## Context
`null_resource.patch_redis_service` uses `triggers = { always = timestamp() }`,
so every `scripts/tg plan` on `stacks/redis` reports `1 to destroy, 1 to add`
even when nothing has changed. That noise hides real drift in the signal and
trains us to ignore redis-stack plans — which is exactly what you don't want
on a load-bearing patch.
The patch itself is still load-bearing (three consumers hard-code bare
`redis.redis.svc.cluster.local` — `stacks/immich/chart_values.tpl:12`,
`stacks/ytdlp/yt-highlights/app/main.py:136`, `config.tfvars:214` — plus
Bitnami's own sentinel scripts set `REDIS_SERVICE=redis.redis.svc.cluster.local`
and call it during pod startup). Removing the null_resource is a follow-up
(beads T0) once those consumers migrate to `redis-master.redis.svc`. For now
the goal is just: stop being noisy.
## This change
1. Replace the `always = timestamp()` trigger with two inputs that only change
when re-patching is genuinely required:
- `chart_version = helm_release.redis.version` — changes only on a Bitnami
chart version bump, which is the one code path that rewrites the `redis`
Service selector back to `component=node`.
- `haproxy_config = sha256(kubernetes_config_map.haproxy.data["haproxy.cfg"])`
— changes only when HAProxy config is edited; aligned with the existing
`checksum/config` annotation that rolls the Deployment on config change.
Both attributes are known at plan time (verified against `hashicorp/helm`
v3.1.1 provider binary). Rejected alternatives — `metadata[0].revision`
(not exposed in the plugin-framework v3 rewrite), `sha256(jsonencode(values))`
(readability unverified on v3), and `kubernetes_deployment.haproxy.id`
(static `namespace/name`, never changes) — don't meet the bar.
2. Add a **Redis Service Naming** section to `AGENTS.md` that explicitly
states the write/sentinel/avoid endpoints, so new consumers start from
`redis-master.redis.svc` (the documented `var.redis_host`) and long-lived
connections (PUBSUB, BLPOP, Sidekiq) route around HAProxy's `timeout
client 30s` via the sentinel headless path. Uptime Kuma's Redis monitor
already learned that lesson the hard way (memory id=748).
## What is NOT in this change
- Deleting `null_resource.patch_redis_service` — still load-bearing (T0).
- Deleting `kubernetes_service.redis_master` — stays as the declared write API.
- Migrating any consumer off bare `redis.redis.svc` — T0 epic.
- Per-client sentinel migration — T1 epic.
- Retiring HAProxy — T2 epic (blocked on T1 + T3).
## Before / after
Before (steady state):
```
scripts/tg plan
Plan: 1 to add, 2 to change, 1 to destroy.
# null_resource.patch_redis_service must be replaced
# triggers = { "always" = "<timestamp>" } -> (known after apply)
```
After (steady state, post-apply):
```
scripts/tg plan
No changes. Your infrastructure matches the configuration.
```
After (chart version bump):
```
scripts/tg plan
# null_resource.patch_redis_service must be replaced
# triggers = { "chart_version" = "25.3.2" -> "25.4.0" }
```
— the trigger fires only when it actually needs to.
## Test Plan
### Automated
`scripts/tg plan` pre-change (confirms baseline noise):
```
# module.redis.null_resource.patch_redis_service must be replaced
-/+ resource "null_resource" "patch_redis_service" {
~ triggers = { # forces replacement
~ "always" = "2026-04-19T10:39:40Z" -> (known after apply)
}
}
Plan: 1 to add, 2 to change, 1 to destroy.
```
`scripts/tg plan` post-edit (confirms the one-time structural replacement):
```
# module.redis.null_resource.patch_redis_service must be replaced
-/+ resource "null_resource" "patch_redis_service" {
~ triggers = { # forces replacement
- "always" = "2026-04-19T10:39:40Z" -> null
+ "chart_version" = "25.3.2"
+ "haproxy_config" = "989bca9483cb9f9942017320765ec0751ac8357ff447acc5ed11f0a14b609775"
}
}
```
Apply is deferred to the operator — the working tree on the same file also
contains an unrelated HAProxy DNS-resolvers fix (for today's immich outage)
that needs its own review before rolling out together. No `scripts/tg apply`
run from this session.
### Manual Verification
Reproduce locally:
1. `cd infra/stacks/redis && ../../scripts/tg plan`
2. Before apply: expect `null_resource.patch_redis_service` to be replaced
exactly once, with the trigger map transitioning from `{always = <ts>}`
to `{chart_version, haproxy_config}`.
3. After apply: `../../scripts/tg plan` twice in a row must both report
`No changes.` (excluding unrelated drift from other work-in-progress).
4. Cluster-side invariant (must hold pre- and post-apply):
`kubectl -n redis get svc redis -o jsonpath='{.spec.selector}'`
→ `{"app":"redis-haproxy"}`
`kubectl -n redis get svc redis-master -o jsonpath='{.spec.selector}'`
→ `{"app":"redis-haproxy"}`
5. Regression test for the trigger doing its job: bump `helm_release.redis.version`
in a branch, `tg plan`, expect the null_resource to replace. Revert.
702db75f84