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Kubernetes (often abbreviated k8s) is a platform for running containers. It is used in Tool Labs to isolate Tools from each other and allow distributing Tools across a pool of servers.
The Tool Labs
webservice command has a
--backend=kubernetes mode that will start, stop, and restart containers designed to run web services for various languages. See our Webservice help for more details.
It is possible to run cron jobs on kubernetes (see upstream documentation for a full description), however this functionality is not officially supported by the Wikimedia Labs team and should be considered an experimental feature.
Kubernetes continuous jobs
The basic unit of managing execution on a Kubernetes cluster is called a "deployment". Each deployment is described with a YAML configuration file which describes the container images to be started ("pods" in the Kubernetes terminology) and commands to be run inside them after the container is initialized. A deployment also specifies where the pods run and what external resources are connected to them. The upstream documentation is comprehensive.
Stashbot is a Python irc bot that runs in a Kubernetes deployment. The deployment.yaml file that it uses to tell Kubernetes how to start the bot is reproduced below. This deployment is launched using a
stashbot.sh wrapper script which runs
kubectl create -f /data/project/stashbot/etc/deployment.yaml.
|/data/project/stashbot/etc/deployment.yaml (copied 2017-05-15)|
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--- # Run stashbot on kubernetes kind: Deployment apiVersion: extensions/v1beta1 metadata: name: stashbot.bot namespace: stashbot spec: replicas: 1 template: metadata: labels: name: stashbot.bot spec: containers: - name: bot image: docker-registry.tools.wmflabs.org/toollabs-python2-base:latest command: [ "/data/project/stashbot/bin/stashbot.sh", "run" ] workingDir: /data/project/stashbot env: - name: HOME value: /data/project/stashbot imagePullPolicy: Always volumeMounts: - name: home mountPath: /data/project/stashbot/ volumes: - name: home hostPath: path: /data/project/stashbot/
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- Uses the 'stashbot' namespace that the tool is authorized to control
- Creates a container using the 'latest' version of the 'docker-registry.tools.wmflabs.org/toollabs-python2-base' Docker image.
- Runs the command
/data/project/stashbot/bin/stashbot.sh runwhen the container starts.
- Mounts the /data/project/stashbot/ NFS directory as /data/project/stashbot/ inside the container.
Each tool has been granted control of a Kubernetes "namespace". Your tool can only create and control objects in its namespace. A tool's namespace is the same as the tool's name (e.g.
The Tool Labs Kubernetes cluster is restricted to loading Docker images published at docker-registry.tools.wmflabs.org. These images are built using the Dockerfiles in the operations/docker-images/toollabs-images git repository.
Available container types
webservice command has an optional type argument that allows you to choose which Docker container to run your Tool in.
Currently provided types:
FIXME: how does one get a list of the images?
php5.6 (Lighttpd + PHP)
Versions & Packages
This is running Debian Jessie, with PHP version 5.6. This is mostly compatible with PHP 5.5 which is present on the GridEngine Ubuntu Trusty nodes - so if your web service is currently running on Trusty with GridEngine, it should work on Kubernetes. Unlike on GridEngine, where all packages for all languages are installed and accessible, only PHP specific packages are available in this environment. The following packages are installed:
This should match the php related packages installed on GridEngine exec nodes. Additional packages can be added on request.