module invocations should support count

[EvanKrall]

I tried to do something like nested loops of sorts by writing code that looks like:

module "group" {
    count = "${var.group_count}"
    source = "./group"
    argument = "${element(split(" ", var.arguments), count.index)}"
}

This results in a crash:

panic: runtime error: invalid memory address or nil pointer dereference
[signal 0xb code=0x1 addr=0x0 pc=0x4db834]

goroutine 518 [running]:
github.com/hashicorp/terraform/terraform.(*Interpolater).valueCountVar(0xc2084b74a0, 0xc208439880, 0xc2081cc990, 0xb, 0xc2080bf200, 0xc20843b0b0, 0x0, 0x0)
    /root/build/src/github.com/hashicorp/terraform/terraform/interpolate.go:89 +0x124
github.com/hashicorp/terraform/terraform.(*Interpolater).Values(0xc2084b74a0, 0xc208439880, 0xc2081d24b0, 0x3, 0x0, 0x0)
    /root/build/src/github.com/hashicorp/terraform/terraform/interpolate.go:58 +0x5a7
github.com/hashicorp/terraform/terraform.(*BuiltinEvalContext).Interpolate(0xc208081980, 0xc2081c7800, 0x0, 0x0, 0x0, 0x0)
    /root/build/src/github.com/hashicorp/terraform/terraform/eval_context_builtin.go:208 +0x118
github.com/hashicorp/terraform/terraform.(*EvalInterpolate).Eval(0xc2084397e0, 0x7f4d5e183300, 0xc208081980, 0x0, 0x0, 0x0, 0x0)
    /root/build/src/github.com/hashicorp/terraform/terraform/eval_interpolate.go:16 +0x68
github.com/hashicorp/terraform/terraform.EvalRaw(0x7f4d5e183550, 0xc2084397e0, 0x7f4d5e183300, 0xc208081980, 0x0, 0x0, 0x0, 0x0)
    /root/build/src/github.com/hashicorp/terraform/terraform/eval.go:53 +0x254
github.com/hashicorp/terraform/terraform.(*EvalSequence).Eval(0xc208439840, 0x7f4d5e183300, 0xc208081980, 0x0, 0x0, 0x0, 0x0)
    /root/build/src/github.com/hashicorp/terraform/terraform/eval_sequence.go:10 +0xf9
github.com/hashicorp/terraform/terraform.EvalRaw(0x7f4d5e183500, 0xc208439840, 0x7f4d5e183300, 0xc208081980, 0x0, 0x0, 0x0, 0x0)
    /root/build/src/github.com/hashicorp/terraform/terraform/eval.go:53 +0x254
github.com/hashicorp/terraform/terraform.Eval(0x7f4d5e183500, 0xc208439840, 0x7f4d5e183300, 0xc208081980, 0x0, 0x0, 0x0, 0x0)
    /root/build/src/github.com/hashicorp/terraform/terraform/eval.go:34 +0x79
github.com/hashicorp/terraform/terraform.func·027(0x99d460, 0xc20812d980, 0x0, 0x0)
    /root/build/src/github.com/hashicorp/terraform/terraform/graph.go:158 +0x754
github.com/hashicorp/terraform/dag.func·006(0x99d460, 0xc20812d980, 0xc20859d980, 0xc20859dc20)
    /root/build/src/github.com/hashicorp/terraform/dag/dag.go:215 +0x106
created by github.com/hashicorp/terraform/dag.(*AcyclicGraph).Walk
    /root/build/src/github.com/hashicorp/terraform/dag/dag.go:224 +0x845

It would be nice to be able to call a module multiple times, passing different arguments each time.

I think I can get around this with judicious use of count=${inner * outer} and modulo and division, but it feels a bit dirty.

[JeanMertz]

I think I have a use case for this as well:

Given three AWS instances, I want to create a round-robin DNS record at DNSMadeEasy.

Current implementation (using ELB) is:

resource "dme_record" "vpn" {
  domainid = "xxx"
  name = "cluster.${var.stack}.vpn"
  type = "A"
  value = "${aws_eip.vpn.public_ip}"
  ttl = 60
}

What I'd like to do is use aws_instance.vpn.{1,2,3}.public_ip in a dynamic way, where I create a single DNS record with the same name but different IP for each AWS instance.

I believe this is currently not possible, and I also believe that this feature request would solve my problem.

[JeanMertz]

I spoke too soon, my use case is solved using count with the element function:

resource "dme_record" "vpn" {
  count = "${var.vpn_count}"

  domainid = "xxx"
  name = "cluster.${var.stack}.vpn"
  type = "A"
  value = "${element(aws_instance.vpn.*.public_ip, count.index)}"
  ttl = 60
}

[jwthomp]

I am also hitting the need for count support in modules support. The use case is for using the docker provider to launch swarm agents across a list of nodes. I have put the swarm agent setup in a module to allow for being able to dynamically set up the docker provider based on a list of nodes.

module "agent" {
  source           = "./agent"
  docker_ip        = "${lookup(var.docker_ip, count.index)}"
  docker_port      = "${lookup(var.docker_port, count.index)}"
  swarm_version    = "${var.swarm_version}"
  swarm_token      = "${var.swarm_token}"
  count            = 3
}

NOTE: I've reposted this here as a similar issue on this topic was closed, and figured it would be more useful to attach to an open issue.

[jjshoe]

My use case is a module with 8 resources used for configuring infrastructure related to applications. For each application I'd like to just adjust things in a tfvars file, and not have to copy/pasta a module call.

[jjshoe]

#953

[catsby]

Hey Friends – I'm closing this as a duplicate of #953

[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 have found a problem that seems similar to this, please open a new issue and complete the issue template so we can capture all the details necessary to investigate further.