[DPE-6089] Update Terraform to new scheme (#520)

## Issue
We would like an easy way to deploy MongoDB using terraform on lxd and
openstack

## Solution
Add 

## Manual Testing
```
terraform init
terraform apply 
```
done on both LXD and on OpenStack

---------

Co-authored-by: Neha Oudin <[email protected]>

.github/workflows/ci.yaml

@@ -32,6 +32,53 @@ jobs:
       - name: Run tests
         run: tox run -e unit
 
+  terraform-test:
+    name: Terraform - Lint and Simple Deployment
+    runs-on: ubuntu-latest
+    timeout-minutes: 120
+    steps:
+      - name: Checkout repo
+        uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+
+      - name: lint charm module
+        working-directory: ./terraform
+        run: |
+          terraform init
+          terraform fmt
+          terraform validate
+      - name: lint test charm module
+         working-directory: ./terraform/tests
+         run: |
+          terraform init
+          terraform fmt
+          terraform validate
+      - name: run checks - prepare
+        run: |
+          sudo snap install juju --channel=3.6/beta --classic
+          sudo snap install juju-wait --channel=latest/stable --classic
+          sudo snap install jq
+      - name: LXD setup
+        run: |
+          sudo snap refresh lxd --channel=latest/stable
+          sudo adduser "$USER" 'lxd'
+          # `newgrp` does not work in GitHub Actions; use `sg` instead
+          sg 'lxd' -c "lxd waitready"
+          sg 'lxd' -c "lxd init --auto"
+          sg 'lxd' -c "lxc network set lxdbr0 ipv6.address none"
+          sudo iptables -F FORWARD
+          sudo iptables -P FORWARD ACCEPT
+      - name: Juju setup
+        run: |
+          sg 'lxd' -c "juju bootstrap 'localhost' --config model-logs-size=10G"
+          juju model-defaults logging-config='<root>=INFO; unit=DEBUG'
+          juju add-model test
+      - name: Terraform deploy
+        working-directory: ./terraform/tests/
+        run: |
+          terraform apply  -var "model=test" -target null_resource.simple_deployment_juju_wait_deployment -auto-approve
+
   lib-check:
     name: Check libraries
     runs-on: ubuntu-latest

.gitignore

@@ -52,8 +52,52 @@ override.tf.json
 # Include tfplan files to ignore the plan output of command: terraform plan -out=tfplan
 # example: *tfplan*
 
+# Ignore CLI configuration files
+
+
+########################################################
+#
+# Terraform .gitignore
+#
+########################################################
+
+
+# Local .terraform directories
+**/.terraform/*
+*.terraform.lock.hcl
+
+# .tfstate files
+*.tfstate
+*.tfstate.*
+
+# Crash log files
+crash.log
+crash.*.log
+
+# Generated files
+*.key
+credentials*
+
+# Exclude all .tfvars files, which are likely to contain sensitive data, such as
+# password, private keys, and other secrets. These should not be part of version 
+# control as they are data points which are potentially sensitive and subject 
+# to change depending on the environment.
+*.tfvars
+*.tfvars.json
+
+# Ignore override files as they are usually used to override resources locally and so
+# are not checked in
+override.tf
+override.tf.json
+*_override.tf
+*_override.tf.json
+
+# Include override files you do wish to add to version control using negated pattern
+# !example_override.tf
+
+# Include tfplan files to ignore the plan output of command: terraform plan -out=tfplan
+# example: *tfplan*
+
 # Ignore CLI configuration files
 .terraformrc
 terraform.rc
-.terraform.lock.hcl
-

terraform/README.md

@@ -1,58 +1,66 @@
-# MongoDB Operator Terraform module
+# Terraform module for mongodb-operator
 
-This folder contains a base [Terraform][Terraform] module for the `mongodb` charm.
+This is a Terraform module facilitating the deployment of the MongoDB charm with [Terraform juju provider](https://github.com/juju/terraform-provider-juju/). For more information, refer to the provider [documentation](https://registry.terraform.io/providers/juju/juju/latest/docs). 
 
-The module uses the [Terraform Juju provider][Terraform Juju provider] to model the charm deployment onto any Kubernetes environment managed by [Juju][Juju].
+## Requirements
+This module requires a `juju` model to be available. Refer to the [usage section](#usage) below for more details.
 
-The base module is not intended to be deployed in separation (it is possible though), but should rather serve as a building block for higher level modules.
+## API
 
-## Module structure
+### Inputs
+The module offers the following configurable inputs:
 
-- **main.tf** - Defines the Juju application to be deployed.
-- **variables.tf** - Allows customization of the deployment such as Juju model name, channel or application name and charm configuration.
-- **output.tf** - Responsible for integrating the module with other Terraform modules, primarily by defining potential integration endpoints (charm integrations), but also by exposing the application name.
-- **terraform.tf** - Defines the Terraform provider.
+| Name | Type | Description | Required |
+| - | - | - | - |
+| `app_name`| string | Application name | False |
+| `channel`| string | Channel that the charm is deployed from | False |
+| `base`| string | The series to be used for this charm | False |
+| `config`| map(string) | Map of the charm configuration options | False |
+| `model_name`| string | Name of the model that the charm is deployed on | True |
+| `resources`| map(string) | Map of the charm resources | False |
+| `revision`| number | Revision number of the charm name | False |
+| `units`| number | Number of units to be deployed | False |
+| `constraints`| string | Machine constraints for the charm | False |
+| `storage`| map(string) | Storage description, must follow the juju provider schema | False |
 
-## Using mongodb base module in higher level modules
 
-If you want to use `mongodb-operator` base module as part of your Terraform module, import it like shown below.
+### Outputs
+Upon applied, the module exports the following outputs:
 
-```text
-module "mongodb-operator" {
-  source = "git::https://github.com/canonical/mongodb-operator.git/terraform"
-  
-  model_name = "juju_model_name"
-  
-  (Customize configuration variables here if needed)
-}
-```
+| Name | Description |
+| - | - |
+| `app_name`|  Application name |
+| `provides`| Map of `provides` endpoints |
+| `requires`| Map of `requires` endpoints |
 
-Please see the link to customize the Grafana configuration variables if needed.
+## Usage
 
-- [MongoDB configuration options][MongoDB configuration options]
+This module is intended to be used as part of a higher-level module. When defining one, users should ensure that Terraform is aware of the `juju_model` dependency of the charm module. There are two options to do so when creating a high-level module:
 
-Create the integrations, for instance:
+### Define a `juju_model` resource
+Define a `juju_model` resource and pass to the `model_name` input a reference to the `juju_model` resource's name. For example:
 
-```text
-resource "juju_integration" "amf-db" {
-  model = var.model_name
-
-  application {
-    name     = module.amf.app_name
-    endpoint = module.amf.database_endpoint
-  }
+```
+resource "juju_model" "mongodb" {
+  name = mongodb
+}
 
-  application {
-    name     = module.mongodb.app_name
-    endpoint = module.mongodb.database_endpoint
-  }
+module "mongodb-operator" {
+  source = "<path-to-this-directory>"
+  model_name = juju_model.mongodb.name
 }
 ```
 
-Please check the available [integration pairs][integration pairs].
+### Define a `data` source
+Define a `data` source and pass to the `model_name` input a reference to the `data.juju_model` resource's name. This will enable Terraform to look for a `juju_model` resource with a name attribute equal to the one provided, and apply only if this is present. Otherwise, it will fail before applying anything.
 
-[Terraform]: https://www.terraform.io/
-[Juju]: https://juju.is
-[Terraform Juju provider]: https://registry.terraform.io/providers/juju/juju/latest
-[MongoDB configuration options]: https://charmhub.io/mongodb/configure?channel=6/edge
-[integration pairs]: https://charmhub.io/mongodb/integrations?channel=6/edge
+```
+data "juju_model" "mongodb" {
+  name = var.model_name
+}
+
+module "mongodb" {
+  source = "<path-to-this-directory>"
+  model_name = data.juju_model.mongodb.name
+}
+```

terraform/main.tf

@@ -2,15 +2,40 @@
 # See LICENSE file for licensing details.
 
 resource "juju_application" "mongodb" {
-  name  = var.app_name
-  model = var.model_name
 
   charm {
-    name    = "mongodb"
-    channel = var.channel
-    base    = "[email protected]"
+    name     = "mongodb"
+    channel  = var.channel
+    revision = var.revision
+    base     =  "[email protected]"
   }
-  config = var.config
-  units  = 1
-  trust  = true
-}
+  config      = var.config
+  model       = var.model
+  name        = var.app_name
+  units       = var.units
+  constraints = var.constraints
+
+
+  # TODO: uncomment once final fixes have been added for:
+  # Error: juju/terraform-provider-juju#443, juju/terraform-provider-juju#182
+  # placement = join(",", var.machines)
+
+  endpoint_bindings = [
+    for k, v in var.endpoint_bindings : {
+      endpoint = k, space = v
+    }
+  ]
+
+  storage_directives = var.storage
+
+  lifecycle {
+    precondition {
+      condition     = length(var.machines) == 0 || length(var.machines) == var.units
+      error_message = "Machine count does not match unit count"
+    }
+    precondition {
+      condition     = length(var.storage) == 0 || lookup(var.storage, "count", 0) <= 1
+      error_message = "Only one storage is supported"
+    }
+  }
+}

terraform/outputs.tf

@@ -13,11 +13,6 @@ output "database_endpoint" {
   value       = "database"
 }
 
-output "obsolete_endpoint" {
-  description = "Name of the endpoint to provide the mongodb interface."
-  value       = "obsolete"
-}
-
 output "cos_agent_endpoint" {
   description = "Name of the endpoint to provide the cos_agent interface."
   value       = "cos-agent"
@@ -33,22 +28,6 @@ output "cluster_endpoint" {
   value       = "cluster"
 }
 
-output "metrics_endpoint" {
-  description = "Name of the endpoint to provide the prometheus_scrape interface."
-  value       = "metrics-endpoint"
-}
-
-output "grafana_dashboard_endpoint" {
-  description = "Name of the endpoint to provide the grafana_dashboard interface."
-  value       = "grafana-dashboard"
-}
-
-output "logging_endpoint" {
-  description = "Name of the endpoint to provide the loki_push_api relation interface."
-  value       = "logging"
-}
-
-
 # Required integration endpoints
 
 output "certificates_endpoint" {
@@ -64,4 +43,4 @@ output "s3_credentials_endpoint" {
 output "sharding_endpoint" {
   description = "Name of the endpoint to provide the shards interface."
   value       = "sharding"
-}
+}

terraform/tests/preamble.tf

@@ -0,0 +1,25 @@
+resource "null_resource" "preamble" {
+  provisioner "local-exec" {
+    command = <<-EOT
+    sudo snap install juju-wait --classic || true
+    EOT
+  }
+}
+
+resource "juju_application" "self-signed-certificates" {
+  charm {
+    name    = "self-signed-certificates"
+    channel = "latest/stable"
+  }
+  model      = var.model_name
+  depends_on = [null_resource.preamble]
+}
+
+resource "juju_application" "data-integrator" {
+  charm {
+    name    = "data-integrator"
+    channel = "latest/stable"
+  }
+  model      = var.model_name
+  depends_on = [null_resource.preamble]
+}

terraform/tests/providers.tf

@@ -0,0 +1,16 @@
+terraform {
+  required_providers {
+    juju = {
+      source  = "juju/juju"
+      version = "~> 0.14.0"
+    }
+    http = {
+      source  = "hashicorp/http"
+      version = "~> 3.4.5"
+    }
+    external = {
+      source  = "hashicorp/external"
+      version = "~> 2.3.4"
+    }
+  }
+}