Summary

Adds three new resources for managing Datadog tag indexing rules via Terraform. Tag indexing rules control which tag keys are indexed for custom metrics, reducing cardinality costs while preserving queryability.

DRAFT — blocked on upstream PRs. See blocker section below.

New resources

datadog_tag_indexing_rule

Full CRUD resource. rule_order is computed-only (server assigns max+1 on create); use datadog_tag_indexing_rule_order for atomic re-sequencing.

resource "datadog_tag_indexing_rule" "example" {
  name                = "index-env-service-for-web"
  metric_name_matches = ["web.request.*", "web.latency.*"]
  tags                = ["env", "service"]

  options {
    version = 1
    data {
      manage_preexisting_metrics = true
      override_previous_rules    = false
    }
  }
}

datadog_tag_indexing_rule_exemption

Exempts a specific metric from all tag indexing rules. metric_name and reason are both RequiresReplace (no in-place update; the API has no PATCH endpoint). Read removes state when kind=legacy_tag_configuration since that state is managed via datadog_metric_tag_configuration, not this resource.

resource "datadog_tag_indexing_rule_exemption" "example" {
  metric_name = "my.special.metric"
  reason      = "This metric has a custom tag configuration predating the rule system."
}

datadog_tag_indexing_rule_order

Singleton list resource (modeled on datadog_logs_pipeline_order) that atomically re-sequences all rules. Create and Update both call POST /api/v2/metrics/tag-indexing-rules/order. Delete is a no-op (ordering cannot be deleted from the API).

resource "datadog_tag_indexing_rule_order" "main" {
  name = "main"
  rule_ids = [
    datadog_tag_indexing_rule.catch_all.id,
    datadog_tag_indexing_rule.web.id,
    datadog_tag_indexing_rule.infra.id,
  ]
}

Design notes

• All three resources use GetMetricsApiV2(), which already exists in api_instances_helper.go.
• datadog_tag_indexing_rule_exemption.Read explicitly handles the kind=legacy_tag_configuration case by removing the resource from state — this resource only manages explicit exemptions, not implicit ones from legacy tag configurations.
• datadog_tag_indexing_rule_order.Read calls ListTagIndexingRules and derives order from rule_order field sorted ascending.

Blocker

This PR is blocked on two upstream PRs that add TagIndexingRule* types and methods to datadogV2.MetricsApi:

1. datadog-api-spec#5837 — adds the spec (approved, awaiting #api-platform merge)
2. datadog-api-client-go PR (auto-generated once #5837 merges)

Once the client PR merges:

1. go get github.com/DataDog/datadog-api-client-go/v2@<new-version>
2. go mod tidy
3. Remove the NOTE: comments from the three resource files
4. go build ./... to verify

Test plan

• Acceptance tests (to be written once client types are available)
• terraform plan and terraform apply with example configs against staging

🤖 Generated with Claude Code