Add parameters to customize the service created by an an Experiment

[ernestovm-st]

Summary

During the creation of an Experiment, is possible to create a service just passing the service name in the template of each pod to be created. Example:

apiVersion: argoproj.io/v1alpha1
kind: Experiment
metadata:
  name: my-experiment
  namespace: default
spec:
  
  duration: 30m
  progressDeadlineSeconds: 300
  templates:
    - name: pod-experiment-a
      replicas: 1
      service:
        name: pod-experiment-a
      selector:
        matchLabels:
          app: pod-experiment-a
      template:
        metadata:
          labels:
            app: pod-experiment-a
        spec:
          containers:
            - name: pod-experiment-a
              image: my-artifacts.dev/docker/pod-experiment:versiona
              imagePullPolicy: Always
              ports:
                - name: flask
                  containerPort: 5000
                  protocol: TCP
    - name: pod-experiment-b
      replicas: 1
      service:
        name: pod-experiment-b
      selector:
        matchLabels:
          app: pod-experiment-b
      template:
        metadata:
          labels:
            app: pod-experiment-b
        spec:
          containers:
            - name: pod-experiment-b
              image: my-artifacts.dev/docker/pod-experiment:versionb
              imagePullPolicy: Always
              ports:
                - name: flask
                  containerPort: 5000
                  protocol: TCP
  # List of AnalysisTemplate references to perform during the experiment
  analyses:
    - name: version-a
      templateName: pods-experiment
      args:
        - name: job
          value: version-a
        - name: namespace
          value: default
    - name: version-b
      templateName: pods-experiment
      args:
        - name: job
          value: version-b
        - name: namespace
          value: default

When the experiment is created, the services created looks like this (I'll just show just one):

apiVersion: v1
kind: Service
metadata:
  annotations:
    experiment.argoproj.io/name: my-experiment
    experiment.argoproj.io/template-name: pod-experiment-a
  creationTimestamp: "2024-12-18T13:01:03Z"
  name: pod-experiment-a
  namespace: default
  ownerReferences:
  - apiVersion: argoproj.io/v1alpha1
    blockOwnerDeletion: true
    controller: true
    kind: Experiment
    name: my-experiment
    uid: 76456f57-b8a1-45ce-979c-07f5761fe878
  resourceVersion: "78448930"
  uid: 4c3f15b0-9fbc-4fba-b235-e3e6ec88903a
spec:
  clusterIP: x.x.x.x
  clusterIPs:
  - x.x.x.x
  internalTrafficPolicy: Cluster
  ipFamilies:
  - IPv4
  ipFamilyPolicy: SingleStack
  ports:
  - name: flask
    port: 5000
    protocol: TCP
    targetPort: 5000
  selector:
    rollouts-pod-template-hash: 89456c669
  sessionAffinity: None
  type: ClusterIP
status:
  loadBalancer: {}

As showed above, the selector used by the service is rollouts-pod-template-hash, instead of the labels applied to the pod template. Additionally, cannot be configured in a different kind of service (i.e. LoadBalancer, Port, NodePort...)

Use Cases

Customize the service can be used for

• Select an appropriate kind of service (useful when you are in a Kubernetes provider)
• Do not reconfigure scrapping configuration in monitoring / observability tools (i.e. Prometheus) in order to gather metrics exposed by experiment's pods
• Add pods into the service out of the scope of the experiment. I.E. you want to mix some pods running in production under the same experiment service.

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