doc: Adds initial structure for module examples cluster_to_advanced_cluster

[EspenAlbert]

Description

• Adds initial structure for module example cluster_to_advanced_cluster
• Future PRs (out of scope for this PR)
  • v2 & v3 implementation of modules
  • Full readme description for each module

Link to any related issue(s): CLOUDP-299312

Type of change:

• Bug fix (non-breaking change which fixes an issue). Please, add the "bug" label to the PR.
• New feature (non-breaking change which adds functionality). Please, add the "enhancement" label to the PR. A migration guide must be created or updated if the new feature will go in a major version.
• Breaking change (fix or feature that would cause existing functionality to not work as expected). Please, add the "breaking change" label to the PR. A migration guide must be created or updated.
• This change requires a documentation update
• Documentation fix/enhancement

Required Checklist:

• I have signed the MongoDB CLA
• I have read the contributing guides
• I have checked that this change does not generate any credentials and that they are NOT accidentally logged anywhere.
• I have added tests that prove my fix is effective or that my feature works per HashiCorp requirements
• I have added any necessary documentation (if appropriate)
• I have run make fmt and formatted my code
• If changes include deprecations or removals I have added appropriate changelog entries.
• If changes include removal or addition of 3rd party GitHub actions, I updated our internal document. Reach out to the APIx Integration slack channel to get access to the internal document.

Further comments

[EspenAlbert]

Notice directory location examples/modules/{module_name}
👍 or 👎 ?

[lantoli]

as we'll have 3 examples of clu2adv and one doesn't have modules, what about something like:

- examples
   - migrate_cluster_to_advanced_cluster  # note that migrate goes alphabetically before mongodb so it'll be the first entry
      - basic
        README.md
        ...
      - module_maintainer
        README.md
        ...
      - module_user
        README.md
        ...

[EspenAlbert]

I like your suggestion 👍
Changed ✅

[lantoli]

should we add it's from module maintainer perspective?

[EspenAlbert]

An alternative to using an inline call (see code snippet below)

The main advantage of this is to demonstrate that the exact same variable files can be used in both v1 and v2 and stay DRY
The main disadvantage is the duplicate variables.tf in both module_maintainer/{version}/variables.tf AND module_user/{version}/variables.tf

module "cluster" {
    source = "../../module_maintainer/v1"

    project_id             = "664619d870c247237f4b86a6"
    cluster_name           = "module-cluster"
    cluster_type           = "SHARDED"
    instance_size          = "M10"
    mongo_db_major_version = "8.0"
    provider_name          = "AWS"
    disk_size              = 40
    tags = {
    env    = "examples"
    module = "cluster_to_advanced_cluster"
    }
    replication_specs = [
    {
        num_shards = 2
        zone_name  = "Zone 1"
        regions_config = [
        {
            region_name     = "US_EAST_1"
            electable_nodes = 3
            priority        = 7
            read_only_nodes = 0
        }
        ]
    }
    ]
}

[lantoli]

not a strong opinion, I'd probably go for the inline version as it's more frequently used, but I'm also ok with tfvars

[marcosuma]

just got a customer example (unrelated to this) that are using tfvars. Of course it's only one, but I'd probably keep that as a reference

[marcosuma]

I think it makes sense to have a "simple" cluster on the example as it'd be overkill for some. We should talk though how to present the "complex" one

[EspenAlbert]

Do you mean changing the module here? Or does the example usage in this comment look ok?

[marcosuma]

shouldn't this be >= 1.10 ? otherwise moved cannot work, right?

[EspenAlbert]

There is no moved inside of v1, so an earlier version of TF CLI is ok.

[maastha]

[q] why is Variables count needed?

[EspenAlbert]

Thought it might be useful as a signal for complexity and the change between module versions