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Kamesh Sampath
Kamesh Sampath

Posted on • Originally published at kubesimplify.com

Continuous Integration with Drone on Kubernetes

#kubernetes #drone #kind #cicd

Overview

Over the past few years, lots of organizations have started to adopt Cloud Native architectures. Despite the adoption of Cloud Native architectures, many companies haven’t achieved optimal results. Wondering why? One of the reasons is our adherence to traditional ways of building and deploying Cloud Native applications.

Kubernetes has become the de facto Cloud Native deployment platform, solving one of the main Cloud Native problems: "deploying" applications quickly, efficiently and reliably. It offers radically easy scaling and fault tolerance. Despite this, not many Continuous Integration(CI) systems utilize the benefits of Kubernetes. None of the existing build systems offer the capabilities that are native to Kubernetes like in-cluster building, defining the build resources using CRDs, leveraging underlying security and access controls, etc. These missing features of Kubernetes made the Cloud Native architectures to be less effective and more complex.

Let me introduce an Open Source project Drone -- a cloud native self-service Continuous Integration platform -- . 10 years ago old Drone was the first CI tool to leverage containers to run pipeline steps independent of each other., Today, with over 100M+ Docker pulls, and the most GitHub stars of any Continuous Integration solution, Drone offers a mature, Kubernetes based CI system harnessing the scaling and fault tolerance characteristics of Cloud Native architectures. Drone help solve the next part of the puzzle by running Kubernetes native in-cluster builds.

In this blog, let see how we setup kind and Drone together on our laptops to build Kubernetes native pipelines which could then be moved to cloud platforms like Harness CI for a broader team based development.

This blog is a tutorial where I explain the steps required to use KinD and Drone to set up CI with Kubernetes on your local machine. At the end of these steps, you will have a completely functional Kubernetes + CI setup that can help you build and deploy Cloud Native applications on to Kubernetes on your laptop.

Required tools

To complete this setup successfully, we need the following tools on your laptop,

All linux distributions adds envsubst via gettext package. On macOS, it can be installed using Homebrew like brew install gettext.

Demo Sources

The accompanying code for this blog i.e. the demo sources is available on my GitHub repo. Let us clone the same on to our machine,



git clone https://github.com/kameshsampath/drone-on-k8s && \
  cd "$(basename "$_" .git)"
export PROJECT_HOME="${PWD}"
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NOTE: Through out this blog we will use the name $PROJECT_HOME to refer to demo sources folder that we cloned above .

Alright, we are all set to get started!!

## Setup Kubernetes Cluster

As said earlier, we will use kind as our local Kubernetes cluster. But for this blog we will do the following customisations,

  • Set up a local container registry where we can push and pull container images that will be used in our Kubernetes. Check the kind docs for more details.
  • Do extra port mappings to make allow us to access the Drone Server and Gitea git repository

To make things easier, all the aforementioned customisations has been compiled into a utility script $PROJECT_HOME/bin/kind.sh. To start the KinD cluster with these customisations just do,



$PROJECT_HOME/bin/kind.sh
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Version Control System

Without Version Control System(VCS) CI makes no sense. One of the primary goal of this blog is to show how to run local VCS so that you can build your applications without a need for external VCS like GitHub, Gitlab etc., For our setup we will use on Gitea -- A painless, self-hosted Git service--. Gitea is so easy to set up and does provide helm charts for Kubernetes based setup.

Helm Values

The contents of the helm values file that will be used to setup Gitea is shown below. The settings are self-explanatory for more details check the cheat sheet.



service:
  http:
    # the Kubernetes service gitea-http'  service type
    type: NodePort 
    # the gitea-http service port
    port: 3000
    # this port will be used in KinD extra port mappings to allow accessing the 
    # Gitea server from our laptops
    nodePort: 30950
gitea:
  # the admin credentials to access Gitea typically push/pull operations
  admin:
    # DON'T use username admin as its reserved and gitea will 
    # fail to start
    username: demo
    password: demo@123
    email: admin@example.com
  config:
    server:
      # for this demo we will use http protocol to access Git repos
      PROTOCOL: http
      # the port gitea will listen on
      HTTP_PORT: 3000
      # the Git domain - all the repositories will be using this domain
      DOMAIN: gitea-127.0.0.1.sslip.io
      # The clone base url e.g. if repo is demo/foo the clone url will be 
      # http://gitea-127.0.0.1.sslip.io:3000/demo/foo
      ROOT_URL: http://gitea-127.0.0.1.sslip.io:3000/
    webhook:
      # since we will deploy to local network we will allow all hosts
      ALLOWED_HOST_LIST: "*"
      # since we are in http mode disable TLS
      SKIP_TLS_VERIFY: true
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Add the gitea helm repo,



helm repo add gitea-charts https://dl.gitea.io/charts/
helm repo update
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Run the following command to deploy Gitea,



helm upgrade \
  --install gitea gitea-charts/gitea \
  --values $PROJECT_HOME/helm_vars/gitea/values.yaml \
  --wait
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A successful deployment of gitea should show the following services in the default namespace when running the command,



kubectl get pods,svc -lapp.kubernetes.io/instance=gitea
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NAME                                  READY   STATUS    RESTARTS   AGE
pod/gitea-0                           1/1     Running   0          4m32s
pod/gitea-memcached-b87476455-4kqvp   1/1     Running   0          4m32s
pod/gitea-postgresql-0                1/1     Running   0          4m32s

NAME                                TYPE        CLUSTER-IP      EXTERNAL-IP   PORT(S)          AGE
service/gitea-http                  NodePort    10.96.55.25     <none>        3000:30950/TCP   4m32s
service/gitea-memcached             ClusterIP   10.96.176.235   <none>        11211/TCP        4m32s
service/gitea-postgresql            ClusterIP   10.96.59.23     <none>        5432/TCP         4m32s
service/gitea-postgresql-headless   ClusterIP   None            <none>        5432/TCP         4m32s
service/gitea-ssh                   ClusterIP   None            <none>        22/TCP           4m32s
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Environment Variables

As a convenience let us set few environment variables which will be used by the commands in upcoming sections of the blog.

Gitea 



# Gitea domain
export GITEA_DOMAIN="gitea-127.0.0.1.sslip.io"
# Gitea URL
export GITEA_URL="http://${GITEA_DOMAIN}:3000"
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You can access Gitea in your browser like open ${GITEA_URL}. Default credentials demo/demo@123.

Gitea Home

Drone 



# the drone server host
export DRONE_SERVER_HOST="drone-127.0.0.1.sslip.io:8080"
# the drone server web console
export DRONE_SERVER_URL="http://${DRONE_SERVER_HOST}"
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Drone Gitea oAuth Application

Drone will use Gitea for pulling/pushing the source code and to add webhooks to trigger builds on source change. To do these actions it requires an oAuth application to be configured on Gitea.

The demo sources has little utility called gitea-config that helps in creating the oAuth application in Gitea and clone and create the quickstart repository as drone-quickstart on Gitea. We will use drone-quickstart* repository to validate our setup.



$PROJECT_HOME/bin/gitea-config-darwin-arm64 \
  -g "${GITEA_URL}" -dh "${DRONE_SERVER_URL}"
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NOTE: Use gitea-config binary corresponding to your os and architecture. In the command above we used macOS arm64 binary

Drone Quickstart Repository

Drone Gitea oAuth2 Application

Drone Gitea oAuth2 Application Details

The gitea-config utility creates a .env file under $PROJECT_HOME/k8s which has few Drone environment variables that will be used while deploying Drone server in upcoming steps,

  • DRONE_GITEA_CLIENT_ID: The Gitea oAuth Client ID
  • DRONE_GITEA_CLIENT_SECRET: The Gitea oAuth Client Secret
  • DRONE_RPC_SECRET: The unique secret to identify the server and runner, a simple generation like openssl rand -hex 16

Deploy Drone

For our demo the Drone server will be deployed on to a namespace called drone,



kubectl create ns drone
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Add drone helm repo,



helm repo add drone https://charts.drone.io
helm repo update
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The following content will be used as helm values file to deploy Drone server,



service:
  # the Drone Kubernetes service type
  type: NodePort
  port: 8080
  # this port will be used in KinD extra port mappings to allow accessing the 
  # drone server from our laptops
  nodePort: 30980

extraSecretNamesForEnvFrom:
   # all the other as $PROJECT_HOME/k8s/.env variables are loaded via this secret
   # https://docs.drone.io/server/reference/
  - drone-demos-secret

env:
  # the Drone server host typically what the drone runners will use to 
  # communicate with the server
  DRONE_SERVER_HOST: drone-127.0.0.1.sslip.io:8080
  # Since we run Gitea in http mode we will skip TLS verification
  DRONE_GITEA_SKIP_VERIFY: true
  # The url where Gitea could be reached, typically used while 
  # cloning the sources
  # https://docs.drone.io/server/provider/gitea/
  DRONE_GITEA_SERVER: http://gitea-127.0.0.1.sslip.io:3000/
  # For this local setup and demo we wil run Drone in http mode
  DRONE_SERVER_PROTO: http
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Run the following helm command to deploy Drone server,



helm upgrade --install drone drone/drone \
  --values $PROJECT_HOME/helm_vars/drone/values.yaml \
  --namespace=drone \
  --post-renderer  k8s/kustomize \
  --wait
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A successful Drone deployment should show the following resources in drone namespace,



kubectl get pods,svc,secrets -n drone
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NAME                         READY   STATUS    RESTARTS   AGE
pod/drone-5bb66b9d97-hbpl5   1/1     Running   0          9s

NAME            TYPE       CLUSTER-IP      EXTERNAL-IP   PORT(S)          AGE
service/drone   NodePort   10.96.184.123   <none>        8080:30980/TCP   9s

NAME                                 TYPE                 DATA   AGE
secret/drone-demos-secret            Opaque               3      9s
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Host Aliases

As you have noticed we use Magic DNS for Gitea and Drone. This will cause name resolution issues inside the Drone and Gitea pods, because the url gitea-127.0.0.1.sslip.io resolves to 127.0.0.1 on the Drone server pod. But for our setup to work we need gitea-127.0.0.1.sslip.io to be resolved to the gitea-http Kubernetes service on our cluster.

In order to achieve that we use the Kubernetes host aliases to add extra host entries(/etc/hosts) in Drone pods that will resolve gitea-127.0.0.1.sslip.io to the ClusterIP of the gitea-http service.

There are multiple techniques that allows us to add host entires to Kubernetes deployments. The first one we used in the earlier helm command to deploy Drone server is called helm post renderer. The post renderer allowed us to patch the Drone deployment from the helm chart with the hostAliases for gitea-127.0.0.1.sslip.io resolving to gitea-http's ClusterIP address.

As we did with Drone deployments to resolve the Gitea, we also need to make the Gitea pods resolve the Drone server when trying to send the webhook payload to trigger the build.

This time let us use kubectl patching technique to update the Gitea statefuleset deployments to resolve drone-127.0.0.1.sslip.io to drone service's ClusterIP .

The patch that will be applied to the Gitea statefulset is as shown below.



{
  "spec": {
    "template": {
      "spec": {
        "hostAliases": [
          {
            "ip": "${DRONE_SERVICE_IP}",
            "hostnames": ["drone-127.0.0.1.sslip.io"]
          }
        ]
      }
    }
  }
}
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Run the following command to patch and update the gitea statefulset deployment,



export DRONE_SERVICE_IP="$(kubectl get svc -n drone drone -ojsonpath='{.spec.clusterIP}')"
kubectl patch statefulset gitea -n default --patch "$(envsubst<$PROJECT_HOME/k8s/patch.json)"
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TIP: To replace the environment variables in the patch we use envsubst

Wait for the Gitea pods to be updated and restarted,



kubectl rollout status statefulset gitea --timeout 30s
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You can check the updates to the gitea pod's /etc/hosts file by running the command,



kubectl exec -it gitea-0 -n default cat /etc/hosts
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It should have a entry like,



# Entries added by HostAliases.
10.96.184.123   drone-127.0.0.1.sslip.io
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Where 10.96.184.123 is the drone service ClusterIP on my setup, run the following command to verify it,



kubectl get svc -n drone drone
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NAME    TYPE       CLUSTER-IP      EXTERNAL-IP   PORT(S)          AGE
drone   NodePort   10.96.184.123   <none>        8080:30980/TCP   6m14s
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You can do similar checks with Drone pods and ensure that Drone pods /etc/hosts has entry for gitea-127.0.0.1.sslip.io mapping to gitea-http ClusterIP.

What we did so far,

  • Deployed a customized Kubernetes cluster using kind
  • Deployed Gitea on to our Kubernetes cluster
  • Deployed Drone Server on to our Kubernetes Cluster
  • Created an oAuth application on Gitea to authorize Drone server
  • Create a repository on Gitea that will be used to test our step

Deploy Drone Kubernetes Runner

To run the Drone pipelines on Kubernetes we need deploy the Drone Kubernetes Runner.

Deploy the drone-runner-kube with following values,



extraSecretNamesForEnvFrom:
   # all the other as env variables are loaded via this secret
  - drone-demos-secret
env:
  # the url to reach the Drone server
  # we point it to the local drone Kubernetes service drone on port 8080
  DRONE_RPC_HOST: "drone:8080"
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Run the helm install to deploy the drone-runner-kube,



helm upgrade --install drone-runner-kube drone/drone-runner-kube \
  --namespace=drone \
  --values $PROJECT_HOME/helm_vars/drone-runner-kube/values.yaml  \
  --wait
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Querying the Kubernetes resources on drone namespace should now return the drone-runner-kube pod and service,



kubectl get pods,svc -n drone -lapp.kubernetes.io/name=drone-runner-kube
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NAME                                     READY   STATUS    RESTARTS   AGE
pod/drone-runner-kube-59f98956b4-mbr9c   1/1     Running   0          41s

NAME                        TYPE        CLUSTER-IP     EXTERNAL-IP   PORT(S)    AGE
service/drone-runner-kube   ClusterIP   10.96.196.54   <none>        3000/TCP   41s
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Open the Drone server web console in your browser using the URL ${DRONE_SERVER_URL} follow the on screen instructions to complete the registration and activation of our drone-quickstart repository.

Drone Registration

Lets run our first pipeline

Let us clone the quickstart repository to the folder of our choice on our local machine,



git clone http://gitea-127.0.0.1.sslip.io:3000/demo/drone-quickstart
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NOTE: The default git credentials to push is demo/demo@123

Open the drone-quickstart project with your favorite editor, try to make some changes for e.g add some dummy text README to trigger a build. Your build will fail as shown below,

Drone Failed Build

Don't worry, that's what we are going to fix now. We need to do the same thing of adding hostAliases to our drone pipeline pods as well update the .drone.yml with ClusterIP of gitea-http and hostnames with entry for gitea-127.0.0.1.sslip.io so that our Drone pipeline pods are able to clone the sources from our Gitea repository.

The following snippet shows the updated .drone.yml with entries for host aliases,

NOTE: Your ClusterIP of gitea-http* may vary, to get the ClusterIP of the **gitea-http service run the command kubectl get svc gitea-http -ojsonpath='{.spec.clusterIP}'



---
kind: pipeline
type: kubernetes
name: default

steps:
- name: say hello
  image: busybox
  commands:
  - echo hello world
- name: good bye hello
  image: busybox
  commands:
  - echo good bye

# updates to match your local setup
host_aliases:
  # kubectl get svc gitea-http -ojsonpath='{.spec.clusterIP}'
  - ip: 10.96.240.234
    hostnames:
      - "gitea-127.0.0.1.sslip.io"

trigger:
  branch:
  - main
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Commit and push the code to trigger a new Drone pipeline build, and you will see it being successful.

Drone Successful Build

Cleanup

When you are done with experimenting, you can clean up the setup by running the following command




kind delete cluster --name=drone-demo
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Summary

We now have a fully functional CI with Drone on Kubernetes. You no longer need to build your Cloud (Kubernetes) Native applications, but can Continuously Integrate with much ease and power.

Just summarize what we did in this blog,

  • Deployed a customized Kubernetes cluster using kind
  • Deployed Gitea on to our Kubernetes cluster
  • Deployed Drone Server on to our Kubernetes Cluster
  • Created an oAuth application on Gitea to authorize drone
  • Created a repository on Gitea that will be used to test our step
  • Deployed Drone Kubernetes runner to run pipelines on Kubernetes Cluster
  • Built our Quick start application using Drone pipelines on Kubernetes
  • Leveraged Kubernetes host aliases to add host entries to our deployments to resolve local URLs

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