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Scale Seldon Deployments based on Prometheus Metrics.

This notebook shows how you can scale Seldon Deployments based on Prometheus metrics via KEDA.

KEDA is a Kubernetes-based Event Driven Autoscaler. With KEDA, you can drive the scaling of any container in Kubernetes based on the number of events needing to be processed.

With the support of KEDA in Seldon, you can scale your seldon deployments with any scalers listed here. In this example we will scale the seldon deployment with Prometheus metrics as an example.

Install Seldon Core

Install Seldon Core as described in docs

Make sure add --set keda.enabled=true

Install Prometheus

!kubectl create namespace seldon-monitoring
!helm upgrade --install seldon-monitoring kube-prometheus \
    --version 8.3.2 \
    --set fullnameOverride=seldon-monitoring \
    --namespace seldon-monitoring \
    --repo https://charts.bitnami.com/bitnami \
    --wait

namespace/seldon-monitoring created
Release "seldon-monitoring" does not exist. Installing it now.
NAME: seldon-monitoring
LAST DEPLOYED: Sun Feb  5 08:41:12 2023
NAMESPACE: seldon-monitoring
STATUS: deployed
REVISION: 1
TEST SUITE: None
NOTES:
CHART NAME: kube-prometheus
CHART VERSION: 8.3.2
APP VERSION: 0.62.0

** Please be patient while the chart is being deployed **

Watch the Prometheus Operator Deployment status using the command:

    kubectl get deploy -w --namespace seldon-monitoring -l app.kubernetes.io/name=kube-prometheus-operator,app.kubernetes.io/instance=seldon-monitoring

Watch the Prometheus StatefulSet status using the command:

    kubectl get sts -w --namespace seldon-monitoring -l app.kubernetes.io/name=kube-prometheus-prometheus,app.kubernetes.io/instance=seldon-monitoring

Prometheus can be accessed via port "9090" on the following DNS name from within your cluster:

    seldon-monitoring-prometheus.seldon-monitoring.svc.cluster.local

To access Prometheus from outside the cluster execute the following commands:

    echo "Prometheus URL: http://127.0.0.1:9090/"
    kubectl port-forward --namespace seldon-monitoring svc/seldon-monitoring-prometheus 9090:9090

Watch the Alertmanager StatefulSet status using the command:

    kubectl get sts -w --namespace seldon-monitoring -l app.kubernetes.io/name=kube-prometheus-alertmanager,app.kubernetes.io/instance=seldon-monitoring

Alertmanager can be accessed via port "9093" on the following DNS name from within your cluster:

    seldon-monitoring-alertmanager.seldon-monitoring.svc.cluster.local

To access Alertmanager from outside the cluster execute the following commands:

    echo "Alertmanager URL: http://127.0.0.1:9093/"
    kubectl port-forward --namespace seldon-monitoring svc/seldon-monitoring-alertmanager 9093:9093

!kubectl rollout status -n seldon-monitoring statefulsets/prometheus-seldon-monitoring-prometheus

statefulset rolling update complete 1 pods at revision prometheus-seldon-monitoring-prometheus-b99bd7cb6...

!cat pod-monitor.yaml

apiVersion: monitoring.coreos.com/v1
kind: PodMonitor
metadata:
  name: seldon-podmonitor
  namespace: seldon-monitoring
spec:
  selector:
    matchLabels:
      app.kubernetes.io/managed-by: seldon-core
  podMetricsEndpoints:
    - port: metrics
      path: /prometheus
  namespaceSelector:
    any: true

!kubectl apply -f pod-monitor.yaml

podmonitor.monitoring.coreos.com/seldon-podmonitor created

Install KEDA

Follow the docs for KEDA to install.

Create model with KEDA

To create a model with KEDA autoscaling you just need to add a KEDA spec referring in the Deployment, e.g.:

kedaSpec:
  pollingInterval: 15                                # Optional. Default: 30 seconds
  minReplicaCount: 1                                 # Optional. Default: 0
  maxReplicaCount: 5                                 # Optional. Default: 100
  triggers:
  - type: prometheus
          metadata:
            # Required
            serverAddress: http://seldon-monitoring-prometheus.seldon-monitoring.svc.cluster.local:9090
            metricName: access_frequency
            threshold: '10'
            query: rate(seldon_api_executor_client_requests_seconds_count{model_name="classifier"}[1m])

The full SeldonDeployment spec is shown below.

VERSION = !cat ../../version.txt
VERSION = VERSION[0]
VERSION

'1.16.0-dev'

%%writefile model_with_keda_prom.yaml
apiVersion: machinelearning.seldon.io/v1
kind: SeldonDeployment
metadata:
  name: seldon-model
spec:
  name: test-deployment
  predictors:
  - componentSpecs:
    - spec:
        containers:
        - image: seldonio/mock_classifier:1.16.0-dev
          imagePullPolicy: IfNotPresent
          name: classifier
          resources:
            requests:
              cpu: '0.5'
      kedaSpec:
        pollingInterval: 15                                # Optional. Default: 30 seconds
        minReplicaCount: 1                                 # Optional. Default: 0
        maxReplicaCount: 5                                 # Optional. Default: 100
        triggers:
        - type: prometheus
          metadata:
            # Required
            serverAddress: http://seldon-monitoring-prometheus.seldon-monitoring.svc.cluster.local:9090
            metricName: access_frequency
            threshold: '10'
            query: rate(seldon_api_executor_client_requests_seconds_count{model_name="classifier"}[1m])
    graph:
      children: []
      endpoint:
        type: REST
      name: classifier
      type: MODEL
    name: example

Overwriting model_with_keda_prom.yaml

!kubectl create -f model_with_keda_prom.yaml

seldondeployment.machinelearning.seldon.io/seldon-model created

!kubectl rollout status deploy/$(kubectl get deploy -l seldon-deployment-id=seldon-model -o jsonpath='{.items[0].metadata.name}')

Waiting for deployment "seldon-model-example-0-classifier" rollout to finish: 0 of 1 updated replicas are available...
deployment "seldon-model-example-0-classifier" successfully rolled out

Create Load

We label some nodes for the loadtester. We attempt the first two as for Kind the first node shown will be the master.

!kubectl label nodes $(kubectl get nodes -o jsonpath='{.items[0].metadata.name}') role=locust
!kubectl label nodes $(kubectl get nodes -o jsonpath='{.items[1].metadata.name}') role=locust

node/kind-control-plane not labeled
node/kind-worker not labeled

Before add loads to the model, there is only one replica

!kubectl get deployment seldon-model-example-0-classifier

NAME                                READY   UP-TO-DATE   AVAILABLE   AGE
seldon-model-example-0-classifier   1/1     1            1           34s

!helm install seldon-core-loadtesting seldon-core-loadtesting --repo https://storage.googleapis.com/seldon-charts \
    --set locust.host=http://seldon-model-example:8000 \
    --set oauth.enabled=false \
    --set locust.hatchRate=1 \
    --set locust.clients=1 \
    --set loadtest.sendFeedback=0 \
    --set locust.minWait=0 \
    --set locust.maxWait=0 \
    --set replicaCount=1

NAME: seldon-core-loadtesting
LAST DEPLOYED: Sun Feb  5 08:48:08 2023
NAMESPACE: seldon
STATUS: deployed
REVISION: 1
TEST SUITE: None

After a few mins you should see the deployment scaled to 5 replicas

import json
import time


def getNumberPods():
    dp = !kubectl get deployment seldon-model-example-0-classifier -o json
    dp = json.loads("".join(dp))
    return dp["status"]["replicas"]


scaled = False
for i in range(60):
    pods = getNumberPods()
    print(pods)
    if pods > 1:
        scaled = True
        break
    time.sleep(5)
assert scaled

1
1
1
1
1
1
1
1
1
1
4

!kubectl get deployment/seldon-model-example-0-classifier scaledobject/seldon-model-example-0-classifier

NAME                                                READY   UP-TO-DATE   AVAILABLE   AGE
deployment.apps/seldon-model-example-0-classifier   5/5     5            5           3m51s

NAME                                                     SCALETARGETKIND      SCALETARGETNAME                     TRIGGERS     AUTHENTICATION   READY   ACTIVE   AGE
scaledobject.keda.sh/seldon-model-example-0-classifier   apps/v1.Deployment   seldon-model-example-0-classifier   prometheus                    True    True     3m51s

Remove Load

!helm delete seldon-core-loadtesting

release "seldon-core-loadtesting" uninstalled

After 5-10 mins you should see the deployment replica number decrease to 1

Cleanup

!kubectl delete -f model_with_keda_prom.yaml

seldondeployment.machinelearning.seldon.io "seldon-model" deleted

!helm delete seldon-monitoring -n seldon-monitoring

release "seldon-monitoring" uninstalled

!kubectl delete namespace seldon-monitoring

namespace "seldon-monitoring" deleted