ALIAS, GSLB and overrides with Terraform

DTM’s global server load balancing (GSLB) features, ALIAS records and override records, are both manageable as code.

ALIAS records (GSLB)

An ALIAS record is a dtm_record with type = "ALIAS" whose values are downstream hostnames rather than IP addresses. DTM resolves those hostnames at query time, health-checks the addresses behind them, applies the load-balancing policy, and returns flattened A/AAAA answers. ALIAS records can sit at the zone apex.

resource "dtm_record" "app" {
  zone_id = dtm_zone.example.id
  name    = "app" # or "@" for the zone apex
  type    = "ALIAS"
  ttl     = 30

  values {
    value  = "app-ne.contoso.com"
    region = "northeurope"
  }
  values {
    value  = "app-we.contoso.com"
    region = "westeurope"
  }

  lb_policy {
    method = "region"
  }

  health_check_template {
    protocol         = "https"
    port             = 443
    path             = "/healthz"
    interval_seconds = 5
  }
}

This steers each client to its own region and fails over across regions automatically. The region on each value is optional; DTM can infer it from the resolved address using your subnet mappings.

See health checks and load balancing for the full lb_policy and health_check_template schema, including authenticated probes.

Override records

An override record (dtm_override_record, role: editor or admin) intercepts a single exact FQDN in a zone that DTM otherwise forwards, and answers it authoritatively with the same health-aware load balancing. Everything else in the zone keeps forwarding. Overrides are an advanced adoption ramp: admins can also manage them from the web UI behind confirmation guardrails, but Terraform remains the recommended steady state, and a Terraform-owned override should keep Terraform as its single owner (see the ownership rule).

resource "dtm_override_record" "api" {
  fqdn        = "api.corp.example."
  type        = "A"
  target_mode = "linked" # "linked" = hostnames resolved at query time; "static" = fixed IPs
  ttl         = 30

  values {
    value  = "api-ne.contoso.com"
    region = "northeurope"
  }
  values {
    value  = "api-we.contoso.com"
    region = "westeurope"
  }

  lb_policy {
    method = "region"
  }

  health_check_template {
    protocol         = "https"
    port             = 443
    path             = "/healthz"
    interval_seconds = 5
  }
}

Attribute	Required	Description
fqdn	Yes	Exact FQDN to intercept, with trailing dot. Must not equal a DTM zone apex. Changing it replaces the resource.
type	Yes	A or AAAA. Changing it replaces the resource.
target_mode	No	static (default; literal IPs) or linked (hostnames resolved at query time, ALIAS-like). Changing it replaces the resource.
ttl	No	TTL in seconds.
enabled	No	Defaults to true.
values (block, 1+)	Yes	IP (static) or hostname (linked) values, with optional region.
lb_policy (block)	No	Same policy schema as records.
health_check_template (block)	No	Same template schema as records, including authenticated probes.

Static override

Pin a name to fixed addresses you control directly:

resource "dtm_override_record" "vip" {
  fqdn        = "legacy.corp.example."
  type        = "A"
  target_mode = "static"
  ttl         = 60

  values { value = "10.0.9.10" }
  values { value = "10.0.9.11" }

  lb_policy {
    method = "failover"
  }
}

Removing the override hands the name straight back to the forwarded zone, so adoption is fully reversible.

Import

# ALIAS records import like any record: "<zone_id>:<record_id>"
terraform import dtm_record.app 8f3a...:c21b...

# Override records import by their ID
terraform import dtm_override_record.api 5d90...