add: monitoring-tools

modules/monitoring-tools/README.md

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+<!-- BEGIN_TF_DOCS -->
+## Requirements
+
+| Name | Version |
+|------|---------|
+| <a name="requirement_terraform"></a> [terraform](#requirement\_terraform) | >=1.7 |
+| <a name="requirement_google"></a> [google](#requirement\_google) | >= 5.22.0 |
+| <a name="requirement_google-beta"></a> [google-beta](#requirement\_google-beta) | >= 5.22.0 |
+
+## Providers
+
+| Name | Version |
+|------|---------|
+| <a name="provider_google"></a> [google](#provider\_google) | >= 5.22.0 |
+
+## Modules
+
+No modules.
+
+## Resources
+
+| Name | Type |
+|------|------|
+| [google_monitoring_alert_policy.main](https://registry.terraform.io/providers/hashicorp/google/latest/docs/resources/monitoring_alert_policy) | resource |
+| [google_monitoring_notification_channel.main](https://registry.terraform.io/providers/hashicorp/google/latest/docs/resources/monitoring_notification_channel) | resource |
+| [google_project_service.main](https://registry.terraform.io/providers/hashicorp/google/latest/docs/resources/project_service) | resource |
+| [google_project.main](https://registry.terraform.io/providers/hashicorp/google/latest/docs/data-sources/project) | data source |
+
+## Inputs
+
+| Name | Description | Type | Default | Required |
+|------|-------------|------|---------|:--------:|
+| <a name="input_channels"></a> [channels](#input\_channels) | Channel variable that contains `error` and `warn` as keys | `map(string)` | n/a | yes |
+| <a name="input_location"></a> [location](#input\_location) | The location of the resource. | `string` | n/a | yes |
+| <a name="input_project_id"></a> [project\_id](#input\_project\_id) | The ID of Google Cloud Platform. | `string` | n/a | yes |
+| <a name="input_secrets"></a> [secrets](#input\_secrets) | The token required for notifications to Slack.<br>    The variable is required for monitoring. | `string` | n/a | yes |
+| <a name="input_target"></a> [target](#input\_target) | The target information for monitoring.<br>    `base_value` is used to calculate a numeric value based on the target resource.<br>    Specifically, it is used to obtain a percentage, as in `floor(base_value * threshold.value)`. | <pre>object({<br>    title         = string<br>    metric        = string<br>    resource_type = string<br>    label         = string<br>    name          = string<br>    filter        = string<br>    reducer       = string<br>    aligner       = string<br>    base_value    = optional(number, 1)<br>    threshold = map(<br>      object({<br>        value  = number<br>        window = string<br>      })<br>    )<br>  })</pre> | n/a | yes |
+
+## Outputs
+
+| Name | Description |
+|------|-------------|
+| <a name="output_enabled_apis"></a> [enabled\_apis](#output\_enabled\_apis) | Already enabled APIs list. |
+| <a name="output_policies"></a> [policies](#output\_policies) | Alert policies name object. |
+<!-- END_TF_DOCS -->

modules/monitoring-tools/alert.tf

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+resource "google_monitoring_alert_policy" "main" {
+  for_each = local.levels
+
+  display_name = "[${upper(each.value)}] ${var.target.name} ${var.target.title}"
+
+  conditions {
+    display_name = "[${upper(each.value)}] ${var.target.name} - ${var.target.title}"
+
+    condition_threshold {
+      filter = <<EOF
+        metric.type = "${var.target.metric}"
+        AND resource.type = "${var.target.resource_type}"
+        AND ${var.target.label} = ${var.target.name}
+        AND ${var.target.filter}
+      EOF
+
+      aggregations {
+        alignment_period     = var.target.threshold[each.value].window
+        cross_series_reducer = var.target.reducer
+        per_series_aligner   = var.target.aligner
+      }
+
+      trigger {
+        count = 1
+      }
+
+      threshold_value = (
+        var.target.base_value == 1 ?
+        var.target.threshold[each.value].value :
+        floor(var.target.base_value * var.target.threshold[each.value].value)
+      )
+
+      comparison = "COMPARISON_GT"
+      duration   = "0s"
+    }
+  }
+
+  alert_strategy {
+    auto_close = "604800s"
+  }
+
+  combiner              = "OR"
+  enabled               = "true"
+  notification_channels = []
+}

modules/monitoring-tools/channel.tf

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+resource "google_monitoring_notification_channel" "main" {
+  for_each = local.levels
+
+  display_name = upper(each.key)
+  type         = "slack"
+
+  labels = {
+    channel_name = each.value
+  }
+
+  sensitive_labels {
+    auth_token = yamldecode(var.secrets)["auth_token"]
+  }
+
+  lifecycle {
+    ignore_changes = [
+      labels["team"]
+    ]
+  }
+}

modules/monitoring-tools/main.tf

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+locals {
+  apis = toset([
+    "monitoring.googleapis.com",
+  ])
+  levels = toset(keys(var.target.threshold))
+}
+
+data "google_project" "main" {}
+
+resource "google_project_service" "main" {
+  for_each = local.apis
+
+  project            = data.google_project.main.project_id
+  service            = each.value
+  disable_on_destroy = false
+}

modules/monitoring-tools/outputs.tf

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+output "enabled_apis" {
+  description = "Already enabled APIs list."
+  value       = [for api in google_project_service.main : api.service]
+}
+
+output "policies" {
+  description = "Alert policies name object."
+  value = {
+    error = google_monitoring_alert_policy.main["error"].name
+    warn  = google_monitoring_alert_policy.main["warn"].name
+  }
+}

modules/monitoring-tools/provider.tf

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+terraform {
+  required_version = ">=1.7"
+
+  required_providers {
+    google = {
+      source  = "hashicorp/google"
+      version = ">= 5.22.0"
+    }
+    google-beta = {
+      source  = "hashicorp/google"
+      version = ">= 5.22.0"
+    }
+  }
+}

modules/monitoring-tools/variables.tf

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+variable "project_id" {
+  description = "The ID of Google Cloud Platform."
+  type        = string
+}
+
+variable "location" {
+  description = "The location of the resource."
+  type        = string
+}
+
+variable "target" {
+  description = <<EOF
+    The target information for monitoring.
+    `base_value` is used to calculate a numeric value based on the target resource.
+    Specifically, it is used to obtain a percentage, as in `floor(base_value * threshold.value)`.
+  EOF
+  type = object({
+    title         = string
+    metric        = string
+    resource_type = string
+    label         = string
+    name          = string
+    filter        = string
+    reducer       = string
+    aligner       = string
+    base_value    = optional(number, 1)
+    threshold = map(
+      object({
+        value  = number
+        window = string
+      })
+    )
+  })
+}
+
+variable "channels" {
+  description = "Channel variable that contains `error` and `warn` as keys"
+  type        = map(string)
+}
+
+variable "secrets" {
+  description = <<EOF
+    The token required for notifications to Slack.
+    The variable is required for monitoring.
+  EOF
+  type        = string
+}