| 1 | ## Features
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| 2 |
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| 3 | * Write reusable CloudFormation snippets, called `particles` that can be used
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| 4 | accross condensation projets
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| 5 | * Package templates and assets then upload full distributions to multiple buckets across
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| 6 | regions with one command.
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| 7 | * Reference another template within the distribution with
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| 8 | [AWS::CloudFormation::Stack](http://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-properties-stack.html)
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| 9 | and the `templateS3Url` helper
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| 10 | * Upload scripts, configuration files and other assets alongside
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| 11 | CloudFormation templates and reference them with asset helpers.
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| 12 |
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| 13 | ## Why?
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| 14 |
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| 15 | CloudFormation templates are great for creating, updating and deleting
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| 16 | AWS resources. Reusing parts of templates, referencing other
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| 17 | templates with `AWS::CloudFormation::Stack` and deploying cloud-init
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| 18 | scripts can be difficult to manage.
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| 19 |
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| 20 | * Sections such as AMI [mappings](http://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/mappings-section-structure.html)
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| 21 | are often re-used by many templates. Particles provide a way to
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| 22 | write the mapping once and reuse it in other templates by reference.
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| 23 | * It is common to set up resources, such as a VPC, with nearly
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| 24 | identical attributes and structure for different applications and
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| 25 | services. Condensation allows that definition to become a independent
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| 26 | stack that can be referenced by other templates that are part of the
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| 27 | same distribution.
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| 28 | * When bootstrapping ec2 instances it is beneficial to have versioned scripts and configuration
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| 29 | files deployed in the same bucket and path as the CloudFormation template
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| 30 | they are associated with.
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| 31 | * When using `AWS::CloudFormation::Authentication` to download assets from
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| 32 | S3 buckets all resources must be in the same region. Condensation
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| 33 | makes it easy to deploy the same templates and assets to multiple
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| 34 | regions and ensure the referencing URLs are always pointing to the
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| 35 | right place.
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| 36 |
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| 37 | For example, templates in a distribution can reference one another based on the
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| 38 | bucket they are deployed to.
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| 39 |
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| 40 | Example:
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| 41 |
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| 42 | "TemplateURL": "{{templateS3Url 'vpc.template' }}"
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| 43 | ...
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| 44 | "TemplateURL": "{{templateS3Url 'subnet.template' }}"
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| 45 |
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| 46 | Output:
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| 47 |
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| 48 | "TemplateURL": "https://s3-us-west-1.amazonaws.com/<BUCKET>/cftemplates/vpc.template"
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| 49 | ...
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| 50 | "TemplateURL": "https://s3-us-west-1.amazonaws.com/<BUCKET>/cftemplates/subnet.template"
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| 51 |
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| 52 | The Handlebars helper, `templateS3Url`, creates a URL that will always reference a template deployed within the same bucket.
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