Here's my scenario,
I want to launch a Job in Kubernetes, the first container that runs will look through a list of custom resources, and launch each of the containers defined in that resource to completion. I don't know whats in the list ahead of time, I only know when the job is kicked off.
Is this possible? Can someone point me to something that shows how to do it?
You can use the Kubernetes Client Libraries to create any Kubernetes resource from inside your code (given that it has the correct service account of course if RBAC is configured in your cluster).
If you want to run a container to completion, a Kubernetes Job would be the best fit.
It is possible to manage jobs programmatically using the kubernetes client-go project.
Here are some examples.
To create a job to completion, refer:
Job APIs
JobInterface
Batch client APIs
Custom resources definitions can be managed using the kubernetes apiextensions-apiserver project.
To manage custom resources definitions, refer:
CRD APIs
CRD API tests
To create custom resources, refer:
This link has steps to access kubernetes API from inside a pod
Example
Related
I have a job, which I want to run regularly in Kubernetes 1.19.3 (DigitalOcean).
For this job, I need to take a snapshot of a PVC and do stuff to it. I know how can I run a job and mount a volume to the pod it runs, but I have a hard time finding out how to take that snapshot at the beginning of this job.
Is there any way to do it?
The tool of choice to take PV snapshots in K8s is VolumeSnapshots.
The trouble with them is that they don't come yet) with functionality for periodic triggering. So, you would have to create them from a K8s CronJob. However, doing so is not terribly straight forward, since your CronJob Pod would need to have a K8s client installed and require access to the K8s API Server with RBAC.
There are a couple of options to get there, reaching from writing your own image from scratch to using open-source solutions based on the clients from this project k8s client libraries.
Seeing that dynamic K8s manifest applying is somewhat badly supported by K8s, I actually started an open source project myself, that you could use for this purpose: K8sCrud.
I'm wondering if there is an option to execute the task from POD? So when I have POD which is, for example, listening for some requests and on request will delegate the task to other POD(worker POD). This worker POD is not alive when there are no jobs to do and if there is more than one job to do more PODs will be created. After the job is done "worker PODs" will be stopped. So worker POD is live during one task then killed and when new task arrived new worker POD is started. I hope that I described it properly. Do you know if this is possible in Kubernetes? Worker POD start may be done by, for example, rest call from the main POD.
There are few ways to achieve this behavior.
Pure Kubernetes Way
This solution requires ServiceAccount configuration. Please take a loot at Kubernetes documentation Configure Service Accounts for Pods.
Your application service/pod can handle different custom task. Applying specific serviceaccount to your pod in order to perform specific task is the best practice. In kubernetes using service account with predefined/specified RBAC rules allows you to handle this task almost out of the box.
The main concept is to configure specific RBAC authorization rules for specific service account by giving different permission (get,list,watch,create) to different Kubernetes resources like (pod,jobs).
In this scenario working pod is waiting for incoming request, after it receives specific request it can perform specific task against kubernetes api.
This can be extend i.e. by using sidecar container inside your working pod. More details about sidecar concept can be found in this article.
Create custom controller
Another way to achieve your goal is to use Custom Controller.
Example presented in Extending the Kubernetes Controller article is showing how custom controller watch kubernetes api in order to instrument underling worker pod (watching kubernetes configuration for any changes and then deletes corresponding pods). In your setup, such controller could watch your api for waiting/not processed request and perform additional task like kubernetes job creation inside k8s cluster.
Using existing solution like Job Processing Using a Work Queue.
RabbitMQ on Kubernetes
Coarse Parallel Processing Using a Work Queue
Kubernetes Message Queue
Keda
I'm building a test automation tool that needs to launch a set of tests, collect logs and results. My plan is to build container with necessary dependency for test framework and launch them in Kubernetes.
Is there any application that abstracts complexity of managing the pod lifecycle and provides a simple API to achieve this use-case preferably through API? Basically my test scheduler need to deploy a container in kubernetes, launch a test and collect log files at the end.
I already looked at Knative and kubeless - they seem to be complex and may over-complicate what I'm trying to do here.
Based on information you provided all I can recomend is kubernetes API itself.
You can create a pod with it, wait for it to finish and gather logs. If thats all you need, you don't need any other fancy applications. Here is a list of k8s client libraries.
If you don't want to use client libraries you can always use REST api.
If you are not sure how to use REST api, run kubectl commands with --v=10 flag for debug output where you can see all requests between kubectl and api-server as a reference guide.
Kubernetes also provided detailed documentation for k8s REST api.
Try looking at https://microk8s.io/, it was built for those purposes.
And you can talk to the API server via the rest API same as in every k8s cluster.
We started using Kubernetes, a few time ago, and now we have deployed a fair amount of services. It's becoming more and more difficult to know exactly what is deployed. I suppose many people are facing the same issue, so is there already a solution to handle this issue?
I'm talking of a solution that when connected to kubernetes (via kubectl for example) can generate a kind of map off the cluster.
In order to display one or many resources you need to use kubectl get command.
To show details of a specific resource or group of resources you can use kubectl describe command.
Please check the links I provided for more details and examples.
You may also want to use Web UI (Dashboard)
Dashboard is a web-based Kubernetes user interface. You can use
Dashboard to deploy containerized applications to a Kubernetes
cluster, troubleshoot your containerized application, and manage the
cluster resources. You can use Dashboard to get an overview of
applications running on your cluster, as well as for creating or
modifying individual Kubernetes resources (such as Deployments, Jobs,
DaemonSets, etc). For example, you can scale a Deployment, initiate a
rolling update, restart a pod or deploy new applications using a
deploy wizard.
Let me know if that helped.
I have work defined in a file/config with the following format,
config1,resource9
config3,resource21
config5,resource10
How can I spin individual pods based on the configuration? If I add one more line to the configuration, Kubernetes need to spin one more pod and send the configuration line to that pod.
How to store the configuration in Kubernetes and spin up pods based on the configuration?
Take a look at Kubernetes Operators. The pattern adds a Kubernetes management layer to an application. Basically you run a kubernetes native app (the operator) that connects to the kubernetes API and takes care of the deployment management for you.
If you are familiar with helm, then a quick way to get started is with the helm example. This example will create a new Nginx deployment for each Custom Resource you create. The Custom Resource contains all the helm values nginx requires for a deployment.
As a first step you could customise the example so that all you need to do is manage the single Custom Resource to deploy or update the app.
If you want to take it further then you may run into some helm limitations pretty quickly, for advanced use cases you can use the go operator-sdk directly.
There are a number of projects operators to browse on https://operatorhub.io/