Lab: Reviewing OpenShift Application Logs

This lab covers how to review application logs in an OpenShift environment.

Theory

There are multiple ways to review application logs in an OpenShift environment:

1. Using the oc command line client:
   1. View the native logs of the pod through the oc logs command.
   2. View log files within a pod by starting a remote shell using the oc rsh command.
   3. Download log files from a pod using the oc cp command.
2. Using the OpenShift web console:
   1. View and/or download the native logs of the pod through the Logs tab on a pod.
   2. View log files within a pod through the Terminal tab on a pod.
3. Publish native logs of pods to OpenShift centralized logging using, most commonly, EFK, and then search logs in the Kibana log viewer. Optionally install sample Kibana dashboards created by the WebSphere team that summarize application log events and statistics.
4. Gather a Liberty server dump using the WebSphere Liberty Operator that includes Liberty log files.

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Lab: Review logs with the command line client or the OpenShift web console pod page

This lab will demonstrate how to review both application native logs (equivalent to the Liberty console.log) and the Liberty messages.log using the oc command line client or the OpenShift web console pod page.

This lab will take approximately 15 minutes.

Step 1: Install example application

Install the sample application.

Step 2: Review Application Logs

Using the command line

1. List the pods for the example application deployment; for example:

   oc get pods
   

   Example output:

   NAME                          READY   STATUS    RESTARTS   AGE
   libertydiag-b98748954-mgj64   1/1     Running   0          97s
   

2. Print the native logs of the pod by replacing $POD with the pod name from the previous command. The native logs are equivalent to the Liberty console.log in a non-cloud deployment.

   oc logs $POD
   

   For example:

   oc logs libertydiag-b98748954-mgj64
   

3. Open a shell into the pod by replacing $POD with the pod name from the previous command:

   oc rsh -t $POD
   

   For example:

   oc rsh -t libertydiag-b98748954-mgj64
   

4. Copy and paste the following command and press Enter to print the full Liberty messages.log:

   cat /logs/messages.log
   

5. Alternatively, if you want to download a file to your computer, exit out of the rsh session and download messages.log by replacing $POD with the pod name from the previous command:

   oc cp $POD:/logs/messages.log messages.log
   

   For example:

   oc cp libertydiag-b98748954-mgj64:/logs/messages.log messages.log
   

Using the browser

1. In the Topology view of the Developer perspective, click on the libertydiag circle, then click the Resources tab in the drawer on the right, and then click on View logs for the one pod that's running. The View logs output is equivalent to the Liberty console.log in a non-cloud deployment.
   
2. You can also download the native logs using the Download button:
   
3. Note that the browser can only download native logs; it cannot download arbitrary logs from the container filesystem. Instead, you can cat the logs through the Terminal.
4. Click on the Terminal tab to open a remote shell into the running container in the pod:
   
5. Copy and paste the following command and press Enter to print the full Liberty messages.log: cat /logs/messages.log

Summary

In summary, this lab demonstrated how to install a sample application and review its logs.