What is the difference between kubernetes and GKE?

Question

I know that GKE is driven by kubernetes underneath. But I don't seem to still get is that what part is taken care by GKE and what by k8s in the layering? The main purpose of both, as it appears to me is to manage containers in a cluster. Basically, I am looking for a simpler explanation with an example.

Answer 1

GKE (Google Container Engine) is only container platform, which Kubernetes can manage. It is not a kubernetes-like with "differences".

As mentioned in "Docker and Kubernetes and AppC " (May 2015, that can change):

Docker is currently the only supported runtime in GKE (Google Container Engine) our commercial containers product, and in GAE (Google App Engine), our Platform-as-a-Service product.

You can see Kubernetes used on GKE in this example: "Spinning Up Your First Kubernetes Cluster on GKE" from Rimantas Mocevicius.

The gcloud API will still make kubernetes commands behind the scene.

GKE will organize its platform through Kubernetes master

Every container cluster has a single master endpoint, which is managed by Container Engine.
The master provides a unified view into the cluster and, through its publicly-accessible endpoint, is the doorway for interacting with the cluster.

The managed master also runs the Kubernetes API server, which services REST requests, schedules pod creation and deletion on worker nodes, and synchronizes pod information (such as open ports and location) with service information.

Answer 2

In short, without getting into technical details, GKE is managed Kubernetes, similar to how Google's Cloud Composer is managed Apache Airflow and Cloud Dataflow is managed Apache Beam.

So, some of Google Cloud Platform's services (GKE, Cloud Composer, Cloud Dataflow) are managed implementations of various open source technologies (Kubernetes, Airflow, Beam).

Answer 3

in short GKE is a managed/hosted Kubernetes (i.e. it is managed for you so you can concentrate on running your pods/containers applications)

Kubernetes does handle:

• running pods, scheduling them on nodes, guarantee nb of replicas per Replication Controller settings (i.e. relaunch pods if they fail, relocate them if the node fails)
• Services: proxying traffic to the right pod wherever it is located.
• Jobs

in addition, there are several 'add-ons' to Kubernetes, some of which are part of what makes GKE:

• DNS (you can't really live without it, even thought it's an add-on)
• Metrics monitoring: with influxdb, grafana
• Dashboard

None of these are out-of-the-box, although they are fairly easy to setup, but you need to maintain them. There is no real 'logging' add-on, but there are various projects to do this (using Logspout, logstash, elasticsearch etc...)

In short Kubernetes does the orchestration, the rest are services that would run on top of Kubernetes.

GKE brings you all these components out-of-the-box, and you don't have to maintain them. They're setup for you, and they're more 'integrated' with the Google portal.

One important thing that everyone needs is the LoadBalancer part: - Since Pods are ephemeral containers, that can be rescheduled anywhere and at any time, they are not static, so ingress traffic needs to be managed separately.

This can be done within Kubernetes by using a DaemonSet to fix a Pod on a specific node, and use a hostPort for that Pod to bind to the node's IP. Obviously this lacks fault tolerance, so you could use multiple and do DNS round robin load balancing.

GKE takes care of all this too with external Load Balancing. (On AWS, it's similar, with ALB taking care of load balancing in Kubernetes)