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Added HealthyHostCount alarm #5

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Mar 16, 2022
Merged

Added HealthyHostCount alarm #5

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bf0fc25
Added HealthyHostCount alarm
tovbinm Mar 16, 2022
350e313
small updates
tovbinm Mar 16, 2022
20c85bd
fix the condition
tovbinm Mar 16, 2022
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44 changes: 24 additions & 20 deletions README.md
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@@ -1,22 +1,25 @@
# Terraform Module for AWS ALB Cloudwatch Alarms
# Terraform Module for AWS ALB CloudWatch Alarms

This Terraform module manages Cloudwatch Alarms for an ALB in the region. It does NOT create or manage Load Balancers, only Metric Alarms.
This Terraform module manages CloudWatch Alarms for an ALB in the region. It does NOT create or manage Load Balancers, only Metric Alarms.

**Requires**:

- AWS Provider
- Terraform 0.12

## Alarms Created

Alarms Always Created:

- Any 5xx errors from the target group
- Any 5xx errors from the load balancer
- Unacceptably high average response times
- Number of unhealthy hosts
- Number of healthy hosts

**Estimated Operating Cost**: $ 0.40 / month
**Estimated Operating Cost**: $ 0.50 / month

- $ 0.10 / month for Metric Alarms (4x)
- $ 0.10 / month for Metric Alarms (5x)

## Example

Expand All @@ -30,22 +33,23 @@ module "aws-alb-alarms" {

## Variables

| Name | Description | Type | Default | Required |
|------|-------------|------|---------|:-----:|
| actions\_alarm | A list of actions to take when alarms are triggered. Will likely be an SNS topic for event distribution. | `list` | `[]` | no |
| actions\_ok | A list of actions to take when alarms are cleared. Will likely be an SNS topic for event distribution. | `list` | `[]` | no |
| evaluation\_period | The evaluation period over which to use when triggering alarms. | `string` | `"5"` | no |
| load\_balancer\_id | ALB ID | `string` | n/a | yes |
| prefix | Alarm Name Prefix | `string` | `""` | no |
| response\_time\_threshold | The average number of milliseconds that requests should complete within. | `string` | `"50"` | no |
| unhealthy\_hosts\_threshold | The number of unhealthy hosts. | `string` | `"0"` | no |
| statistic\_period | The number of seconds that make each statistic period. | `string` | `"60"` | no |
| target\_group\_id | Target Group ID | `string` | n/a | yes |
| Name | Description | Type | Default | Required |
| ------------------------- | -------------------------------------------------------------------------------------------------------- | -------- | ------- | :------: |
| actions_alarm | A list of actions to take when alarms are triggered. Will likely be an SNS topic for event distribution. | `list` | `[]` | no |
| actions_ok | A list of actions to take when alarms are cleared. Will likely be an SNS topic for event distribution. | `list` | `[]` | no |
| evaluation_period | The evaluation period over which to use when triggering alarms. | `string` | `"5"` | no |
| load_balancer_id | ALB ID | `string` | n/a | yes |
| prefix | Alarm Name Prefix | `string` | `""` | no |
| response_time_threshold | The average number of milliseconds that requests should complete within. | `string` | `"50"` | no |
| unhealthy_hosts_threshold | The number of unhealthy hosts. | `string` | `"0"` | no |
| healthy_hosts_threshold | The number of healthy hosts. | `string` | `"0"` | no |
| statistic_period | The number of seconds that make each statistic period. | `string` | `"60"` | no |
| target_group_id | Target Group ID | `string` | n/a | yes |

## Outputs

| Name | Description |
|------|-------------|
| alarm\_httpcode\_lb\_5xx\_count | The CloudWatch Metric Alarm resource block for 5xx errors on the load balancer |
| alarm\_httpcode\_target\_5xx\_counts | The CloudWatch Metric Alarm resource block for 5xx errors on the target group |
| alarm\_target\_response\_time\_average | The CloudWatch Metric Alarm resource block for unacceptably high response time averages |
| Name | Description |
| ---------------------------------- | --------------------------------------------------------------------------------------- |
| alarm_httpcode_lb_5xx_count | The CloudWatch Metric Alarm resource block for 5xx errors on the load balancer |
| alarm_httpcode_target_5xx_counts | The CloudWatch Metric Alarm resource block for 5xx errors on the target group |
| alarm_target_response_time_average | The CloudWatch Metric Alarm resource block for unacceptably high response time averages |
19 changes: 19 additions & 0 deletions main.tf
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Expand Up @@ -72,3 +72,22 @@ resource "aws_cloudwatch_metric_alarm" "unhealthy_hosts" {
"LoadBalancer" = var.load_balancer_id
}
}

resource "aws_cloudwatch_metric_alarm" "healthy_hosts" {
alarm_name = "${var.prefix}alb-tg-${var.target_group_id}-healthy-hosts"
comparison_operator = "LessThanOrEqualToThreshold"
evaluation_periods = var.evaluation_period
metric_name = "HealthyHostCount"
namespace = "AWS/ApplicationELB"
period = var.statistic_period
statistic = "Minimum"
threshold = var.healthy_hosts_threshold
alarm_description = format("Healthy host count is less than or equal to %s", var.healthy_hosts_threshold)
alarm_actions = var.actions_alarm
ok_actions = var.actions_ok

dimensions = {
"TargetGroup" = var.target_group_id
"LoadBalancer" = var.load_balancer_id
}
}
6 changes: 6 additions & 0 deletions variables.tf
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Expand Up @@ -26,6 +26,12 @@ variable "unhealthy_hosts_threshold" {
description = "The number of unhealthy hosts."
}

variable "healthy_hosts_threshold" {
type = string
default = "0"
description = "The number of healthy hosts."
}

variable "evaluation_period" {
type = string
default = "5"
Expand Down