Merge pull request #1434 from Felixnoo/sync-argo

Sync argo

content/en/blogs/argo-cd-a-tool-for-devops.md

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+---
+title: 'Argo CD: A Tool for Kubernetes DevOps'
+keywords: Kubernetes, KubeSphere, DevOps, Argo CD, GitOps
+description: A Quick Introduction about Argo CD.
+tag: 'Kubernetes, KubeSphere, DevOps, Argo CD, GitOps'
+createTime: '2021-04-16'
+author: 'Shaowen Chen, Felix, Sherlock'
+snapshot: '/images/blogs/en/argo-cd-a-tool-for-devops/argo-schematics.png'
+---
+
+In this post, I'll show you how Argo CD betters Kubernetes DevOps process. Before we begin, let's look at some background information.
+
+## Argo CD Capability
+
+### GitOps: The origin
+
+As you may already know, Weaveworks published a post titled [GitOps - Operations by Pull Request](https://www.weave.works/blog/gitops-operations-by-pull-request) in 2017. Alexis, the author, introduced a way of deployment by using Git as source of truth.
+
+In GitOps practices, we need to define and manage software infrastructures in Git repositories. Software infrastructures involve not only IaaS and Kubernetes but also applications. Everyone can make modifications to software infrastructures by submitting a Pull Request, and an automated program will perform those modifications.
+
+Thus, everyone will be able to focus on developing new features instead of worrying about operation and maintenance including installation, modification, and migration.
+
+### Argo CD: GitOps coming true
+
+Argo CD is a GitOps continuous delivery (CD) tool on top of Kubernetes. Here is the schematic diagram from the Argo CD community.
+
+![argo-schematics](/images/blogs/en/argo-cd-a-tool-for-devops/argo-schematics.png)
+
+You can see from the diagram that:
+
+1. Argo CD pulls application configurations from Git Repo and deploys applications in Kubernetes clusters.
+2. If someone wants to add a new feature, he or she just needs to submit a Pull Request to Git Repo to modify application deployment configurations. Then, wait for merging.
+3. Once the Pull Request gets merged, Argo CD will run an update per Webhook triggers.
+4. Applications updated and notifications sent.
+
+To sum it up, automated operation and maintenance and continuous delivery. Simple and easy to understand, right?
+
+### Argo CD: Powerful and extensible
+
+The above functions will be able to cover ordinary Kubernetes operation and maintenance. What if things get more complicated? We cannot escape from scenarios involving multi-cloud, multi-platform, and multi-middleware.
+
+![argocd-2](/images/blogs/en/argo-cd-a-tool-for-devops/argocd-2.png)
+
+Argo CD defines four components in its processing logic:
+
+- [Event Source](https://argoproj.github.io/argo-events/concepts/event_source/): An `EventSource` defines the configurations required to consume events from external sources.
+- [Sensor](https://argoproj.github.io/argo-events/concepts/sensor/): It listens to events on the eventbus and acts as an event dependency manager to resolve and execute the triggers.
+- [Eventbus](https://argoproj.github.io/argo-events/concepts/eventbus/): It acts as the transport layer of Argo-Events by connecting the event-sources and sensors.
+- [Trigger](https://argoproj.github.io/argo-events/concepts/trigger/): A Trigger is the resource/workload executed by the sensor once the event dependencies are resolved.
+
+For more information, see [Architecture](https://argoproj.github.io/argo-events/concepts/architecture/).
+
+As for operation and maintenance folks, you just need to focus on two aspects:
+
+- Events Argo CD can process: AMQP, AWS SNS, AWS SQS, Cron Schedules, GCP PubSub, GitHub, GitLab, HDFS, File Based Events, Kafka, Minio, NATS, MQTT, K8s Resources, Slack, NetApp StorageGrid, Webhooks, Stripe, NSQ, Emitter, Redis, and Azure Events Hub.
+- Actions Argo CD can perform: Argo Workflows, Standard K8s Objects, HTTP Requests, AWS Lambda, NATS Messages, Kafka Messages, Slack Notifications, Argo Rollouts CR, Custom/Build Your Own Triggers, and Apache OpenWhisk.
+
+## Argo CD on Kubernetes
+
+I'll use Kubernetes v1.18.3 to deploy Argo CD.
+
+### Step 1: Deploy Argo CD
+
+1. Run the following command to create a namespace. Name it argocd.
+
+   ```bash
+   kubectl create namespace argocd
+   ```
+
+2. Run the following command to deploy Argo CD.
+
+   ```bash
+   kubectl apply -n argocd -f https://raw.githubusercontent.com/argoproj/argo-cd/v1.8.3/manifests/install.yaml
+   ```
+
+   {{< notice note >}}
+
+   The Argo CD community also provides an HA deployment method by running the command `kubectl apply -n argocd -f https://raw.githubusercontent.com/argoproj/argo-cd/v1.8.3/manifests/ha/install.yaml`. It's for deployment in production.
+
+   {{</ notice >}}
+
+3. Run the following command to set the Service type to NodePort.
+
+   ```bash
+   kubectl patch svc argocd-server -p '{"spec": {"type": "NodePort"}}' -n argocd
+   ```
+
+4. Run the following command to view all the Services in the namespace `argocd`.
+
+   ```bash
+   $ kubectl -n argocd get svc
+   
+   NAME                    TYPE        CLUSTER-IP      EXTERNAL-IP   PORT(S)                      AGE
+   argocd-dex-server       ClusterIP   10.233.34.191   <none>        5556/TCP,5557/TCP,5558/TCP   5m37s
+   argocd-metrics          ClusterIP   10.233.54.3     <none>        8082/TCP                     5m36s
+   argocd-redis            ClusterIP   10.233.18.86    <none>        6379/TCP                     5m36s
+   argocd-repo-server      ClusterIP   10.233.3.171    <none>        8081/TCP,8084/TCP            5m36s
+   argocd-server           NodePort    10.233.61.3     <none>        80:31808/TCP,443:30992/TCP   5m36s
+   argocd-server-metrics   ClusterIP   10.233.36.228   <none>        8083/TCP                     5m36s
+   ```
+
+### Step 2: Log in to Argo CD
+
+1. Run the following command to get the admin account's password.
+
+   ```bash
+   $ kubectl get pod -n argocd |grep argocd-server
+      
+   argocd-server-7d597d9bcd-6nzct        1/1     Running   0          22m
+   ```
+
+   The Pod ID is the password, namely, `argocd-server-7d597d9bcd-6nzct`.
+
+2. Access Argo CD Web page through `http://{HOST_IP}:31808`, and use `admin/argocd-server-7d597d9bcd-6nzct` as account and password to log in.
+
+   ![argocd-page](/images/blogs/en/argo-cd-a-tool-for-devops/argocd-page.png)
+
+   ![argocd-log-in](/images/blogs/en/argo-cd-a-tool-for-devops/argocd-log-in.png)
+
+### Step 3: Install CLI tool
+
+Let's use Linux as an example.
+
+1. Run the following commands to download CLI tool and make it executable.
+
+   ```bash
+   curl -sSL -o /usr/local/bin/argocd https://github.com/argoproj/argo-cd/releases/download/v1.8.3/argocd-linux-amd64
+   chmod +x /usr/local/bin/argocd
+   ```
+
+2. Run the following command to use the CLI tool to log in to the Argo CD running on your Kubernetes cluster. Make sure you replace `HOST_IP` with your host IP address.
+
+   ```bash
+   $ argocd login {HOST_IP}:31808 --username admin --password argocd-server-7d597d9bcd-6nzct
+   
+   'admin' logged in successfully
+   Context '{HOST_IP}:31808' updated
+   ```
+
+3. You can use the following command to update the admin password to `password` for your convenience.
+
+   ```bash
+   $ argocd account update-password --account admin --current-password argocd-server-7d597d9bcd-6nzct --new-password password
+   
+   Password updated
+   Context '{HOST_IP}:31808' updated
+   ```
+
+### Step 4: Create an application
+
+We surely can create an application through the Web UI, but let's use the CLI tool here so that you can better understand Argo CD by using the commands below.
+
+1. Run the following command to create an application.
+
+   ```bash
+   argocd app create guestbook --repo https://github.com/argoproj/argocd-example-apps.git --path guestbook --dest-server https://kubernetes.default.svc --dest-namespace default
+   ```
+
+   As for the flags in the command:
+
+   - `--repo`: specify the Git repository.
+   - `--path`: specify the relative path of the deployment files in the Git repository.
+   - `--dest-server`: address for accessing the cluster.
+   - `--dest-namespace`: namespace for deploying the application.
+
+   If you go to the directory `https://github.com/argoproj/argocd-example-apps/tree/master/guestbook`, you can find two YAML files for Deployment and Service respectively.
+
+2. After a while, you can view the service created shown on the Argo CD web page.
+
+   ![argocd-service](/images/blogs/en/argo-cd-a-tool-for-devops/argocd-service.png)
+
+3. Click it to see its details. You can also click the icon in the upper right corner to view its topology diagram.
+
+   ![argocd-topology](/images/blogs/en/argo-cd-a-tool-for-devops//argocd-topology.png)
+
+4. Run the following command to see the Services created.
+
+   ```bash
+   $ kubectl get all -n default
+   
+   NAME                                READY   STATUS    RESTARTS   AGE
+   pod/guestbook-ui-65b878495d-wjmxh   1/1     Running   0          60s
+   
+   NAME                   TYPE        CLUSTER-IP      EXTERNAL-IP   PORT(S)   AGE
+   service/guestbook-ui   ClusterIP   10.233.55.230   <none>        80/TCP    61s
+   service/kubernetes     ClusterIP   10.233.0.1      <none>        443/TCP   12d
+   
+   NAME                           READY   UP-TO-DATE   AVAILABLE   AGE
+   deployment.apps/guestbook-ui   1/1     1            1           60s
+   
+   NAME                                      DESIRED   CURRENT   READY   AGE
+   replicaset.apps/guestbook-ui-65b878495d   1         1         1       60s
+   ```
+
+5. Now, run the following command to delete the application. Argo CD will delete the application from its records, and relevant workloads will also be deleted in Kubernetes.
+
+   ```
+   argocd app delete guestbook
+   ```
+
+## Recap
+
+This blog walks you through the basic functions of Argo CD. I guess you have had a better understanding through the above demonstration about how to deploy Argo CD and how to create an application with it.
+
+As a matter of fact, Argo CD functionality goes beyond this blog. Argo CD can also realize functions such as synchronizing modifications in Git repository to make updates in Kubernetes and automatically trigger updates after image modifications. As you can see from the above schematic diagram, various needs for automated deployment can be met through Event Source and Trigger.
+
+Last but not the least, when updating Kubernetes, Argo CD also supports various resource description methods, including Kustomize, Helm, Ksonnet, Yaml, Json, and customized extension. Wouldn't that make our life easier in using Kubernetes?
+
+## See Also
+
+- [Argo CD website](https://argoproj.github.io/argo-cd/)
+- [Argo CD Git Repo](https://github.com/argoproj/argo-cd/)