add validation to check existing stack prefix before provisioning (#205)

Issue Fixed:
- [JCS-13837](https://jira.oraclecorp.com/jira/browse/JCS-13837) Enh
35251378 - Script to check existing stack prefix before provisioning

Validation:
- The validation fails if another stack with the service name is already
present in the same stack compartment

Limitations:
- Only the stacks in the current stack compartment are checked. Other
compartments are not checked.
- Validation is done for UI mode only. No validation is done for CLI
mode.

Tests PASS: 
- PASS: create second stack with the same prefix in the same
compartment, and verify the apply fails with the validation error.

![image](https://github.com/oracle-quickstart/oci-weblogic-server/assets/101137416/ad92e2c7-1892-47c8-98f3-7aebb6afd111)
- PASS: validation succeeds if there is no other stack with the same
service_name in the same compartment
- PASS: destroy fails

Author: HarshadVilekar

builds/build_cli.sh

@@ -69,6 +69,7 @@ mkdir -p ${SCRIPT_DIR}/binaries/tmpbuild
 create_cli_bundle()
 {
   cp -Rf ${SCRIPT_DIR}/../terraform/modules ${SCRIPT_DIR}/../terraform/edition.tf ${SCRIPT_DIR}/../terraform/*.tf ${SCRIPT_DIR}/../terraform/images ${TMP_BUILD}
+  rm ${TMP_BUILD}/modules/validators/stack_validators.tf
   replace_variables
   (cd ${TMP_BUILD}; zip -r ${SCRIPT_DIR}/binaries/wlsoci-terraform.zip *; rm -Rf ${TMP_BUILD}/*)
 }

terraform/main.tf

@@ -350,7 +350,7 @@ module "vcn-peering" {
 module "validators" {
   #depends_on = [module.network-validation]
   source     = "./modules/validators"
-
+  compartment_id             = var.compartment_ocid
   service_name               = var.service_name
   wls_ms_port                = var.wls_ms_extern_port
   wls_ms_ssl_port            = var.wls_ms_extern_ssl_port

terraform/modules/validators/stack_validators.tf

@@ -0,0 +1,35 @@
+# Copyright (c) 2023, Oracle and/or its affiliates.
+# Licensed under the Universal Permissive License v1.0 as shown at https://oss.oracle.com/licenses/upl.
+
+# If any of the existing stacks is the same stack compartment is already using the same "service_name" as the current stack, then fail the validation.
+# To pass the validation, recreate the stack with a different service name.
+# This is to prevent trying to create another compute instance using the same prefix, which will lead to DNS issues.
+# This validation is applicable only for resource manager stacks. Not applicable for terraform CLI mode.
+
+data "oci_resourcemanager_stacks" "all_stacks_in_the_compartment" {
+  compartment_id = var.compartment_id
+}
+
+# collect id of each stack
+locals {
+  stack_list = data.oci_resourcemanager_stacks.all_stacks_in_the_compartment.stacks
+  num_stacks = length(local.stack_list)
+  stack_ids = [for stack in local.stack_list : { id = stack.id }]
+}
+
+# get details of each stack from the list of stack_ids
+data "oci_resourcemanager_stack" "all_stacks" {
+  count = local.num_stacks
+  #Required
+  stack_id = local.stack_ids[count.index].id
+}
+
+locals {
+  stack_variables = [for stack in data.oci_resourcemanager_stack.all_stacks : { variables = stack.variables }]
+  service_names_used_by_existing_stacks = [for stack_variables in local.stack_variables : lookup(stack_variables.variables, "service_name", "?_not_found_?")]
+  duplicate_service_names_list = [for service_name in local.service_names_used_by_existing_stacks : service_name if service_name == var.service_name]
+  # There will be always one entry for the name of the current stack. Set duplicate to true if there are more than one entries.
+  service_name_already_exists = length(local.duplicate_service_names_list) > 1 ? true : false
+  service_name_already_exists_msg      = "WLSC-ERROR: Another stack with the service_name [${var.service_name}] already exisits in the stack compartment. Try again with a different service name."
+  validate_service_name_is_not_already_used = local.service_name_already_exists ? local.validators_msg_map[local.service_name_already_exists_msg] : null
+}

terraform/modules/validators/variables.tf

@@ -1,6 +1,11 @@
 # Copyright (c) 2023, Oracle and/or its affiliates.
 # Licensed under the Universal Permissive License v1.0 as shown at https://oss.oracle.com/licenses/upl.
 
+variable "compartment_id" {
+  type        = string
+  description = "The OCID of the compartment where the stack resources are created"
+}
+
 variable "service_name" {
   type        = string
   description = "Prefix for stack resources"