#初始化
terraform init
#验证
terraform validate
#生成执行计划文件
terraform plan -out=apim-autoscale.tfplan
#开始执行修改
terraform apply apim-autoscale.tfplan

terraform {
  required_version = ">= 1.5.0"
  required_providers {
    azurerm = {
      source  = "hashicorp/azurerm"
      version = "~> 5.11"
    }
  }
}
provider "azurerm" {
  environment = "china"
  features {}
  subscription_id = "**********  your subscription id"
  # Authenticate externally; do not store credentials in this file.
}
# Read only: this configuration does not create, import, or manage the APIM itself.
# Existing ID: /subscriptions/**********/resourceGroups/lb-*******-rg/providers/Microsoft.ApiManagement/service/lb**********02
data "azurerm_api_management" "apim" {
  name                = "your apim name **********
  resource_group_name = "your reousrce group **********
}
variable "apim_scale_step" {
  type        = number
  description = "Units per scaling action. If APIM explicitly selects availability zones, set this to the number of selected zones; otherwise leave 1."
  default     = 1
  validation {
    condition     = var.apim_scale_step >= 1 && var.apim_scale_step <= 3 && floor(var.apim_scale_step) == var.apim_scale_step
    error_message = "apim_scale_step must be an integer from 1 to 3 matching the explicit zone count, or 1 for automatic/no explicit zones."
  }
}
locals {
  apim_tier = split("_", data.azurerm_api_management.apim.sku_name)[0]
  is_v2     = endswith(lower(local.apim_tier), "v2")
  # Capacity is not supported on v2. Scale out on either CPU or memory;
  # Azure Monitor requires all scale-in rules to be satisfied before scaling in.
  scale_metrics = local.is_v2 ? ["CpuPercent_Gateway", "MemoryPercent_Gateway"] : ["Capacity"]
  # This provider's APIM data source does not export zones. For explicitly
  # selected zones, set apim_scale_step to the zone count before applying.
  scale_step = var.apim_scale_step
  # Preserve the requested cap of 5 where supported; classic Basic/Standard
  # have lower limits. Round down to a valid explicit-zone multiple.
  requested_maximum = min(5, lookup({ Basic = 2, Standard = 4 }, local.apim_tier, 5))
  maximum_units     = floor(local.requested_maximum / local.scale_step) * local.scale_step
}
resource "azurerm_monitor_autoscale_setting" "apim" {
  name                = "${data.azurerm_api_management.apim.name}-autoscale"
  resource_group_name = data.azurerm_api_management.apim.resource_group_name
  location            = data.azurerm_api_management.apim.location
  target_resource_id  = data.azurerm_api_management.apim.id
  enabled             = true
  profile {
    name = "default"
    capacity {
      # Default is a fallback for missing metrics, not the initial APIM count.
      default = local.scale_step
      minimum = local.scale_step
      maximum = local.maximum_units
    }
    # Scale out: 30-minute average > 70%; wait 60 minutes between actions.
    dynamic "rule" {
      for_each = local.scale_metrics
      iterator = metric
      content {
        metric_trigger {
          metric_name              = metric.value
          metric_namespace         = "Microsoft.ApiManagement/service"
          metric_resource_id       = data.azurerm_api_management.apim.id
          divide_by_instance_count = false
          time_grain               = "PT1M"
          statistic                = "Average"
          time_window              = "PT30M"
          time_aggregation         = "Average"
          operator                 = "GreaterThan"
          threshold                = 70
          # Only the primary region can be autoscaled. v2 metrics have no dimensions.
          dynamic "dimensions" {
            for_each = local.is_v2 ? [] : [data.azurerm_api_management.apim.location]
            content {
              name     = "Location"
              operator = "Equals"
              values   = [dimensions.value]
            }
          }
        }
        scale_action {
          direction = "Increase"
          type      = "ChangeCount"
          value     = tostring(local.scale_step)
          cooldown  = "PT60M"
        }
      }
    }
    # Scale in: all 30-minute averages < 35%; wait 90 minutes between actions.
    dynamic "rule" {
      for_each = local.scale_metrics
      iterator = metric
      content {
        metric_trigger {
          metric_name              = metric.value
          metric_namespace         = "Microsoft.ApiManagement/service"
          metric_resource_id       = data.azurerm_api_management.apim.id
          divide_by_instance_count = false
          time_grain               = "PT1M"
          statistic                = "Average"
          time_window              = "PT30M"
          time_aggregation         = "Average"
          operator                 = "LessThan"
          threshold                = 35
          dynamic "dimensions" {
            for_each = local.is_v2 ? [] : [data.azurerm_api_management.apim.location]
            content {
              name     = "Location"
              operator = "Equals"
              values   = [dimensions.value]
            }
          }
        }
        scale_action {
          direction = "Decrease"
          type      = "ChangeCount"
          value     = tostring(local.scale_step)
          cooldown  = "PT90M"
        }
      }
    }
  }
  lifecycle {
    precondition {
      condition     = contains(["Basic", "Standard", "Premium", "BasicV2", "StandardV2", "PremiumV2"], local.apim_tier)
      error_message = "Autoscale requires a supported dedicated APIM tier; Developer and Consumption are not supported by this configuration."
    }
    precondition {
      condition     = local.maximum_units >= local.scale_step
      error_message = "The maximum unit count must accommodate the configured availability zones."
    }
  }
}
# If an autoscale setting already exists for this APIM, import that setting
# into azurerm_monitor_autoscale_setting.apim instead of creating a second one.
# Protect Terraform state: data sources can include sensitive APIM properties.