to true to enable."
+  type        = bool
+  default     = false
+}
+
+variable "cluster_log_retention_days" {
+  description = "Number of days to retain ECS Exec logs. Set to 0 for never expire."
+  type        = number
+  default     = 30
+}
+
+variable "cluster_strategy_type" {
+  description = <<-EOD
+  Defines the ECS capacity provider strategy. Possible values are:
+  - "default": Uses the default capacity provider strategy defined in the ECS cluster.
+  - "fargate": Preferentially uses Fargate for task deployments.
+  - "fargate_spot": Preferentially uses Fargate Spot for task deployments.
+  - "fargate_spot_with_fallback": Uses Fargate Spot by default but ensures at least one task runs on Fargate as a fallback.
+  EOD
+  type        = string
+  default     = "default"
+
+  validation {
+    condition     = contains(["default", "fargate", "fargate_spot", "fargate_spot_with_fallback"], var.cluster_strategy_type)
+    error_message = "Invalid ECS strategy type. Allowed values are 'default', 'fargate', 'fargate_spot', 'fargate_spot_with_fallback'."
+  }
+}
 variable "disk_kms_key_id" {
   type        = string
   description = "KMS key ID or ARN for EBS volume encryption. Use full ARN for custom keys. AWS managed key used if not specified."
   default     = ""
-}
+}