Here we have 2 containers: `container1` and `container2`.
When you have multiple containers in a pod we call them sidecar containers. Most of the time you have a "primary" container, the one with containing your application, and "secondary", hence the sidecar terminology.
All the containers of a given pod share the same network, and can share the same volumes.
Sidecars are useful for containers that are tightly coupled. A good use case is when you migrate an app from one machine to containers. The application will have a lot of `localhost` or `127.0.0.1` hardcoded. So with sidecars you can work around this.
Another use case is to have sidecars helping the main container, like sending logs to a centralized system, sending the metrics to a specific system, doing SSL termination, etc.
Istio, the service mesh tool, installs a sidecar container to do its job: https://istio.io/docs/setup/kubernetes/additional-setup/sidecar-injection/
Review and apply the file [01-sidecar.yml](01-sidecar.yml).
Connect to the `nginx` container (`kubectl exec -it two-containers -c nginx -- /bin/sh`) and look at the file system in `/var/log/nginx`.
Do the same for the `fluentd` container and this time look in `/logs`. What do you see?
Tail the logs from the fluentd pod (`kubectl logs -f two-containers -c fluentd`) and in another terminal window, send requests to the nginx service with a `curl` from a separate pod (or nginx's pod itself). What do you see? How do you explain it?
This exercice is taken from the [official Kubernetes documentation](https://kubernetes.io/docs/tasks/access-application-cluster/communicate-containers-same-pod-shared-volume/#creating-a-pod-that-runs-two-containers).