Declarative & workflow based infrastructure with Terraform

@radeksimko
Declarative & workflow based
infrastructure

@radeksimko
Radek Simko
@radeksimko

@radeksimko
Terraform Goals
● Describe infrastructure as code
● Provision efficiently (get as far as APIs allow at a time)
● Cover the whole lifecycle of the infrastructure
● Provide composability within and across multiple tiers (IaaS, PaaS, SaaS)

@radeksimko
Terraform is NOT solving
● OS-level provisioning
○ Chef
○ Puppet
○ Ansible
○ SaltStack
○ …
● But integrates with these tools

File
resource "google_compute_instance" "server" {
name = "server"
machine_type = "g1-small"
zone = "us-central1-a"
disk {
image = "ubuntu-1404-trusty-v20160114e"
}
network_interface { network = "default" }
}
resource "dnsimple_record" "hello" {
domain = "example.com"
name = "server"
value = "${google_compute_instance.server.network_interface.0.address}"
type = "A"
}

Terminal
$ terraform plan
+ google_compute_instance.server
can_ip_forward: "false"
create_timeout: "4"
disk.#: "1"
disk.0.auto_delete: "true"
disk.0.disk_encryption_key_sha256: "<computed>"
disk.0.image: "ubuntu-1404-trusty-v20160114e"
machine_type: "g1-small"
metadata_fingerprint: "<computed>"
name: "server"
network_interface.#: "1"
network_interface.0.address: "<computed>"
network_interface.0.name: "<computed>"
self_link: "<computed>"
tags_fingerprint: "<computed>"
zone: "us-central1-a"
...
Plan: 2 to add, 0 to change, 0 to destroy.

Terminal
$ terraform apply
google_compute_instance.server: Creating...
can_ip_forward: "" => "false"
create_timeout: "" => "4"
disk.#: "" => "1"
disk.0.auto_delete: "" => "true"
disk.0.disk_encryption_key_sha256: "" => "<computed>"
disk.0.image: "" => "ubuntu-1404-trusty-v20160114e"
machine_type: "" => "g1-small"
metadata_fingerprint: "" => "<computed>"
name: "" => "server"
...
zone: "" => "us-central1-a"
google_compute_instance.server: Still creating... (10s elapsed)
google_compute_instance.server: Still creating... (20s elapsed)
...
Apply complete! Resources: 2 added, 0 changed, 0 destroyed.

@radeksimko
Infrastructure as Code

@radeksimko
https://www.youtube.com/watch?v=SLh_6Ievi7A
Infrastructure as Code Might be Literally Impossible

@radeksimko
high-level
language
language
for dataDSL
JSON
{}
YAML
-- :

@radeksimko
http://jsonnet.org

@radeksimko
HCL
● github.com/hashicorp/hcl
● Used in various HashiCorp projects
○ Consul
○ Vault
○ Nomad
○ Terraform
● JSON compatible
○ Useful for generated code

Terminal
@radeksimko
service {
key = "hi ${var.world}"
}

@radeksimko
https://github.com/alphagov/govuk-dns

Terminal
@radeksimko
#!/bin/sh
aws rds create-instance ...
aws ec2 run-instance ...
aws s3 create-bucket ...
aws route53 create-recordset ...

Terminal
@radeksimko
resource "aws_s3_bucket" "b" {
...
}
data "aws_ami" "ubuntu" {
...
}
resource "aws_instance" "web" {
count = 3
...
}
resource "aws_db_instance" "default" {
...
}
resource "aws_route53_record" "www" {
...
}

Terminal
@radeksimko
$ terraform graph | dot -Tpng > graph.png
$

@radeksimko
Applying Graph Theory
● Build a graph
● Transform, find cycles
● Run operations in parallel

@radeksimko
Applying Graph Theory
The only limit is the sky
(Cloud API throttling)

@radeksimko
https://www.youtube.com/watch?v=Ce3RNfRbdZ0

@radeksimko
Life of
Pi Resource

Terminal
@radeksimko
#!/bin/sh
# Creation
aws rds create-instance ...
aws s3 create-bucket ...
aws route53 create-recordset ...

Terminal
@radeksimko
#!/bin/sh
# Renaming DB instance
aws rds create-instance … # new one
aws rds restore-from-snapshot …
aws route53 update-recordset …
aws rds destroy-instance … # old one

Terminal
@radeksimko
#!/bin/sh
# Renaming DB instance
aws rds create-instance … # new one
# wait until state == launched
aws rds restore-from-snapshot …
# wait until restored
aws route53 update-recordset …
# wait until DNS in sync
aws rds destroy-instance … # old one
# wait until instance gone

Terminal
@radeksimko
"identifier": {
Type: schema.TypeString,
Optional: true,
ForceNew: true,
ConflictsWith: []string{"identifier_prefix"},
ValidateFunc: validateRdsIdentifier,
},
"username": { …
"password": { …

Terminal
@radeksimko
stateConf := &resource.StateChangeConf{
Pending: []string{"creating", "backing-up", "modifying",
"resetting-master-credentials", "maintenance",
"renaming", "rebooting", "upgrading"},
Target: []string{"available"},
Refresh: resourceAwsDbInstanceStateRefreshFunc(d, meta),
Timeout: 40 * time.Minute,
MinTimeout: 10 * time.Second,
Delay: 30 * time.Second,
}

@radeksimko
Resource Schema
● More or less mapped to API structures
● Allows TF make decisions during the lifecycle
○ Creation
○ Updates
○ Destruction
● Allows TF to present accurate plan ahead of applying it
● Non-updatable fields

Terminal
@radeksimko
$ terraform plan
~ aws_instance.app
tags.%: "0" => "1"
tags.Name: "" => "HelloWorld"

Terminal
@radeksimko
$ terraform plan
-/+ aws_instance.app
ami: "ami-408c7f28" => "ami-4d795c5a" (forces new resource)
associate_public_ip_address: "true" => "<computed>"
availability_zone: "us-east-1d" => "<computed>"
ebs_block_device.#: "0" => "<computed>"
ephemeral_block_device.#: "0" => "<computed>"
instance_state: "running" => "<computed>"
instance_type: "t1.micro" => "t1.micro"
key_name: "" => "<computed>"
network_interface_id: "eni-8d666460" => "<computed>"
...

@radeksimko
Schema + DSL + graph theory
allow Terraform to make the right decisions
during the whole lifecycle

@radeksimko
● S3
● CloudFront
● Route 53
● RDS
● ...
● Cloud DNS
● Cloud CDN
● Cloud Storage
● Spanner
● BigTable
● ...

@radeksimko
What is infrastructure then?
A lot of things

@radeksimko
Providers
Amazon Bitbucket CenturyLink Cloud
CloudFlare CloudStack Cobbler
Consul Datadog DigitalOcean
DNSMadeEasy DNSimple Docker
Dyn GitHub Fastly
Google Heroku Librato
Microsoft Azure MySQL OpenStack
Packet PostgreSQL SoftLayer
UltraDNS VMware vSphere and more...

@radeksimko
Provider
● Group of resources
● Responsible for validating creds, setting up connection to API(s)
● Works in isolation
○ Terraform core is responsible for relationships between providers
● Is pluggable
○ Binary which talks RPC
○ Can be written in any language
■ But nobody has written helper libraries outside of Go land so far

Terminal
@radeksimko
provider "aws" {
region = "eu-west-1"
profile = "prod"
}

@radeksimko
Resource
● CR(U)D
○ Create()
○ Read()
○ Update()
○ Delete()
● API specifics
● Responsible for eventually making API calls
● Arguments (e.g. tags to assign to EC2 instance, AMI ID to use)
● Attributes (e.g. instance ID, ...)

Terminal
@radeksimko
ami = "${data.aws_ami.ubuntu.id}"
instance_type = "t2.micro"
tags {
Name = "HelloWorld"
}
}

@radeksimko
Data Source
● The “R” from resources (CRUD)
● Useful for
○ building on existing infrastructure
○ Keeping configs reusable
● Never modify loaded resource

File
data "aws_availability_zones" "available" {}
# Create 1 subnet per availability zone
resource "aws_subnet" "primary" {
count = "${length(data.aws_availability_zones.available.names)}"
availability_zone = "${data.aws_availability_zones.available.names[count.index]}"
...
}

File
data "aws_vpc" "selected" {
cidr_block = "10.0.1.0/20"
}
resource "aws_subnet" "primary" {
vpc_id = "${data.aws_vpc.selected.id}"
}

File
data "aws_cloudformation_stack" "network" {
name = "my-network-stack"
}
ami = "ami-abb07bcb"
subnet_id = "${data.aws_cloudformation_stack.network.outputs["SubnetId"]}"
tags {
Name = "HelloWorld"
}
}

@radeksimko
POST / HTTP/1.1
Host: ec2.eu-west-2.amazonaws.com
User-Agent: aws-sdk-go/1.8.13
Authorization: ...
Content-Type: ...
Action=RunInstances&...
ImageId=ami-63342007&InstanceType=
t2.micro...
HTTP/1.1 200 OK
Connection: close
Content-Type: ...
Server: AmazonEC2
<?xml version="1.0" encoding="UTF-8"?>
<RunInstancesResponse
xmlns="http://ec2.amazonaws.com/doc/2016-11-1
5/">
…
<instanceId>i-02228e28962ee478b</instanceId>

@radeksimko
Plz change this tag
from old to new, Ta!
For which
instance?
Few days later...

@radeksimko
Existing resources
● Lookups via tags or names
○ Not everything AWS supports tags
○ Not every provider supports tags
○ Tags may not be unique
○ Unique names don’t allow graceful recreation
○ 1 extra lookup API call to get the real unique ID for modify/delete API calls
● Storing unique ID in a state (Terraform)
○ Guaranteed to be unique
○ Provider-agnostic solution

@radeksimko
Worst case scenario
● Duplicate/wrong tag/name
■ Changed wrong resource
■ Destroyed wrong resource
● Drifted/decoupled state
○ Duplicate infrastructure
○ Original (production?) resources intact

@radeksimko
State Mgmt in Terraform
● Part of Remote Backend
○ Remote State
○ Locking
○ Environments
● Many supported backends
○ Consul, etcd
○ Azure Storage, S3, Google Cloud Storage
○ TFE
○ ...

Terminal
@radeksimko
# main.tf
resource "aws_instance" "app" {
count = 5
ami = "ami-408c7f28"
}

Terminal
@radeksimko
terraform {
backend "s3" {
bucket = "my-tfstate-prod"
key = "terraform.tfstate"
region = "eu-west-2"
}
}

@radeksimko
Summary
● Infrastructure as Code
● Efficiency
● Full lifecycle
● Composability
● State Management

Thanks!
Questions?
@radeksimko

Declarative & workflow based infrastructure with Terraform

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