Plan shows and apply does some changes to "network_interface.*" of most instances on every run, without change in the code

[gdubicki]

Terraform Version

Terraform v0.10.2

Affected Resource(s)

• google_compute_instance

Terraform Configuration Files

We are using old-style networks:

resource "google_compute_network" "mon" {
  name       = "mon"
  ipv4_range = "10.116.11.0/24"
}

And our nodes are defined like this:

resource "google_compute_instance" "gateway" {
  count = "${var.gateway_count}"

  name           = "mon-gateway0${count.index + 1}"
  machine_type   = "n1-standard-1"
  zone           = "${lookup(var.zones, count.index)}"
  tags           = ["gateway", "mon-allow-ssh", "mon-allow-https", "mon-allow-opentsdb-traffic", "mon-allow-http"]
  can_ip_forward = true

  lifecycle {
    prevent_destroy = true
    ignore_changes  = ["metadata_startup_script", "create_timeout", "disk"]
  }

  disk {
    image = "${var.centos_image}"
  }

  network_interface {
    network = "${google_compute_network.mon.name}"

    access_config {
      nat_ip = "${element(google_compute_address.gateway.*.address, count.index)}"
    }
  }

  metadata {
    puppet_master      = "${var.puppetmaster}"
    puppet_environment = "production"
  }

  metadata_startup_script = "${file("../common/scripts/bootstrap.sh")}"
}
}

Debug Output

(I am checking possibility to share it with the rest of my team.)

Expected Behavior

We are not changing tf code, so plan should return no changes. Apply should make no changes.

Actual Behavior

Plan returns some changes do be done.

Example for those changes for nodes with external IPs:

  ~ google_compute_instance.gateway[0]
      network_interface.#:                                 "1" => "1"
      network_interface.0.access_config.#:                 "1" => "1"
      network_interface.0.access_config.0.assigned_nat_ip: "xxx.yyy.zzz.vvv" => "<computed>"
      network_interface.0.access_config.0.nat_ip:          "xxx.yyy.zzz.vvv" => "xxx.yyy.zzz.vvv"
      network_interface.0.address:                         "10.116.11.3" => "<computed>"
      network_interface.0.name:                            "nic0" => "<computed>"
      network_interface.0.network:                         "https://www.googleapis.com/compute/v1/projects/my-project/global/networks/mon" => "mon"
      network_interface.0.subnetwork_project:              "" => "<computed>"

(Note that "xxx.yyy.zzz.vvv" is the same, current external IP in all 3 places above.)

Example for other nodes:

  ~ google_compute_instance.stack_graph_satellite[2]
      network_interface.#:                    "1" => "1"
      network_interface.0.address:            "10.116.11.4" => "<computed>"
      network_interface.0.name:               "nic0" => "<computed>"
      network_interface.0.network:            "https://www.googleapis.com/compute/v1/projects/my-project/global/networks/mon" => "mon"
      network_interface.0.subnetwork_project: "" => "<computed>"

Apply does those changes.

On the next run plan and apply to the same.

Steps to Reproduce

1. terraform plan or terraform apply

Important Factoids

This has started to happen somewhere in the last few weeks, after some Terraform upgrade.

It also does not happen for new nodes, created within the last few weeks.

[gdubicki]

Update to Terraform 0.10.3 didn't help.

[gdubicki]

Upgrading to google provider v0.1.3 (I was using 0.1.0 before - I expected it to autoupdate/notify me about new version the same way Terraform itself does...) didn't help too.

[rosbo]

Hum... In 0.1.3, we added a method to suppress the diff between a self-link and a name.

As a work-around, try using the self-link of the network instead of the name:

...
network_interface {
    network = "${google_compute_network.mon.self_link}"
    ...
}
...

Let me know if that fixes your problem.

[gdubicki]

Yay! It helped. :)

(Note to self: I had to change it for google_compute_instances only because changing it in all my project files resulted in changing google_compute_firewalls too and that would recreate them.)

[rosbo]

I filed an issue (#377) to make sure google_compute_firewall support both name or self_link for its network field. Right now, only the name field works properly.

[paddycarver]

Hey @gdubicki, I'm building off 676a2a9 for the GCP provider and 9504d17 for Terraform, and I can't seem to recreate this. I've gotten a diff for the compute address region (weirdly enough) but never for the network interfaces.

Here's my minimal reproduction. Can you give it a try and see if it's reproducible for you?

resource "google_compute_instance" "gateway" {
  name           = "paddy-gcp-371-test"
  machine_type   = "n1-standard-1"
  zone           = "us-central1-b"
  tags           = ["gateway", "mon-allow-ssh", "mon-allow-https", "mon-allow-opentsdb-traffic", "mon-allow-http"]
  can_ip_forward = true

  lifecycle {
    ignore_changes = ["metadata_startup_script", "create_timeout", "disk"]
  }

  disk {
    image = "ubuntu-1404-trusty-v20170831"
  }

  network_interface {
    network = "${google_compute_network.default.name}"

    access_config {
      nat_ip = "${google_compute_address.gateway.address}"
    }
  }
}

resource "google_compute_address" "gateway" {
  name   = "paddy-gcp-371-test"
  region = "us-central1"
}

resource "google_compute_network" "default" {
  name       = "paddy-gcp-371-test"
  ipv4_range = "10.116.11.0/24"
}

[rileykarson]

@paddycarver: #375 may have fixed this by coincidence

[paddycarver]

Good point. I'll do a before/after test and see if I can confirm that as the source of the fix. If so, I'll close this.

[paddycarver]

Hmm, I'm not seeing this even on 9bd35d7, which is the commit before #375 was merged. I'm going to close this out as unreproducible, but if you're still seeing it @gdubicki, please feel free to comment on the issue again and we'll reopen it for investigation.

[ghost]

I'm going to lock this issue because it has been closed for 30 days ⏳. This helps our maintainers find and focus on the active issues.

If you feel this issue should be reopened, we encourage creating a new issue linking back to this one for added context. If you feel I made an error 🤖 🙉 , please reach out to my human friends 👉 [email protected]. Thanks!