outscale_vm : adding a block_device_mappings forces replacement even on non-root volumes

[zeylos]

---

name: Bug report
about: adding a block_device_mappings forces replacement even on non-root volumes
labels: bug, new

---

Hello,

I have an issue with block_device_mappings which is whenever I try to add or remove a non-root block_device from the list terraform tries to recreate the machine.

Terraform Version

OpenTofu v1.9.0
on linux_amd64
+ provider registry.opentofu.org/outscale/outscale v1.0.0

Terraform Configuration Files

resource "outscale_vm" "xxx" {
    image_id = "ami-xxxx"
    vm_type = "tinav5.c1r1p2"
    subnet_id          = xxx
    private_ips        = [xxx]
    block_device_mappings {
        device_name = "/dev/sda1" # /
        bsu {
            volume_size = 10
            volume_type = "gp2"
        }
    }
    block_device_mappings {
        device_name = "/dev/xvdb"
        bsu {
            volume_size = 4
            volume_type = "gp2"
        }
    }
    block_device_mappings {         <<<<<<< this one was added after the vm was created
        device_name = "/dev/xvdc"
        bsu {
            volume_size = 4
            volume_type = "gp2"
        }
    }
}

### Output

  # outscale_vm.xxx must be replaced
-/+ resource "outscale_vm" "xxx" {
      ~ block_device_mappings_created  = [
          - {
              - bsu         = [
                  - {
                      - delete_on_vm_deletion = false
                      - link_date             = "2025-03-03T11:48:58.828Z"
                      - state                 = "attached"
                      - tags                  = []
                      - volume_id             = "vol-7d918f81"
                    },
                ]
              - device_name = "/dev/sda1"
            },
          - {
              - bsu         = [
                  - {
                      - delete_on_vm_deletion = false
                      - link_date             = "2025-03-03T11:48:58.828Z"
                      - state                 = "attached"
                      - tags                  = []
                      - volume_id             = "vol-c7ab9b29"
                    },
                ]
              - device_name = "/dev/xvdb"
            },
        ] -> (known after apply)
.....
      ~ block_device_mappings {
            # (1 unchanged attribute hidden)

          - bsu {
              - delete_on_vm_deletion = false -> null
              - iops                  = 0 -> null
              - volume_size           = 10 -> null
              - volume_type           = "gp2" -> null
            }
          + bsu {
              + delete_on_vm_deletion = (known after apply)
              + volume_size           = 10
              + volume_type           = "gp2"
            }
        }
      ~ block_device_mappings {
            # (1 unchanged attribute hidden)

          - bsu {
              - delete_on_vm_deletion = false -> null
              - iops                  = 0 -> null
              - volume_size           = 4 -> null
              - volume_type           = "gp2" -> null
            }
          + bsu {
              + delete_on_vm_deletion = (known after apply)
              + volume_size           = 4
              + volume_type           = "gp2"
            }
        }
      + block_device_mappings {
          + device_name = "/dev/xvdc" # forces replacement

          + bsu { # forces replacement
              + delete_on_vm_deletion = (known after apply)
              + volume_size           = 4
              + volume_type           = "gp2"
            }
        }
....

Expected Behavior

I would expect modifying only the device which has device_name "/dev/xvdc" in my case.

Actual Behavior

Terraform tries to modify all the volumes and recreate the instance.

Steps to Reproduce

provider "outscale" {
# bla
}
resource "outscale_vm" "xxx" {
    image_id = "xxx"
    vm_type = "tinav5.c1r1p2"
    subnet_id          = xxx
    private_ips        = ["xxx"]
    block_device_mappings {
        device_name = "/dev/sda1" # /
        bsu {
            volume_size = 10
            volume_type = "gp2"
        }
    }
    block_device_mappings {
        device_name = "/dev/xvdb"
        bsu {
            volume_size = 4
            volume_type = "gp2"
        }
    }
#   block_device_mappings {                          # apply one time then uncomment and apply again
#       device_name = "/dev/xvdc"
#       bsu {
#           volume_size = 4
#           volume_type = "gp2"
#       }
#   }
}

Additional Context

References

[outscale-toa]

Hi @zeylos,

Updating/adding additional block_device_mappings to an existing VM is not possible actually with our terraform plugin.
This will come with the hot volume update ref #200 , #310

In your case, you can use the outscale_volume_link resource.

....
resource "outscale_volume_link" "volume_link01" {
    device_name = "/dev/xvdc"
    volume_id   = outscale_volume.volume01.volume_id
    vm_id       = outscale_vm.vm01.vm_id
}
....

Best regards,

[zeylos]

Hi,

Thanks for the quick answer, I found #200 but I thought it was unrelated, sorry.

Regards,