assign pod spec when scheduling k8s pods https://asciinema.org/a/230498

my-scheduler.sh

#!/bin/bash

set -e
set -o pipefail

SERVER='localhost:8001'
while true;
do
    for POD in $(kubectl --server $SERVER get pods -o json --all-namespaces | \
                 jq -r '.items[] |
                 select(.spec.schedulerName == "my-scheduler") |
                 select(.spec.nodeName == null) |
                 .metadata.namespace+","+.metadata.name')
    do
        NAMESPACE=$(echo "$POD" | cut -d',' -f1)
        PODNAME=$(echo "$POD" | cut -d',' -f2)
        NODES=($(kubectl --server $SERVER get nodes -o json | \
                 jq '.items[].metadata.name' | tr -d '"'))
        NUMNODES=${#NODES[@]}

        ### scheduling algorithm here
        CHOSEN=${NODES[$[$RANDOM % $NUMNODES]]}
        ###

        ### check limit
        LIMIT=$(kubectl --server $SERVER get -n $NAMESPACE pods $PODNAME \
                -o jsonpath='{$.spec.containers[0].resources.limits}')

        ### recreate pod for updating pod spec
        if [[ "$LIMIT" == "" ]]; then
            NEW=$(kubectl --server $SERVER get -n $NAMESPACE pods $PODNAME \
                  --export -o json | \
                  jq ".metadata.namespace = \"$NAMESPACE\"" | \
                  jq ".spec.containers[0].resources.limits.cpu = \"1000m\"")
            kubectl --server $SERVER delete -n $NAMESPACE pods $PODNAME
            echo "$NEW" | kubectl --server $SERVER create -f -
            continue
        fi

        ### binding pod
        curl --header "Content-Type:application/json" --request POST \
        --data '''{
            "apiVersion":"v1",
            "kind": "Binding",
            "metadata": {"name": "'$PODNAME'"},
            "target": {"apiVersion": "v1", "kind": "Node", "name": "'$CHOSEN'"}
        }''' http://$SERVER/api/v1/namespaces/$NAMESPACE/pods/$PODNAME/binding/
        echo "Assigned $PODNAME to $CHOSEN"
    done
    sleep 1
done

target.yaml

apiVersion: v1
kind: Pod
metadata:
  name: nginx
  labels:
    app: nginx
spec:
  schedulerName: my-scheduler
  containers:
  - name: nginx
    image: nginx:1.10