Create reusable resource configurations that can be included across templates with CloudFormation modules
Modules are a way for you to package resource configurations for inclusion across stack templates, in a transparent, manageable, and repeatable way. Modules can encapsulate common service configurations and best practices as modular, customizable building blocks for you to include in your stack templates. Modules enable you to include resource configurations that incorporate best practices, expert domain knowledge, and accepted guidelines (for areas such as security, compliance, governance, and industry regulations) in your templates, without having to acquire deep knowledge of the intricacies of the resource implementation.
For example, a domain expert in networking could create a module that contains built-in security groups and ingress/egress rules that adhere to security guidelines. You could then include that module in your template to provision secure networking infrastructure in your stack—without having to spend time figuring out how VPCs, subnets, security groups, and gateways work. And because modules are versioned, if security guidelines change over time, the module author can create a new version of the module that incorporates those changes.
Characteristics of using modules in your templates include:
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Predictability – A module must adhere to the schema it registers in the CloudFormation registry, so you know what resources it can resolve to once you include it in your template.
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Reusability – You can use the same module across multiple templates and accounts.
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Traceability – CloudFormation retains knowledge of which resources in a stack were provisioned from a module, enabling you to easily understand the source of resource changes.
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Manageability – Once you've registered a module, you can manage it through the CloudFormation registry, including versioning and account and regional availability.
A module can contain:
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One or more resources to be provisioned from the module, along with any associated data, such as outputs or conditions.
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Any module parameters, which enable you to specify custom values whenever the module is used.
For information about developing modules, see Developing modules in the CloudFormation CLI User Guide.
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Considerations when using modules
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There is no additional charge for using modules. You pay only for the resources those modules resolve to in your stacks.
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CloudFormation quotas, such as the maximum number of resources allowed in a stack, or the maximum size of the template body, apply to the processed template whether the resources included in that template come from modules or not. For more information, see Understand CloudFormation quotas.
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Tags you specify at the stack level are assigned to the individual resources derived from the module.
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Helper scripts specified at the module level don't propagate to the individual resources contained in the module when CloudFormation processes the template.
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Outputs specified in the module are propagated to outputs at the template level.
Each output will be assigned a logical ID that's a concatenation of the module logical name and the output name as defined in the module. For more information, see Get exported outputs from a deployed CloudFormation stack.
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Parameters specified in the module aren't propagated to parameters at the template level.
However, you can create template-level parameters that reference module-level parameters. For more information, see Use parameters to specify module values.
