feat: Support application-controlled session stickiness (#95)

ref:  https://docs.aws.amazon.com/elasticloadbalancing/latest/classic/elb-sticky-sessions.html#enable-sticky-sessions-application
ref: https://registry.terraform.io/providers/hashicorp/aws/latest/docs/resources/lb_target_group#stickiness

Author: abeluck

README.md

@@ -273,8 +273,9 @@ Available targets:
 | <a name="input_slow_start"></a> [slow\_start](#input\_slow\_start) | The amount of time for targets to warm up before the load balancer sends them a full share of requests. The range is 30-900 seconds or 0 to disable. The default value is `0` seconds | `number` | `0` | no |
 | <a name="input_stage"></a> [stage](#input\_stage) | ID element. Usually used to indicate role, e.g. 'prod', 'staging', 'source', 'build', 'test', 'deploy', 'release' | `string` | `null` | no |
 | <a name="input_stickiness_cookie_duration"></a> [stickiness\_cookie\_duration](#input\_stickiness\_cookie\_duration) | The time period, in seconds, during which requests from a client should be routed to the same target. After this time period expires, the load balancer-generated cookie is considered stale. The range is 1 second to 1 week (604800 seconds). The default value is 1 day (86400 seconds) | `number` | `86400` | no |
+| <a name="input_stickiness_cookie_name"></a> [stickiness\_cookie\_name](#input\_stickiness\_cookie\_name) | Name of the application based cookie. AWSALB, AWSALBAPP, and AWSALBTG prefixes are reserved and cannot be used. Only needed when `stickiness_type` is app\_cookie | `string` | `null` | no |
 | <a name="input_stickiness_enabled"></a> [stickiness\_enabled](#input\_stickiness\_enabled) | Boolean to enable / disable `stickiness`. Default is `true` | `bool` | `true` | no |
-| <a name="input_stickiness_type"></a> [stickiness\_type](#input\_stickiness\_type) | The type of sticky sessions. The only current possible value is `lb_cookie` | `string` | `"lb_cookie"` | no |
+| <a name="input_stickiness_type"></a> [stickiness\_type](#input\_stickiness\_type) | The type of sticky sessions. The possible values are `lb_cookie` or `app_cookie` | `string` | `"lb_cookie"` | no |
 | <a name="input_tags"></a> [tags](#input\_tags) | Additional tags (e.g. `{'BusinessUnit': 'XYZ'}`).<br/>Neither the tag keys nor the tag values will be modified by this module. | `map(string)` | `{}` | no |
 | <a name="input_target_group_arn"></a> [target\_group\_arn](#input\_target\_group\_arn) | Existing ALB target group ARN. If provided, set `default_target_group_enabled` to `false` to disable creation of the default target group | `string` | `""` | no |
 | <a name="input_target_group_name"></a> [target\_group\_name](#input\_target\_group\_name) | Override the target group name | `string` | `""` | no |

docs/terraform.md

@@ -94,8 +94,9 @@
 | <a name="input_slow_start"></a> [slow\_start](#input\_slow\_start) | The amount of time for targets to warm up before the load balancer sends them a full share of requests. The range is 30-900 seconds or 0 to disable. The default value is `0` seconds | `number` | `0` | no |
 | <a name="input_stage"></a> [stage](#input\_stage) | ID element. Usually used to indicate role, e.g. 'prod', 'staging', 'source', 'build', 'test', 'deploy', 'release' | `string` | `null` | no |
 | <a name="input_stickiness_cookie_duration"></a> [stickiness\_cookie\_duration](#input\_stickiness\_cookie\_duration) | The time period, in seconds, during which requests from a client should be routed to the same target. After this time period expires, the load balancer-generated cookie is considered stale. The range is 1 second to 1 week (604800 seconds). The default value is 1 day (86400 seconds) | `number` | `86400` | no |
+| <a name="input_stickiness_cookie_name"></a> [stickiness\_cookie\_name](#input\_stickiness\_cookie\_name) | Name of the application based cookie. AWSALB, AWSALBAPP, and AWSALBTG prefixes are reserved and cannot be used. Only needed when `stickiness_type` is app\_cookie | `string` | `null` | no |
 | <a name="input_stickiness_enabled"></a> [stickiness\_enabled](#input\_stickiness\_enabled) | Boolean to enable / disable `stickiness`. Default is `true` | `bool` | `true` | no |
-| <a name="input_stickiness_type"></a> [stickiness\_type](#input\_stickiness\_type) | The type of sticky sessions. The only current possible value is `lb_cookie` | `string` | `"lb_cookie"` | no |
+| <a name="input_stickiness_type"></a> [stickiness\_type](#input\_stickiness\_type) | The type of sticky sessions. The possible values are `lb_cookie` or `app_cookie` | `string` | `"lb_cookie"` | no |
 | <a name="input_tags"></a> [tags](#input\_tags) | Additional tags (e.g. `{'BusinessUnit': 'XYZ'}`).<br/>Neither the tag keys nor the tag values will be modified by this module. | `map(string)` | `{}` | no |
 | <a name="input_target_group_arn"></a> [target\_group\_arn](#input\_target\_group\_arn) | Existing ALB target group ARN. If provided, set `default_target_group_enabled` to `false` to disable creation of the default target group | `string` | `""` | no |
 | <a name="input_target_group_name"></a> [target\_group\_name](#input\_target\_group\_name) | Override the target group name | `string` | `""` | no |

main.tf

@@ -34,6 +34,7 @@ resource "aws_lb_target_group" "default" {
   stickiness {
     type            = var.stickiness_type
     cookie_duration = var.stickiness_cookie_duration
+    cookie_name     = var.stickiness_cookie_name
     enabled         = var.stickiness_enabled
   }
 

variables.tf

@@ -284,7 +284,11 @@ variable "slow_start" {
 variable "stickiness_type" {
   type        = string
   default     = "lb_cookie"
-  description = "The type of sticky sessions. The only current possible value is `lb_cookie`"
+  description = "The type of sticky sessions. The possible values are `lb_cookie` or `app_cookie`"
+  validation {
+    condition     = contains(["lb_cookie", "app_cookie"], var.stickiness_type)
+    error_message = "The only current possible values are lb_cookie and app_cookie for ALBs"
+  }
 }
 
 variable "stickiness_cookie_duration" {
@@ -293,6 +297,12 @@ variable "stickiness_cookie_duration" {
   description = "The time period, in seconds, during which requests from a client should be routed to the same target. After this time period expires, the load balancer-generated cookie is considered stale. The range is 1 second to 1 week (604800 seconds). The default value is 1 day (86400 seconds)"
 }
 
+variable "stickiness_cookie_name" {
+  type        = string
+  default     = null
+  description = "Name of the application based cookie. AWSALB, AWSALBAPP, and AWSALBTG prefixes are reserved and cannot be used. Only needed when `stickiness_type` is app_cookie"
+}
+
 variable "stickiness_enabled" {
   type        = bool
   default     = true