GitOps Workflow with Argo CD

20 MINUTE EXERCISE

In this lab you will learn about deploying and managing Kubernetes resources using a GitOps tool.

GitOps Methodology

GitOps is a set of practices that leverages Git workflows to manage infrastructure and application configurations. By using Git repositories as the source of truth, it allows the DevOps team to store the entire state of the cluster configuration in Git so that the trail of changes are visible and auditable.

GitOps simplifies the propagation of infrastructure and application configuration changes across multiple clusters by defining your infrastructure and applications definitions as “code”.

Ensure that the clusters have similar states for configuration, monitoring, or storage.
Recover or recreate clusters from a known state.
Create clusters with a known state.
Apply or revert configuration changes to multiple clusters.
Associate templated configuration with different environments.

Gitops is also beneficial for application configuration management. It ensures consistency in applications when you deploy them to different clusters in different environments, like development, stage, and production.

Promote applications across clusters, from stage to production.
Apply or revert application changes to multiple OpenShift clusters.

OpenShift provides the flexibility to choose when and how you integrate GitOps methodology into your business practices and pipelines.

Export OpenShift Resources

First, you need to export the project resources from OpenShift.

In your Workspace, click on 'Terminal' → 'Run Task…' → 'GitOps - Export Coolstore'

A terminal should be opened with the following output:

--- Export Kubernetes resources for GitOps from my-project%USER_ID% to cn-project%USER_ID% ---
Exporting resources for inventory-coolstore...
Exporting resources for catalog-coolstore...
Exporting resources for gateway-coolstore...
Exporting resources for web-coolstore...
--- Kubernetes resources has been exported! ---

This operation exports the project resources (deploymentconfig, route, secret, service) and cleans them up. As a result, you should have all resources in YAML files under the /projects/workshop/labs/gitops folder.

Create a Git Repository for Your Configuration

The next step is to store all Kubernetes/OpenShift resources in a source code repository.

In your Git Repository, create a new Repository as follows:

Table 1. GitOps Repository
Parameter	Value
Owner*	user%USER_ID%
Repository Name*	gitops-cn-project

Push the Configuration of Inventory Service into the Git Repository

Now that you have a Git repository for the configuration, you should push the exported Inventory configuration into it.

In your Workspace, click on 'Terminal' → 'Run Task…' → 'GitOps - Commit Inventory'

A terminal should be opened with the following output:

Initialized empty Git repository in /projects/workshop/labs/gitops/.git/
[master (root-commit) b066fd2] Initial Inventory GitOps
 6 files changed, 251 insertions(+)
 create mode 100644 inventory-coolstore-configmap.yaml
 create mode 100644 inventory-coolstore-deployment.yaml
 create mode 100644 inventory-coolstore-deploymentconfig.yaml
 create mode 100644 inventory-coolstore-route.yaml
 create mode 100644 inventory-coolstore-secret.yaml
 create mode 100644 inventory-coolstore-service.yaml
Enumerating objects: 8, done.
Counting objects: 100% (8/8), done.
Delta compression using up to 16 threads.
Compressing objects: 100% (7/7), done.
Writing objects: 100% (8/8), 2.47 KiB | 2.47 MiB/s, done.
Total 8 (delta 1), reused 0 (delta 0)
remote: . Processing 1 references
remote: Processed 1 references in total
To http://gitea-server.gitea.svc:3000/user%USER_ID%/gitops-cn-project.git
 * [new branch]      master -> master

Once done, in Git Repository, refresh the page of your 'gitops-cn-project' repository. You should see the files in the repository.

What is Argo CD?

Argo CD is a declarative, GitOps continuous delivery tool for Kubernetes.

It follows the GitOps pattern of using Git repositories as the source of truth for defining the desired application state.

It automates the deployment of the desired application states in the specified target environments. Application deployments can track updates to branches, tags, or pinned to a specific version of manifests at a Git commit.

Log in to Argo CD

Click on the 'Developer GitOps' button below

Then login via OpenShift as user%USER_ID%/%OPENSHIFT_PASSWORD%, click on 'Allow selected permissions'

Once completed, you will be redirected to the following page.

Add your Newly Created GitOps Repository

In Argo CD, Select the 'Configuration menu' then click on 'Repositories'

Click on 'CONNECT REPO USING HTTPS' and enter the following:

Table 2. Repository Configuration
Parameter	Value
Type	git
Repository URL	http://gitea-server.gitea.svc:3000/user%USER_ID%/gitops-cn-project.git

Finally, Click on 'CONNECT'.

Your GitOps repository is now added to Argo CD.

Create a GitOps Application

In Argo CD, Select the 'Application menu' then click on '+ New App' and enter the following details:

Table 3. Application Configuration
Section	Parameter	Value
GENERAL	Application Name	cn-project%USER_ID%
GENERAL	Project	default
GENERAL	SYNC POLICY	Manual
SOURCE	Repository URL	http://gitea-server.gitea.svc:3000/user%USER_ID%/gitops-cn-project.git
SOURCE	Revision	HEAD
SOURCE	Path	. (dot)
DESTINATION	Cluster	https://kubernetes.default.svc
DESTINATION	Namespace	cn-project%USER_ID%
ALL OTHER SECTIONS	*	leave them empty/by default

Finally, Click on 'CREATE'.

Your Coolstore Application has been created in Argo CD.

The application status is initially in yellow OutOfSync state since the application has yet to be deployed into cn-project%USER_ID% OpenShift project, and no Kubernetes resources have been created.

Deploy a Resource on OpenShift

In Argo CD, click on the 3 dots menu at the left of the 'CM Inventory' resource then select 'Sync'

Then click on the 'Synchonize' button. Now the ConfigMap of Inventory has been deployed and synchronized with your environment.

In the OpenShift Web Console, from the Developer view, select your 'cn-project%USER_ID%' and click on 'Config Maps'. You should find the resource you just deployed via Argo CD.

Recover from a Configuration Drift

A Configuration Drift is a term used whenever someone makes ad hoc changes in a (production) environment which are not recorded or tracked.

In the OpenShift Web Console, from the Developer view, select your 'cn-project%USER_ID%' and click on 'Config Maps' → 'CM inventory' → 'YAML'.

Add the following line in your configuration then click on 'Save'

simple.adhoc.change=This is a configuration drift

OpenShift - CM Inventory Configuration Drift

In Argo CD, the 'CM Inventory' resource is no longer synchronized. Click on it then select 'Diff' tab and check 'Compact diff'.

Argo CD detects automatically your modification which is not compliant with the desired state described in Git - the source of truth. Indeed, from now, when you want to change the configuration, you will have to update the Git Repository first to record and track your changes to avoid configuration drifts.

You can leave the configuration drift as it is. You will fix it in the next lab.

Push the Coolstore Configuration to the Git Repository

To prepare the next lab, you need to push the remaining coolstore application configuration to the Git repository.

In your Workspace, click on 'Terminal' → 'Run Task…' → 'GitOps - Commit Coolstore'

A terminal should be opened with the following output:

Reinitialized existing Git repository in /projects/gitops/.git/
[master 7d5e824] Initial Coolstore GitOps
 18 files changed, 612 insertions(+)
 [...]
Enumerating objects: 15, done.
Counting objects: 100% (15/15), done.
Delta compression using up to 16 threads.
Compressing objects: 100% (14/14), done.
Writing objects: 100% (14/14), 3.80 KiB | 3.80 MiB/s, done.
Total 14 (delta 8), reused 0 (delta 0)
remote: . Processing 1 references
remote: Processed 1 references in total
To http://gitea-server.gitea.svc:3000/user%USER_ID%/gitops-cn-project.git
   d35eafe..7d5e824  master -> master

Once done, in your Git Repository, refresh the page of your 'gitops-cn-project' repository. You should see the project files in the repository.

In Argo CD, the application status is once again in yellow OutOfSync state since the Catalog, Gateway and Web services have not yet been deployed into cn-project%USER_ID% OpenShift project.

You are going to fix it in the next lab.

Well done! You are ready for the next lab.