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Argo CD applications

Red Hat OpenShift GitOps 1.12

Creating and deploying applications on the OpenShift cluster by using the Argo CD dashboard, oc tool, or GitOps CLI

Red Hat OpenShift Documentation Team

Abstract

This document provides instructions for creating and deploying your applications to the OpenShift cluster by using the Argo CD dashboard, oc tool, or GitOps CLI. It also discusses how to verify the self-healing behavior in Argo CD.

With Argo CD, you can deploy your applications to the OpenShift Container Platform cluster either by using the Argo CD dashboard or by using the oc tool.

Argo CD provides a dashboard which allows you to create applications.

Prerequisites

  • You have logged in to the OpenShift Container Platform cluster as an administrator.
  • You have installed the Red Hat OpenShift GitOps Operator on your OpenShift Container Platform cluster.
  • You have logged in to Argo CD instance.

Procedure

  1. In the Argo CD dashboard, click NEW APP to add a new Argo CD application.

  2. For this workflow, create a spring-petclinic application with the following configurations:

    Application Name
    spring-petclinic
    Project
    default
    Sync Policy
    Automatic
    Repository URL
    https://github.com/redhat-developer/openshift-gitops-getting-started
    Revision
    HEAD
    Path
    app
    Destination
    https://kubernetes.default.svc
    Namespace
    spring-petclinic
  3. Click CREATE to create your application.
  4. Open the Administrator perspective of the web console and expand Administration → Namespaces.
  5. Search for and select the namespace, then enter argocd.argoproj.io/managed-by=openshift-gitops in the Label field so that the Argo CD instance in the openshift-gitops namespace can manage your namespace.

1.2. Creating an application by using the oc tool
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You can create Argo CD applications in your terminal by using the oc tool.

Prerequisites

  • You have installed the Red Hat OpenShift GitOps Operator on your OpenShift Container Platform cluster.
  • You have logged in to an Argo CD instance.

Procedure

  1. Download the sample application: 

    $ git clone git@github.com:redhat-developer/openshift-gitops-getting-started.git
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  2. Create the application: 

    $ oc create -f openshift-gitops-getting-started/argo/app.yaml
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  3. Run the oc get command to review the created application: 

    $ oc get application -n openshift-gitops
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  4. Add a label to the namespace your application is deployed in so that the Argo CD instance in the openshift-gitops namespace can manage it: 

    $ oc label namespace spring-petclinic argocd.argoproj.io/managed-by=openshift-gitops
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1.3. Verifying Argo CD self-healing behavior
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Argo CD constantly monitors the state of deployed applications, detects differences between the specified manifests in Git and live changes in the cluster, and then automatically corrects them. This behavior is referred to as self-healing.

You can test and observe the self-healing behavior in Argo CD.

Prerequisites

  • You have installed the Red Hat OpenShift GitOps Operator on your OpenShift Container Platform cluster.
  • You have logged in to an Argo CD instance.
  • The sample app-spring-petclinic application is deployed and configured.

Procedure

  1. In the Argo CD dashboard, verify that your application has the Synced status.
  2. Click the app-spring-petclinic tile in the Argo CD dashboard to view the application resources that are deployed to the cluster.
  3. In the OpenShift Container Platform web console, navigate to the Developer perspective.

  4. Modify the Spring PetClinic deployment and commit the changes to the app/ directory of the Git repository. Argo CD will automatically deploy the changes to the cluster.

    1. Fork the OpenShift GitOps getting started repository.
    2. In the deployment.yaml file, change the failureThreshold value to 5.

    3. In the deployment cluster, run the following command to verify the changed value of the failureThreshold field: 

      $ oc edit deployment spring-petclinic -n spring-petclinic
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  5. Test the self-healing behavior by modifying the deployment on the cluster and scaling it up to two pods while watching the application in the OpenShift Container Platform web console.

    1. Run the following command to modify the deployment: 

      $ oc scale deployment spring-petclinic --replicas 2  -n spring-petclinic
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    2. In the OpenShift Container Platform web console, notice that the deployment scales up to two pods and immediately scales down again to one pod. Argo CD detected a difference from the Git repository and auto-healed the application on the OpenShift Container Platform cluster.
  6. In the Argo CD dashboard, click the app-spring-petclinic tile → APP DETAILS → EVENTS. The EVENTS tab displays the following events: Argo CD detecting out of sync deployment resources on the cluster and then resyncing the Git repository to correct it.

With Argo CD, you can create your applications on an OpenShift Container Platform cluster by using the GitOps argocd CLI.

You can create applications in the default mode by using the GitOps argocd CLI.

Prerequisites

  • You have installed the Red Hat OpenShift GitOps Operator on your OpenShift Container Platform cluster.
  • You have installed the OpenShift CLI (oc).
  • You have installed the Red Hat OpenShift GitOps argocd CLI.
  • You have logged in to Argo CD instance.

Procedure

  1. Get the admin account password for the Argo CD server: 

    $ ADMIN_PASSWD=$(oc get secret openshift-gitops-cluster -n openshift-gitops -o jsonpath='{.data.admin\.password}' | base64 -d)
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  2. Get the Argo CD server URL: 

    $ SERVER_URL=$(oc get routes openshift-gitops-server -n openshift-gitops -o jsonpath='{.status.ingress[0].host}')
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  3. Log in to the Argo CD server by using the admin account password and enclosing it in single quotes:

    Important

    Enclosing the password in single quotes ensures that special characters, such as $, are not misinterpreted by the shell. Always use single quotes to enclose the literal value of the password. 

    $ argocd login --username admin --password ${ADMIN_PASSWD} ${SERVER_URL}
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    Example

    $ argocd login --username admin --password '<password>' openshift-gitops.openshift-gitops.apps-crc.testing
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  4. Verify that you are able to run argocd commands in the default mode by listing all applications: 

    $ argocd app list
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    If the configuration is correct, then existing applications will be listed with the following header:

    Sample output

    NAME CLUSTER NAMESPACE  PROJECT  STATUS  HEALTH   SYNCPOLICY  CONDITIONS  REPO PATH TARGET
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  5. Create an application in the default mode: 

    $ argocd app create app-spring-petclinic \
    --repo https://github.com/redhat-developer/openshift-gitops-getting-started.git \
    --path app \
    --revision main \
    --dest-server  https://kubernetes.default.svc \
    --dest-namespace spring-petclinic \
    --directory-recurse \
    --sync-policy automated \
    --self-heal \
    --sync-option Prune=true \
    --sync-option CreateNamespace=true
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  6. Label the spring-petclinic destination namespace to be managed by the openshif-gitops Argo CD instance: 

    $ oc label ns spring-petclinic "argocd.argoproj.io/managed-by=openshift-gitops"
    Copy to Clipboard Toggle word wrap

  7. List the available applications to confirm that the application is created successfully and repeat the command until the application has the Healthy and Synced statuses: 

    $ argocd app list
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You can create applications in core mode by using the GitOps argocd CLI.

Prerequisites

  • You have installed the Red Hat OpenShift GitOps Operator on your OpenShift Container Platform cluster.
  • You have installed the OpenShift CLI (oc).
  • You have installed the Red Hat OpenShift GitOps argocd CLI.

Procedure

  1. Log in to the OpenShift Container Platform cluster by using the oc CLI tool: 

    $ oc login -u <username> -p <password> <server_url>
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    Example

    $ oc login -u kubeadmin -p '<password>' https://api.crc.testing:6443
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  2. Check whether the context is set correctly in the kubeconfig file: 

    $ oc config current-context
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  3. Set the default namespace of the current context to openshift-gitops: 

    $ oc config set-context --current --namespace openshift-gitops
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  4. Set the following environment variable to override the Argo CD component names: 

    $ export ARGOCD_REPO_SERVER_NAME=openshift-gitops-repo-server
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  5. Verify that you are able to run argocd commands in core mode by listing all applications: 

    $ argocd app list --core
    Copy to Clipboard Toggle word wrap

    If the configuration is correct, then existing applications will be listed with the following header:

    Sample output

    NAME CLUSTER NAMESPACE  PROJECT  STATUS  HEALTH   SYNCPOLICY  CONDITIONS  REPO PATH TARGET
    Copy to Clipboard Toggle word wrap

  6. Create an application in core mode: 

    $ argocd app create app-spring-petclinic --core \
    --repo https://github.com/redhat-developer/openshift-gitops-getting-started.git \
    --path app \
    --revision main \
    --dest-server  https://kubernetes.default.svc \
    --dest-namespace spring-petclinic \
    --directory-recurse \
    --sync-policy automated \
    --self-heal \
    --sync-option Prune=true \
    --sync-option CreateNamespace=true
    Copy to Clipboard Toggle word wrap

  7. Label the spring-petclinic destination namespace to be managed by the openshif-gitops Argo CD instance: 

    $ oc label ns spring-petclinic "argocd.argoproj.io/managed-by=openshift-gitops"
    Copy to Clipboard Toggle word wrap

  8. List the available applications to confirm that the application is created successfully and repeat the command until the application has the Healthy and Synced statuses: 

    $ argocd app list --core
    Copy to Clipboard Toggle word wrap

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