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What's new in Terraform 0.12

Erik R. Rygg

Enterprise Architect

erik@hashicorp.com | @errygg

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Terraform

Write, Plan, and Create Infrastructure as Code

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Infrastructure as Code

Provide a codified workflow to create infrastructure
Expose a workflow for managing updates to existing infrastructure
Integrate with application code workflows (Git, SCM, Code Review)
Provide modular, sharable components for separation of concerns

Infrastructure as Code

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Configuration Syntax

Configurations are written in HashiCorp Configuration Language (HCL)
Designed to strike a balance between human-readable and machine-parsable
Terraform can also read syntax in JSON, but we recommend using HCL

Infrastructure as Code

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State

Terraform stores the state of your managed infrastructure from the last time Terraform was run
Terraform uses this state to create plans and make changes to your infrastructure
It is critical that this state is maintained appropriately so future runs operate as expected

Infrastructure as Code

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Terraform 0.11

`random_pet` Simple Example

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variable "count" {� default = 1�}��variable "default_prefix" {� default = "linus"�}��resource "random_pet" "my_pet" {� count = "${var.count}"� prefix = "${var.default_prefix}"�}�

Terraform 0.11 Examples

Terraform

0.11

main.tf

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terraform apply��random_pet.my_pet: Creating...� length: "" => "2"� prefix: "" => "linus"� separator: "" => "-"�random_pet.my_pet: Creation complete after 0s (ID: linus-excited-goldfish)��Apply complete! Resources: 1 added, 0 changed, 0 destroyed.��Outputs:��pet_names = [� Pet: linus-excited-goldfish�]�

Terraform 0.11 Examples

Terraform

0.11

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TERMINAL

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Terraform 0.11

`random_pet` Example - a bit more complicated

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Terraform 0.11

main.tf

Terraform 0.11 Examples

variable "count" { default = 1 }�variable "default_prefix" { default = "linus" }��variable "zoo_enabled" {� default = "0"�}��variable "prefix_list" {� default = []�}��resource "random_pet" "my_pet" {� count = "${var.count}"� prefix = "${var.zoo_enabled == "0" ?

var.default_prefix :

element(var.prefix_list, count.index)}"�}��

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Terraform 0.11

terraform.tfvars

Terraform 0.11 Examples

zoo_enabled = "1"�prefix_list = [ "linus", "cheetarah", "li-shou"]�count = 3�

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Terraform 0.11

Terraform 0.11 Examples

random_pet.my_pet[1]: Creating...� length: "" => "2"� prefix: "" => "cheetarah"� separator: "" => "-"�[…] ��Apply complete! Resources: 3 added, 0 changed, 0 destroyed.��Outputs:��pet_names = [� Pet: linus-special-goblin,� Pet: cheetarah-loyal-drake,� Pet: li-shou-witty-turtle�]�

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Terraform 0.11

Terraform 0.11 Examples

$ terraform apply��Error: random_pet.my_pet: 1 error(s) occurred:��* random_pet.my_pet: element: element() may not be used with an empty list in:��${var.zoo_enabled == "0" ? var.default_prefix : element(var.prefix_list, count.index)}�

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The hack

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Terraform 0.11

terraform.tfvars

Terraform 0.11 Examples

variable "count" { default = 1 }�variable "default_prefix" { default = "linus" }��variable "zoo_enabled" {� default = "0"�}��variable "prefix_list" {� default = []�}��resource "random_pet" "my_pet" {� count = "${var.count}"� prefix = "${var.zoo_enabled == "0" ?

var.default_prefix :

element(concat(var.prefix_list, list("")),

count.index)}"�}�

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Terraform 0.11

Terraform 0.11 Examples

$ terraform apply��random_pet.my_pet: Creating...� length: "" => "2"� prefix: "" => "linus"� separator: "" => "-"�random_pet.my_pet: Creation complete after 0s (ID: linus-driving-giraffe)��Apply complete! Resources: 1 added, 0 changed, 0 destroyed.��Outputs:��pet_names = [� Pet: linus-driving-giraffe�]�

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Terraform 0.12

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Terraform 0.11 & Earlier

HCL - HashiCorp Configuration Language

Terraform 0.12

variable "foo" { � default = "bar"�}�

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Terraform 0.11 & Earlier

HIL - HashiCorp Interpolation Language

Terraform 0.12

foo = "hello ${var.world}"��"${format(“Hello %s”, var.world)}"�

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Terraform Configuration Language - Terraform v0.12

Terraform 0.12

HCL2

Merges HCL and HIL
Introduces a robust type system
Addresses large list of enhancements and feature requests

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So many improvements...

Terraform 0.12

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First-class expressions. Prior to 0.12, expressions had to be wrapped in interpolation sequences with double quotes, such as "${var.foo}". With 0.12, expressions are a native part of the language and can be used directly. Example: ami = var.ami[1]
For expressions. A for expression is available for iterating and filtering lists and map values. This expression always can be used anywhere a list or map is expected.
Dynamic blocks. Child blocks such as rule in aws_security_group can now be dynamically generated based on lists/maps and support iteration.
Generalized "Splat" Operator. The special resource.*.field syntax used to only work for resources with countset. This is now a generalized operator that works for any list value.
Conditional improvements. The conditional operator ... ? ... : ... now supports any value type and lazily evaluates results, as those familiar with this operator in other languages would expect. Also, the special value nullcan now be assigned to any field to represent the absence of a value. This causes Terraform to omit the field from upstream API calls, which is important in some cases for triggering certain default behaviors.
Rich types in module inputs and outputs. Terraform has supported basic lists and maps as inputs/outputs since Terraform 0.7, but elements were limited to only simple values. Terraform 0.12 allows arbitrarily complex lists and maps for any inputs and outputs, including with modules.
Template syntax. Within string values, a new template syntax can be used for looping without complex nested interpolation. Example: %{ for instance in aws_instance.example ~}server ${instance.id}%{ endfor }.
Reliable JSON syntax. Terraform 0.12 HCL configuration has an exact 1:1 mapping to and from JSON.
References as first-class values. References to resources and modules for fields such as depends_on used to be arbitrary strings. In Terraform 0.12, the resource identifier can be used exactly such as aws_kms_grant.example (no quotes!). This improves the validation and error messages we can provide. Similarly, a resource reference can be returned from a module as an output or accepted as a parameter.

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Terraform 0.12

First Class Expressions

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First-Class Expressions

First Class Expressions

Operations and variables can be used outside of string interpolation

buh-bye "${ }"

Lists and maps can be used directly with expressions

less list(""), more []

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Terraform 0.11

main.tf

First Class Expressions

variable "ami" {}�variable "instance_type" {}�variable "vpc_security_group_ids" {� type = "list"�}��resource "aws_instance" "example" {� ami = "${var.ami}"� instance_type = "${var.instance_type}"�� vpc_security_group_ids = "${var.vpc_security_group_ids}"�}�

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Terraform 0.12

main.tf

First Class Expressions

variable "ami" {}�variable "instance_type" {}�variable "vpc_security_group_ids" {� type = list(string)�}��resource "aws_instance" "example" {� ami = var.ami� instance_type = var.instance_type�� vpc_security_group_ids = var.vpc_security_group_ids�}�

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Terraform 0.11

main.tf

First Class Expressions

variable "ami" {}�variable "instance_type" {}�variable "vpc_security_group_id" {� type = "string"� default = ""�}��resource "aws_instance" "example" {� ami = "${var.ami}"� instance_type = "${var.instance_type}"�� vpc_security_group_ids = "${var.vpc_security_group_id != "" ?

[var.vpc_security_group_id] :

list("")

}"�}�

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Terraform 0.12

main.tf

First Class Expressions

variable "ami" {}�variable "instance_type" {}�variable "vpc_security_group_id" {� type = string� default = ""�}��resource "aws_instance" "example" {� ami = var.ami� instance_type = var.instance_type�� vpc_security_group_ids = var.security_group_id != "" ?

[var.security_group_id] :

[]�}�

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Terraform 0.12

Rich Value Types

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Rich Value Types

enhances simple type system
complex values

maps and lists!
maps of maps!!
maps of lists of maps of lists!!!

entire resources and modules as values

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Terraform

Module Layout

Rich Value Types

$ tree�.�├── main.tf�├── terraform.tfvars�└── modules� └── subnets� └── subnets.tf�

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Terraform 0.11

main.tf

Rich Value Types

variable "networks" {� type = "list"�}��module "subnets" {� source = "./modules/subnets"� networks = "${var.networks}"� ...�}��output "vpc_id" {� value = "${module.subnets.vpc_id}"�}�

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Terraform 0.11

main.tf

Rich Value Types

# "subnets" module��variable "networks" {� type = "list"�}��resource "aws_vpc" "example" {� networks = "${var.networks}"� ...�}��output "vpc_id" {� value = "${aws_vpc.example.id}"�}�

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Terraform 0.12

main.tf

Rich Value Types

variable "networks" {� type = map(object({� network_number = number� availability_zone = string� tags = map(string)� }))�}��module "subnets" {� source = "./modules/subnets"� networks = var.networks�}��output "vpc_id" {� value = module.subnets.vpc_id�}�

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Terraform 0.12

terraform.tfvars

Rich Value Types

networks = {� "production" = {� network_number = 1� availability_zone = "us-east-1a"� }� "staging" = {� network_number = 2� availability_zone = "us-east-1a"� }�}�

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Terraform 0.12

subnets.tf

Rich Value Types

# "subnets" modules��variable "networks" {� type = map(object({� network_number = number� availability_zone = string� tags = map(string)� }))�}��resource "aws_vpc" "example" {� networks = var.networks� ...�}��output "vpc" {� value = aws_vpc.example�}�

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Terraform 0.12

main.tf

Rich Value Types

variable "networks" {� type = map(object({� network_number = number� availability_zone = string� tags = map(string)� }))�}��module "subnets" {

source = "./modules/subnets"� networks = var.networks�}��resource "aws_instance" "my_server" {� subnet_id = module.subnets.vpc.id� az = module.subnets.vpc.availability_zone� ... �}�

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Terraform 0.12

Improved Error Messages

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Terraform 0.11

Improved Error Messages

$ terraform plan��Error: Error parsing main.tf: object expected closing RBRACE got: EOF�

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Terraform 0.12

Improved Error Messages

$ terraform plan��Error: Argument or block definition required�� on main.tf line 24:� 24: :wq��An argument or block definition is required here.�

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Terraform 0.12

Improved Error Messages

$ terraform plan��Error: Invalid operand�� on main.tf line 16, in output "foobar":� 16: value = "${1 + var.foo}"��Unsuitable value for right operand: a number is required.�

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Terraform 0.12

Improved Error Messages

$ terraform plan��Error: Unsupported block type�� on main.tf line 36, in outptu "item":� 1: outptu "item" {��Blocks of type "outptu" are not expected here. Did you mean "output"?�

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Terraform 0.12

For Expressions

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For Expressions

for: list and map transformations
for_each: for dynamic nested blocks
dynamic nested blocks

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Terraform 0.11

main.tf

For Expressions

output "instance_private_ip_addresses_map" {� value = "${zipmap(aws_instance.id,aws_instance.private_ip)}"�}�

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Terraform 0.12

main.tf

For Expressions

output "instance_private_ip_addresses" {� value = {� for instance in aws_instance.example:� instance.id => instance.private_ip� }�}�

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Terraform 0.12

For Expressions

$ terraform output��instance_private_ip_addresses = {� "i-1234" = "192.168.1.1"� "i-5678" = "192.168.1.2"� "i-9876" = "192.168.1.3"�}�

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Terraform 0.11

main.tf

For Expressions

resource "aws_autoscaling_group" "example" {� # ...� tag {� key = "Component"� value = "user-service"� propagate_at_launch = true� }�� tag {� key = "Environment"� value = "production"� propagate_at_launch = false� }��tag { ... }�tag { ... }�tag { ... }�tag { ... }�}�

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Terraform 0.12

main.tf

For Expressions

locals {� standard_tags = {� Component = "user-service"� Environment = "production"� }�}��resource "aws_autoscaling_group" "example" {� # ...�� dynamic "tag" {� for_each = local.standard_tags�� content {� key = tag.key� value = tag.value� propagate_at_launch = true� }� }�}�

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Terraform 0.12

Back to `random_pet` Example

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Terraform 0.11

main.tf

Terraform 0.12 Examples

variable "count" { default = 1 }�variable "default_prefix" { default = "linus" }��variable "zoo_enabled" {� default = "0"�}��variable "prefix_list" {� default = []�}��resource "random_pet" "my_pet" {� count = "${var.count}"� prefix = "${var.zoo_enabled == "0" ?

var.default_prefix :

element(concat(var.prefix_list, list("")), count.index)}"�}�

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The same example - HCL2

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Terraform 0.12

main.tf

Terraform 0.12 Examples

variable "pet_count" { default = 1 }��variable "default_prefix" { default = “linus” }��variable "zoo_enabled" {� default = false�}��variable "prefix_list" {� default = []�}��resource "random_pet" "my_pet" {� count = var.pet_count� prefix = var.zoo_enabled ?

element(var.prefix_list,count.index) :

var.default_prefix�}�

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Terraform 0.12

Terraform 0.12 Examples

$ terraform apply�random_pet.my_pet[0]: Creating...�random_pet.my_pet[0]: Creation complete after 0s��Apply complete! Resources: 1 added, 0 changed, 0 destroyed.��Outputs:��pet_names = [� Pet: linus-beloved-mako�]�

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But what does it mean?

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Terraform 0.12 Enhancements

configuration is easier to read and reason about
consistent, predictable behavior in complex functions
improved support for loosely-coupled modules

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Demo?

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CFPs Open:

HashiConf USA

(closes 2nd April)

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hello@hashicorp.com

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Thank you