Merge pull request #2225 from steveperry-53/container-hooks

Write new Task: Attaching Handlers to Container Lifecycle Events.

_data/tasks.yml

@@ -13,7 +13,8 @@ toc:
   - docs/tasks/configure-pod-container/pull-image-private-registry.md
   - docs/tasks/configure-pod-container/configure-liveness-readiness-probes.md
   - docs/tasks/configure-pod-container/communicate-containers-same-pod.md
-  - docs/tasks/configure-pod-container/configure-pod-initialization.md 
+  - docs/tasks/configure-pod-container/configure-pod-initialization.md
+  - docs/tasks/configure-pod-container/attach-handler-lifecycle-event.md
 
 - title: Accessing Applications in a Cluster
   section:

docs/tasks/configure-pod-container/attach-handler-lifecycle-event.md

@@ -0,0 +1,94 @@
+---
+title: Attaching Handlers to Container Lifecycle Events
+---
+
+{% capture overview %}
+
+This page shows how to attach handlers to Container lifecycle events. Kubernetes supports
+the postStart and preStop events. Kubernetes sends the postStart event immediately
+after a Container is started, and it sends the preStop event immediately before the
+Container is terminated.
+
+{% endcapture %}
+
+
+{% capture prerequisites %}
+
+{% include task-tutorial-prereqs.md %}
+
+{% endcapture %}
+
+
+{% capture steps %}
+
+### Defining postStart and preStop handlers
+
+In this exercise, you create a Pod that has one Container. The Container has handlers
+for the postStart and preStop events.
+
+Here is the configuration file for the Pod:
+
+{% include code.html language="yaml" file="lifecycle-events.yaml" ghlink="/docs/tasks/configure-pod-container/lifecycle-events.yaml" %}
+
+In the configuration file, you can see that the postStart command writes a `message`
+file to the Container's `/usr/share` directory. The preStop command shuts down
+nginx gracefully. This is helpful if the Container is being terminated because of a failure.
+
+Create the Pod:
+
+    kubectl create -f http://k8s.io/docs/tasks/configure-pod-container/lifecycle-events.yaml
+
+Verify that the Container in the Pod is running:
+
+    kubectl get pod lifecycle-demo
+
+Get a shell into the Container running in your Pod:
+
+    kubectl exec -it lifecycle-demo -- /bin/bash
+
+In your shell, verify that the `postStart` handler created the `message` file:
+
+    root@lifecycle-demo:/# cat /usr/share/message
+
+The output shows the text written by the postStart handler:
+
+    Hello from the postStart handler
+
+{% endcapture %}
+
+
+
+{% capture discussion %}
+
+### Discussion
+
+Kubernetes sends the postStart event immediately after the Container is created.
+There is no guarantee, however, that the postStart handler is called before
+the Container's entrypoint is called. The postStart handler runs asynchronously
+relative to the Container's code, but Kubernetes' management of the container
+blocks until the postStart handler completes. The Container's status is not
+set to RUNNING until the postStart handler completes.
+
+Kubernetes sends the preStop event immediately before the Container is terminated.
+Kubernetes' management of the Container blocks until the preStop handler completes,
+unless the Pod's grace period expires. For more details, see
+[Termination of Pods](/docs/user-guide/pods/#termination-of-pods).
+
+{% endcapture %}
+
+
+{% capture whatsnext %}
+
+* Learn more about [Container lifecycle hooks](/docs/user-guide/container-environment/.)
+* Learn more about the [lifecycle of a Pod](https://kubernetes.io/docs/user-guide/pod-states/).
+
+
+#### Reference
+ 
+* [Lifecycle](https://kubernetes.io/docs/resources-reference/1_5/#lifecycle-v1)
+* [Container](https://kubernetes.io/docs/resources-reference/1_5/#container-v1)
+* See `terminationGracePeriodSeconds` in [PodSpec](/docs/resources-reference/v1.5/#podspec-v1)
+
+{% endcapture %}
+
+{% include templates/task.md %}

docs/tasks/configure-pod-container/lifecycle-events.yaml

@@ -0,0 +1,33 @@
+apiVersion: v1
+kind: Pod
+metadata:
+  name: lifecycle-demo
+spec:
+  containers:
+  - name: lifecycle-demo-container
+    image: nginx
+
+    lifecycle:
+      postStart:
+        exec:
+          command: ["/bin/sh", "-c", "echo Hello from the postStart handler > /usr/share/message"]
+      preStop:
+        exec:
+          command: ["/usr/sbin/nginx","-s","quit"]
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+

docs/tasks/index.md

@@ -17,6 +17,7 @@ single thing, typically by giving a short sequence of steps.
 * [Configuring Liveness and Readiness Probes](/docs/tasks/configure-pod-container/configure-liveness-readiness-probes/)
 * [Communicating Between Pods Running in the Same Container](/docs/tasks/configure-pod-container/communicate-containers-same-pod/)
 * [Configuring Pod Initialization](/docs/tasks/configure-pod-container/configure-pod-initialization/)
+* [Attaching Handlers to Container Lifecycle Events](/docs/tasks/configure-pod-container/attach-handler-lifecycle-event/)
 
 #### Accessing Applications in a Cluster