Terraform output

As explained in Infrastructure as Code, Patterns and Practices: With examples in Python and Terraform

A Terraform output is a named value exported by a module for access by other configurations or users.

A Terraform output is a named value exported by a module so dependent configurations or users can retrieve selected resource attributes. Outputs create an interface between infrastructure components without requiring direct references to internal resources. section 4.2.1 section 4.3

Use outputs to:

• Pass a network name, subnet address range, bucket name, or other required attribute to dependent resources. section 4.2.1
• Limit the information returned by a low-level module while improving composability and evolvability. section 4.2.1
• Provide an abstraction between high-level and low-level resources through module outputs or infrastructure state. section 4.2.2

Connecting a server to a network

A network module exports its subnet name in terraform.tfstate. A server module reads that output and uses the value to create the server on the correct network. If a queue later needs the subnet IP range, the network module can add that attribute to its outputs. section 4.2.1

Figure 4.8 The facade simplifies attributes to the name of the storage bucket for use by the access control module.

Shows outputs simplifying a storage bucket’s attributes for an access-control module. section 4.3

How Infrastructure as Code, Patterns and Practices: With examples in Python and Terraform covers it

How deep it goes

Explains outputs through dependency patterns, state JSON, and implementation examples, including abstraction trade-offs between modules.

Examples

Uses network names, subnet ranges, server creation, storage buckets, access-control rules, and Terraform state JSON.

What it assumes

Assumes familiarity with modules and resources, while defining inversion of control, dependency inversion, and dependency injection.

What you can do after

Apply it via module outputs to pass infrastructure attributes while reducing direct references between resources.

How it connects

Ties outputs to inversion of control, dependency inversion, dependency injection, facade pattern, and infrastructure state.

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Also explained in

• 

  liveBookmanning.com
  Terraform in Depth: Infrastructure as Code with Terraform and OpenTofuA Terraform output is a named configuration value exposed from a module for display or consumption by its caller.

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Related concepts

• terraform_remote_stateproduced by · terraform_remote_state is a built-in Terraform data source that reads outputs from another Terraform state without modifying that state.
• moduleproduces · A module is a distinct, bounded software unit that groups related code or functionality and provides an organizational or interaction boundary within a larger system.
• facade patternused by · The facade pattern is a structural design pattern that provides a simplified interface to a complex subsystem or set of underlying components.

This explainer was generated by Manning's knowledge graph from the text of Infrastructure as Code, Patterns and Practices: With examples in Python and Terraform. The section links point to the parts of the book it draws on.