Combining Jenkins Pipeline and ArgoCD
Published: 2023-03-14 22:51:06

As organizations move to adopt cloud-native technologies and architectures, deploying applications to Kubernetes clusters has become increasingly complex. There are many moving parts involved in the deployment process, from building the container images to deploying them to Kubernetes and managing the infrastructure.

To manage this complexity, organizations have turned to tools like Jenkins Pipeline and ArgoCD to automate the deployment process and manage the infrastructure as code. Jenkins Pipeline provides a way to automate and orchestrate the continuous delivery pipeline, while ArgoCD provides a declarative way to manage deployments using GitOps principles.

Combining Jenkins Pipeline and ArgoCD can provide several benefits to organizations that are deploying applications to Kubernetes clusters. It can help to automate the entire deployment process, from code check-in to deployment to Kubernetes, while also providing scalability, improved collaboration, consistency and reliability, and visibility and monitoring into the deployment process.

In this way, the combination of Jenkins Pipeline and ArgoCD can help organizations to manage the complexity of deploying applications to Kubernetes clusters, while also providing a way to maintain consistency, reliability, and visibility into the deployment process.

## Several benefits to organizations
Combining Jenkins Pipeline and ArgoCD can provide several benefits to organizations that are deploying applications to Kubernetes clusters:

1. Automated continuous delivery: ArgoCD provides a declarative way to manage deployments using GitOps principles, while Jenkins Pipeline provides a way to automate and orchestrate the continuous delivery pipeline. Combining these two tools allows organizations to automate the entire deployment process, from code check-in to deployment to Kubernetes.
2. Scalability: Kubernetes is designed to scale horizontally, and with that comes the challenge of managing multiple environments and applications across multiple clusters. ArgoCD and Jenkins Pipeline can help to automate the deployment process and provide a way to manage the scale of the deployment process.
3. Improved collaboration: With GitOps principles, changes to the infrastructure can be made through a pull request in Git, making it easier for teams to collaborate on changes. Jenkins Pipeline and ArgoCD can help to automate the process of merging these changes and deploying them to the Kubernetes cluster.
4. Consistency and reliability: With ArgoCD, the desired state of the infrastructure is defined in a Git repository, making it easier to maintain a consistent and reliable infrastructure. Jenkins Pipeline can help to automate the process of applying these changes to the Kubernetes cluster, ensuring that the infrastructure is always in the desired state.
5. Visibility and monitoring: ArgoCD provides a UI for monitoring and managing deployments, while Jenkins Pipeline provides visibility into the deployment process. Combining these two tools allows organizations to have a complete view of the deployment process, from code check-in to deployment to Kubernetes.

Overall, combining Jenkins Pipeline and ArgoCD can help organizations to automate the deployment process, scale the deployment process, improve collaboration, maintain consistency and reliability, and provide visibility and monitoring into the deployment process.

## Jenkins & ArgoCD Roles
Jenkins Pipeline and ArgoCD each play distinct roles in the deployment process and provide different benefits to organizations.

Jenkins Pipeline is a tool for automating and orchestrating the continuous delivery pipeline. It provides a way to define and execute the steps of the pipeline, including building the application, testing it, packaging it into a container image, and deploying it to Kubernetes. Jenkins Pipeline is highly configurable and can be extended with plugins, making it a flexible tool for automating the deployment process.

ArgoCD, on the other hand, is a tool for managing deployments to Kubernetes clusters using GitOps principles. It provides a declarative way to manage the desired state of the infrastructure, with the desired state defined in a Git repository. ArgoCD continuously monitors the Kubernetes cluster and ensures that the current state matches the desired state, making it easier to maintain a consistent and reliable infrastructure. ArgoCD also provides a UI for monitoring and managing deployments, making it easier to visualize the deployment process and identify issues.

Together, Jenkins Pipeline and ArgoCD can provide end-to-end automation for deploying applications to Kubernetes clusters. Jenkins Pipeline handles the build, test, and package steps of the deployment process, while ArgoCD handles the deployment and management of the infrastructure. By combining these two tools, organizations can automate the entire deployment process and maintain a consistent and reliable infrastructure, all while providing visibility and monitoring into the deployment process.

## Pipeline Example
In this example, we will compare two Jenkins Pipeline scripts for deploying an application to a Kubernetes cluster. The first script deploys the application without using ArgoCD, while the second script deploys the application using ArgoCD.

```typescript
pipeline {
  agent any

  stages {
    stage('Build') {
      steps {
        sh 'docker build -t myorg/myapp:${BUILD_NUMBER} .'
      }
    }

    stage('Push to Registry') {
      steps {
        withCredentials([usernamePassword(credentialsId: 'registry-creds', usernameVariable: 'REGISTRY_USERNAME', passwordVariable: 'REGISTRY_PASSWORD')]) {
          sh "docker login -u ${REGISTRY_USERNAME} -p ${REGISTRY_PASSWORD} myregistry.example.com"
        }
        sh "docker push myorg/myapp:${BUILD_NUMBER}"
      }
    }

    stage('Deploy to Kubernetes') {
      steps {
        sh 'kubectl apply -f kubernetes/deployment.yaml'
        sh 'kubectl apply -f kubernetes/service.yaml'
      }
    }
  }
}

```

The first script uses Kubernetes YAML files to deploy the application. It builds a Docker image for the application, pushes the image to a Docker registry, and deploys the application to Kubernetes using the kubectl apply command to apply the Kubernetes YAML files for the deployment and service.

```typescript
pipeline {
  agent any

  environment {
    ARGOCDSERVER = "https://argocd-server.example.com"
    ARGOCDPROJECT = "my-project"
    ARGOCDAPP = "my-app"
    K8SCONTEXT = "my-k8s-context"
    K8SNAMESPACE = "my-namespace"
    ARGOCDSYNCOPTIONS = "--sync-policy=auto --prune"
  }

  stages {
    stage('Deploy') {
      steps {
        script {
          def argocdToken = credentials('argocd-token')

          def appSpecFile = readFile("argocd/myapp.yaml")

          def argocd = new Argocd(server: ARGOCDSERVER, token: argocdToken)
          argocd.createApplication(appSpecFile, project: ARGOCDPROJECT)
          argocd.syncApplication(ARGOCDAPP, ARGOCDSYNCOPTIONS)
        }
      }
    }
  }
}

```

The second script uses ArgoCD to deploy the application. It defines the ArgoCD server URL, token, project, and application name, as well as the Kubernetes context and namespace where the application will be deployed. The ArgoCD Application manifest is defined in a YAML file, which is read into the script using the readFile function. The script then uses the Argocd class to create the application in ArgoCD and sync it to the Kubernetes cluster using the specified sync options.

## Yaml Example
In this example, we will compare the use of Kubernetes YAML files and ArgoCD YAML application manifests for deploying an application to a Kubernetes cluster.

deployment.yaml:
```yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: myapp
  labels:
    app: myapp
spec:
  replicas: 1
  selector:
    matchLabels:
      app: myapp
  template:
    metadata:
      labels:
        app: myapp
    spec:
      containers:
      - name: myapp
        image: myorg/myapp:latest
        ports:
        - containerPort: 8080
        env:
        - name: MYAPP_ENV
          value: "prod"

```

service.yaml:
```yaml
apiVersion: v1
kind: Service
metadata:
  name: myapp
  labels:
    app: myapp
spec:
  selector:
    app: myapp
  ports:
  - name: http
    port: 80
    targetPort: 8080
  type: LoadBalancer

```

myapp.yaml:
```yaml
apiVersion: argoproj.io/v1alpha1
kind: Application
metadata:
  name: myapp
spec:
  destination:
    server: https://kubernetes.default.svc
    namespace: myapp
  project: default
  source:
    repoURL: https://github.com/myorg/myapp.git
    targetRevision: HEAD
    path: kubernetes/overlays/dev
  syncPolicy:
    automated:
      prune: true
      selfHeal: true
  syncOptions:
    - --skip-hooks
  helm:
    valueFiles:
      - values.yaml

```

## Conclusion
In conclusion, both Kubernetes YAML files and ArgoCD provide declarative ways to manage deployments to Kubernetes clusters. When you define a Kubernetes YAML file for a deployment, you are defining the desired state of the infrastructure, and when you apply that YAML file using kubectl apply, Kubernetes will ensure that the current state of the infrastructure matches the desired state.

However, while Kubernetes YAML files are also declarative, using them for managing deployments can be challenging when you have multiple environments and applications across multiple clusters. Kubernetes YAML files require manual synchronization and deployment, which can be time-consuming and error-prone.

ArgoCD provides a way to manage deployments using GitOps principles, which enables automated continuous delivery and provides a UI for monitoring and managing deployments. By using ArgoCD, you can define the desired state of the infrastructure in a Git repository and let ArgoCD handle the deployment process. This makes it easier to automate the deployment process and ensures that the infrastructure is always in the desired state.

Overall, while both approaches are declarative, using ArgoCD can provide a more streamlined and automated approach to managing deployments to Kubernetes clusters, making it easier to maintain a consistent and reliable infrastructure.