PubSub Domain

Optional Feature

The PubSub domain is part of the optional Event feature. It is managed by the Event and Spectre domains — users do not interact with PubSub resources directly.

The PubSub domain provides the runtime configuration layer for publish/subscribe messaging. It acts as a thin bridge between the Control Plane and the Horizon runtime component, translating Kubernetes custom resources into REST API calls that configure the external messaging system.

Custom Resources

EventStore

EventStore is the Schema for the eventstores API. It stores the resolved connection and authentication details for the configuration backend. EventStore resources are created and managed by the EventConfig handler in the event domain.

Group: pubsub.cp.ei.telekom.de · Version: v1 · Scope: Namespaced

EventStoreSpec

Appears in: EventStore

EventStoreSpec defines the desired state of EventStore. EventStore holds resolved operational values for connecting to the configuration backend, including OAuth2 credentials. It is created by the EventConfig handler.

Field	Type	Default	Validation
clientId	string	—	Required, minLength: 1
clientSecret	string	—	Required, minLength: 1
overwriteEnvironmentName	string	—	Optional
tokenUrl	string	—	Required, Format: uri, minLength: 1
url	string	—	Required, Format: uri, minLength: 1

EventStoreStatus

Appears in: EventStore, Publisher

EventStoreStatus defines the observed state of EventStore.

Field	Type	Default	Validation
conditions	Condition[]	—	Optional

Condition

Appears in: EventStoreStatus, SubscriberStatus

Field	Type	Default	Validation
lastTransitionTime	string	—	Required, Format: date-time
message	string	—	Required, maxLength: 32768
observedGeneration	integer	—	Optional, Format: int64, minimum: 0
reason	string	—	Required, minLength: 1, maxLength: 1024, pattern: ^[A-Za-z]([A-Za-z0-9_,:]*[A-Za-z0-9_])?$
status	string	—	Required, Enum: True \| False \| Unknown
type	string	—	Required, maxLength: 316, pattern: ^([a-z0-9]([-a-z0-9]*[a-z0-9])?(\.[a-z0-9]([-a-z0-9]*[a-z0-9])?)*/)?(([A-Za-z0-9][-A-Za-z0-9_.]*)?[A-Za-z0-9])$

Publisher

Publisher is the Schema for the publishers API. It represents an event publisher registration in the configuration backend. Publisher resources are created and managed by the EventExposure handler in the event domain or by the SpectreApplication handler in the spectre domain.

Group: pubsub.cp.ei.telekom.de · Version: v1 · Scope: Namespaced

PublisherSpec

Appears in: Publisher

PublisherSpec defines the desired state of Publisher. Publisher represents a registered event publisher in the configuration backend. It is created by the EventExposure handler in the event domain or by the SpectreApplication handler in the spectre domain.

Field	Type	Default	Validation
additionalPublisherIds	string[]	—	Optional
eventStore	EventStore	—	Required
eventType	string	—	Required, minLength: 1
jsonSchema	string	—	Optional
publisherId	string	—	Required, minLength: 1

EventStore

Appears in: PublisherSpec, SubscriberSpec

EventStore references the EventStore CR that provides configuration connection details.

Field	Type	Default	Validation
name	string	—	Required
namespace	string	—	Required
uid	string	—	Optional

Subscriber

Subscriber is the Schema for the subscribers API. It represents an event subscription registration in the configuration backend. Subscriber resources are created and managed by the EventSubscription handler in the event domain or by the Listener handler in the spectre domain.

Group: pubsub.cp.ei.telekom.de · Version: v1 · Scope: Namespaced

SubscriberSpec

Appears in: Subscriber

SubscriberSpec defines the desired state of Subscriber. Subscriber represents an event subscription registration in the configuration backend. It is created by the EventSubscription handler in the event domain or by the Listener handler in the spectre domain.

Field	Type	Default	Validation
appliedScopes	string[]	—	Optional
delivery	Delivery	—	Required
publisher	EventStore	—	Required
publisherTrigger	PublisherTrigger	—	Optional
subscriberId	string	—	Required, minLength: 1
trigger	PublisherTrigger	—	Optional

Delivery

Appears in: SubscriberSpec

Delivery configures how events are delivered to the subscriber.

Field	Type	Default	Validation
callback	string	—	Optional
circuitBreakerOptOut	boolean	—	Optional
enforceGetHttpRequestMethodForHealthCheck	boolean	—	Optional
eventRetentionTime	string	—	Optional
payload	string	Data	Required, Enum: Data \| DataRef
redeliveriesPerSecond	integer	—	Optional
retryableStatusCodes	integer[]	—	Optional
type	string	Callback	Required, Enum: Callback \| ServerSentEvent

PublisherTrigger

Appears in: SubscriberSpec

PublisherTrigger defines publisher-side filtering criteria for event delivery.

Field	Type	Default	Validation
responseFilter	ResponseFilter	—	Optional
selectionFilter	SelectionFilter	—	Optional

ResponseFilter

Appears in: PublisherTrigger

ResponseFilter controls payload shaping (which fields to return).

Field	Type	Default	Validation
mode	string	Include	Optional, Enum: Include \| Exclude
paths	string[]	—	Optional

SelectionFilter

Appears in: PublisherTrigger

SelectionFilter controls event matching (which events to deliver).

Field	Type	Default	Validation
attributes	map<string, string>	—	Optional
expression	object	—	Optional

SubscriberStatus

Appears in: Subscriber

SubscriberStatus defines the observed state of Subscriber.

Field	Type	Default	Validation
conditions	Condition[]	—	Optional
subscriptionId	string	—	Optional

Dependency Chain

Resources in the PubSub domain follow a strict dependency chain:

EventStore  ◀── Publisher  ◀── Subscriber
   (zone)        (app)         (subscription)

• A Subscriber can only be created if its Publisher is ready.
• A Publisher can only be created if its EventStore is ready.
• An EventStore is created by the Event domain when an EventConfig is applied.

Domain Interactions

• Event domain — Creates PubSub resources as part of the event publishing/subscribing lifecycle:
  • EventConfig → EventStore
  • EventExposure → Publisher
  • EventSubscription → Subscriber
• Spectre domain — Creates PubSub resources for application listeners:
  • SpectreApplication → Publisher
  • Listener → Subscriber
• Horizon (external) — The Subscriber controller makes REST API calls to the Horizon Configuration Backend to register and deregister subscriptions.

EventStore is created exclusively by EventConfig. Spectre reads it but does not own or modify it.

note

The PubSub domain is intentionally self-contained. It does not import API types from other Control Plane domains, making it possible to replace the Horizon runtime with a different messaging backend in the future.

Related Pages

• Architecture: Event Domain
• Architecture: Spectre Domain
• User Journey: Exposing Events
• User Journey: Subscribing to Events