k8s-wait-for

This tool is still actively used and working stably despite not too frequent commits! Pull requests are most welcome!

Important: For kubernetes versions <=1.23, use k8s-wait-for version 2.1 or higher or k8s-wait-for versions 1.*. See here.

A simple script that allows waiting for a k8s service, job or pods to enter the desired state.

Running

You can start simple. Run it on your cluster in a namespace you already have something deployed:

kubectl run k8s-wait-for --rm -it --image ghcr.io/groundnuty/k8s-wait-for:v1.6 --restart Never --command /bin/sh

Read --help and play with it!

/ > wait_for.sh -h
This script waits until a job, pod or service enter a ready state. 

wait_for.sh job [<job name> | -l<kubectl selector>]
wait_for.sh pod [<pod name> | -l<kubectl selector>]
wait_for.sh service [<service name> | -l<kubectl selector>]

Examples:
Wait for all pods with a following label to enter 'Ready' state:
wait_for.sh pod -lapp=develop-volume-gluster-krakow

Wait for all selected pods to enter the 'Ready' state:
wait_for.sh pod -l"release in (develop), chart notin (cross-support-job-3p)"

Wait for all pods with a following label to enter 'Ready' or 'Error' state:
wait_for.sh pod-we -lapp=develop-volume-gluster-krakow

Wait for at least one pod to enter the 'Ready' state, even when the other ones are in 'Error' state:
wait_for.sh pod-wr -lapp=develop-volume-gluster-krakow

Wait for all the pods in that job to have a 'Succeeded' state:
wait_for.sh job develop-volume-s3-krakow-init

Wait for all the pods in that job to have a 'Succeeded' or 'Failed' state:
wait_for.sh job-we develop-volume-s3-krakow-init

Wait for at least one pod in that job to have 'Succeeded' state, does not mind some 'Failed' ones:
wait_for.sh job-wr develop-volume-s3-krakow-init

Example

A complex Kubernetes deployment manifest (generated by helm). This deployment waits for one job to finish and 2 pods to enter a ready state.

kind: StatefulSet
metadata:
  name: develop-oneprovider-krakow
  labels:
    app: develop-oneprovider-krakow
    chart: oneprovider-krakow
    release: develop
    heritage: Tiller
    component: oneprovider
  annotations:
    version: "0.2.17"
spec:
  selector:
    matchLabels:
      app: develop-oneprovider-krakow
      chart: oneprovider-krakow
      release: develop
      heritage: Tiller
      component: "oneprovider"
  serviceName: develop-oneprovider-krakow
  template:
    metadata:
      labels:
        app: develop-oneprovider-krakow
        chart: oneprovider-krakow
        release: develop
        heritage: Tiller
        component: "oneprovider"
      annotations:
        version: "0.2.17"
    spec:
      initContainers:
        - name: wait-for-onezone
          image: ghcr.io/groundnuty/k8s-wait-for:v1.6
          imagePullPolicy: Always
          args:
            - "job"
            - "develop-onezone-ready-check"
        - name: wait-for-volume-ceph
          image: ghcr.io/groundnuty/k8s-wait-for:v1.6
          imagePullPolicy: Always
          args:
            - "pod"
            - "-lapp=develop-volume-ceph-krakow"
        - name: wait-for-volume-gluster
          image: ghcr.io/groundnuty/k8s-wait-for:v1.6
          imagePullPolicy: Always
          args:
            - "pod"
            - "-lapp=develop-volume-gluster-krakow"
      containers:
      - name: oneprovider
        image: docker.onedata.org/oneprovider:ID-a3a9ff0d78
        imagePullPolicy: Always

Complex deployment use case

This container is used extensively in deployments of Onedata system onedata/charts to specify dependencies. It leverages Kubernetes init containers, thus providing:

- a detailed event log in `kubectl describe <pod>`, on what init container is pod hanging at the moment.
- a comprehensive view in `kubectl get pods` output where init containers are shown in a form `Init:<ready>/<total>`

Example output from the deployment run of ~16 pod with dependencies just after deployment:

NAME                                                   READY     STATUS              RESTARTS   AGE
develop-cross-support-job-3p-krk-3-lis-c-b4nv1         0/1       Init:0/1            0          11s
develop-cross-support-job-3p-krk-3-par-c-lis-n-z7x6w   0/1       Init:0/1            0          11s
develop-cross-support-job-3p-krk-3-x9719               0/1       Init:0/1            0          11s
develop-cross-support-job-3p-krk-g-par-3-ztvz0         0/1       Init:0/1            0          11s
develop-cross-support-job-3p-krk-g-v5lf2               0/1       Init:0/1            0          11s
develop-cross-support-job-3p-krk-n-par-3-pnbcm         0/1       Init:0/1            0          11s
develop-cross-support-job-3p-lis-3-cpj3f               0/1       Init:0/1            0          11s
develop-cross-support-job-3p-par-n-8zdt2               0/1       Init:0/1            0          11s
develop-cross-support-job-3p-par-n-lis-c-kqdf0         0/1       Init:0/1            0          11s
develop-oneclient-krakow-2773392814-wc1dv              0/1       Init:0/3            0          11s
develop-oneclient-lisbon-3267879054-2v6cg              0/1       Init:0/3            0          9s
develop-oneclient-paris-2076479302-f6hh9               0/1       Init:0/3            0          9s
develop-onedata-cli-krakow-1801798075-b5wpj            0/1       Init:0/1            0          11s
develop-onedata-cli-lisbon-139116355-fwtjv             0/1       Init:0/1            0          10s
develop-onedata-cli-paris-2662312307-9z9l1             0/1       Init:0/1            0          11s
develop-oneprovider-krakow-3634465102-tftc6            0/1       Pending             0          10s
develop-oneprovider-lisbon-3034775369-8n31x            0/1       Init:0/3            0          8s
develop-oneprovider-paris-3034358951-19mhf             0/1       Init:0/3            0          10s
develop-onezone-304145816-dmxn1                        0/1       ContainerCreating   0          11s
develop-volume-ceph-krakow-479580114-mkd1d             0/1       ContainerCreating   0          11s
develop-volume-ceph-lisbon-1249181958-1f0mt            0/1       ContainerCreating   0          9s
develop-volume-ceph-paris-400443052-dc347              0/1       ContainerCreating   0          9s
develop-volume-gluster-krakow-761992225-sj06m          0/1       Running             0          11s
develop-volume-gluster-lisbon-3947152141-jlmvb         0/1       Running             0          8s
develop-volume-gluster-paris-3588749681-9bnw8          0/1       ContainerCreating   0          11s
develop-volume-nfs-krakow-2528947555-6mxzt             1/1       Running             0          10s
develop-volume-nfs-lisbon-3473018547-7nljf             0/1       ContainerCreating   0          11s
develop-volume-nfs-paris-2956540513-4bdzt              0/1       ContainerCreating   0          11s
develop-volume-s3-krakow-23786741-pdxtj                0/1       Running             0          9s
develop-volume-s3-krakow-init-gqmmp                    0/1       Init:0/1            0          11s
develop-volume-s3-lisbon-3912793669-d4xh5              0/1       Running             0          10s
develop-volume-s3-lisbon-init-mq9nk                    0/1       Init:0/1            0          11s
develop-volume-s3-paris-124394749-qwt18                0/1       Running             0          8s
develop-volume-s3-paris-init-jb4k3                     0/1       Init:0/1            0          11s

1 min after, you can see the changes in the Status column:

develop-cross-support-job-3p-krk-3-lis-c-b4nv1         0/1       Init:0/1          0          1m
develop-cross-support-job-3p-krk-3-par-c-lis-n-z7x6w   0/1       Init:0/1          0          1m
develop-cross-support-job-3p-krk-3-x9719               0/1       Init:0/1          0          1m
develop-cross-support-job-3p-krk-g-par-3-ztvz0         0/1       Init:0/1          0          1m
develop-cross-support-job-3p-krk-g-v5lf2               0/1       Init:0/1          0          1m
develop-cross-support-job-3p-krk-n-par-3-pnbcm         0/1       Init:0/1          0          1m
develop-cross-support-job-3p-lis-3-cpj3f               0/1       Init:0/1          0          1m
develop-cross-support-job-3p-par-n-8zdt2               0/1       Init:0/1          0          1m
develop-cross-support-job-3p-par-n-lis-c-kqdf0         0/1       Init:0/1          0          1m
develop-oneclient-krakow-2773392814-wc1dv              0/1       Init:0/3          0          1m
develop-oneclient-lisbon-3267879054-2v6cg              0/1       Init:0/3          0          58s
develop-oneclient-paris-2076479302-f6hh9               0/1       Init:0/3          0          58s
develop-onedata-cli-krakow-1801798075-b5wpj            0/1       Init:0/1          0          1m
develop-onedata-cli-lisbon-139116355-fwtjv             0/1       Init:0/1          0          59s
develop-onedata-cli-paris-2662312307-9z9l1             0/1       Init:0/1          0          1m
develop-oneprovider-krakow-3634465102-tftc6            0/1       Init:1/3          0          59s
develop-oneprovider-lisbon-3034775369-8n31x            0/1       Init:2/3          0          57s
develop-oneprovider-paris-3034358951-19mhf             0/1       PodInitializing   0          59s
develop-onezone-304145816-dmxn1                        0/1       Running           0          1m
develop-volume-ceph-krakow-479580114-mkd1d             1/1       Running           0          1m
develop-volume-ceph-lisbon-1249181958-1f0mt            1/1       Running           0          58s
develop-volume-ceph-paris-400443052-dc347              1/1       Running           0          58s
develop-volume-gluster-krakow-761992225-sj06m          1/1       Running           0          1m
develop-volume-gluster-lisbon-3947152141-jlmvb         1/1       Running           0          57s
develop-volume-gluster-paris-3588749681-9bnw8          1/1       Running           0          1m
develop-volume-nfs-krakow-2528947555-6mxzt             1/1       Running           0          59s
develop-volume-nfs-lisbon-3473018547-7nljf             1/1       Running           0          1m
develop-volume-nfs-paris-2956540513-4bdzt              1/1       Running           0          1m
develop-volume-s3-krakow-23786741-pdxtj                1/1       Running           0          58s
develop-volume-s3-lisbon-3912793669-d4xh5              1/1       Running           0          59s
develop-volume-s3-paris-124394749-qwt18                1/1       Running           0          57s

Troubleshooting

Verify that you can access the Kubernetes API from within the k8s-wait-for container by running kubectl get services. If you get a permissions error like

Error from server (Forbidden): services is forbidden: User "system:serviceaccount:default:default" cannot list resource "services" in API group "" in the namespace "default"

the pod lacks the permissions to perform the kubectl get query. To fix this, follow the instrctions for the 'pod-reader' role and clusterrole here.

or use these command lines which add services and deployments to the pods in those examples: kubectl create role pod-reader --verb=get --verb=list --verb=watch --resource=pods,services,deployments

kubectl create rolebinding default-pod-reader --role=pod-reader --serviceaccount=default:default --namespace=default

An extensive discussion on the problem of granting necessary permissions and a number of example solutions can be found here.

Make sure the service account is mounted. The connection to the server localhost:8080 was refused - did you specify the right host or port? might indicate that the service account is not mounted to the pod. Double check whether your service account and pod define automountServiceAccountToken: true. If the service account is mounted, you should see files inside /var/run/secrets/kubernetes.io/serviceaccount folder, otherwise /var/run/secrets/kubernetes.io might not exist at all.