Terraform does mot respect explicit dependency in some cases

[HWE70]

Terraform Version

Terraform v0.10.7

Terraform Configuration Files

# -------------------------------------------------------------------------------------------------------------
# Allocate block storage for Service VMs
# -------------------------------------------------------------------------------------------------------------

resource "null_resource" "service_voldef" {
  count       = "${length(local.os_service_vols_def)}"

  triggers {
        node                = "${element(local.os_service_vols_node, count.index)}"
        volume_type         = "${element(split(":",element(local.os_service_vols_def, count.index)),0)}"
        device              = "${element(split(":",element(local.os_service_vols_def, count.index)),1)}"
        rel_name            = "${element(split(":",element(local.os_service_vols_def, count.index)),2)}"
        size                = "${element(split(":",element(local.os_service_vols_def, count.index)),3)}"
        mountpoint          = "${element(split(":",element(local.os_service_vols_def, count.index)),4)}"
        availability_zone   = "${element(local.os_service_vols_az, count.index)}"
  }
}

resource "openstack_blockstorage_volume_v2" "setup_service_volumes" {
  depends_on           = ["null_resource.service_voldef"]
  count                = "${length(local.os_service_vols_def)}"
  name                 = "${element(null_resource.service_voldef.*.triggers.node, count.index)}_${element(null_resource.service_voldef.*.triggers.rel_name, count.index)}"
  description          = "Persitent storage for ${element(null_resource.service_voldef.*.triggers.node, count.index)} device ${element(null_resource.service_voldef.*.triggers.device, count.index)}"
  size                 = "${element(null_resource.service_voldef.*.triggers.size, count.index)}"
  volume_type          = "${element(null_resource.service_voldef.*.triggers.volume_type, count.index)}"
  availability_zone    = "${element(null_resource.service_voldef.*.triggers.availability_zone, count.index)}"

  #lifecycle {
  #    prevent_destroy = true
  #}
}

# --------------------------------------------------------------------------------------------------
# Attach block storage to Service VMs
# --------------------------------------------------------------------------------------------------

#
# Search for matching pairs of instance and volume ids
#
resource "null_resource" "service_volid" {
  depends_on           = ["openstack_blockstorage_volume_v2.setup_service_volumes","openstack_compute_instance_v2.service"]
  count                = "${length(local.os_service_vols_def)}"

  triggers {
        volume_id      = "${element(openstack_blockstorage_volume_v2.setup_service_volumes.*.id, count.index)}"
        instance_id    = "${element(openstack_compute_instance_v2.service.*.id, index(openstack_compute_instance_v2.service.*.name, element(local.os_service_vols_node, count.index)))}"
  }
}

#
# Attach persistent storage
#
resource "openstack_compute_volume_attach_v2" "service" {
  depends_on  = ["null_resource.service_volid","openstack_blockstorage_volume_v2.setup_service_volumes","openstack_compute_instance_v2.service"]
  count       = "${length(local.os_service_vols_def)}"
  instance_id = "${element(null_resource.service_volid.*.triggers.instance_id, count.index)}"
  volume_id   = "${element(null_resource.service_volid.*.triggers.volume_id, count.index)}"
  device      = "${element(null_resource.service_voldef.*.triggers.device, count.index)}"
}

#
# Dummy resource for build process
#
resource "null_resource" "target_service_volumes" {
        depends_on = ["openstack_blockstorage_volume_v2.setup_service_volumes",
                      "openstack_compute_volume_attach_v2.service",
                      "null_resource.service_volid"]
}

Output

Refreshing Terraform state in-memory prior to plan...
The refreshed state will be used to calculate this plan, but will not be
persisted to local or remote state storage.

null_resource.nodes_service[0]: Refreshing state... (ID: 6013027129072800198)
null_resource.nodes_service[1]: Refreshing state... (ID: 1842577283801475772)
null_resource.volumes_service[0]: Refreshing state... (ID: 931939086905373848)
null_resource.volumes_service[2]: Refreshing state... (ID: 4302373968823752440)
null_resource.volumes_service[1]: Refreshing state... (ID: 8676549776352687611)
null_resource.volumes_service[3]: Refreshing state... (ID: 3907152824123562973)
openstack_compute_instance_v2.service[0]: Refreshing state... (ID: 39749ebf-f15a-4547-bd3d-0e7344acddf9)
openstack_compute_instance_v2.service[1]: Refreshing state... (ID: 7605c41d-71a1-42d2-a4a9-5e94fe07241c)

------------------------------------------------------------------------
Error running plan: 1 error(s) occurred:

* openstack_compute_volume_attach_v2.service: 4 error(s) occurred:

* openstack_compute_volume_attach_v2.service[1]: Resource 'null_resource.service_volid' does not have attribute 'triggers.instance_id' for variable 'null_resource.service_volid.*.triggers.instance_id'
* openstack_compute_volume_attach_v2.service[3]: Resource 'null_resource.service_volid' does not have attribute 'triggers.instance_id' for variable 'null_resource.service_volid.*.triggers.instance_id'
* openstack_compute_volume_attach_v2.service[0]: Resource 'null_resource.service_volid' does not have attribute 'triggers.instance_id' for variable 'null_resource.service_volid.*.triggers.instance_id'
* openstack_compute_volume_attach_v2.service[2]: Resource 'null_resource.service_volid' does not have attribute 'triggers.volume_id' for variable 'null_resource.service_volid.*.triggers.volume_id'

Expected Behavior

The instnaces are already in place. Volumes should be created and attached in one step. Expected behaviour is:

1. Calculate plan
2. Create volumes
3. Generate ids in "null_resource.service_volid"
4. Attach volumes

Actual Behavior

Between setting up the volumes in "openstack_blockstorage_volume_v2.setup_service_volumes" and attaching them in "openstack_compute_volume_attach_v2.service" I need generate the imstnace ids the volumes have to be attached to using "null_resource.service_volid". For this reason explicite dependencies are defined. But terraform ignores the dependecy for "openstack_blockstorage_volume_v2.setup_service_volumes" in "null_resource.service_volid" and fails with the errors above.

Steps to Reproduce

1. terraform plan -target=null_resource.target_service_volumes -out=/tmp/.sh_9398.tfplan
2. terraform apply /tmp/.sh_9398.tfplan

Important Factoids

If splitting it off in two parts end first create the volumes:

terraform plan -target=openstack_blockstorage_volume_v2.setup_service_volumes -out=/tmp/tfplan
terraform apply /tmp/tfplan

Everything works fine.

References

[ghost]

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