From a7b66a78a38619f8962bbf3c425141a5919188e3 Mon Sep 17 00:00:00 2001 From: "Elijah C. Voigt" Date: Fri, 17 Feb 2017 17:12:13 -0800 Subject: [PATCH] concepts/abstractions: init containers example. --- docs/concepts/abstractions/init-containers.md | 94 ++++++++++++++++++- 1 file changed, 93 insertions(+), 1 deletion(-) diff --git a/docs/concepts/abstractions/init-containers.md b/docs/concepts/abstractions/init-containers.md index 1bea00b3a2..89738eef56 100644 --- a/docs/concepts/abstractions/init-containers.md +++ b/docs/concepts/abstractions/init-containers.md @@ -95,6 +95,98 @@ Here are some ideas for how to use Init Containers: More detailed usage examples can be found in the [StatefulSets documentation](/docs/concepts/abstractions/controllers/statefulsets/) and the [Production Pods guide](/docs/user-guide/production-pods.md#handling-initialization). +### Init Containers in use + +The following yaml file outlines a simple Pod which has two Init Containers. +The first waits for `myservice` and the second waits for `mydb`. Once both +containers complete the Pod will begin. + +```yaml +apiVersion: v1 +kind: Pod +metadata: + name: myapp-pod + labels: + app: myapp + annotations: + pod.beta.kubernetes.io/init-containers: '[ + { + "name": "init-myservice", + "image": "busybox", + "command": ["sh", "-c", "until nslookup myservice; do echo waiting for myservice; sleep 2; done;"] + }, + { + "name": "init-mydb", + "image": "busybox", + "command": ["sh", "-c", "until nslookup mydb; do echo waiting for mydb; sleep 2; done;"] + } + ]' +spec: + containers: + - name: myapp-container + image: busybox + command: ['sh', '-c', 'echo The app is running! && sleep 3600'] +``` + +This Pod can be started and debugged with the following commands: + +``` +$ kubectl create -f myapp.yaml +pod "myapp-pod" created +$ kubectl get -f myapp.yaml +NAME READY STATUS RESTARTS AGE +myapp-pod 0/1 Init:0/2 0 6m +$ kubectl describe -f myapp.yaml +i11:32 $ kubectl describe -f examples/init-container.yaml +Name: myapp-pod +Namespace: default +[...] +Labels: app=myapp +Status: Pending +[...] +Init Containers: + init-myservice: +[...] + State: Running +[...] + init-mydb: +[...] + State: Running +[...] +Containers: + myapp-container: +[...] + State: Waiting + Reason: PodInitializing + Ready: False +[...] +Events: + FirstSeen LastSeen Count From SubObjectPath Type Reason Message + --------- -------- ----- ---- ------------- -------- ------ ------- + 16s 16s 1 {default-scheduler } Normal Scheduled Successfully assigned myapp-pod to 172.17.4.201 + 16s 16s 1 {kubelet 172.17.4.201} spec.initContainers{init-myservice} Normal Pulling pulling image "busybox" + 13s 13s 1 {kubelet 172.17.4.201} spec.initContainers{init-myservice} Normal Pulled Successfully pulled image "busybox" + 13s 13s 1 {kubelet 172.17.4.201} spec.initContainers{init-myservice} Normal Created Created container with docker id 5ced34a04634; Security:[seccomp=unconfined] + 13s 13s 1 {kubelet 172.17.4.201} spec.initContainers{init-myservice} Normal Started Started container with docker id 5ced34a04634 +$ kubectl logs myapp-pod -c init-myservice # Inspect the first init container +$ kubectl logs myapp-pod -c init-mydd # Inspect the second init container +``` + +Once we start the `mydb` and `myservice` Services we can see the Init Containers +complete and the `myapp-pod` is created: + +``` +$ kubectl create -f services.yaml +service "myservice" created +service "mydb" created +$ kubectl get -f myapp.yaml +NAME READY STATUS RESTARTS AGE +myapp-pod 1/1 Running 0 9m +``` + +This example is very simple but should provide some inspiration for you to +create your own Init Containers. + ## Detailed behavior During the startup of a Pod, the Init Containers are started in order, after the @@ -181,4 +273,4 @@ Kubelet and Apiserver versions; see the [release notes](https://github.com/kuber {% endcapture %} -{% include templates/concept.md %} \ No newline at end of file +{% include templates/concept.md %}