CloudFormation tips, tricks & best practices

Tips and tricks on using complementary tools to help you create and manage CloudFormation templates.

Includes discussion on Ansible and Ruby and using them with CloudFormation.

Organising and partitioning stacks

Getting out of trouble

Migrations

Transcript

1. CloudFormation Best practices, tips & tricks
2. “...an easy way to create and manage a collection of related AWS resources, provisioning and updating them in an orderly and predictable fashion.”
3. Writing templates by hand? Good luck :-)
4. Generators
5. https://github.com/bazaarvoice/ cloudformation-ruby-dsl
6. Other generators • https://github.com/cloudtools/troposphere (Python) • https://github.com/tongueroo/lono (Ruby) • https://github.com/MonsantoCo/cloudformation-template- generator (Scala)
7. Organising
8. God stack • Single stack for all resources • Good for small deployments • Size limits • Reuse only by using a generator tool
9. Nested stacks ┌─────────────────┐ │ │ │ │ │ Solution │ │ │ │ │ └─────────────────┘ │ ┌───────────────────┬─────────┴─────────┬───────────────────┐ ▼ ▼ ▼ ▼ ┌─────────────────┐ ┌─────────────────┐ ┌─────────────────┐ ┌─────────────────┐ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ VPC │ │ Database │ │ Servers │ │ Security Groups │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ └─────────────────┘ └─────────────────┘ └─────────────────┘ └─────────────────┘
10. Nested stacks • CloudFormation invokes child templates • Atomic execution • One fails, all fail • Pass parameters through "references" • Need to pass parameters for child template "through" the parent
11. Pipelined stacks Executor ┌─────────────────┐ ┌─────────────────┐ ┌─────────────────┐ ┌─────────────────┐ │ 1 │ │ 2 │ │ 3 │ │ 4 │ │ │ │ │ │ │ │ │ │ VPC │ │ Database │ │ Servers │ │ Security Groups │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ └─────────────────┘ └─────────────────┘ └─────────────────┘ └─────────────────┘
12. Pipelined stacks • Execute each template manually, requires orchestration • Non-atomic execution • One fails, only that template fails • Pass parameters directly • Chain outputs to inputs
13. Partitioning
14. Horizontal ┌─────────────────┐ ┌─────────────────┐ ┌─────────────────┐ ┌─────────────────┐ │ │ │ Database │ │ Servers │ │ Security Groups │ │ │ ├─────────────────┤ ├─────────────────┤ ├─────────────────┤ │ │ │ Application 1 │ │ Application 1 │ │ Application 1 │ │ VPC │ │ │ ├─────────────────┤ ├─────────────────┤ │ │ ├─────────────────┤ │ Application 2 │ │ Application 2 │ │ │ │ Application 2 │ ├─────────────────┤ ├─────────────────┤ │ │ │ │ │ Application 3 │ │ Application 3 │ └─────────────────┘ └─────────────────┘ └─────────────────┘ └─────────────────┘
15. Vertical ┌─────────────────┐ ┌─────────────────┐ ┌─────────────────┐ ┌─────────────────┐ │ │ │ Application 1 │ │ Application 2 │ │ Application 3 │ │ │ ├─────────────────┤ ├─────────────────┤ ├─────────────────┤ │ │ │ Servers │ │ Servers │ │ │ │ VPC │ ├─────────────────┤ ├─────────────────┤ │ Servers │ │ │ │ Database │ │ Database │ │ │ │ │ ├─────────────────┤ ├─────────────────┤ ├─────────────────┤ │ │ │ Security Groups │ │ Security Groups │ │ Security Groups │ └─────────────────┘ └─────────────────┘ └─────────────────┘ └─────────────────┘
16. Partitioning • Keep templates simple • Reuse parameters and mappings via a DSL • Choose vertical or horizontal scaling • Decide if you want to rollback the stack or not
17. Orchestration
18. Shell • Simple batch script • Use aws-cli to invoke CloudFormation templates: aws cloudformation create-stack... • Capture output variables for input variables for next stack • Returns immediately, therefore must check status: aws cloudformation create-describe-stacks...
19. Ansible - name: launch ansible cloudformation example cloudformation: stack_name: ansible-cloudformation state: present region: us-east-1 disable_rollback: true template: files/cloudformation-example.json template_parameters: KeyName: jmartin DiskType: ephemeral InstanceType: m1.small ClusterSize: 3 tags: Stack: ansible-cloudformation
20. Ansible - include: key_pairs.yml tags: always - include: compile.yml tags: always - include: vpc.yml tags: always - include: nat.yml tags: nat - include: titan.yml tags: titan
21. Ansible - name: delete old cloudformation templates file: path: "{{ item }}" state: absent with_fileglob: ../cloudformation/compiled/*.json when: clean is defined and clean|bool - name: compile the cloudformation templates shell: "{{ item }} expand --nopretty" with_fileglob: ../cloudformation/dsl/*.rb register: compiled - name: write and validate templates template: src: templates/cloudformation.json dest: cloudformation/compiled/{{ item.item | basename | regex_replace('\.rb$', '.json') }} validate: aws cloudformation validate-template --region {{ region }} --template-body file://%s environment: AWS_ACCESS_KEY_ID: "{{ aws_credentials[env].access_key }}" AWS_SECRET_ACCESS_KEY: "{{ aws_credentials[env].secret_key }}" with_items: compiled.results
22. Ansible - name: execute vpc cloudformation template cloudformation: aws_access_key: "{{ aws_credentials[env].access_key }}" aws_secret_key: "{{ aws_credentials[env].secret_key }}" stack_name: vpc-{{ env }} region: "{{ region }}" template: ./cloudformation/compiled/vpc.json disable_rollback: true template_parameters: Environment: "{{ env }}" tags: Environment: "{{ env }}" Region: "{{ region }}" register: vpc
23. Ansible - name: execute titan cloudformation template cloudformation: aws_access_key: "{{ aws_credentials[env].access_key }}" aws_secret_key: "{{ aws_credentials[env].secret_key }}" stack_name: titan-{{ env }} region: "{{ region }}" template: ./cloudformation/compiled/titan.json disable_rollback: true template_parameters: Environment: "{{ env }}" CochlearLinkHostedZone: "{{ vpc.stack_outputs.HostedZone }}" CochlearLinkVpc: "{{ vpc.stack_outputs.Vpc }}" TitanSubnets: "{{ vpc.stack_outputs.TitanSubnets }}" tags: Environment: "{{ env }}" Region: "{{ region }}" register: titan
24. Configuration
25. Configuration • Keep configuration in Git, S3 or DynamoDB • raw files from GitHub work well
26. { "ap-southeast-2": { "dev": { "productVersion": "3.0.0", "installationId": "eeeeeeee-f057-40c7-b365-792cc7faeccb" }, "sit": { "productVersion": "3.1.8", "installationId": "17171717-f057-40c7-b365-792cc7faeccb" } }, "us-east-1": { "prd": { "productVersion": "2.1.0", "installationId": "e047ac6f-f057-40c7-b365-792cc7faeccb" } } }
27. { "components": { "3.1.8": { "app": "3.1.8", "db": "1.0.1", } } }
28. { "versions": { "3.1.8": { "ap-southeast-2": { "image": "ami-9f266aa5" }, "eu-west-1": { "image": "ami-0914307e" } }, "3.1.2": { "ap-southeast-2": { "image": "ami-170e422d" }, "eu-west-1": { "image": "ami-5dbf9a2a" } } } }
29. - name: get environments config uri: url: https://your-git-repo.com/application/config/raw/master/environments.json return_content: yes register: environments_meta_raw
30. Getting out of trouble
31. The dreaded _FAILED states CREATE_FAILED DELETE_FAILED ROLLBACK_FAILED UPDATE_ROLLBACK_FAILED
32. The dreaded _FAILED states • Resolve manually • Console will give you indication of which resource failed to update • Delete offending resource or its dependencies manually • Run delete stack again • When in real shit, call support
33. The first rule of Fight Club CloudFormation
34. Resources not provisioned by CloudFormation are not recognised by CloudFormation
35. Resources provisioned by CloudFormation but changed outside of CloudFormation have a high probability of failing in subsequent updates
36. Migrating to CloudFormation
37. Creating the templates • Use CloudFormer to instrospect your VPC. • http://docs.aws.amazon.com/AWSCloudFormation/latest/ UserGuide/cfn-using-cloudformer.html • http://aws.amazon.com/developertools/6460180344805680 • Uses a Micro instance inside your VPC to interrogate and dumps results to S3 • Parse with the ruby cloudformation-ruby-dsl :-)
38. Incorporating templates • Resources must be provisioned by CloudFormation • Use a phased approach. Use Ref to refer to existing resources, passed as parameters. • Usually in reverse of your pipeline — machines first, VPCs last • e.g. "VpcId" : { "Ref" : "VpcId" }
39. Policies • Use DependsOn and WaitConditions to control dependency creation • Use UpdatePolicy for ASG changes. • Use DeletionPolicy to ensure are not deleted by CloudFormation (instance termination protection on steroids) • Note the Update requires property in the documentation
40. Best practices • http://docs.aws.amazon.com/AWSCloudFormation/latest/ UserGuide/best-practices.html
42. Other • Test deploys in a sandbox environment that mirrors production. Smaller resource types can help reduce costs. • Parameterise everything. • Use the http://docs.aws.amazon.com/AWSCloudFormation/ latest/UserGuide/template-reference.html
44. Thanks :-) Steven Ringo steven@stevenringo.com