Implementation:SeldonIO Seldon core Seldon Experiment CRD

Field	Value
Type	Pattern Doc
Overview	Concrete pattern for declaring Seldon Core 2 Experiment resources as Kubernetes YAML manifests.
Domains	MLOps, Experimentation
Related Principle	SeldonIO_Seldon_core_Experiment_Configuration
Source	samples/experiments/ab-default-model.yaml:L1-11, samples/experiments/sklearn-mirror.yaml:L1-13
Knowledge Sources	Repo, Doc
Last Updated	2026-02-13 00:00 GMT

Description

This implementation provides the concrete YAML patterns for declaring Seldon Core 2 Experiment resources. An Experiment CRD defines the traffic routing rules for A/B tests, canary deployments, and traffic mirroring. The Experiment resource is applied to the Kubernetes cluster and interpreted by the Seldon scheduler, which updates its routing table accordingly.

Code Reference

A/B Test with Default Model

apiVersion: mlops.seldon.io/v1alpha1
kind: Experiment
metadata:
  name: experiment-sample
spec:
  default: iris
  candidates:
  - name: iris
    weight: 50
  - name: iris2
    weight: 50

This experiment splits traffic 50/50 between the iris and iris2 models. The default: iris field means that requests sent to the iris endpoint will be routed according to the experiment weights. The iris endpoint effectively becomes the experiment entry point.

Traffic Mirroring

apiVersion: mlops.seldon.io/v1alpha1
kind: Experiment
metadata:
  name: sklearn-mirror
spec:
  default: iris
  candidates:
  - name: iris
    weight: 100
  mirror:
    name: iris2
    percent: 100

This experiment serves all traffic from iris (weight 100) while mirroring 100% of requests to iris2. The mirror's responses are not returned to the caller.

I/O Contract

Direction	Description
Inputs	Deployed model or pipeline names and desired traffic split. All referenced models/pipelines must be loaded and available before the experiment is started.
Outputs	An Experiment CRD YAML manifest ready to be applied via seldon experiment start or kubectl apply.

Key Parameters

Parameter	Description	Required
spec.default	The default model/pipeline name whose endpoint will be shared by the experiment. Requests to this name will be routed by the experiment.	Yes
spec.candidates[].name	Name of a candidate model/pipeline. Must match a loaded resource.	Yes
spec.candidates[].weight	Relative traffic weight for this candidate. Traffic share = weight / sum(all weights).	Yes
spec.mirror.name	Name of the model/pipeline to receive mirrored (shadow) traffic.	No (mirror mode only)
spec.mirror.percent	Percentage (0-100) of requests to mirror to the shadow target.	No (mirror mode only)
spec.resourceType	Set to "pipeline" for pipeline-level experiments. Defaults to model.	No

Usage Examples

Weighted A/B Test (80/20 Split)

apiVersion: mlops.seldon.io/v1alpha1
kind: Experiment
metadata:
  name: canary-rollout
spec:
  default: my-model-v1
  candidates:
  - name: my-model-v1
    weight: 80
  - name: my-model-v2
    weight: 20

Three-Way A/B Test

apiVersion: mlops.seldon.io/v1alpha1
kind: Experiment
metadata:
  name: three-way-test
spec:
  default: model-a
  candidates:
  - name: model-a
    weight: 34
  - name: model-b
    weight: 33
  - name: model-c
    weight: 33

Partial Traffic Mirroring

apiVersion: mlops.seldon.io/v1alpha1
kind: Experiment
metadata:
  name: partial-mirror
spec:
  default: production-model
  candidates:
  - name: production-model
    weight: 100
  mirror:
    name: experimental-model
    percent: 50

Pipeline Experiment

apiVersion: mlops.seldon.io/v1alpha1
kind: Experiment
metadata:
  name: pipeline-ab-test
spec:
  default: pipeline-v1
  resourceType: pipeline
  candidates:
  - name: pipeline-v1
    weight: 50
  - name: pipeline-v2
    weight: 50

External Dependencies

• Kubernetes API (mlops.seldon.io/v1alpha1) — The Experiment CRD must be registered in the cluster
• Seldon scheduler — Interprets the Experiment CRD and updates routing tables
• Deployed candidates — All models/pipelines referenced in candidates and mirror must be loaded

Related Pages

• SeldonIO_Seldon_core_Experiment_Configuration — principle for this implementation — Declarative specification of traffic routing rules for A/B tests and traffic mirroring experiments.
• SeldonIO_Seldon_core_Seldon_Model_Load_For_Experiment — prerequisite — Loading candidate models before defining the experiment.
• SeldonIO_Seldon_core_Seldon_Experiment_Start — next step — Starting the experiment after defining the CRD.
• Environment:SeldonIO_Seldon_core_Kubernetes_Cluster_Environment
• Environment:SeldonIO_Seldon_core_Go_Build_Toolchain_Environment