local: make platform detection a module (#69)

terraform/platform/main.tf

@@ -0,0 +1,27 @@
+provider "local" {
+  version = "~> 1.4"
+}
+
+provider "null" {
+  version = "~> 2.1"
+}
+
+locals {
+  filename = pathexpand("/tmp/convox.platform")
+}
+
+resource "null_resource" "platform" {
+  triggers = {
+    hash = fileexists(local.filename) ? filebase64(local.filename) : "none"
+  }
+
+  provisioner "local-exec" {
+    command = "mkdir -p ${dirname(local.filename)} && uname -s > ${local.filename}"
+  }
+}
+
+data "local_file" "platform" {
+  depends_on = [null_resource.platform]
+
+  filename = local.filename
+}

terraform/platform/outputs.tf

@@ -0,0 +1,3 @@
+output "name" {
+  value = data.local_file.platform.content
+}

terraform/system/local/main.tf

@@ -10,10 +10,6 @@ provider "kubernetes" {
   version = "~> 1.10"
 }
 
-locals {
-  platform_filename = "/tmp/convox.platform"
-}
-
 data "http" "releases" {
   url = "https://api.github.com/repos/convox/convox/releases"
 }
@@ -23,16 +19,8 @@ locals {
   release = coalesce(var.release, local.current)
 }
 
-resource "null_resource" "platform" {
-  provisioner "local-exec" {
-    command = "uname -s > ${local.platform_filename}"
-  }
-}
-
-data "local_file" "platform" {
-  depends_on = [null_resource.platform]
-
-  filename = local.platform_filename
+module "platform" {
+  source = "../../platform"
 }
 
 module "rack" {
@@ -43,6 +31,6 @@ module "rack" {
   }
 
   name     = var.name
-  platform = trimspace(data.local_file.platform.content)
+  platform = module.platform.name
   release  = local.release
 }