API compatibility

The API group is operator.ptah.run and its only version is v1alpha1. Alpha means here what it means in Kubernetes: there is no compatibility guarantee. A change that breaks objects you have already stored can be made before v1, and this page does not promise otherwise.

What the project does hold to is that such a change is a decision somebody makes rather than something that slips in. Each rule below is enforced by a check, and the check is named, so what you are reading is the code rather than an intention.

What cannot change by accident

These are refused when the generated CRDs are compared against the previous commit, by make verify-crd-schema-history:

Change	Why it is refused
A field that goes from optional to required, or a new field that arrives already required, without a default	A stored object that never set the field fails the requirement on its next write. A default rescues this: structural defaulting fills an absent field from its schema default before anything validates it, on every decode, so a field that carries one is exempt.
An enum that lost a value	Every stored object holding the removed value stops validating, and there is no migration for it.
A numeric or length bound that tightened — a minimum that rose, a maximum that fell, a bound that newly appeared, or one that turned exclusive at the same value	A stored value the old bound allowed and the new one refuses fails on the same next write.
A pattern that changed, in either direction	Refused conservatively: proving a changed regular expression only ever widens is its own project, so any change is treated as tightening unless a declared break says otherwise.
A new or changed x-kubernetes-validations rule on a field that already existed	The rule runs against the stored value the first time anything writes the object, whether or not the write touches that field.
A changed x-kubernetes-list-type or x-kubernetes-map-type	Both are enforced against whatever the field already holds, not just against what a write changes: a list that was fine as atomic can hold entries a set or map list-type refuses.
A default that appeared, changed, or was taken away	It changes what a stored object reads back as, on objects nobody edited.

A field the new schema no longer declares is not refused. Structural pruning drops a value for any property the current schema does not carry when it decodes a stored object, required or not, so removing a field — and whatever required-ness it had — reaches no object already in etcd. An earlier version of this check refused a removed required field anyway, on a claim about a decode order that pruning code in k8s.io/apiextensions-apiserver did not bear out; two changes that tightened validation the other way, stokaro/ptah-operator#470 and #482, went unrefused because the check was watching the harmless direction.

The comparison is against the storage version of each kind, because that is the schema an object in etcd is read back through. A kind the baseline does not carry is new and has nothing stored to break.

Breaking any of them is still possible: it means editing that check, which puts the consequence in front of whoever makes the change and into the diff of whoever reviews it. The edit is a declared break in hack/crdschemahistory/compatibility.go: it names the schema version that makes the break, why, and every refusal it excuses, word for word. It excuses nothing in any other version, and it is refused itself if it names a refusal the change does not produce. That is the whole of it before v1 — not that the API will not move under you, but that it will not move quietly.

What must move when the schema moves

Every shipped CRD carries operator.ptah.run/crd-schema-version and a digest of its normalized spec. The same verifier requires the version to strictly increase when the specs change, and to stay exactly equal when they do not. A schema that changed without the version moving is refused, and so is a version bumped without a change.

So the annotation is a fact about the bytes rather than a release number, and every shipped kind carries the same one.

Contract counters

The schema version is one of several numbers that version something a release stores in a cluster or speaks to another component. Each is written down in code and held there by a check:

Counter	Where it is declared	What it versions
CRD schema version	CRD_SCHEMA_VERSION in the Makefile and CurrentCRDSchemaVersion in internal/crdupgrade, stamped on every CRD as operator.ptah.run/crd-schema-version	The generated schemas, held to the previous commit as described above.
Controller-state version	CONTROLLER_STATE_VERSION in the Makefile and controllerstate.CurrentVersion, stamped on every CRD and both webhook configurations as operator.ptah.run/controller-state-version	The durable status a manager can read; see the controller-state contract.
Plan contract	fingerprint.CurrentPlanContractVersion for a plan computed from an OCI artifact and fingerprint.SourcePlanContractVersion for one computed from a ConfigMap or a Git commit, which the PtahSchemaPlan spec.contractVersion enum and the plan write guard repeat	What a schema plan’s fingerprint binds, and so what an approval names. A manager writes both and reads both; one that knows only version 1 refuses a version 2 plan.
Migration plan contract	migrationplan.ContractVersion and migrationplan.SourceContractVersion, the same two numbers, which the PtahMigrationPlan spec.contractVersion bound repeats	The same for a migration plan.
Realm digest contract	coordinationContractVersion in internal/fingerprint	How a coordination key or a PtahRealm becomes the digest that names a database.
Runner protocol	runner.ProtocolVersion, recorded in support/runner-protocol.json and in the edge row of support/ptah.json	What the runner accepts, enforces and returns. hack/verifyrunnerprotocol holds it to the runner’s source.
Drift vocabulary	dataplane.DriftFindingVocabularyVersion	The closed set of drift finding categories, and the form of the kind a feature category may carry.
Admission contract	CurrentAdmissionContractVersion in internal/crdupgrade, stamped on both webhook configurations as operator.ptah.run/admission-contract-version	The admission configuration every release serves.
Certificate staging format	certrotation.StagingFormat, the format key of the rotator’s staging Secret	The record a certificate rotation resumes from after a restart.
Admission snapshot format	podintent.SnapshotVersion, which the admissionSnapshot.version enum in an operation’s status repeats	The Pod admission rules an operation’s snapshot was taken under.

Every counter is 1 in the 0.2.0 development tree. They previously counted commits, and no release could hold version 32 of anything, so they were all reset to 1 during release preparation. The schema-history check compares each change with the commit before it, and would read 32 to 1 as a rollback. That restart is recorded in hack/crdschemahistory/restart.go: it leaves only the schemas it names, by version and by the digest of every CRD, it arrives at version 1 and at nothing else, and it excuses only the stored-object transitions it lists. Any other move below the baseline is refused as a rollback, and every change after it is held to the rules above.

From the first release on, a counter moves only when something a tagged release could have stored or spoken changes. A change that leaves every stored and spoken form as it was keeps its number: the runner protocol records such a change in support/runner-protocol.json with its reason instead of moving. The CRD schema version is the strictest of them, because its check compares every change with the commit before it: any change to a generated schema moves it.

What the operator refuses at runtime

The durable state and the release order carry versions of their own, and both are fences rather than documentation.

Durable state. operator.ptah.run/controller-state-version says which status a manager can interpret. A manager reads state stamped at its own version or below and refuses anything above, at startup and before every CRD update. Which version carries which state, and what each refusal looks like, is the controller-state contract.

Chart and image pairing. The reconcile hook refuses a chart whose controller-state version its own manager image does not compile, before it reads or changes anything. That is what stops a --reuse-values upgrade that keeps an old image under a new chart, or an old chart paired with a new image. helm rollback renders nothing: it runs the CRD hook of the release it returns to, and that hook refuses stored state newer than that release reads. Upgrading is allowed to move forward and rolling back below state that has already been written is not.

The set of kinds cannot change quietly

The generated set is the schema family and the migration family, each with its plan and its approval. The schema-history verifier refuses a set that added or removed a kind, so one cannot appear or disappear without that refusal being addressed deliberately.

Go packages for other programs

Two packages outside internal/ are there for programs that read what the operator stored. pkg/planread reads a schema plan back through the store’s own checks; kubectl ptah plan reads through it, so there is one reader. pkg/planread/planreadtest holds the stored states such a reader has to answer, each with the answer planread gives, so a program that wraps the reader can run the same cases. A test refuses an exported declaration in either package that names an internal type.

They stand where v1alpha1 stands: no compatibility promise. Pin the module version and read what a release changed before you move to it.

Before v1

There are no deprecations. A field that has to go, goes, in a release that says so. Nothing is kept working for a window first, because a window is a compatibility promise and v1alpha1 does not make one.

There is no dated transition to v1. Until there is, the only way to stay safe is to pin the chart version you deploy and read what a release changed before you move to it. An upgrade can require you to edit your resources, and Release notes is where that is said, one entry per version.