Testing
Contents
Testing¶
Running the test suite for dask-kubernetes doesn’t require an existing Kubernetes cluster but does require
Docker, kubectl and helm.
Start by installing dask-kubernetes in editable mode - this will ensure that pytest can import dask-kubernetes:
$ pip install -e .
You will also need to install the test dependencies:
$ pip install -r requirements-test.txt
Tests are run using pytest:
$ pytest
============================================== test session starts ==============================================
platform darwin -- Python 3.8.8, pytest-6.2.2, py-1.10.0, pluggy-0.13.1 --
cachedir: .pytest_cache
rootdir: /Users/jtomlinson/Projects/dask/dask-kubernetes, configfile: setup.cfg
plugins: anyio-2.2.0, asyncio-0.14.0, kind-21.1.3
collected 64 items
...
================= 56 passed, 1 skipped, 6 xfailed, 1 xpassed, 53 warnings in 404.19s (0:06:44) ==================
Note
Running pytest compiles the Custom Resource Definitions from source using k8s-crd-resolver, tests against them and then uninstalls them. You may have to install them again manually.
Kind¶
To test dask-kubernetes against a real Kubernetes cluster we use the pytest-kind plugin.
Kind stands for Kubernetes in Docker and will create a full Kubernetes cluster within a single Docker container on your system.
Kubernetes will then make use of the lower level containerd runtime to start additional containers, so your Kubernetes pods will not
appear in your docker ps output.
By default we set the --keep-cluster flag in setup.cfg which means the Kubernetes container will persist between pytest runs
to avoid creation/teardown time. Therefore you may want to manually remove the container when you are done working on dask-kubernetes:
$ docker stop pytest-kind-control-plane
$ docker rm pytest-kind-control-plane
When you run the tests for the first time a config file will be created called .pytest-kind/pytest-kind/kubeconfig which is used for authenticating
with the Kubernetes cluster running in the container. If you wish to inspect the cluster yourself for debugging purposes you can set the environment
variable KUBECONFIG to point to that file, then use kubectl or helm as normal:
$ export KUBECONFIG=.pytest-kind/pytest-kind/kubeconfig
$ kubectl get nodes
NAME STATUS ROLES AGE VERSION
pytest-kind-control-plane Ready control-plane,master 10m v1.20.2
$ helm list
NAME NAMESPACE REVISION UPDATED STATUS CHART APP VERSION
Docker image¶
Within the test suite there is a fixture which creates a Docker image called dask-kubernetes:dev from this Dockerfile.
This image will be imported into the kind cluster and then be used in all Dask clusters created.
This is the official Dask Docker image but with the very latest trunks of dask and distrubuted installed. It is recommended that you also have the
latest development install of those projects in your local development environment too.
This image may go stale over time so you might want to periodically delete it to ensure it gets recreated with the latest code changes:
$ docker rmi dask-kubernetes:dev
Linting and formatting¶
To accept Pull Requests to dask-kubernetes we require that they pass black formatting and flake8 linting.
To save developer time we support using pre-commit which runs black and flake8 every time
you attempt to locally commit code:
$ pip install pre-commit
$ pre-commit install
Testing Operator Controller PRs¶
Sometimes you may want to try out a PR of changes made to the operator controller before it has been merged.
To do this you’ll need to build a custom Docker image and push it to a registry that your k8s cluster can pull from.
The custom image needs to take the latest stable release of the controller and install the development branch into it. You can do this directly from GitHub repos with pip or you can copy your local files in and install that.
FROM ghcr.io/dask/dask-kubernetes-operator:<latest stable release>
RUN pip install git+https://github.com/dask/dask-kubernetes.git@refs/pull/<PR>/head
$ docker build -t <image>:<tag> .
$ docker push -t <image>:<tag> .
Then you can use helm to install the controller with your custom image.
$ helm install --repo https://helm.dask.org \
--create-namespace \
-n dask-operator \
--generate-name \
dask-kubernetes-operator \
--set image.name=<image> \
--set image.tag=<tag>