Autoscaling CI on Kubernetes in Kraken CI

Kraken CI is a new Continuous Integration tool. It is a modern, open-source, on-premise CI/CD system that is highly scalable and focused on testing. It is licensed under Apache 2.0 license. Its source code is available on Kraken CI GitHub page.

This tutorial is the fifth installment of the series of articles about Kraken CI. Part 1, Kraken CI, New Kid on the CI block, presented the installation of Kraken. The second part covered how to prepare a workflow for a simple Python project. The part 3 was about autoscaling on AWS and Azure. The last part was introducing to Webhooks in Kraken CI.

This time we would like to show the latest feature that was developed in Kraken CI: deploying Kraken CI and autoscaling in Kubernetes.

Intro

One of the methods of deploying Kraken CI is installing it into
Kubernetes cluster. Kraken CI is natively divided into several
services packed in Docker images so they can be nicely laid
out in the cluster. The other aspect is running Kraken jobs. In this
case, they are run in containers natively scheduled onto Kubernetes
nodes.

This guide shows how to install and configure Kraken CI in Kubernetes
to leverage its potential.

Pre-requisites

Several things are required to install Kraken CI in Kubernetes using Helm.
In short:

- Kubernetes cluster and kubectl tool
- Helm tool

Helm is used to deploy several Kraken services and expose them to an external network. These Kraken services are described in Architecture chapter.

Kubernetes Clusters

There are multiple ways for setting up a Kubernetes cluster. One of
the easiest ones that is most often used for experimenting is
Minikube. There are also managed clusters like EKS (Elastic Kubernetes
Service) in AWS.

This manual will show how to install Kraken CI in Minikube but the
steps are similar for other Kubernetes environments as well.

Install in Minikube

First, download minikube from https://minikube.sigs.k8s.io/docs/.

And then create a cluster:

minikube start

Now you may install Kraken CI, but first, let’s add a repo with Kraken Helm charts:

helm repo add kraken-ci https://kraken.ci/helm-repo/charts
helm repo update

and now install Kraken CI:

helm upgrade --install --create-namespace --namespace kraken \
  --debug --wait \
  --set access.method='external-ips' \
  --set access.external_ips={`minikube ip`} \
  kraken-ci kraken-ci/kraken-ci

This command actually upgrades Kraken CI if it is already installed
but if it was not yet installed, then it installs it.

More details about using Helm to install Kraken CI can be found in installation docs.

When everything completes successfully, then at the end of the whole
output there should be presented short instruction about getting
the URL of Kraken service like that:

NOTES:
Get the application URL by running these commands:
 export NODE_PORT=$(kubectl get — namespace kk-1 -o jsonpath=”{.spec.ports[0].port}” services ui)
 export NODE_IP=$(kubectl get nodes — namespace kk-1 -o jsonpath=”{.items[0].status.addresses[0].address}”)
 echo http://$NODE_IP:$NODE_PORT

Now you may check if Kraken is working by visiting the URL
given by this code and by checking if Kubernetes is running Kraken’s
services with this command:

kubectl get all -n kraken

This will show Kraken’s pods, services, deployments and replica sets.

At this moment, Kraken CI should be operating. Please visit the
website on the URL presented above. You should see a login page:

Enter admin for Username and admin for Password.

Global Settings

First, let’s set some global settings. In Web UI, click Settings in
the top menu bar.

In the General tab, fill the following fields:

• Kraken Server URL — an URL with a port of the server that is visible inside the Kubernetes cluster
• MinIO/S3 Address — the IP address and port of Kraken’s internal artifacts storage address
• Clickhouse Proxy Address — the IP address and port of Kraken’s internal logs storage address

In all these cases minikube IP address can be used. It can be obtained
using minikube ip command.

Having set the General settings, let’s move to the Cloud tab.

Here, please move to Kubernetes section and set only the Namespace
field to the value that was provided in helm command above (if it
was not changed, then it should be kraken).

API Server URL field must be empty as Kraken CI is installed inside
Kubernetes and it knows where the API server is.

After saving the settings, check if connectivity is ok using Test
Kubernetes Access button.

Configuration in Agents Groups

After setting global settings, it is possible now to configure aspects
of spawning Kubernetes pods for Kraken jobs. This can be done on
Kraken -> Agents -> Groups page. Let’s create a new Agents Group by
clicking Add New Group button and naming it k8s. The newly created
group’s details will be presented on a separate tab. On this tab,
there is a section Agents Deployment — select Kubernetes. In this
case, there is only one field to set: Instances Limit.

This limit value will not allow having more running pods than it — here 5.

Job Definition

Now, to use the defined k8s Agents Group, we need to prepare
a project with a branch and a stage. More details about that can be
found in Introductory Guide. So let’s concentrate now on defining a job.

{
  "parent": "root",
  "triggers": {
    "parent": True
  },
  "configs": [],
  "jobs": [{
    "name": "hello",
    "timeout": 500,
    "steps": [{
      "tool": "shell",
      "cmd": "echo 'hello world'"
    }],
    "environments": [{
      "system": "ubuntu:20.04",
      "agents_group": "k8s",
      "config": "default"
    }]
  }]
}

There is not much difference compared to regular Kraken jobs. The job
has a defined environments section where we are pointing to our k8s
Agents Group. In the case of system field here, we have a
Ubuntu:20.04 Docker image.

Run

Now when a job is assigned to an agents group with configured Agents
Deployment then a new pod will be spawned for that job if agents
are not available in the Kraken.

Let’s change the view to Branch Results view and trigger a new flow by
clicking Run Flow button. On the run page, the list of jobs shows our
AWS job:

That’s it!