[CI] Make premerge_resources accept Github ARC version

This allows for easily controlling the ARC version of the premerge clusters
separately which allows for zero downtime upgrades, assuming the upgrade is
performed correctly (shown in the documentation). This patch also makes the
docs a bit more clear.

Author: boomanaiden154

premerge/cluster-management.md

@@ -219,9 +219,13 @@ terraform destroy -target module.premerge_cluster_us_central_resources.kubernete
 ### Bumping the Version Number
 
 This is necessary only for bumping the version of ARC. This involves simply
-updating the version field for the `helm_release` objects in `main.tf`. Make sure
-to commit the changes and push them to `llvm-zorg` to ensure others working on
-the terraform configuration have an up to date state when they pull the repository.
+updating the version field for the `premerge_resources` objects in `main.tf`.
+Each premerge cluster (`llvm-premerge-cluster-us-central` and
+`llvm-premerge-cluster-us-west`) has a separate version. This allows for
+updating them separately which allows for zero-downtime upgrades when the
+system is operating at low capacity. Make sure to commit the changes and push
+them to `llvm-zorg` to ensure others working on the terraform configuration
+have an up to date state when they pull the repository.
 
 ### Bringing the Cluster Back Up
 

premerge/main.tf

@@ -132,6 +132,7 @@ module "premerge_cluster_us_central_resources" {
   runner_group_name                   = "llvm-premerge-cluster-us-central"
   linux_runners_namespace_name        = "llvm-premerge-linux-runners"
   windows_2022_runners_namespace_name = "llvm-premerge-windows-2022-runners"
+  github_arc_version                  = "0.11.0"
   providers = {
     kubernetes = kubernetes.llvm-premerge-us-central
     helm       = helm.llvm-premerge-us-central
@@ -148,6 +149,7 @@ module "premerge_cluster_us_west_resources" {
   runner_group_name                   = "llvm-premerge-cluster-us-west"
   linux_runners_namespace_name        = "llvm-premerge-linux-runners"
   windows_2022_runners_namespace_name = "llvm-premerge-windows-2022-runners"
+  github_arc_version                  = "0.11.0"
   providers = {
     kubernetes = kubernetes.llvm-premerge-us-west
     helm       = helm.llvm-premerge-us-west

premerge/premerge_resources/main.tf

@@ -136,7 +136,7 @@ resource "helm_release" "github_actions_runner_controller" {
   name       = "llvm-premerge-controller"
   namespace  = "llvm-premerge-controller"
   repository = "oci://ghcr.io/actions/actions-runner-controller-charts"
-  version    = "0.11.0"
+  version    = var.github_arc_version
   chart      = "gha-runner-scale-set-controller"
 
   depends_on = [
@@ -148,7 +148,7 @@ resource "helm_release" "github_actions_runner_set_linux" {
   name       = "llvm-premerge-linux-runners"
   namespace  = var.linux_runners_namespace_name
   repository = "oci://ghcr.io/actions/actions-runner-controller-charts"
-  version    = "0.11.0"
+  version    = var.github_arc_version
   chart      = "gha-runner-scale-set"
 
   values = [
@@ -166,7 +166,7 @@ resource "helm_release" "github_actions_runner_set_windows_2022" {
   name       = "llvm-premerge-windows-2022-runners"
   namespace  = var.windows_2022_runners_namespace_name
   repository = "oci://ghcr.io/actions/actions-runner-controller-charts"
-  version    = "0.11.0"
+  version    = var.github_arc_version
   chart      = "gha-runner-scale-set"
 
   values = [
@@ -184,7 +184,7 @@ resource "helm_release" "github_actions_runner_set_libcxx" {
   name       = "llvm-premerge-libcxx-runners"
   namespace  = "llvm-premerge-libcxx-runners"
   repository = "oci://ghcr.io/actions/actions-runner-controller-charts"
-  version    = "0.11.0"
+  version    = var.github_arc_version
   chart      = "gha-runner-scale-set"
 
   values = [
@@ -202,7 +202,7 @@ resource "helm_release" "github_actions_runner_set_libcxx_release" {
   name       = "llvm-premerge-libcxx-release-runners"
   namespace  = "llvm-premerge-libcxx-release-runners"
   repository = "oci://ghcr.io/actions/actions-runner-controller-charts"
-  version    = "0.11.0"
+  version    = var.github_arc_version
   chart      = "gha-runner-scale-set"
 
   values = [
@@ -220,7 +220,7 @@ resource "helm_release" "github_actions_runner_set_libcxx_next" {
   name       = "llvm-premerge-libcxx-next-runners"
   namespace  = "llvm-premerge-libcxx-next-runners"
   repository = "oci://ghcr.io/actions/actions-runner-controller-charts"
-  version    = "0.11.0"
+  version    = var.github_arc_version
   chart      = "gha-runner-scale-set"
 
   values = [

premerge/premerge_resources/variables.tf

@@ -21,6 +21,10 @@ variable "grafana_token" {
   type = string
 }
 
+variable "github_arc_version" {
+  type = string
+}
+
 variable "externalservices_prometheus_host" {
   type    = string
   default = "https://prometheus-prod-13-prod-us-east-0.grafana.net"