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Terraform Version and Provider Version

Terraform v1.11.0
OCI Provider v6.28.0

Affected Resource(s)

• oci_core_instance
• oci_core_compute_capacity_reservation (related, but the bug is in the the instance resource)

Terraform Configuration Files

variable "compartment_id" {}
variable "availability_domain" {}
variable "fault_domain" {}

variable "shape_index" {
  type    = number
  default = 0
}

variable "shapes" {
  type = list(string)

  default = [
    "VM.Standard.E4.Flex",
    "VM.Standard.E5.Flex",
  ]
}

resource "oci_core_compute_capacity_reservation" "example" {
  count = length(var.shapes)

  compartment_id      = var.compartment_id
  availability_domain = var.availability_domain
  display_name        = "example-${count.index}"

  instance_reservation_configs {
    instance_shape = var.shapes[count.index]
    reserved_count = 1
    fault_domain   = var.fault_domain

    instance_shape_config {
      memory_in_gbs = 4
      ocpus         = 1
    }
  }
}

resource "oci_core_instance" "example" {
  compartment_id          = var.compartment_id
  availability_domain     = var.availability_domain
  fault_domain            = var.fault_domain
  capacity_reservation_id = oci_core_compute_capacity_reservation.example[var.shape_index].id
  display_name            = "example"
  shape                   = var.shapes[var.shape_index]

  shape_config {
    memory_in_gbs = 4
    ocpus         = 1
  }

  # ...
}

Full working example:
https://gist.github.com/b-dean/0cccde387e8dcc57167b08e5e45ef80c

Debug Output

Will include in an Oracle SR if needed.

Expected Behavior

The compute instance should modify its shape and capacity reservation in a single request. This is how it works when you change them in the OCI website. You can change both simultaneously.

Actual Behavior

│ Error: 400-InvalidParameter, Invalid Shape Config: No valid reservation configs in the reservation to move the resize to.
│ Suggestion: Please update the parameter(s) in the Terraform config as per error message Invalid Shape Config: No valid reservation configs in the reservation to move the resize to.
│ Documentation: https://registry.terraform.io/providers/oracle/oci/latest/docs/resources/core_instance
│ API Reference: https://docs.oracle.com/iaas/api/#/en/iaas/20160918/Instance/UpdateInstance
│ Request Target: PUT https://iaas.us-ashburn-1.oraclecloud.com/20160918/instances/ocid1.instance.oc1.iad.xxxxxxxxxxxxxxxx
│ Provider version: 6.28.0, released on 2025-03-02.
│ Service: Core Instance
│ Operation Name: UpdateInstance
│ OPC request ID: xxxxxxxxxxxxxxxx
│
│
│   with oci_core_instance.example,
│   on main.tf line 46, in resource "oci_core_instance" "example":
│   46: resource "oci_core_instance" "example" {
│

Steps to Reproduce

Using the code in the gist, https://gist.github.com/b-dean/0cccde387e8dcc57167b08e5e45ef80c

run the following:

# this one works
terraform apply -var shape_index=0

# this one will fail
terraform apply -var shape_index=1

It will ask you for compartment_id and subnet_id variables, which you can put in a .tfvars file if you like.

References

I previously created #2209 for this, but it was closed for some reason. I'm logging this as a bug, for which I will create a new PR.

I also logged a SR 4-0000144019 which was closed without a solution.