74 lines
2.5 KiB
Markdown
74 lines
2.5 KiB
Markdown
---
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layout: "random"
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page_title: "Provider: Random"
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sidebar_current: "docs-random-index"
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description: |-
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The Random provider is used to generate randomness.
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---
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# Random Provider
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The "random" provider allows the use of randomness within Terraform
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configurations. This is a *logical provider*, which means that it works
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entirely within Terraform's logic, and doesn't interact with any other
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services.
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Unconstrained randomness within a Terraform configuration would not be very
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useful, since Terraform's goal is to converge on a fixed configuration by
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applying a diff. Because of this, the "random" provider provides an idea of
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*managed randomness*: it provides resources that generate random values during
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their creation and then hold those values steady until the inputs are changed.
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Even with these resources, it is advisable to keep the use of randomness within
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Terraform configuration to a minimum, and retain it for special cases only;
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Terraform works best when the configuration is well-defined, since its behavior
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can then be more readily predicted.
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Unless otherwise stated within the documentation of a specific resource, this
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provider's results are **not** sufficiently random for cryptographic use.
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For more information on the specific resources available, see the links in the
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navigation bar. Read on for information on the general patterns that apply
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to this provider's resources.
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## Resource "Keepers"
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As noted above, the random resources generate randomness only when they are
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created; the results produced are stored in the Terraform state and re-used
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until the inputs change, prompting the resource to be recreated.
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The resources all provide a map argument called `keepers` that can be populated
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with arbitrary key/value pairs that should be selected such that they remain
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the same until new random values are desired.
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For example:
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```hcl
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resource "random_id" "server" {
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keepers = {
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# Generate a new id each time we switch to a new AMI id
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ami_id = "${var.ami_id}"
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}
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byte_length = 8
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}
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resource "aws_instance" "server" {
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tags = {
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Name = "web-server ${random_id.server.hex}"
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}
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# Read the AMI id "through" the random_id resource to ensure that
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# both will change together.
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ami = "${random_id.server.keepers.ami_id}"
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# ... (other aws_instance arguments) ...
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}
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```
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Resource "keepers" are optional. The other arguments to each resource must
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*also* remain constant in order to retain a random result.
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To force a random result to be replaced, the `taint` command can be used to
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produce a new result on the next run.
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