Use lookup() for VPC name getting

cloudwatch.tf

@@ -6,7 +6,7 @@
 resource "aws_cloudwatch_metric_alarm" "cache_cpu" {
   count = "${var.redis_clusters}"
 
-  alarm_name          = "alarm-${var.name}-${data.aws_vpc.vpc.tags["Name"]}-CacheCluster00${count.index + 1}CPUUtilization"
+  alarm_name          = "alarm-${var.name}-${local.vpc_name}-CacheCluster00${count.index + 1}CPUUtilization"
   alarm_description   = "Redis cluster CPU utilization"
   comparison_operator = "GreaterThanThreshold"
   evaluation_periods  = "1"
@@ -27,7 +27,7 @@ resource "aws_cloudwatch_metric_alarm" "cache_cpu" {
 resource "aws_cloudwatch_metric_alarm" "cache_memory" {
   count = "${var.redis_clusters}"
 
-  alarm_name          = "alarm-${var.name}-${data.aws_vpc.vpc.tags["Name"]}-CacheCluster00${count.index + 1}FreeableMemory"
+  alarm_name          = "alarm-${var.name}-${local.vpc_name}-CacheCluster00${count.index + 1}FreeableMemory"
   alarm_description   = "Redis cluster freeable memory"
   comparison_operator = "LessThanThreshold"
   evaluation_periods  = "1"

main.tf

@@ -2,13 +2,17 @@ data "aws_vpc" "vpc" {
   id = "${var.vpc_id}"
 }
 
+locals {
+  vpc_name = "${lookup(data.aws_vpc.vpc.tags, "Name", var.vpc_id)}"
+}
+
 resource "random_id" "salt" {
   byte_length = 8
 }
 
 resource "aws_elasticache_replication_group" "redis" {
   replication_group_id          = "${format("%.20s","${var.name}-${var.env}")}"
-  replication_group_description = "Terraform-managed ElastiCache replication group for ${var.name}-${var.env}-${data.aws_vpc.vpc.tags["Name"]}"
+  replication_group_description = "Terraform-managed ElastiCache replication group for ${var.name}-${var.env}-${local.vpc_name}"
   number_cache_clusters         = "${var.redis_clusters}"
   node_type                     = "${var.redis_node_type}"
   automatic_failover_enabled    = "${var.redis_failover}"
@@ -21,13 +25,13 @@ resource "aws_elasticache_replication_group" "redis" {
   maintenance_window            = "${var.redis_maintenance_window}"
   snapshot_window               = "${var.redis_snapshot_window}"
   snapshot_retention_limit      = "${var.redis_snapshot_retention_limit}"
-  tags                          = "${merge(map("Name", format("tf-elasticache-%s-%s", var.name, lookup(data.aws_vpc.vpc.tags,"Name",""))), var.tags)}"
+  tags                          = "${merge(map("Name", format("tf-elasticache-%s-%s", var.name, local.vpc_name)), var.tags)}"
 }
 
 resource "aws_elasticache_parameter_group" "redis_parameter_group" {
-  name = "${replace(format("%.255s", lower(replace("tf-redis-${var.name}-${var.env}-${data.aws_vpc.vpc.tags["Name"]}-${random_id.salt.hex}", "_", "-"))), "/\\s/", "-")}"
+  name = "${replace(format("%.255s", lower(replace("tf-redis-${var.name}-${var.env}-${local.vpc_name}-${random_id.salt.hex}", "_", "-"))), "/\\s/", "-")}"
 
-  description = "Terraform-managed ElastiCache parameter group for ${var.name}-${var.env}-${data.aws_vpc.vpc.tags["Name"]}"
+  description = "Terraform-managed ElastiCache parameter group for ${var.name}-${var.env}-${local.vpc_name}"
 
   # Strip the patch version from redis_version var
   family    = "redis${replace(var.redis_version, "/\\.[\\d]+$/","")}"
@@ -39,6 +43,6 @@ resource "aws_elasticache_parameter_group" "redis_parameter_group" {
 }
 
 resource "aws_elasticache_subnet_group" "redis_subnet_group" {
-  name       = "${replace(format("%.255s", lower(replace("tf-redis-${var.name}-${var.env}-${data.aws_vpc.vpc.tags["Name"]}", "_", "-"))), "/\\s/", "-")}"
+  name       = "${replace(format("%.255s", lower(replace("tf-redis-${var.name}-${var.env}-${local.vpc_name}", "_", "-"))), "/\\s/", "-")}"
   subnet_ids = ["${var.subnets}"]
 }

security_groups.tf

@@ -1,10 +1,10 @@
 resource "aws_security_group" "redis_security_group" {
-  name        = "${format("%.255s", "tf-sg-ec-${var.name}-${var.env}-${data.aws_vpc.vpc.tags["Name"]}")}"
-  description = "Terraform-managed ElastiCache security group for ${var.name}-${var.env}-${data.aws_vpc.vpc.tags["Name"]}"
+  name        = "${format("%.255s", "tf-sg-ec-${var.name}-${var.env}-${local.vpc_name}")}"
+  description = "Terraform-managed ElastiCache security group for ${var.name}-${var.env}-${local.vpc_name}"
   vpc_id      = "${data.aws_vpc.vpc.id}"
 
   tags {
-    Name = "tf-sg-ec-${var.name}-${var.env}-${data.aws_vpc.vpc.tags["Name"]}"
+    Name = "tf-sg-ec-${var.name}-${var.env}-${local.vpc_name}"
   }
 }