resource "google_monitoring_custom_service" "customsrv" {
  for_each = var.custom_service_level
  display_name = each.value.service_display_name
  service_id = each.value.service_id
  project = var.project_id
}

// Google Monitoring SLO objects can support many different metric types, for more info see our documenation. 
resource "google_monitoring_slo" "custom_request_based_slo" {
   for_each = var.custom_sli
   service = google_monitoring_custom_service.customsrv[each.key].service_id
  display_name = each.value.metric_display_name
  goal = each.value.goal
  rolling_period_days = each.value.rolling_period_days // Replacable with calendar_period = "DAY", "WEEK", "FORTNIGHT", or "MONTH"
  request_based_sli {
    // Alternate implementation could use distribution_cut instead of good_total_ratio. 
    good_total_ratio {
      // Any combination of two elements: good_service_filter, bad_service_filter, total_service_filter. 
      good_service_filter = join(" AND ", each.value.good_service_filter)
      total_service_filter = join(" AND ", each.value.total_service_filter)
    }
  }
  depends_on = [ google_monitoring_custom_service.customsrv ]
}

======================
using .tfvars values:-
=======================
custom_service_level = {
  "composer-service" = {
    service_id = "custom-srv-slos"
    service_display_name = "My Custom SLO"    
  }
}

custom_sli = {
  "composer-health" = { 
    metric_display_name = "test slo with service based SLI"
    goal = 0.9
    rolling_period_days = 28
    window_period = "300s"
    good_service_filter = [
          "metric.type="composer.googleapis.com/workflow/run_count"",
          "resource.type="cloud_composer_workflow"",
          "metric.labels.state="success"",
      ],
    total_service_filter = [
          "metric.type="composer.googleapis.com/workflow/run_count"",
          "resource.type="cloud_composer_workflow"",
      ]
  },
  }

=============================== variables used ====================== variable “custom_service_level” { type = map(object({ service_id = string, service_display_name = string, })) } variable “custom_sli” { type = map(object({ metric_display_name = string, goal = number, rolling_period_days = number, good_service_filter = list(string), total_service_filter = list(string) # service = string })) }

getting this error on plan:-

│ Error: Invalid index
│
│   on main.tf line 600, in resource "google_monitoring_slo" "custom_request_based_slo":
│  600:    service = google_monitoring_custom_service.customsrv[each.key].service_id
│     ├────────────────
│     │ each.key is "composer-health"
│     │ google_monitoring_custom_service.customsrv is object with 1 attribute "composer-service"
│
│ The given key does not identify an element in this collection value.
╵