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Gain insights into building serverless applications on Kubernetes, using Knative, Tekton for CI/CD pipelines, and integrating GitHub for automated builds and deployments through GitHub events.

How to Build a Serverless App Platform on Kubernetes-01.png

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Install Knative

​​Businesses are modernizing and adopting multi-cloud approaches to deliver services. This shift in application deployment has given rise to containerization and Kubernetes for the deployment, management, and scaling of containerized applications. 

This course introduces you to serverless computing and shows you how to build serverless applications using Knative. It teaches CI/CD using Tekton and shows you how to build pipelines triggered by GitHub events. You will create a pipeline that builds container images using Build and, later, Cloud Native Buildpacks. 

In the last part of the course, you will build a web application that integrates with GitHub using a GitHub App, and triggers application build and deployment in response to GitHub events.

Building a Serverless App Platform on Kubernetes


We'll create a new Pipeline that compiles source code to OCI images using Cloud Native Buildpacks. First, we need a Task that compiles the downloaded source code to an OCI image and then pushes the image to a registry. We'll install the Task from the Tekton Catalog. **Tekton Catalog** is a Git repository of community-contributed Tekton entities (Tasks, Pipelines, and so on) ready for use in our Pipelines. We can access Tekton Catalog through a web interface known as Tekton Hub.

# Install the buildpacks

We need to first install the buildpacks Task from Tekton Hub by running the command given in the `1_installBuildpack.sh` file.



This Task builds source code into a container image. To do this, it uses builders to run buildpacks against our application source. A **builder** is an image that contains an ordered combination of buildpacks and all the components necessary to execute a build.

The Task expects some required parameters and workspaces and returns the digest of the [built image](https://hub.tekton.dev/tekton/task/buildpacks). 

# Install the git-clone Task
Install the [git-clone task](https://hub.tekton.dev/tekton/task/git-clone) on Tekton Catalog that will be used to clone the repository. Run the command given in the `2_gitcloneTask.sh` file to install this task.

# Create a persistent volume claim (PVC)
The next step is to create the persistent volume claim (PVC) that the Pipeline will use. Run the command given in the `3_PVC.sh` file to create the PVC.

# Creating the Pipeline
Now that the buildpacks and git-clone Tasks are installed, alongside the PVC that will be used later, let's move on to creating the Pipeline and the necessary Tekton Trigger entities.

We'll create the Pipeline by using the manifest given in the `pipeline-buildpacks-deploy.yaml` file.


In the new `buildpacks-deploy` pipeline, we specified workspaces used by the buildpacks and git-clone Tasks. The `BUILDER_IMAGE` params specify the builder image needed to build the application. The default value uses a Paketo buildpack, which uses Ubuntu bionic as the base image and contains buildpacks for Java, .NET Core, Node.js, Go, Ruby, NGINX, and Procfile. There are other builders that we can use as well. The following are the suggested builders from the Cloud Native Buildpacks project:

- **gcr**.**io/buildpacks/builder:v1:** This contains the Ubuntu 18 base image with buildpacks for .NET, Go, Java, Node.js, and Python.

- **heroku/buildpacks:18:** This is the base builder for the Heroku-18 stack and is based on the ubuntu:18.04 base image.
- **heroku/buildpacks:20:** This is the base builder for the Heroku-20 stack and is based on the ubuntu:20.04 base image.
- **paketobuildpacks/builder:base:** This contains the Ubuntu bionic base image with buildpacks for Java, .NET Core, Node.js, Go, Ruby, NGINX, and Procfile.
- **paketobuildpacks/builder:full:** This contains the Ubuntu bionic base image with buildpacks for Java, .NET Core, Node.js, Go, PHP, Ruby, Apache HTTPD, NGINX, and Procfile.
- **paketobuildpacks/builder:tiny:** This contains a tiny base image (bionic build image, distroless-like run image) with buildpacks for Java Native Image and Go.

## Tekton Triggers

When an event is triggered, we need to configure the Tekton Trigger to use the `buildpacks-deploy` pipeline. For this purpose, the manifest is given in the `trigger-template-buildpacks.yaml` file. Replace `<REGISTRY>/<REGISTRY_USERNAME>` with our #key# registry server and username: For example, docker.io/Dockerhub's username #key#.


The Trigger Template specifies two workspaces, `cache-workspace` and `source-workspace`, which use the `tekton-workspace-pvc` PVC created earlier. It also specifies a **source-directory** parameter that will be used by the buildpacks Task to determine which path in the repository contains the source code to build. The default value will be used for this chapter, but we'll get to use it in the mini-project where it can be specified from the web application we'll build.

We'll use the same TriggerBinding and EventListener from the previous chapter. However, we'll modify the EventListener to use the `buildpacks-deploy` Trigger Template. Open the `trigger-listener.yaml` file and change the template reference from `build-deploy` to `buildpacks-deploy`. We'll find the `template` field on line 24.

Now, run the command below to apply the changes.

```shell
kubectl apply -f pipeline-buildpacks-deploy.yaml \
-f trigger-template-buildpacks.yaml \
-f trigger-listener.yaml
```

> **Note:** We should replace the `<REGISTRY>/<REGISTRY_USERNAME>` in the `trigger-template-buildpacks.yaml` file and also replace `build-deploy` with `buildpacks-deploy` (only on line 24) in the `trigger-listener.yaml` file before clicking the "Run" button.
>
>To run all the commands written in a `.sh` file, just type `./file-name.sh` in the terminal.




Let's create a Tekton Pipeline by using Buildpacks.

Before We Begin

Introduction

Using Knative to Run Serverless Applications

CI/CD Using Tekton

Automate Tekton Pipeline Execution

Build Container Images without Dockerfile

Build the UI For the Platform

Using Buildpacks in Tekton Pipelines