SQL Database Instance does not have attribute ip_address.0.ip_address

[genevieve]

Terraform Version

Terraform v0.11.1

• provider.google v0.1.3
• provider.random v1.0.0
• provider.tls v1.0.0

Affected Resource(s)

• google_sql_database_instance

Terraform Configuration Files

resource "google_sql_database_instance" "master" {
  region           = "${var.region}"
  database_version = "MYSQL_5_6"
  name             = "${var.env_name}-${replace(lower(random_id.db-name.b64), "_", "-")}"

  settings {
    tier = "${var.sql_db_tier}"

    ip_configuration = {
      ipv4_enabled = true

      authorized_networks = [
        {
          name  = "all"
          value = "0.0.0.0/0"
        },
      ]
    }
  }

  count = "${var.count}"
}

output "sql_db_ip" {
  value = "${google_sql_database_instance.master.*.ip_address.0.ip_address}"
}

Debug Output

* module.external_database.output.sql_db_ip: Resource 'google_sql_database_instance.master' does not have attribute 'ip_address.0.ip_address' for variable 'google_sql_database_instance.master.*.ip_address.0.ip_address'

Expected & Actual Behavior

If I were to change the output value to:

output "sql_db_ip" {
  value = "${google_sql_database_instance.master.*.ip_address}"
}

I get:

sql_db_ip = [
    [
        map[ip_address:35.184.66.76 time_to_retire:]
    ]
]

I expect that in the former version of the output syntax (as is specified in the docs), it would print 35.184.66.76 and not an error that the attribute is not available. I additionally expect the output not to cause an error when the instance was not created.

It seems that trying to use the splat syntax and asking for nested attributes (conditionally) is not possible in terraform. If there is a single ip address assigned, why does the attribute have to be gathered by indexing with ip_address.0.ip_address? Could the instance have a single, non-nested attribute for returning the address?

Other Attempts

• Using the element syntax is not possible as master.*.ip_address will return a nested map and not a flat list. We can flatten this list with flatten(google_sql_database_instance.master.*.ip_address) but this is a list of maps and so we cannot select the first map with element(). We can't element(concat(flatten(...), list(SOMETHING))) because you need to concat the flatted list with another list of maps. list() only takes strings.

• We cannot do conditionals because they are not lazily evaluated and for the case where the instance is not created (count == 0), it still tries to get attributes.

  value = "${length(google_sql_database_instance.master.*.ip_address) > 0 ? lookup(google_sql_database_instance.master.*.ip_address[0], "ip_address", "") : ""}"

Steps to Reproduce

1. terraform apply

[danawillow]

I can get to the "why was it implemented that way?" questions tomorrow, but for now- is it possible to just output the working value and then when you're trying to use it in a resource, grab the value you need from the list of maps? (does that make sense? I can try to come up with a sample config if not)

[genevieve]

When this instance has a count of 1, we want to grab the value of it's ip address and expose it as a terraform output. It's possible to get that value when the instance is present, but we haven't yet found a way to make the output "empty" so that terraform does not fail.

If we know the instance is there, we tired to say google_sql_db_instance.master.0.ip_address.0.ip_address but that also returns an error.

[genevieve]

It seems like the combination of splat syntax + nested map attributes is hard for terraform to follow. We tried splitting it into multiple small local vars:

(This code might be a little off, I checked out the changes and am trying to remember one of dozens of things we tried 😄.)

locals {
  thing = "${google_sql_db_instance.master.*.ip_address}" // so we get the list of maps
  thing2 = "${local.thing[0]}" // To get the first map
  thing3 = "${local.thing2.ip_address}" //To get the ip addr
}

output "ip" {
  value = "${var.count == 0 ? "" : local.thing3}"
}

And this will fail when the count is 0.

[genevieve]

This is obviously only breaking us since the v0.11.0 change to terraform output errors when empty (and forcing the splat syntax).

[danawillow]

Ah, ok. In that case I'd recommend filing an issue in the core repository: github.com/hashicorp/terraform, since even though you're using the Google provider, the actual problem could have happened with any of them if they followed this pattern. Probably best to make a note that you filed here first and I sent you there, so they don't try to send you back here.

As for why we use a nested resource for ip addresses, that's just to mirror what the GCP API gives us: https://cloud.google.com/sql/docs/mysql/admin-api/v1beta4/instances. Since that documentation makes it sound like there could be more than one value in the list, we allow for more than one value in Terraform as well.

[genevieve]

Thanks Dana! Will do!

[genevieve]

@rosbo Would it be possible to re-open this issue as there is something that can be done in this provider that would fix the issue and also be convenient for users?

The suggestion is from this comment: hashicorp/terraform#17048 (comment)

To work around the current limitations of the language, in principle the Google Cloud provider could export a simple attribute like first_ip_address that provides a convenience syntax for the presumably-common case of accessing the IP address in the first element of that list, which we could discuss with the team working on terraform-provider-google to see if they'd be interested in supporting such a thing.

[rosbo]

Oh. I missed that part. Reopening.

[genevieve]

@danawillow Would you be interested in a PR that added a first_ip_address to the sql db instance resource to provide a convenient syntax for accessing the first ip in the list?

[genevieve]

Going to close this since the above PR got merged!

[ghost]

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