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Making any container part of your Kubernetes namespace

Simple Usecase

This example demonstrates how to run a local Ubuntu container instance as part of your Kubernetes namespace.

What you will learn​

  • Run a Ubuntu container as part of a Kubernetes namespace
  • Install additional software to that instance
  • Use this container to call Kubernetes services

What you will need​

  • Gefyra
  • Getdeck for setting up the development infrastructure (runs on k3d)
  • kubectl
  • Optionally: k3d or any other preferred Kubernetes cluster

Table of contents​

  1. TOC

Creating the local development infrastructure​

First, we need a Kubernetes-based development infrastructure which contains all required components. Luckily this can be achieved quite easily with the Deck CLI from here.

Just run: 

deck get https://github.com/Blueshoe/buzzword-charts.git

and you will get a fresh k3d cluster running locally with all required components installed.

Important: These workloads are intended for demonstration purposes and are not safe for production deployments.

Optional: If you don't want to create the development infrastructure using Getdeck you can also provide it yourself. You need:

  • a Kubernetes cluster
  • some workload, you can choose the example from here and helm install it yourself
  • a node port at 31820:31820/UDP (if running it locally)

Getting the App Running​

Optional: In order to observe the workload booting up, check out the Kubernetes dashboard coming with this deck.

Connecting Gefyra to the Kubernetes cluster​

The first would be to spin up Gefyra with gefyra up. Please be sure to still have the development cluster active in your current kubectl context.

Important: If you are running a remote Kubernetes cluster you need to specify the --host argument with IP of one of your data plane nodes. The default port is 31820 (--port), it may be different depending on firewalls and the cluster networking.

Running a container in a Kubernetes namespace​

In this example, a Ubuntu will become part of the cluster namespace buzzword. Start the container instance like so :

$> gefyra run -i ubuntu -N myubuntu -n buzzword -c "bash -c 'tail -f /dev/null'"
> [INFO] Container image 'ubuntu:latest' started with name 'myubuntu' in Kubernetes namespace 'buzzword'

No worries, the following explains the parameter list:

  • -i ubuntu: run the public Docker image ob Ubuntu from here: https://hub.docker.com/_/ubuntu
  • -N myubuntu: name this local Docker instance myubuntu for further reference
  • -n buzzword: place this Docker instance in the Kubernetes namespace buzzword (where this example plays)
  • -c "bash -c 'tail -f /dev/null'": start this Docker instance and keep it running forever

You can check the output of docker ps to see your container instance running. It should look something like this:

CONTAINER ID   IMAGE                         COMMAND                  CREATED          STATUS          PORTS                                                            NAMES
660ce52ce4e1   ubuntu                        "bash -c 'tail -f /d…"   9 seconds ago    Up 8 seconds                                                                     myubunut
e0add97dee80   gefyra-cargo:20220426153151   "/init"                  14 seconds ago   Up 13 seconds                                                                    gefyra-cargo
97f9908c55df   rancher/k3d-proxy:4.4.8       "/bin/sh -c nginx-pr…"   12 minutes ago   Up 12 minutes   0.0.0.0:8080->80/tcp, :::8080->80/tcp, 0.0.0.0:34089->6443/tcp   k3d-another-cluster-serverlb
1dccf93fc087   rancher/k3s:v1.20.4-k3s1      "/bin/k3s agent"         12 minutes ago   Up 12 minutes   0.0.0.0:31820->31820/udp, :::31820->31820/udp                    k3d-another-cluster-agent-0
91ef49d000b5   rancher/k3s:v1.20.4-k3s1      "/bin/k3s server --t…"   12 minutes ago   Up 12 minutes                                                                    k3d-another-cluster-server-0

Enter the container and call a service​

Now that the container is running, you can enter a bash by running: docker exec -it myubuntu bash

root@6178770cd6b1:/#

In order to call an http service from this Kubernetes namespace a terminal application could be handy. The official Ubuntu Docker image does not provide on of my favorites out of the box, but it is easy to add it.

root@6178770cd6b1:/# apt update && apt install wget -y
[...]

On another terminal (so not in your Ubuntu bash) you can consult kubectl to inspect the services in the buzzword namespace. For this example it tells:

$> kubectl -n buzzword get services
NAME                                   TYPE        CLUSTER-IP      EXTERNAL-IP   PORT(S)                                 AGE
dashboard-kubernetes-dashboard         ClusterIP   10.43.147.1     <none>        8080/TCP                                18m
[...]
buzzword-counter                       ClusterIP   10.43.221.222   <none>        9000/TCP                                18m
buzzword-counter-postgresql            ClusterIP   10.43.140.176   <none>        5432/TCP                                18m
buzzword-counter-postgresql-headless   ClusterIP   None            <none>        5432/TCP                                18m
buzzword-counter-rabbitmq              ClusterIP   10.43.0.48      <none>        4369/TCP,5672/TCP,25672/TCP,15672/TCP   18m
buzzword-counter-rabbitmq-headless     ClusterIP   None            <none>        4369/TCP,5672/TCP,25672/TCP,15672/TCP   18m

Let's see how this works. From within your running Ubuntu bash, you can now call the buzzword-counter service on port 9000:

root@6178770cd6b1:/# wget -O- buzzword-counter:9000
--2022-04-26 13:41:43--  http://buzzword-counter:9000/
Resolving buzzword-counter (buzzword-counter)... 10.43.221.222
Connecting to buzzword-counter (buzzword-counter)|10.43.221.222|:9000... connected.
HTTP request sent, awaiting response... 200 OK
Length: 565 [text/html]
Saving to: 'STDOUT'

-                                                0%[                                                                                                   ]       0  --.-KB/s               <h1>Buzzwords</h1>
<form action="/increase-counter/" method="post">
    <input type="hidden" name="csrfmiddlewaretoken" value="HrGPa8q6GyjVi5ZeHsf4noTFZoOpxA78OmpOEe8cWut8uyeuVxyZ8wPLN0e3QISM">
    <table>
        <tr>
            <th>Buzzword</th>
            <th>Count</th>
            <th>Increase</th>
            <th>Decrease</th>
        </tr>
    
    </table>
    <div>
        <label for="new_buzzword">New Buzzword:</label>
        <input type="text" id="new_buzzword" name="new_buzzword">
        <button type="submit">Submit</button>
    </div>
</form>
-                                              100%[==================================================================================================>]     565  --.-KB/s    in 0s      

2022-04-26 13:41:43 (18.9 MB/s) - written to stdout [565/565]

Et voila! The service responded to the HTTP Get request with the same answer you would get with your browser at: http://buzzword-counter.127.0.0.1.nip.io:8080. You can now look around and make yourself familiar with the services in this namespace - or even connect with the psql client to the PostgreSQL instance running in the cluster.

Remove the Ubuntu container​

Once you are done with your work, you can remove this Ubuntu instance again with: docker kill myubuntu. That's it.

Remove the Development Infrastructure​

First run gefyra down to uninstall Gefyra's components. If you have initially created the development infrastructure using Getdeck you can now run:

$> deck remove --cluster https://github.com/Blueshoe/buzzword-charts.git
[INFO] Deleting the k3d cluster with name another-cluster

If you created the infrastructure yourself, you probably already know how to get rid of everything yourself ;-)

Additional Notes​

If you want maximum convenience for your developers and a supported team oriented workflow, we recommend you check out Unikube. Gefyra is part of Unikube's development workflow.