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Step 3: Logs

There are various "production-ready" ways to do log gathering and viewing across a Kubernetes/OpenShift cluster. Many folks like some flavor of ELK or EFK.

The focus here is on stuff a developer needs to get access to do help understand the behavior of their application running inside of a pod.

Make sure you are running 3 replicas (3 pods/instances of your application)

$ kubectl scale --replicas=3 deployment/myboot

and you can see them with kubectl get pods

$ kubectl get pods
NAME                      READY     STATUS    RESTARTS   AGE
myboot-68d666dd8d-cwtls   1/1       Running   0          3m
myboot-68d666dd8d-n874b   1/1       Running   0          3m
myboot-68d666dd8d-r8zpn   1/1       Running   0          11m

There is kubectl logs which is useful

$ kubectl logs myboot-68d666dd8d-r8zpn -f

or you can try stern, easily installable via homebrew on Mac https://github.com/wercker/stern

$ brew install stern

and use it like so

$ stern myboot

and in another terminal window, poll the various instances of the application

while true
do
  curl $(minikube ip):$(kubectl get service/myboot -o jsonpath="{.spec.ports[*].nodePort}")
  sleep .5;
done

and stern will let you see the logs across the 3 different pods.

Stern
Figure 1. stern output

This is more exciting when you might have 3 different microservices where the names are similiar enough to use stern.

stern also offers a --label selector

and if you are running Istio make sure to add the -c to specify your business logic container, instead of the sidecar…​unless you wish to view the sidecar’s logs :-)

Another option is kail

$ brew tap boz/repo
$ brew install boz/repo/kail
$ kail

This will output the logs across your namespace, in our case, the 3 replicas of myboot are all in the same namespace

You can use use kail and isolate a specific deployment, specific container (a pod can have more than one container) and look back in time

$ kail --deploy=myboot -c myboot --since=1h