Merge pull request #1720 from steveperry-53/debug-message

Write new task: Determining the Reason for Pod Failure.

_data/tasks.yml

@@ -15,6 +15,14 @@ toc:
   section:
   - title: Using Port Forwarding to Access Applications in a Cluster
     path: /docs/tasks/access-application-cluster/port-forward-access-application-cluster/
+
+
+- title: Debugging Applications in a Cluster
+  section:
+  - title: Determining the Reason for Pod Failure
+    path: /docs/tasks/debug-application-cluster/determine-reason-pod-failure/
+
+
 - title: Accessing the Kubernetes API
   section:
   - title: Using an HTTP Proxy to Access the Kubernetes API

docs/tasks/debug-application-cluster/determine-reason-pod-failure.md

@@ -0,0 +1,110 @@
+---
+---
+
+{% capture overview %}
+
+This page shows how to write and read a Container
+termination message.
+
+Termination messages provide a way for containers to write
+information about fatal events to a location where it can
+be easily retrieved and surfaced by tools like dashboards
+and monitoring software. In most cases, information that you
+put in a termination message should also be written to
+the general
+[Kubernetes logs](/docs/user-guide/logging/).
+
+{% endcapture %}
+
+
+{% capture prerequisites %}
+
+{% include task-tutorial-prereqs.md %}
+
+{% endcapture %}
+
+
+{% capture steps %}
+
+### Writing and reading a termination message
+
+In this exercise, you create a Pod that runs one container.
+The configuration file specifies a command that runs when
+the container starts.
+
+{% include code.html language="yaml" file="termination.yaml" ghlink="/docs/tasks/debug-pod-container/termination.yaml" %}
+
+1. Create a Pod based on the YAML configuration file:
+
+        export REPO=https://raw.githubusercontent.com/kubernetes/kubernetes.github.io/master
+        kubectl create -f $REPO/docs/tasks/debug-pod-container/termination.yaml
+
+    In the YAML file, in the `cmd` and `args` fields, you can see that the
+    container sleeps for 10 seconds and then writes "Sleep expired" to
+    the `/dev/termination-log` file. After the container writes
+    the "Sleep expired" message, it terminates.
+
+1. Display information about the Pod:
+
+        kubectl get pod termination-demo
+
+    Repeat the preceding command until the Pod is no longer running.
+
+1. Display detailed information about the Pod:
+
+        kubectl get pod --output=yaml
+
+    The output includes the "Sleep expired" message:
+
+        apiVersion: v1
+        kind: Pod
+        ...
+            lastState:
+              terminated:
+                containerID: ...
+                exitCode: 0
+                finishedAt: ...
+                message: |
+                  Sleep expired
+                ...
+
+1. Use a Go template to filter the output so that it includes
+only the termination message:
+        
+```
+{% raw %}    kubectl get pod termination-demo -o go-template="{{range .status.containerStatuses}}{{.lastState.terminated.message}}{{end}}"{% endraw %}
+```
+
+### Setting the termination log file
+
+By default Kubernetes retrieves termination messages from
+`/dev/termination-log`. To change this to a different file,
+specify a `terminationMessagePath` field for your Container.
+
+For example, suppose your Container writes termination messages to
+`/tmp/my-log`, and you want Kubernetes to retrieve those messages.
+Set `terminationMessagePath` as shown here:
+
+    apiVersion: v1
+    kind: Pod
+    metadata:
+      name: msg-path-demo
+    spec:
+      containers:
+      - name: msg-path-demo-container
+        image: debian
+        terminationMessagePath: "/tmp/my-log"
+
+{% endcapture %}
+
+{% capture whatsnext %}
+
+* See the `terminationMessagePath` field in 
+  [Container](/docs/api-reference/v1/definitions#_v1_container).
+* Learn about [retrieving logs](/docs/user-guide/logging/).
+* Learn about [Go templates](https://golang.org/pkg/text/template/).
+
+{% endcapture %}
+
+
+{% include templates/task.md %}

docs/tasks/debug-application-cluster/termination.yaml

@@ -0,0 +1,10 @@
+apiVersion: v1
+kind: Pod
+metadata:
+  name: termination-demo
+spec:
+  containers:
+  - name: termination-demo-container
+    image: debian
+    command: ["/bin/sh"]
+    args: ["-c", "sleep 10 && echo Sleep expired > /dev/termination-log"]