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concepts/abstractions: init containers example.

reviewable/pr2564/r1^2
Elijah C. Voigt 2017-02-17 17:12:13 -08:00 committed by Andrew Chen
parent f1ecafcdb1
commit a7b66a78a3
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docs/concepts/abstractions/init-containers.md
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@ -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 %}
{% include templates/concept.md %}