GASW-Kubernetes-Plugin

Kubernetes !?

Note

If you never used Kubernetes or have bad knownledges about you should take a look as those links !

• Basis
• Components
• Pods
• Jobs
• Persistent Volumes

Plugin

Description

This plugin is used in the case of Virtual-Imaging-Platform project.
It is called from the engine motor and then utilised in completition of GASW.

Prerequisite

To run this plugin you need to use at least Java 21 runtime environnement cause of the Kubernetes Dependency.
You should also provide config.json file witch contain the information about the plugin it self (the location shall be /var/www/cgi-bin/kubernetes/config.json).

Job lifecycle

When a job is requested for the moteur engine, there is few steps before the job is submitted to kubernetes :

• check if the manager is inited
• check if the workflow volume is ready

Job Statuses

Something important is the status of a job. In the code there is two statuses (but represented by one variable):

• the local status : this status isn't stored in the database and just use inside the code to check some completions steps.
• the dao status : this status is when we choose to make visible to the client the local status.

For example when the job is ready to be submitted we don't change the status for the client, for him it just in queued.
So, you just have to understand that sometimes the KJobData.status variable is synchronized with the dao and sometimes not.

Configuration File

There is an example configuration file provided in the repository and it should be located in /var/www/cgi-bin/m2Server-gasw3/conf/kubernetes_plugin.conf

Code

Structure

I've made a figma scheme the represent briefly the code structure of the plugin.

Upgrades and Modification

If you want to make some changes there is the class KConstants that contain some hardcoded values (like the config file path).
There is also the possibility to change to a remoteClient instead of configClient (see in KConfiguration).

If you want to make the plugin support multi-container per pods, it should be possible but you need to make some change around the statuses and the container builder (configure function).

Debug

Note

Have a look at Kubectl

Tip

By default kubectl use the default namespace, if you configured a different one. Please use the flag -n [namespace] or --all-namespaces

You may need to debug your code or your Kubernetes cluster sometimes. Here is a few commands that might help you :

• kubectl get [pods/jobs/nodes] : list all the [pods/jobs/nodes]
• kubectl exec -it [pod-ID] -- bash : spawn a bash terminal inside the pod container
• kubectl get [pv/pvc] : list all the persistent volume and persistent volume claim of the cluster
• kubectl describe [pods/jobs/pv/pvc/nodes] : describe all the [pods/jobs/pv/pvc/nodes]
• kubectl describe [pod/job/pv/pvc/node] [value-ID] : describe a specific [pod/job/pv/pvc/node]

Known issues

Important

Those issues might have been solved by some kubernetes-api updates, but we recommand to have a look !

If your cluster crashes or is unavailable during a workflow execution (and exceed the retries values of KConstants), you might have a lost pvc and pv.
The pv and pvc won't be deleted automaticly and should do it manually.