feat: Create launch template for Managed Node Groups (#1138)

Signed-off-by: Kevin Lefevre <lefevre.kevin@gmail.com>

modules/node_groups/launchtemplate.tf

@@ -0,0 +1,111 @@
+data "cloudinit_config" "workers_userdata" {
+  for_each      = { for k, v in local.node_groups_expanded : k => v if v["create_launch_template"] }
+  gzip          = false
+  base64_encode = true
+  boundary      = "//"
+
+  part {
+    content_type = "text/x-shellscript"
+    content = templatefile("${path.module}/templates/userdata.sh.tpl",
+      {
+        pre_userdata       = each.value["pre_userdata"]
+        kubelet_extra_args = each.value["kubelet_extra_args"]
+      }
+    )
+
+  }
+}
+
+# This is based on the LT that EKS would create if no custom one is specified (aws ec2 describe-launch-template-versions --launch-template-id xxx)
+# there are several more options one could set but you probably dont need to modify them
+# you can take the default and add your custom AMI and/or custom tags
+#
+# Trivia: AWS transparently creates a copy of your LaunchTemplate and actually uses that copy then for the node group. If you DONT use a custom AMI,
+# then the default user-data for bootstrapping a cluster is merged in the copy.
+resource "aws_launch_template" "workers" {
+  for_each               = { for k, v in local.node_groups_expanded : k => v if v["create_launch_template"] }
+  name_prefix            = lookup(each.value, "name", join("-", [var.cluster_name, each.key, random_pet.node_groups[each.key].id]))
+  description            = lookup(each.value, "name", join("-", [var.cluster_name, each.key, random_pet.node_groups[each.key].id]))
+  update_default_version = true
+
+  block_device_mappings {
+    device_name = "/dev/xvda"
+
+    ebs {
+      volume_size           = lookup(each.value, "disk_size", null)
+      volume_type           = lookup(each.value, "disk_type", null)
+      delete_on_termination = true
+    }
+  }
+
+  instance_type = each.value["set_instance_types_on_lt"] ? element(each.value.instance_types, 0) : null
+
+  monitoring {
+    enabled = lookup(each.value, "enable_monitoring", null)
+  }
+
+  network_interfaces {
+    associate_public_ip_address = lookup(each.value, "public_ip", null)
+    delete_on_termination       = lookup(each.value, "eni_delete", null)
+    security_groups = flatten([
+      var.worker_security_group_id,
+      var.worker_additional_security_group_ids,
+      lookup(
+        each.value,
+        "additional_security_group_ids",
+        null,
+      ),
+    ])
+  }
+
+  # if you want to use a custom AMI
+  # image_id      = var.ami_id
+
+  # If you use a custom AMI, you need to supply via user-data, the bootstrap script as EKS DOESNT merge its managed user-data then
+  # you can add more than the minimum code you see in the template, e.g. install SSM agent, see https://github.com/aws/containers-roadmap/issues/593#issuecomment-577181345
+  #
+  # (optionally you can use https://registry.terraform.io/providers/hashicorp/cloudinit/latest/docs/data-sources/cloudinit_config to render the script, example: https://github.com/terraform-aws-modules/terraform-aws-eks/pull/997#issuecomment-705286151)
+
+  user_data = data.cloudinit_config.workers_userdata[each.key].rendered
+
+  key_name = lookup(each.value, "key_name", null)
+
+  # Supplying custom tags to EKS instances is another use-case for LaunchTemplates
+  tag_specifications {
+    resource_type = "instance"
+
+    tags = merge(
+      var.tags,
+      lookup(var.node_groups_defaults, "additional_tags", {}),
+      lookup(var.node_groups[each.key], "additional_tags", {}),
+      {
+        Name = lookup(each.value, "name", join("-", [var.cluster_name, each.key, random_pet.node_groups[each.key].id]))
+      }
+    )
+  }
+
+  # Supplying custom tags to EKS instances root volumes is another use-case for LaunchTemplates. (doesnt add tags to dynamically provisioned volumes via PVC tho)
+  tag_specifications {
+    resource_type = "volume"
+
+    tags = merge(
+      var.tags,
+      lookup(var.node_groups_defaults, "additional_tags", {}),
+      lookup(var.node_groups[each.key], "additional_tags", {}),
+      {
+        Name = lookup(each.value, "name", join("-", [var.cluster_name, each.key, random_pet.node_groups[each.key].id]))
+      }
+    )
+  }
+
+  # Tag the LT itself
+  tags = merge(
+    var.tags,
+    lookup(var.node_groups_defaults, "additional_tags", {}),
+    lookup(var.node_groups[each.key], "additional_tags", {}),
+  )
+
+  lifecycle {
+    create_before_destroy = true
+  }
+}