amazon-web-services - 启用计数时创建 Terraform 输出

Question

我正在尝试为 Terraform 中已设置计数的资源创建一个 output.tf。当计数为 1 时，一切正常，但是当计数为 0 时，它不会:

如果我像这样创建输出

output "ec2_instance_id" {
  value = aws_instance.ec2_instance.id
}

它出错

because aws_instance.ec2_instance has "count" set, its attributes must be accessed on specific instances.

但是，将其更改为

output "ec2_instance_id" {
  value = aws_instance.ec2_instance[0].id
}

适用于计数为 1，但当计数为 0 时给出

aws_instance.ec2_instance is empty tuple

The given key does not identify an element in this collection value.

所以我看到了 this post并尝试

output "ec2_instance_id" {
  value = aws_instance.ec2_instance[count.index].id
}

但这给

The "count" object can be used only in "resource" and "data" blocks, and only when the "count" argument is set.

什么是正确的语法？

Answer 1

只要你只关心1个或0个实例，就可以访问整个列表可以使用splat expression aws_instance.ec2_instance[*].id与 join函数和一个空字符串，根据资源是否被创建而产生 ID 或空字符串。

output "ec2_instance_id" {
  value = join("", aws_instance.ec2_instance[*].id)
}

例子:

variable "thing1" {
  default = [
    { id = "one" }
  ]
}

variable "thing2" {
  default = []
}

output "thing1" {
  value = join("", var.thing1[*].id)
}

output "thing2" {
  value = join("", var.thing2[*].id)
}

结果是

➜ terraform apply

Apply complete! Resources: 0 added, 0 changed, 0 destroyed.

Outputs:

thing1 = one
thing2 =