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fix(infra): address Objecten by a dotted host so NRC accepts its notifications (refs #152)
The worker published and NRC answered 400 on every message:

  {"hoofdObject":["Voer een geldige URL in."],"resourceUrl":["Voer een geldige URL in."]}

NRC types both as DRF `URLField`, and Django's URLValidator refuses a single-label host.
Objecten fills them from the object `url` DRF built with `request.build_absolute_uri` —
the Host the *caller* used — so `SITE_DOMAIN` never entered into it. Dropped that env pair;
it was a wrong guess at the mechanism.

The fix is on the caller side: keep the `objecten.local` network alias and point every
writer whose writes must be notified at it — the ACL, the gateway integration tests, and
this slice's verify driver. Readers keep the plain service name.

ADR-0029 updated with the real mechanism and the ceiling it leaves: a new writer using
`objecten:8000` gets a 201 and silently no notification.
2026-08-28 11:31:31 +02:00

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6.4 KiB
Markdown

# ADR-0029: Objecten publishes register events to NRC
- **Status:** Accepted
- **Date:** 2026-08-14
- **Deciders:** Respellion engineering
- **Slice:** S-19b-1 (#152), first of the S-19b (#150) split
- **Supersedes in part:** ADR-0028's "Objecten's notifications are off for this slice"
## Context
ADR-0028 put the authoritative register record in the Objecten API and had the ACL write
it on approval. It also switched Objecten's notifications **off** — deliberately, with a
stated ceiling: there was no broker, no worker, no `objecten` kanaal and no abonnement, so
turning the client side on alone would have produced a delivery path that looks wired and
drops every message.
S-19b-2 (#153) wants the read projection sourced from register writes rather than
re-derived from ZGW zaak events. That needs the notifications to actually arrive. This ADR
builds the four missing pieces and lifts the ceiling.
## Decision
**Objecten publishes to the same NRC OpenZaak already publishes to, on the `objecten`
kanaal, delivered by its own Celery worker — provisioned declaratively on both sides,
exactly as ADR-0007 did for OpenZaak.**
- **Objecten** (`infra/objecten/setup_configuration/data.yaml`): a `zgw_consumers` service
`nrc` (api_type `nrc`) plus a `notifications_config` step naming it, and
`NOTIFICATIONS_DISABLED: "false"` in both compose files.
- **NRC** (`infra/opennotificaties/setup_configuration/data.yaml`): an `objecten` kanaal
alongside `zaken`.
- **`objecten-celery`**: a worker container on the Objecten image (`/celery_worker.sh`),
mirroring `oz-celery`, with `CELERY_BROKER_URL`/`CELERY_RESULT_BACKEND` on
`objecten-redis` db 1 (db 0 is already the cache).
### One NRC, one credential, one kanaal per publisher
Objecten reuses the `big-reference-seed` client OpenZaak publishes with. NRC verifies its
JWT and authorizes it against OpenZaak's Autorisaties API (ADR-0007), which grants that
client `heeft_alle_autorisaties` — so no second credential and no publisher-specific
authorization is needed. A second NRC, or a second credential, would buy isolation this
reference application has no use for.
The kanaal name is **not ours to choose**: the Objects API sends
`NOTIFICATIONS_KANAAL = "objecten"`. NRC rejects a publish to an unregistered kanaal
(`"Kanaal met deze naam bestaat niet"`), which is precisely what the failing check for this
slice reported first. Its filter set (`object_type`) matches the kenmerken the Objects API
sends, so an abonnement can narrow to one objecttype instead of receiving every write.
### Writers address Objecten as `objecten.local` — NRC rejects single-label hosts
NRC types a notification's `hoofdObject` and `resourceUrl` as DRF `URLField`s, so Django's
`URLValidator` runs on them — and it refuses a **single-label** host. Objecten fills both
from the object `url` that DRF built with `request.build_absolute_uri`, i.e. **the Host the
caller used**. Write to `http://objecten:8000` and NRC answers every publish with
```
{"hoofdObject":["Voer een geldige URL in."],"resourceUrl":["Voer een geldige URL in."]}
```
which `objecten-celery` then retries with exponential backoff, forever, in the background —
the write itself having returned 201.
`SITE_DOMAIN` does **not** fix this; it is not what builds those URLs. The fix is on the
caller side: the `objecten` service carries an `objecten.local` network alias, and every
component whose writes must be notified — the ACL (`Acl__Objecten__BaseUrl`), the gateway
integration tests, this slice's verify check — addresses it there. An alias rather than a
plain dotted `SITE_DOMAIN` so the host still **resolves in-network**: a subscriber that
follows `resourceUrl` reaches the record it points at, which S-19b-2 will do. Readers are
unaffected and keep using the plain service name.
This is the same class of constraint as ADR-0028's "the ACL's Objecttypen base URL must
match Objecten's configured `api_root`": these modules put request-derived hosts into data
another module then validates or dereferences.
- ponytail ceiling: nothing *enforces* that a new writer uses the alias — it would get a 201
and silently no notification.
- Upgrade path: if a second writer ever appears, rename the compose service to `objecten.local`
so the plain name stops working, rather than adding a lint.
### A worker, not a synchronous send
`notifications_api_common` only schedules the send on transaction commit. Without a worker
the task sits in redis forever and every register write is silently undelivered — the exact
half-wired state ADR-0028 refused to ship. No `beat` for Objecten: it is a publisher, not a
subscriber, and `nrc-beat` already drains NRC's delivery queue.
## Verification
`make verify-objecten-notifications` (`infra/run-objecten-notifications-check.sh`, in the
CI `verify-stack` job) registers an abonnement on the `objecten` kanaal pointing at a
throwaway webhook sink, writes a `RegisterRecord` exactly as the ACL does on approval, and
asserts the notification reaches the sink. That is the whole chain in one assertion:
Objecten → `objecten-celery` → NRC → `nrc-beat` → the callback. Any missing piece — broker,
worker, kanaal, notifications config — shows up as a non-delivery rather than as a green
config.
## Consequences
**Positive**
- A register write is now observable by anything that subscribes, which is what S-19b-2
(#153) needs to make the projection a cache of Objecten rather than a re-derivation of ZGW.
- ADR-0028's ceiling is lifted: the delivery path is proven end to end, not merely configured.
**Negative / costs**
- One more long-running container (`objecten-celery`) on an already memory-tight CI runner.
- A second publisher on the shared `big-reference-seed` credential — a credential rotation
now touches two modules.
- Objecten now has two in-network names, and which one a caller uses silently decides
whether its writes are notified (ceiling above).
- ponytail ceiling: notification delivery has no dead-letter or alerting — a failed publish
is visible only in the worker log.
- Upgrade path: if undelivered register events start mattering, subscribe an audit sink or
read NRC's own delivery admin rather than building a retry layer here.
## Coupling rules touched (CLAUDE.md §8)
None bent. This is infrastructure between two upstream modules, over their documented
APIs; no service reaches another's database. §8.6 (idempotency at every event boundary)
applies to whatever consumes the new kanaal — S-19b-2's problem, not this slice's.