Upgrade redis server

We have observed timeouts in the application log and some users are
impacted.
This upgrades production to Premium and high availibilty across
availibity zones.

Also pinned server version to 6 and increased replicas to 2.

terraform/aks/config/production_aks.tfvars.json

@@ -6,5 +6,9 @@
   "cluster": "production",
   "namespace": "git-production",
   "enable_monitoring": false,
-  "enable_statuscake_alerts": true
+  "enable_statuscake_alerts": true,
+  "replicas": 2,
+  "redis_capacity": 1,
+  "redis_family": "P",
+  "redis_sku_name": "Premium"
 }

terraform/aks/databases.tf

@@ -14,6 +14,10 @@ module "redis-cache" {
   azure_enable_monitoring = var.enable_monitoring
   azure_patch_schedule    = [{ "day_of_week" : "Sunday", "start_hour_utc" : 01 }]
   azure_maxmemory_policy  = "allkeys-lfu"
+  server_version          = 6
+  azure_capacity          = var.redis_capacity
+  azure_family            = var.redis_family
+  azure_sku_name          = var.redis_sku_name
 }
 
 module "postgres" {

terraform/aks/variables.tf

@@ -43,6 +43,19 @@ variable "azure_enable_backup_storage" { default = true }
 variable "replicas" { default = 1 }
 variable "memory_max" { default = "1Gi" }
 
+variable "redis_capacity" {
+  type    = number
+  default = 1
+}
+variable "redis_family" {
+  type    = string
+  default = "C"
+}
+variable "redis_sku_name" {
+  type    = string
+  default = "Standard"
+}
+
 locals {
   azure_credentials       = try(jsondecode(var.azure_credentials), null)
   app_resource_group_name = "${var.azure_resource_prefix}-${var.service_short}-${var.config_short}-rg"