Issue

Since we need to move to workload tracks for charms, our product component (the charm TF modules) tracks will no longer be in sync. This means that the channel input is not useful in products and we really only care about risk.

Blocked by:

• fix: Remove the TF channel input validation #274

Cross-track upgrades will be covered by:

• feat: Cross-track upgrade documentation #174

Solution

We can hardcode the tracks of the components e.g., 0.31 for alertmanager and 3.10 for prometheus in the module TF tag 3.0.n. The user should not have to concern themselves with what track of COS they want because this has caused confusion in the past i.e., the reason we added channel input validation, which is simplified if we only expose a risk.

Checklist

• I have added or updated relevant documentation.
  • Create a doc for COS day-2 charm revisions updated to latest in track #288
• PR title makes an appropriate release note and follows conventional commits syntax.
• Merge target is the correct branch, and relevant tandem backport PRs opened.

Context

We decided that it is okay for the product module to not surface the channel input, but charm modules must continue to surface this in their API to match the TF Juju provider API and the rest of the Juju TF ecosystem. We can require channel validation for each charm module to improve the user experience by not allowing the TF to outlive the charm.

Testing Instructions

COS Lite

Since we do not have the workload tracks ready yet, I hardcoded the tracks to dev:

locals {
  tracks = {
    alertmanager = "dev"
    catalogue    = "dev"
    grafana      = "dev"
    loki         = "dev"
    prometheus   = "dev"
    ssc          = "1"
    traefik      = "latest"
}

and applied with:

module "cos-lite" {
  source       = "../../terraform/cos-lite"
  model_uuid   = juju_model.cos-lite.uuid
  risk         = "edge"
  internal_tls = false

Apply complete! Resources: 32 added, 0 changed, 0 destroyed.

COS

Since we do not have the workload tracks ready yet, I hardcoded the tracks to dev:

locals {
  tracks = {
    alertmanager = "dev"
    catalogue    = "dev"
    grafana      = "dev"
    loki         = "dev"
    mimir        = "dev"
    otelcol      = "dev"
    tempo        = "dev"
    s3_integrator = "2"
    ssc           = "1"
    traefik       = "latest"
}

module "cos" {
  source       = "../../terraform/cos"
  model_uuid   = juju_model.cos.uuid
  risk         = "edge"
  internal_tls = false

  s3_endpoint   = "http://${data.external.juju_nori_address.result.address}:8333" # Seaweed
  s3_secret_key = "placeholder"
  s3_access_key = "placeholder"

  loki_coordinator  = { units = 1 }
  loki_worker       = { backend_units = 1, read_units = 1, write_units = 1 }
  mimir_coordinator = { units = 1 }
  mimir_worker      = { backend_units = 1, read_units = 1, write_units = 1 }
  tempo_coordinator = { units = 1 }
  tempo_worker      = { compactor_units = 1, distributor_units = 1, ingester_units = 1, metrics_generator_units = 1, querier_units = 1, query_frontend_units = 1 }
}

Apply complete! Resources: 85 added, 0 changed, 0 destroyed.

Upgrade Notes

Previously, if you deploy COS on day 1 and then on day 2, you would always get the same revisions. This is no longer the case and charm revisions might change per apply because they are picked "latest in track". To pin these revisions, use the revision input per COS component.