Added create_namespace to make it possible to install prometheus into…

… an existing namespace.

main.tf

@@ -1,14 +1,31 @@
 
 resource "kubernetes_namespace" "ns" {
+  count = var.create_namespace == true ? 1 : 0
+
   metadata {
     name = var.namespace
+    labels = {
+      istio-injection = "enabled"
+    }
   }
 }
 
+data "kubernetes_namespace" "existing-ns" {
+  count = var.create_namespace == true ? 0 : 1
+
+  metadata {
+    name = var.namespace
+  }
+}
+
+locals {
+  ns = try(kubernetes_namespace.ns[0].metadata[0].name, data.kubernetes_namespace.existing-ns[0].metadata[0].name)
+}
+
 resource "helm_release" "prometheus" {
   chart      = "prometheus"
   name       = "prometheus"
-  namespace  = kubernetes_namespace.ns.metadata[0].name
+  namespace  = local.ns
   version    = var.prometheus_chart_version
   repository = "https://prometheus-community.github.io/helm-charts"
 

variables.tf

@@ -19,6 +19,12 @@ variable "namespace" {
   default     = "prometheus"
 }
 
+variable "create_namespace" {
+  description = "Indicates whether the `namespace` needs to be created ('true') or already exists (not `true`)"
+  type        = bool
+  default     = true
+}
+
 # helm repo add prometheus-community https://prometheus-community.github.io/helm-charts
 # helm search repo prometheus-community/prometheus | head -2
 variable "prometheus_chart_version" {