terraform/website/source/docs/enterprise/faq/rolling-deployments.html.md

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enterprise	FAQ: Rolling Deployments	docs-enterprise-faq-deployments	How do I configure rolling deployments in Terraform Enterprise?

Rolling Deployments

How do I configure rolling deployments?

User are able to quickly change out an Artifact version that is being utilized by Terraform, using variables within Terraform Enterprise. This is particularly useful when testing specific versions of the given artifact without performing a full rollout. This configuration also allows one to deploy any version of an artifact with ease, simply by changing a version variable in Terraform and re-deploying.

Here is an example:

variable "type"           { default = "amazon.image" }
variable "region"         { }
variable "atlas_username" { }
variable "pinned_name"    { }
variable "pinned_version" { default = "latest" }

resource "atlas_artifact" "pinned" {
  name     = "${var.atlas_username}/${var.pinned_name}"
  type     = "${var.type}"
  version  = "${var.pinned_version}"

  lifecycle { create_before_destroy = true }

  metadata {
    region = "${var.region}"
  }
}

output "pinned" { value = "${atlas_artifact.pinned.metadata_full.ami_id}" }

In the above example we have an atlas_artifact resource where you pass in the version number via the variable pinned_version. (note: this variable defaults to latest). If you ever want to deploy any other version, you just update the variable pinned_version and redeploy.

Below is similar to the first example, but it is in the form of a module that handles the creation of artifacts:

variable "type"             { default = "amazon.image" }
variable "region"           { }
variable "atlas_username"   { }
variable "artifact_name"    { }
variable "artifact_version" { default = "latest" }

resource "atlas_artifact" "artifact" {
  name    = "${var.atlas_username}/${var.artifact_name}"
  type    = "${var.type}"
  count   = "${length(split(",", var.artifact_version))}"
  version = "${element(split(",", var.artifact_version), count.index)}"

  lifecycle { create_before_destroy = true }
  metadata  { region = "${var.region}" }
}

output "amis" { value = "${join(",", atlas_artifact.artifact.*.metadata_full.ami_id)}" }

One can then use the module as follows (note: the source will likely be different depending on the location of the module):

module "artifact_consul" {
  source = "../../../modules/aws/util/artifact"

  type             = "${var.artifact_type}"
  region           = "${var.region}"
  atlas_username   = "${var.atlas_username}"
  artifact_name    = "${var.consul_artifact_name}"
  artifact_version = "${var.consul_artifacts}"
}

In the above example, we have created artifacts for Consul. In this example, we can create two versions of the artifact, "latest" and "pinned". This is useful when rolling a cluster (like Consul) one node at a time, keeping some nodes pinned to current version and others deployed with the latest Artifact.

There are additional details for implementing rolling deployments in the Best-Practices Repo, as there are some things uncovered in this FAQ (i.e Using the Terraform Enterprise Artifact in an instance).