Principle:Kserve Kserve Controller Reconciliation
| Knowledge Sources | |
|---|---|
| Domains | Kubernetes, Operator_Pattern, Reconciliation |
| Last Updated | 2026-02-13 00:00 GMT |
Overview
A control loop pattern that continuously reconciles the declared InferenceService spec against the actual cluster state, creating and updating runtime resources to achieve the desired serving endpoint.
Description
Controller Reconciliation is the Kubernetes operator pattern applied to ML model serving. The InferenceService reconciler watches for changes to InferenceService resources and drives the cluster toward the desired state by:
- Loading configuration from the central ConfigMap
- Determining the deployment mode (Serverless, Standard, or ModelMesh)
- Reconciling predictor, transformer, and explainer components
- Creating Knative Services (Serverless) or raw Deployments (Standard)
- Reconciling ingress resources (VirtualService, HTTPRoute)
- Updating status conditions (PredictorReady, IngressReady, Ready)
This pattern solves the complexity of managing the lifecycle of ML serving infrastructure by encoding the operational logic in a controller that automatically responds to changes.
Usage
This principle is automatically active for every InferenceService in the cluster. Understanding the reconciliation loop is essential for:
- Debugging deployment issues (check status conditions)
- Extending KServe with new deployment modes
- Understanding the relationship between InferenceService spec and runtime resources
Theoretical Basis
The reconciliation follows a level-triggered control loop:
# Abstract reconciliation flow (NOT implementation code)
1. Watch: Detect InferenceService create/update/delete events
2. Fetch: Load InferenceService spec from Kubernetes API
3. Configure: Load central ConfigMap for runtime defaults
4. Route: Determine DeploymentMode (Serverless/Standard/ModelMesh)
5. Reconcile Components:
- For each component (predictor, transformer, explainer):
a. Select serving runtime
b. Create/update Knative Service or Deployment
c. Collect component status
6. Reconcile Ingress:
- Create VirtualService/HTTPRoute
- Set external URL
7. Update Status:
- Aggregate component conditions
- Set Ready condition when PredictorReady AND IngressReady
The controller is idempotent: running reconciliation multiple times with the same input produces the same output. This property ensures convergence even after transient failures.