How to wait until Kubernetes assigned an external IP to a LoadBalancer service?

Question

Creating a Kubernetes LoadBalancer returns immediatly (ex: kubectl create -f ... or kubectl expose svc NAME --name=load-balancer --port=80 --type=LoadBalancer).

I know a manual way to wait in shell:

external_ip=""
while [ -z $external_ip ]; do
    sleep 10
    external_ip=$(kubectl get svc load-balancer --template="{{range .status.loadBalancer.ingress}}{{.ip}}{{end}}")
done

This is however not ideal:

• Requires at least 5 lines Bash script.
• Infinite wait even in case of error (else requires a timeout which increases a lot line count).
• Probably not efficient; could use --wait or --wait-once but using those the command never returns.

Is there a better way to wait until a service external IP (aka LoadBalancer Ingress IP) is set or failed to set?

Answer 1

Just to add to the answers here, the best option right now is to use a bash script. For convenience, I've put it into a single line that includes exporting an environmental variable.

Command to wait and find Kubernetes service endpoint

bash -c 'external_ip=""; while [ -z $external_ip ]; do echo "Waiting for end point..."; external_ip=$(kubectl get svc NAME_OF_YOUR_SERVICE --template="{{range .status.loadBalancer.ingress}}{{.ip}}{{end}}"); [ -z "$external_ip" ] && sleep 10; done; echo "End point ready-" && echo $external_ip; export endpoint=$external_ip'

I've also modified your script so it only executes a wait if the ip isn't available. The last bit will export an environment variable called "endpoint"

Bash Script to Check a Given Service

Save this as check-endpoint.sh and then you can execute $sh check-endpoint.sh SERVICE_NAME

#!/bin/bash
# Pass the name of a service to check ie: sh check-endpoint.sh staging-voting-app-vote
# Will run forever...
external_ip=""
while [ -z $external_ip ]; do
  echo "Waiting for end point..."
  external_ip=$(kubectl get svc $1 --template="{{range .status.loadBalancer.ingress}}{{.ip}}{{end}}")
  [ -z "$external_ip" ] && sleep 10
done
echo 'End point ready:' && echo $external_ip

Using this in a Codefresh Step

I'm using this for a Codefresh pipeline and it passes a variable $endpoint when it's done.

  GrabEndPoint:
    title: Waiting for endpoint to be ready
    image: codefresh/plugin-helm:2.8.0
    commands:
      - bash -c 'external_ip=""; while [ -z $external_ip ]; do echo "Waiting for end point..."; external_ip=$(kubectl get svc staging-voting-app-vote --template="{{range .status.loadBalancer.ingress}}{{.ip}}{{end}}"); [ -z "$external_ip" ] && sleep 10; done; echo "End point ready-" && echo $external_ip; cf_export endpoint=$external_ip'

Answer 2

This is little bit tricky by working solution:

kubectl get service -w load-balancer -o 'go-template={{with .status.loadBalancer.ingress}}{{range .}}{{.ip}}{{"\n"}}{{end}}{{.err}}{{end}}' 2>/dev/null | head -n1