Implementation:SeldonIO Seldon core Seldon Experiment Start

Field	Value
Type	External Tool Doc
Overview	Concrete CLI tool for starting A/B test and traffic mirroring experiments in Seldon Core 2.
Domains	MLOps, Experimentation
Related Principle	SeldonIO_Seldon_core_Experiment_Execution
Source	docs-gb/cli/seldon_experiment_start.md:L1-25, samples/local-experiments.md:L109-127
Knowledge Sources	Repo, Doc
Last Updated	2026-02-13 00:00 GMT

Description

This implementation provides the concrete CLI commands for starting A/B test and traffic mirroring experiments in Seldon Core 2. The seldon experiment start command submits an Experiment CRD to the Seldon scheduler, which activates traffic routing according to the specified weights and mirror configuration. Alternatively, kubectl apply can be used to apply the experiment manifest directly to the Kubernetes API.

Code Reference

CLI Signature

seldon experiment start -f <experiment.yaml> [--scheduler-host string] [--force]

Alternative: kubectl

kubectl apply -f <experiment.yaml>

Full Example: Start an A/B Test

# Ensure candidates are loaded and ready
seldon model status iris -w ModelAvailable
seldon model status iris2 -w ModelAvailable

# Start the experiment
seldon experiment start -f samples/experiments/ab-default-model.yaml

# Verify experiment is active
seldon experiment status experiment-sample -w | head -1

Full Example: Start a Mirror Experiment

# Start mirroring experiment
seldon experiment start -f samples/experiments/sklearn-mirror.yaml

# Verify mirror experiment is active
seldon experiment status sklearn-mirror -w | head -1

I/O Contract

Direction	Description
Inputs	Experiment CRD YAML file. All candidate models and/or pipelines referenced in the manifest must be deployed and ready before starting the experiment.
Outputs	Experiment active: traffic splitting or mirroring engaged on the default endpoint. The scheduler updates its routing table and begins probabilistically routing requests to candidates.

Key Parameters

Parameter	Description	Default	Required
-f / --file-path	Path to the experiment manifest YAML file	—	Yes
--scheduler-host	Address of the Seldon scheduler	0.0.0.0:9004	No
--force	Force start even if experiment is already running	false	No

Usage Examples

Start A/B Test Between Two Models

# Define the experiment manifest (ab-test.yaml)
# Then start it
seldon experiment start -f ab-test.yaml

Start with Custom Scheduler Host

seldon experiment start -f ab-test.yaml --scheduler-host scheduler.seldon-mesh:9004

Start and Immediately Verify

# Start experiment and wait for active status
seldon experiment start -f ab-test.yaml
seldon experiment status experiment-sample -w | head -1

# Run a quick inference to verify routing
seldon model infer iris '{"inputs": [{"name": "predict", "shape": [1, 4], "datatype": "FP32", "data": [[1, 2, 3, 4]]}]}' --show-headers

Using kubectl

# Apply the experiment
kubectl apply -f samples/experiments/ab-default-model.yaml

# Check experiment status
kubectl get experiments experiment-sample -o yaml

External Dependencies

• seldon CLI — Command-line tool for interacting with Seldon Core 2 scheduler
• kubectl — Kubernetes CLI for applying CRD manifests (alternative method)
• Seldon scheduler — Orchestrates experiment routing; must be running and accessible

Related Pages

• SeldonIO_Seldon_core_Experiment_Execution — principle for this implementation — Activating an experiment to begin traffic splitting or mirroring between model candidates.
• SeldonIO_Seldon_core_Seldon_Experiment_CRD — prerequisite — The Experiment CRD manifest that defines the traffic routing rules.
• SeldonIO_Seldon_core_Seldon_Model_Infer_With_Headers — next step — Monitoring experiment traffic distribution using inference with response headers.
• SeldonIO_Seldon_core_Seldon_Experiment_Stop — lifecycle — Stopping the experiment when analysis is complete.
• Environment:SeldonIO_Seldon_core_Kubernetes_Cluster_Environment