Merge branch '87-random-scheduling' into 'master'

Allow using a random scheduler

Closes #87

See merge request !61

execution/infrastructure/random-scheduler/Dockerfile

+FROM alpine:3.12
+
+RUN apk update && apk add bash curl jq
+RUN curl -LO https://storage.googleapis.com/kubernetes-release/release/$(curl -s https://storage.googleapis.com/kubernetes-release/release/stable.txt)/bin/linux/amd64/kubectl \
+  && chmod +x ./kubectl \
+  && mv ./kubectl /usr/local/bin/kubectl
+
+ADD schedule.sh /bin/schedule
+
+CMD /bin/schedule

execution/infrastructure/random-scheduler/README.md

+# Theodolite Random Scheduler
+This directory contains the Theodolite Random Scheduler that schedules pods on random nodes.
+
+## Build and Push
+Run the following commands
+
+- `docker build -t theodolite-random-scheduler .`
+- `docker tag theodolite-random-scheduler <user>/theodolite-random-scheduler`
+- `docker push <user>/theodolite-random-scheduler`
+
+## Deployment
+Deploy the `deployment.yaml` file into Kubernetes. Note, that the `TARGET_NAMESPACE` environment variable specifies the operating namespace of the random scheduler.
\ No newline at end of file

execution/infrastructure/random-scheduler/deployment.yaml

+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: random-scheduler
+  labels:
+    app: random-scheduler
+  namespace: kube-system
+spec:
+  replicas: 1
+  selector:
+    matchLabels:
+      app: random-scheduler
+  template:
+    metadata:
+      labels:
+        app: random-scheduler
+    spec:
+      serviceAccount: random-scheduler
+      containers:
+        - name: random-scheduler
+          image: theodolite/random-scheduler:latest
+          imagePullPolicy: Always
+          env:
+            - name: TARGET_NAMESPACE
+              value: default

execution/infrastructure/random-scheduler/rbac.yaml

+apiVersion: v1
+kind: ServiceAccount
+metadata:
+  namespace: kube-system
+  name: random-scheduler 
+  labels:
+    app: random-scheduler 
+    component: random-scheduler
+---
+apiVersion: rbac.authorization.k8s.io/v1
+kind: ClusterRoleBinding
+metadata:
+  name: random-scheduler
+subjects:
+- kind: ServiceAccount
+  name: random-scheduler
+  namespace: kube-system
+roleRef:
+  kind: ClusterRole
+  apiGroup: rbac.authorization.k8s.io
+  name: system:kube-scheduler
\ No newline at end of file

execution/infrastructure/random-scheduler/schedule.sh

+#!/bin/bash
+
+# use kubectl in proxy mode in order to allow curl requesting the k8's api server
+kubectl proxy --port 8080 &
+
+echo "Target Namespace: $TARGET_NAMESPACE"
+while true;
+do
+    for PODNAME in $(kubectl get pods -n $TARGET_NAMESPACE -o json | jq '.items[] | select(.spec.schedulerName == "random-scheduler") | select(.spec.nodeName == null) | .metadata.name' | tr -d '"');
+    do
+        NODES=($(kubectl get nodes -o json | jq '.items[].metadata.name' | tr -d '"'))
+        NUMNODES=${#NODES[@]}
+        CHOSEN=${NODES[$[$RANDOM % $NUMNODES]]}
+        curl --header "Content-Type:application/json" --request POST --data '{"apiVersion":"v1", "kind": "Binding", "metadata": {"name": "'$PODNAME'"}, "target": {"apiVersion": "v1", "kind": "Node", "name": "'$CHOSEN'"}}' localhost:8080/api/v1/namespaces/$TARGET_NAMESPACE/pods/$PODNAME/binding/
+        echo "Assigned $PODNAME to $CHOSEN"
+    done
+    sleep 1
+done
\ No newline at end of file