In this article we will see how to use kubebuilder and Kind to create a local test cluster and an operator, then deploy that operator in the cluster and test it, the repository with the files can be found here, also if you want to learn more about the idea and the project go: forward.
Basically what the code does is create an alpine/socat pod and you can specify the host, port and protocol and it will make a tunnel for you, so then you can use port-forward or a service or ingress or whatever to expose things that are in another private subnet, while this might not sound like a good idea it has some use cases, so check your security constraints before doing any of that in a normal scenario it should be safe, it can be useful for testing or for reaching a DB while doing some debugging or test, but well, that is for another discussion, the tools used here is what makes this so interesting, this is a cloud native application, since it native to kubernetes and that’s what we will explore here.
While Kind is not actually a requirement I used that for testing and really liked it, it’s faster and simpler than minikube.
Also if you are interested how I got the idea to make this operator check this github issue.
In this step we need to create the kubebuilder project, so in an empty folder we run:
Next let’s create an API, something for us to have control of (our controller).
Right until here we only have some boilerplate and basic or empty project with defaults, if you test it now it will work, but it won’t do anything interesting, but it covers a lot of ground and we should be grateful that such a tool exists.
First we will add it to
api/v1beta1/map_types.go, which will add our fields to our type.
Basically we just edited the
MapSpec and the
Now we need to add the code to our controller in
In this controller we added two functions one to create a pod and modified basically the entire Reconcile function (this one takes care of checking the status and make the transitions in other words makes a controller work like a controller), also notice the kubebuilder annotations which will generate the rbac config for us, pretty handy! right?
Now we will use Kind to create a local cluster to test it could be that easy!?!?! yes, it is!
For testing you can run your operator locally like this:
First we spin up a pod, and launch
nc -l -p 8000
Then we edit our manifest and apply it, check that everything is in place, and do the port-forward and launch another
nc localhost 8000 to test if everything went well.
First the manifest
Then the port-forward and test
Here we just build and push the docker image to dockerhub or our favorite public registry.
Then you can install it with
make deploy IMG=kainlite/forward:0.0.1 and uninstall it with
If you spot any error or have any suggestion, please send me a message so it gets fixed.