Developer Guide

This developer guide includes complete instructions for setting up a developer environment.


To work on this operator you should:

  • Have a recent version of Go installed (1.18.1)

  • Have minikube or kind installed

Important For minikube, make sure to enable DNS plugins.

$ minikube addons enable ingress
$ minikube addons enable ingress-dns

Note that for production clusters (e.g., GKE) I believe this addon is enabled by default. The basic Flux networking (pods seeing one another) won’t work if your cluster does not support DNS. You also won’t be able to expose the service with minikube service if you don’t do the above (but port-forward would technically work) You’ll then also want to clone the repository.

# Clone the source code
$ git clone
$ cd flux-operator

Local Development

After cloning, you need to create your MiniKube or Kind cluster before doing anything else!

1. Quick Start

Here is a quick start for doing that, making the namespace, and installing the operator.

# Start a minikube cluster
$ minikube start

# Start a Kind cluster
$ kind create cluster

# Make a flux operator namespace
$ kubectl create namespace flux-operator
namespace/flux-operator created

Here is how to build and install the operator - we recommend you build and load into MiniKube with this command:

$ make deploy-local
$ minikube image load
$ kubectl apply -f examples/dist/flux-operator-local.yaml

But you can also try the manual steps:

# Build the operator
$ make

# How to make your manifests
$ make manifests

# And install. This places an executable "bin/kustomize"
$ make install

Note that the local build required you to have external libraries to generate the curve certificate:

sudo apt-get install -y libsodium-dev libzmq3-dev libczmq-dev

If you are unable to install zeromq locally, we recommend the make deploy-local command shown above. Finally, the way that I usually develop locally is with make test-deploy targeting a registry I have write to, which will also save that image name to examples/dist/flux-operator-dev.yaml:

make test-deploy DEVIMG=vanessa/flux-operator:latest
kubectl apply -f examples/dist/flux-operator-dev.yaml

During development, ensure that you delete and re-apply the YAML between new builds so the image is re-pulled. For developing, you can find many examples in the examples directory.

2. Headless Tests

Our headless tests are modified examples intended to be run without the web interface. These tests are found under examples/tests:

$ tree examples/tests/
├── hello-world           (- name=hello-world
│   └── minicluster.yaml
└── lammps                (- name=lammps
    └── minicluster.yaml

Thus, to run the full example for the hello-world test you can do:

$ bash script/ hello-world

or (for a less scripted run):

$ make name=hello-world redo_test

If you just want to just apply the new job without a cleanup, do:

$ make name=hello-world applytest
$ make run

Note that there is a default sleep time for all jobs (so the worker nodes start after the broker) so they will not run instantly. You can list pods to get an id, and then view logs:

$ make list
$ bash script/ <pod>

Also note that these headless tests have logging->quiet: true in the config, meaning you will only see output with the command above from what you actually ran. We do this because we test them in CI, and we don’t want the other verbose output to get in the way! If you want to disable this quiet mode, just set this same field to false.

Interacting with Services

Currently, the most reliable thing to do is port forward:


If we run as a ClusterIP, we can accomplish the same with a one off kubectl port-forward:

kubectl port-forward -n flux-operator flux-sample-0-zdhkp 5000:5000
Forwarding from -> 5000

This means you can open http://localhost:5000 to see the restful API (and interact with it there).

If you want to use a minikube service, this seems to work, but is spotty - I think because minikube is expecting the service to be available from any pod (it is only running from index 0). If you want to try this:

$ minikube service -n flux-operator flux-restful-service --url=true

But for now I’m developing with port forward.

Build Images

If you want to build the “production” images - here is how to do that! This happens in our Docker CI, however you can build (and deploy if you are an owner) them too!

$ make docker-build
$ make docker-push

You can also build helm charts:

$ make helm

We do not currently provide a catalog or bundle build, typical of the Operator SDK, because we have not needed them Also note that these are done in CI so you shouldn’t need to do anything from the command line.

Other Developer Commands

Build Operator Yaml

To generate the CRD to install to a cluster, we’ve added a make build-config command:

$ make build-config

That will generate a yaml to install the operator (with default container image) to a cluster in examples/dist. This file being updated is tested in the PR, so you should do it before opening.

Build API

We use openapi to generate our Python SDK! You can update it as follows:

$ make api


We likely want to build the config and API generation in one swoop. We have a courtesy command for that:

$ make pre-push

Container Requirements

If you are looking to build a container to use with the Flux Operator, we have a set of example containers here and general guidelines are below. Generally we recommend using the flux-sched base image so that install locations and users are consistent. This assumes that:

  • we are currently starting focus on supporting debian bases

  • if you created the flux user, it has uid 1000 (unless you customize fluxUser.Uid)

  • sudo is available in the container (apt-get install -y sudo)

  • /etc/flux is used for configuration and general setup

  • /usr/libexec/flux has executables like flux-imp, flux-shell

  • flux-core / flux-sched with flux-security should be installed and ready to go.

  • If you haven’t created a flux user, one will be created for you (with a common user id 1000 or fluxuser.Uid)

  • Any executables that the flux user needs for your job should be on the path (if launching command directly)

  • Do not have any requirements (data or executables in root’s home)

  • The container (for now) should start with user root, and we run commands on behalf of flux.

  • You don’t need to install the flux-restful-api (it will be installed by the operator)

  • munge should be install, and a key generated at /etc/munge/munge.key

For the last point, since all Flux running containers should have the same munge key in that location, we simply use it. The pipeline will fail if the key is missing from any Flux runner container. For the curve.cert that we need to secure the cluster, we will be running your flux runner container before the indexed job is launched, generating the certificate, and then mapping it into the job pods via another config map. Note that we considered generating this natively in Gom, however the underlying library to do this generation that is available in Go requires system libraries, and thus would be annoying to add as a dependency.

These criteria are taken from the flux-sched base image available on Docker hub as fluxrm/flux-sched:focal, and we strongly suggest you use this for your base container to make development easier! If you intend to use the Flux RESTful API to interact with your cluster, ensure that flux (python bindings) are on the path, along with either python or python3 (depending on which you used to install Flux). If/when needed we can lift some of these constraints, but for now they are reasonable. If you use this image, you should have python3 and pip3 available to you, and the active user is fluxuser. This means if you want to add content, either you’ll need to change the user to root in a build (and back to fluxuser at the end), use sudo, or install to /home/fluxuser.


Testing is underway! From a high level, we want three kinds of testing:

  • Unit tests, which will be more traditional *_test.go files alongside others in the repository (not done yet)

  • End to end “e2e” tests, also within Go, to test an entire submission of a job, also within Go. (not done yet)

  • Integration testing, likely some within Go and some external to it. (in progress)


For the integration testing outside of Go, we currently have basic tests written that allow the following:

  1. Write a custom resource definition (CRD) for a named MiniCluster under examples/tests/${name} as minicluster.yaml.

  2. The CRD should set test:true and include a command to run, and a container to do it.

  3. Add your test name, container, and estimated running time to .github/workflows/main.yaml

  4. If your tests require a working directory, it must be set in the CRD for the headless test.

  5. If a test is deterministic, add a test.out to the output folder that we can validate results for.

  6. We will validate output (if provided) and that containers exit with 0.

To run the test (and you can also do this locally) we use the script/ and provide a name and the estimated job time, just like in actions. The below example runs the “hello-world” test and gives it 30 seconds to finish.

./bin/bash script/ hello-world 10
NAME                  READY   STATUS    RESTARTS   AGE
flux-sample-0-ng8c5   1/1     Running   0          3s
flux-sample-1-nxqj9   1/1     Running   0          3s
flux-sample-2-vv7jr   1/1     Running   0          3s
flux-sample-3-kh2br   1/1     Running   0          3s
Pods: flux-sample-0-ng8c5 flux-sample-1-nxqj9 flux-sample-2-vv7jr flux-sample-3-kh2br
Pod: flux-sample-0-ng8c5
hello world
hello world

What you don’t see in the above is that we also use kubectl to ensure that the exit code for all containers (typically 4) is 0. Also note that the “sleep” time doesn’t have to be exact, it’s technically not necessary because we are waiting for the output to finish coming (and the job to stop). I added it to provide a courtesy message to the user and developer. Finally, note that for big containers it’s suggested to pull them first, e.g.,:

$ minikube ssh docker pull

The tests above are headless, meaning they submit commands directly, and that way we don’t need to do it in the UI and can programmatically determine if they were successful. Finally, note that if you have commands that you need to run before or after the tests, you can add a or in the directory. As an example, because minikube is run inside of a VM, if you are using a host volume mount, it won’t actually show up on your host! This is because it’s inside the VM. This you might want to move files there before the test, e.g.,:


HERE=$( cd -- "$( dirname -- "${BASH_SOURCE[0]}" )" &> /dev/null && pwd )

echo "Copying local volume to /tmp/data-volumes in minikube"

# We don't care if this works or not - mkdir -p seems to bork
minikube ssh -- mkdir -p /tmp/data-volumes
minikube cp ${HERE}/data/pancakes.txt /tmp/data-volumes/pancakes.txt
minikube ssh ls /tmp/data-volumes

and then clean up after


echo "Cleaning up /tmp/data-volumes in minikube"
minikube ssh -- sudo rm -rf /tmp/data-volumes

This would be the same for anytime you use minikube and want to create a local volume. It’s not actually on your host, but rather in the VM. For an example test that does this, see the examples/tests/volumes example.


The documentation is provided in the docs folder of the repository, and generally most content that you might want to add is under getting_started. For ease of contribution, files that are likely to be updated by contributors (e.g., mostly everything but the module generated files) are written in markdown. If you need to use toctree you should not use extra newlines or spaces (see files for examples). The documentation is also provided in Markdown (instead of rst or restructured syntax) to make contribution easier for the community.

Finally, we recommend you use the same development environment also to build and work on documentation. The reason is because we import the app to derive docstrings, and this will require having Flux.

Install Dependencies and Build

The documentation is built using sphinx, and generally you can create a virtual environment:

$ cd docs
$ python -m venv env
$ source env/bin/activate

And then install dependencies:

$ pip install -r requirements.txt

# Build the docs into _build/html
$ make html

Preview Documentation

After make html you can enter into _build/html and start a local web server to preview:

$ python -m http.server 9999

And open your browser to localhost:9999

Last update: Sep 10, 2023