Chapter 6. Automating application management with the GitOps controller
GitOps with Argo CD for MicroShift is a lightweight, optional add-on controller derived from the Red Hat OpenShift GitOps Operator. GitOps for MicroShift uses the command-line interface (CLI) of Argo CD to interact with the GitOps controller that acts as the declarative GitOps engine. You can consistently configure and deploy Kubernetes-based infrastructure and applications across clusters and development lifecycles.
6.1. What you can do with the GitOps agent
By using the GitOps with Argo CD agent with MicroShift, you can utilize the following principles:
Implement application lifecycle management.
- Create and manage your clusters and application configuration files using the core principles of developing and maintaining software in a Git repository.
- You can update the single repository and GitOps automates the deployment of new applications or updates to existing ones.
- For example, if you have 1,000 edge devices, each using MicroShift and a local GitOps agent, you can easily add or update an application on all 1,000 devices with just one change in your central Git repository.
- The Git repository contains a declarative description of the infrastructure you need in your specified environment and contains an automated process to make your environment match the described state.
- You can also use the Git repository as an audit trail of changes so that you can create processes based on Git flows such as review and approval for merging pull requests that implement configuration changes.
6.2. Creating GitOps applications on MicroShift
You can create a custom YAML configuration to deploy and manage applications in your MicroShift service. To install the necessary packages to run GitOps applications, follow the documentation in "Installing the GitOps Argo CD manifests from an RPM package".
Prerequisites
-
You installed the
microshift-gitopspackages. -
The Argo CD pods are running in the
openshift-gitopsnamespace.
Procedure
Create a YAML file and add your customized configurations for the application:
Example YAML for a
spring-petclinicapplicationkind: AppProject apiVersion: argoproj.io/v1alpha1 metadata: name: default namespace: openshift-gitops spec: clusterResourceWhitelist: - group: '*' kind: '*' destinations: - namespace: '*' server: '*' sourceRepos: - '*' --- kind: Application apiVersion: argoproj.io/v1alpha1 metadata: name: spring-petclinic namespace: openshift-gitops spec: destination: namespace: spring-petclinic server: https://kubernetes.default.svc project: default source: directory: recurse: true path: app repoURL: https://github.com/siamaksade/openshift-gitops-getting-started syncPolicy: automated: {} syncOptions: - CreateNamespace=true - ServerSideApply=trueTo deploy the applications defined in the YAML file, run the following command:
$ oc apply -f <my_app.yaml> 1
- 1
- Replace
<my_app.yaml>with the name of your application YAML.
Verification
To verify your application is deployed and synced, run the following command:
$ oc get applications -A
It might take a few minutes for the application to show the
Healthystatus.Example output
NAMESPACE NAME SYNC STATUS HEALTH STATUS openshift-gitops spring-petclinic Synced Healthy
Additional resources
6.3. Limitations of using the GitOps agent with MicroShift
GitOps with Argo CD for MicroShift has the following differences from the Red Hat OpenShift GitOps Operator:
-
The
gitops-operatorcomponent is not used with MicroShift. - To maintain the small resource use of MicroShift, the Argo CD web console is not available. You can use the Argo CD CLI.
- Because MicroShift is single-node, there is no multi-cluster support. Each instance of MicroShift is paired with a local GitOps agent.
-
The
oc adm must-gathercommand is not available in MicroShift.
6.4. Troubleshooting GitOps
If you have problems with your GitOps controller, you can use the OpenShift CLI (oc) tool.
6.4.1. Debugging GitOps with oc adm inspect
You can debug GitOps by using the OpenShift CLI (oc).
Prerequisites
-
The
occommand line tool is installed.
Procedure
Run the
oc adm inspectcommand when in the GitOps namespace:$ oc adm inspect ns/openshift-gitops
Example output
Gathering data for ns/openshift-gitops... W0501 20:34:35.978508 57625 util.go:118] the server doesn't have a resource type egressfirewalls, skipping the inspection W0501 20:34:35.980881 57625 util.go:118] the server doesn't have a resource type egressqoses, skipping the inspection W0501 20:34:36.040664 57625 util.go:118] the server doesn't have a resource type servicemonitors, skipping the inspection Wrote inspect data to inspect.local.2673575938140296280.
Next steps
-
If
oc adm inspectdid not provide the information you need, you can run an sos report.
