Argo CD

Argo CD is a Kubernetes deployment tool that uses Git repositories as the source of truth. It monitors running applications and compares the deployed state against the desired one in Git. Argo CD lets you visualize the differences and provides methods to automatically or manually update the live state with the desired target state. For more information, see the Argo CD documentation.

In a multicluster Verrazzano environment, Argo CD integration depends on Rancher being enabled on the admin cluster. Argo CD connects to managed clusters using the Rancher proxy, to create the required resources for Argo CD cluster registration.

Before you begin

• Install Verrazzano and set up a multicluster environment by following these instructions.
  • Because Argo CD is not enabled by default, you must first enable argoCD on the admin cluster.
  • When you register managed clusters, they are automatically registered in Argo CD.
• Access the Argo CD console using the instructions at Access Verrazzano.
• After you set up your application in the Argo CD console, those registered clusters will be available for you to select, deploy, and manage applications.

Configure repositories

In the Argo CD console, configure repositories that will contain the Kubernetes resources for deploying an application.

The following is a sample procedure to configure a private Git repository through HTTPS.

1. Log in to the Argo CD console.
2. In the left navigation, click Settings.
3. Click Repositories.
4. Click Connect Repo.
5. Select VIA HTTPS as the connection method.
6. For Project, specify default.
   NOTE: Unless they are grouped together, all the projects are defined in the default level.
7. For Repository URL, provide the required URL.
8. If it is a private repository and a user name and password is required to connect to the repository, enter the required credentials.
   NOTE: The other fields are optional and based on how the Git repository is configured.
9. Click Connect and verify that the connection status displayed is Successful.

Deploy applications

To deploy applications in a custom namespace, create Argo CD applications that specify the Git repository path, which Argo CD requires to synchronize and deploy the applications in the specified namespace.

NOTE: You can either pre-create a namespace and label it or auto-create a namespace when deploying an application.

This example provides information about how to deploy the Hello-helidon application. The Hello-helidon application and component YAML files are available at Hello World Helidon.

1. Log in to the Argo CD console.
2. Click New App.
3. Specify a name for the application.
4. For Project Name, select default.
5. Select the required Sync Policy option:
   • Automatic - By default, every three minutes, Argo CD checks the specified Git repository and synchronizes the updates in Kubernetes to the Git repository.
   • Manual - For manually synchronizing the updates to the Git repository, use the Manual option.
6. If you want to auto-create a namespace, in the Sync Options section, select Auto-Create Namespace.
   By auto-creating the namespace, the application will be deployed outside of the service mesh. The best practice is to pre-create the namespace and label it.
7. Under the Source section, enter the following:
   • Repository URL: https://github.com/verrazzano/verrazzano/
   • Revision: release-1.5
   • Path: Path in the repository where the Kubernetes resource definitions are listed. For example: examples/helidon-config
8. Under the Destination section, do the following:
   • Cluster URL: Select the cluster to which you want to deploy the applications.
   • Namespace: Specify the namespace in which you want to deploy the applications. The instructions in this sample use hello-helidon as the namespace.
9. Click Create.
10. If you selected Manual as the Sync Policy option, then click Sync. In the Synchronize Resources section, select all the resources, and then click Synchronize.
    This creates the Argo CD application and a pictorial representation of the deployed applications is displayed.

Verify the deployed application

The Hello World Helidon microservices application implements a REST API endpoint, /config, which returns a message {"message":"Hello World!"} when invoked.

NOTE: The following instructions assume that you are using a Kubernetes environment such as OKE. Other environments or deployments may require alternative mechanisms for retrieving addresses, ports, and such.

Follow these steps to test the endpoints.

1. Get the generated host name for the application.

   $ HOST=$(kubectl get gateways.networking.istio.io hello-helidon-helidon-config-appconf-gw \
        -n hello-helidon \
        -o jsonpath='{.spec.servers[0].hosts[0]}')
   $ echo $HOST
   
   # Sample output
   helidon-config-appconf.hello-helidon.11.22.33.44.nip.io
   

2. Get the EXTERNAL_IP address of the istio-ingressgateway service.

   $ ADDRESS=$(kubectl get service \
        -n istio-system istio-ingressgateway \
        -o jsonpath='{.status.loadBalancer.ingress[0].ip}')
   $ echo $ADDRESS
   
   # Sample output
   11.22.33.44
   

3. Access the application.

   • Using the command line

     $ curl -sk \
        -X GET \
        https://${HOST}/config \
        --resolve ${HOST}:443:${ADDRESS}
     
     # Expected response output
     {"message":"Hello World!"}
     

     If you are using nip.io, then you do not need to include --resolve.

   • Local testing with a browser

     Temporarily, modify the /etc/hosts file (on Mac or Linux) or c:\Windows\System32\Drivers\etc\hosts file (on Windows 10), to add an entry mapping the host name to the ingress gateway’s EXTERNAL-IP address. For example:

     11.22.33.44 hello-helidon.example.com
     

     Then you can access the application in a browser at https://<host>/config.

     • If you are using nip.io, then you can access the application in a browser using the HOST variable (for example, https://${HOST}/config).
     • If you are going through a proxy, then you may need to add *.nip.io to the NO_PROXY list.

   • Using your own DNS name

     Point your own DNS name to the ingress gateway’s EXTERNAL-IP address.

     • In this case, you would need to edit the hello-helidon-app.yaml file to use the appropriate value under the hosts section (such as yourhost.your.domain), before deploying the hello-helidon application.
     • Then, you can use a browser to access the application at https://<yourhost.your.domain>/config.

4. A variety of endpoints associated with the deployed application are available to further explore the logs, metrics, and such. You can access them according to the directions here.

Undeploy applications

1. Log in to the Argo CD console.
2. Select the application that you want to undeploy and then click Delete.
3. Enter the name of the application and then click OK.
   This deletes all the resources created by the specific application except for the namespaces.