neiam /mutant-operator

An Experimental Operator

API: scale a variant in place

8cbd453 · gmorell · 2026-11-09 15:46

3 files +56 -3

Message

{commit_body(@commit)}

modified README.md

+7 −1

@@ -162,7 +162,7 @@ Every `/api` request needs `Authorization: Bearer <token>`, and which token

162	162	depends on the request:
163	163
164	164	- A Mutation's own token (`token` in its `<name>-secret`) allows getting
165		− that Mutation and listing, adding and removing its variants, and nothing
	165	+ that Mutation and listing, adding, scaling and removing its variants, and nothing
166	166	else. An app in the Mutation's namespace reads it from that Secret, so it
167	167	can manage its own Mutation's variants without credentials for anything
168	168	else. The operator only accepts a Secret owned by the Mutation, so one

@@ -185,9 +185,13 @@ DELETE /api/v1/namespaces/{ns}/mutations/{name}

185	185	GET /api/v1/namespaces/{ns}/mutations/{name}/variants
186	186	POST /api/v1/namespaces/{ns}/mutations/{name}/variants {label, env, instances}
187	187	GET /api/v1/namespaces/{ns}/mutations/{name}/variants/{label}
	188	+PATCH /api/v1/namespaces/{ns}/mutations/{name}/variants/{label} {instances}
188	189	DELETE /api/v1/namespaces/{ns}/mutations/{name}/variants/{label}
189	190	```
190	191
	192	+`PATCH` scales a variant in place: its Deployment's replica count changes
	193	+and the running pods are kept.
	194	+
191	195	Creating answers 201, or 400 if invalid and 409 if the name or label is
192	196	taken. Deleting answers 204, or 404 if absent. Changes to an Argo-synced
193	197	Mutation answer 409. Concurrent variant edits are serialised on the

@@ -209,6 +213,8 @@ WEB=$(kubectl -n default get secret web-secret -o jsonpath='{.data.token}' | bas

209	213	AUTH="Authorization: Bearer $WEB"
210	214	curl -H "$AUTH" -H 'Content-Type: application/json' \
211	215	-d '{"label":"beta","env":{"FEATURE_X":"on"},"instances":2}' $NS/mutations/web/variants
	216	+curl -X PATCH -H "$AUTH" -H 'Content-Type: application/json' \
	217	+ -d '{"instances":4}' $NS/mutations/web/variants/beta
212	218	curl -X DELETE -H "$AUTH" $NS/mutations/web/variants/beta
213	219	# list
214	220	curl -H "$AUTH" $NS/mutations

modified src/api.rs

+49 −2

@@ -10,13 +10,15 @@

10	10	//! GET /api/v1/namespaces/{ns}/mutations/{name}/variants
11	11	//! POST /api/v1/namespaces/{ns}/mutations/{name}/variants {label, env, instances}
12	12	//! GET /api/v1/namespaces/{ns}/mutations/{name}/variants/{label}
	13	+//! PATCH /api/v1/namespaces/{ns}/mutations/{name}/variants/{label} {instances}
13	14	//! DELETE /api/v1/namespaces/{ns}/mutations/{name}/variants/{label}
14	15	//! ```
15	16	//!
16	17	//! ## Authorization
17	18	//!
18	19	//! Requests carry `Authorization: Bearer <token>`. A request about one
19		−//! Mutation -- getting it, listing, adding or removing its variants -- is
	20	+//! Mutation -- getting it, listing, adding, scaling or removing its
	21	+//! variants -- is
20	22	//! allowed with that Mutation's own token: the `token` in the
21	23	//! `<name>-secret` the operator generated for it, in its namespace. An app
22	24	//! reads that Secret from its own namespace and can then manage that one

@@ -87,7 +89,7 @@ pub fn router(state: AppState) -> Router {

87	89	)
88	90	.route(
89	91	"/namespaces/{ns}/mutations/{name}/variants/{label}",
90		− get(get_variant).delete(delete_variant),
	92	+ get(get_variant).patch(update_variant).delete(delete_variant),
91	93	);
92	94	Router::new()
93	95	.route("/healthz", get(\|\| async { "ok" }))

@@ -224,6 +226,14 @@ struct VariantView {

224	226	read_only: bool,
225	227	}
226	228
	229	+/// A change to an existing variant. Only its replica count, for now: a
	230	+/// variant's label and env are what make it that variant.
	231	+#[derive(Deserialize)]
	232	+#[serde(deny_unknown_fields)]
	233	+struct UpdateVariant {
	234	+ instances: i32,
	235	+}
	236	+
227	237	#[derive(Deserialize)]
228	238	struct CreateMutation {
229	239	name: String,

@@ -365,6 +375,34 @@ async fn delete_variant(

365	375	Ok(StatusCode::NO_CONTENT)
366	376	}
367	377
	378	+/// Scales a variant in place: its Deployment's replicas change, and the
	379	+/// pods already running are kept.
	380	+async fn update_variant(
	381	+ State(st): State<AppState>,
	382	+ headers: HeaderMap,
	383	+ Path((ns, name, label)): Path<(String, String, String)>,
	384	+ Json(req): Json<UpdateVariant>,
	385	+) -> ApiResult<Json<Variant>> {
	386	+ authorize_mutation(&st, &headers, &ns, &name).await?;
	387	+ if req.instances < 0 {
	388	+ return Err(ApiError::BadRequest(format!("instances must be >= 0, got {}", req.instances)));
	389	+ }
	390	+ let updated = std::sync::Mutex::new(None);
	391	+ update_variants(&st.mutations(&ns), &name, \|list\| {
	392	+ let v = list
	393	+ .iter_mut()
	394	+ .find(\|v\| v.label == label)
	395	+ .ok_or_else(\|\| ApiError::NotFound(format!("variant {label:?} not found")))?;
	396	+ v.instances = req.instances;
	397	+ *updated.lock().unwrap() = Some(v.clone());
	398	+ Ok(())
	399	+ })
	400	+ .await?;
	401	+ info!(%ns, %name, %label, instances = req.instances, "variant scaled");
	402	+ let variant = updated.into_inner().unwrap().expect("set by the successful edit");
	403	+ Ok(Json(variant))
	404	+}
	405	+
368	406	fn refuse_if_gitops(m: &Mutation) -> ApiResult<()> {
369	407	if is_gitops_managed(m) {
370	408	return Err(ApiError::Conflict(format!(

@@ -424,6 +462,15 @@ mod tests {

424	462	assert!(admin_ok(None, true, None));
425	463	}
426	464
	465	+ #[test]
	466	+ fn update_variant_body() {
	467	+ let ok: UpdateVariant = serde_json::from_str(r#"{"instances": 3}"#).unwrap();
	468	+ assert_eq!(ok.instances, 3);
	469	+ // A label or env change is not a scale; refused rather than ignored.
	470	+ assert!(serde_json::from_str::<UpdateVariant>(r#"{"instances": 3, "label": "x"}"#).is_err());
	471	+ assert!(serde_json::from_str::<UpdateVariant>(r#"{}"#).is_err());
	472	+ }
	473	+
427	474	#[test]
428	475	fn mutation_token_auth() {
429	476	use k8s_openapi::apimachinery::pkg::apis::meta::v1::OwnerReference;

Parents: 241f400