These tutorials will show you how to run a “sidecar” service container (one per Flux node) alongside your flux install, along with a service for the entire cluster (a deployment next to the cluster).

Sidecar Tutorials

Sidecar NGINX Container

Tutorial File

This is one of the simplest examples, implemented as a test, to run a sidecar with NGINX and then curl localhost to get a response from flux.

kind: MiniCluster
  name: flux-sample

    quiet: true

  # Number of pods to create for MiniCluster
  size: 2

  # This is a list because a pod can support multiple containers
    - image: rockylinux:9
      runFlux: true
      command: curl -s localhost
    - image: nginx
      name: nginx
        - 80

Create it (after you have the flux-operator namespace):

$ kubectl create -f ./examples/tests/nginx-sidecar-service/minicluster.yaml

See nginx is running:

$ kubectl logs flux-sample-0-zlpwx -c nginx -f
/ /docker-entrypoint.d/ is not empty, will attempt to perform configuration
/ Looking for shell scripts in /docker-entrypoint.d/
/ Launching /docker-entrypoint.d/ info: Getting the checksum of /etc/nginx/conf.d/default.conf info: Enabled listen on IPv6 in /etc/nginx/conf.d/default.conf
/ Launching /docker-entrypoint.d/
/ Launching /docker-entrypoint.d/
/ Configuration complete; ready for start up
2023/03/18 05:01:31 [notice] 1#1: using the "epoll" event method
2023/03/18 05:01:31 [notice] 1#1: nginx/1.23.3
2023/03/18 05:01:31 [notice] 1#1: built by gcc 10.2.1 20210110 (Debian 10.2.1-6) 
2023/03/18 05:01:31 [notice] 1#1: OS: Linux 5.15.0-67-generic
2023/03/18 05:01:31 [notice] 1#1: getrlimit(RLIMIT_NOFILE): 1048576:1048576
2023/03/18 05:01:31 [notice] 1#1: start worker processes
2023/03/18 05:01:31 [notice] 1#1: start worker process 29
2023/03/18 05:01:31 [notice] 1#1: start worker process 30
2023/03/18 05:01:31 [notice] 1#1: start worker process 31

And then look at the main logs to see the output of curl, run by Flux:

$ kubectl logs flux-sample-0-zlpwx -c flux-sample -f
<!DOCTYPE html>
<title>Welcome to nginx!</title>
html { color-scheme: light dark; }
body { width: 35em; margin: 0 auto;
font-family: Tahoma, Verdana, Arial, sans-serif; }
<h1>Welcome to nginx!</h1>
<p>If you see this page, the nginx web server is successfully installed and
working. Further configuration is required.</p>

<p>For online documentation and support please refer to
<a href=""></a>.<br/>
Commercial support is available at
<a href=""></a>.</p>

<p><em>Thank you for using nginx.</em></p>

And that’s it! In a real world use case, you’d have some service running alongside an analysis. Clean up:

$ kubectl delete -f ./examples/tests/nginx-sidecar-service/minicluster.yaml

Sidecar Registry with ORAS

Create an interactive MiniCluster with a sidecar registry container

As an example, we will run a local container registry to push/pull artifacts with ORAS. I don’t know why, I just like ORAS :) In all seriousness, you could imagine interesting use cases like needing an API to save and get artifacts for your analysis.

Tutorial File

This example demonstrates bringing up a MiniCluster and then interacting with a service (a registry) to push / pull artifacts. Here is our example custom resource definition:

kind: MiniCluster
  name: flux-sample

  # Number of pods to create for MiniCluster
  size: 2

  # Interactive so we can submit commands
  interactive: true

  # This is a list because a pod can support multiple containers
    # The container URI to pull (currently needs to be public)
    - image: rockylinux:9
      runFlux: true

        # This is going to install oras for the demo
        pre: |
          curl -LO "${VERSION}/oras_${VERSION}_linux_amd64.tar.gz"
          mkdir -p oras-install/
          tar -zxf oras_${VERSION}_*.tar.gz -C oras-install/
          sudo mv oras-install/oras /usr/local/bin/
          rm -rf oras_${VERSION}_*.tar.gz oras-install/

      # This is our registry we want to run
    - image:
      name: registry
        - 5000

When interactive is true, we tell the Flux broker to start without a command. This means the cluster will remain running until you shutdown Flux or kubectl delete the MiniCluster itself. The container you choose should have the software you are interested in having for each node. Apply the MiniCluster CRD:

$ kubectl apply -f examples/services/sidecar/minicluster-registry.yaml

If you are curious, the entrypoint for the service sidecar container is registry serve /etc/docker/registry/config.yml to start the registry. Since it’s not a flux runner, not providing an entrypoint means we use the container’s default entrypoint. We can then wait for our pods to be running

$ kubectl get pods
NAME                         READY   STATUS      RESTARTS   AGE
flux-sample-0-p5xls          1/1     Running     0          7s
flux-sample-1-nmtt7          1/1     Running     0          7s

To see logs, since we have 2 containers per pod, you can either leave out the pod (and get the first or default) or specify a container with -c:

$ kubectl logs flux-sample-0-d5jbb -c registry
$ kubectl logs flux-sample-0-d5jbb -c flux-sample
$ kubectl logs flux-sample-0-d5jbb

And then shell into the broker pod, index 0, which is “flux-sample”

$ kubectl exec -it flux-sample-0-d5jbb -c flux-sample -- bash

Let’s first make and push an artifact. First, just using oras natively (no flux)

cd /tmp
echo "hello dinosaur" > artifact.txt

And push! The registry, by way of being a container in the same pod, is on port 5000:

At this point, remember the broker is running, and we need to connect to it. We do this via flux proxy and targeting the socket, which is a local reference at /run/flux/local:

source /mnt/flux/
# Connect to the flux socket at /run/flux/local as the flux instance owner "flux"
$ flux proxy $fluxsocket oras push localhost:5000/dinosaur/artifact:v1 \
   --artifact-type application/vnd.acme.rocket.config \
Uploading 07f469745bff artifact.txt
Uploaded  07f469745bff artifact.txt
Pushed [registry] localhost:5000/dinosaur/artifact:v1
Digest: sha256:3a6cb1d1d1b1d80d4c4de6abc66a6c9b4f7fef0b117f87be87fea9b725053ead

Now try pulling, deleting the original first, and again without flux:

rm -f artifact.txt
flux proxy $fluxsocket oras pull localhost:5000/dinosaur/artifact:v1
cat artifact.txt
hello dinosaur

We did this under the broker assuming your actual use case will be running in the Flux instance. Feel free to play with oras outside of that context! When you are done, exit from the instance, and exit from the pod, and then delete the MiniCluster.

$ kubectl delete -f examples/services/sidecar/minicluster-registry.yaml

That’s it. Please do something more useful than my terrible example.

Service Containers Alongside the Cluster

Registry Service

Tutorial File

Unlike the example above, it’s more reasonable that you would want a single registry that your pods can access. E.g., perhaps you use it like a pull-through cache - first pulling to this service node (or pushing from another pod) and then having your worker pods pull from there. Let’s do that now. If you are using MiniKube, remember to pull large containers first. Apply the MiniCluster CRD:

$ kubectl apply -f examples/services/single/minicluster-registry.yaml

You’ll see a services pod! The current design deploys one pod to share your services, and the services share the same cluster networking space.

$ kubectl get -n flux-operator pods
NAME                         READY   STATUS      RESTARTS   AGE
flux-sample-0-4wt26          1/1     Running     0          38s
flux-sample-1-sr5zx          1/1     Running     0          38s
flux-sample-services         1/1     Running     0          38s

And then shell into the broker pod, index 0, which is “flux-sample”

$ kubectl exec -it flux-sample-0-d5jbb -- bash

The registry hostname should be in the environment (it’s defined in the CRD):

# echo $REGISTRY 

Let’s make an artifact to push.

$ echo "hello dinosaur" > artifact.txt

Now let’s push to the oras registry

$ oras push $REGISTRY:5000/vanessa/artifact:latest ./artifact.txt  --plain-http

Great! Now you could, theoretically, push a single SIF to your registry (as a local cache) and have the other nodes pull it! Here is an example, shelling in to the second worker:

rm artifact.txt
oras pull $REGISTRY:5000/vanessa/artifact:latest --plain-http

And artifact.txt is back. Super cool! We will have more examples in the examples folder of how this can be used for workflow containers.

Last update: Jun 14, 2024