terraform/website/docs/internals/resource-addressing.html.ma...

108 lines
2.5 KiB
Markdown

---
layout: "docs"
page_title: "Internals: Resource Address"
sidebar_current: "docs-internals-resource-addressing"
description: |-
Resource addressing is used to target specific resources in a larger
infrastructure.
---
# Resource Addressing
A __Resource Address__ is a string that references a specific resource in a
larger infrastructure. An address is made up of two parts:
```
[module path][resource spec]
```
__Module path__:
A module path addresses a module within the tree of modules. It takes the form:
```
module.A.module.B.module.C...
```
Multiple modules in a path indicate nesting. If a module path is specified
without a resource spec, the address applies to every resource within the
module. If the module path is omitted, this addresses the root module.
__Resource spec__:
A resource spec addresses a specific resource in the config. It takes the form:
```
resource_type.resource_name[resource index]
```
* `resource_type` - Type of the resource being addressed.
* `resource_name` - User-defined name of the resource.
* `[resource index]` - an optional index into a resource with multiple
instances, surrounded by square brace characters (`[` and `]`).
-> In Terraform v0.12 and later, a resource spec without a module path prefix
matches only resources in the root module. In earlier versions, a resource spec
without a module path prefix will match resources with the same type and name
in any descendent module.
__Resource index__:
* `[N]` where `N` is a `0`-based numerical index into a resource with multiple
instances specified by the `count` meta-argument. Omitting an index when
addressing a resource where `count > 1` means that the address references
all instances.
* `["INDEX"]` where `INDEX` is a alphanumerical key index into a resource with
multiple instances specified by the `for_each` meta-argument.
## Examples
### count Example
Given a Terraform config that includes:
```hcl
resource "aws_instance" "web" {
# ...
count = 4
}
```
An address like this:
```
aws_instance.web[3]
```
Refers to only the last instance in the config, and an address like this:
```
aws_instance.web
```
Refers to all four "web" instances.
### for_each Example
Given a Terraform config that includes:
```hcl
resource "aws_instance" "web" {
# ...
for_each = {
"terraform": "value1",
"resource": "value2",
"indexing": "value3",
"example": "value4",
}
}
```
An address like this:
```
aws_instance.web["example"]
```
Refers to only the "example" instance in the config.