# Hello World - Deno A simple web app written in Deno. Follow the steps below to create the sample code and then deploy the app to your cluster. You can also download a working copy of the sample, by running the following commands: ```bash git clone https://github.com/knative/docs.git knative-docs cd knative-docs/code-samples/community/serving/helloworld-deno ``` ## Before you begin - A Kubernetes cluster with Knative installed. Follow the [Knative installation instructions](https://knative.dev/docs/install/) if you need to create one. - [Docker](https://www.docker.com) installed and running on your local machine, and a Docker Hub account configured (we'll use it for a container registry). ## Recreating the sample code 1. Create a new file named `deps.ts` and paste the following script: ```ts export { serve } from "https://deno.land/std@std@0.50.0/http/server.ts"; ``` 1. Create a new file named `main.ts` and paste the following script: ```ts import { serve } from "./deps.ts"; import "https://deno.land/x/dotenv/mod.ts"; const PORT = Deno.env.get('PORT') || 8080; const s = serve(`0.0.0.0:${PORT}`); const body = new TextEncoder().encode("Hello Deno\n"); console.log(`Server started on port ${PORT}`); for await (const req of s) { req.respond({ body }); } ``` 1. Create a new file named `Dockerfile` and copy the code block below into it. ```docker FROM hayd/alpine-deno:1.0.0-rc2 WORKDIR /app # These steps will be re-run upon each file change in your working directory: COPY . ./ # Added to ENTRYPOINT of base image. CMD ["run", "--allow-env", "--allow-net", "main.ts"] ``` 1. Create a new file, `service.yaml` and copy the following service definition into the file. Make sure to replace `{username}` with your Docker Hub username. ```yaml apiVersion: serving.knative.dev/v1 kind: Service metadata: name: helloworld-deno namespace: default spec: template: spec: containers: - image: docker.io/{username}/helloworld-deno ``` ## Building and deploying the sample Once you have recreated the sample code files (or used the files in the sample folder) you're ready to build and deploy the sample app. 1. Use Docker to build the sample code into a container. To build and push with Docker Hub, run these commands replacing `{username}` with your Docker Hub username: ```bash # Build and push the container on your local machine. docker buildx build --platform linux/arm64,linux/amd64 -t "{username}/helloworld-deno" --push . ``` 1. After the build has completed and the container is pushed to docker hub, you can deploy the app into your cluster. Ensure that the container image value in `service.yaml` matches the container you built in the previous step. Apply the configuration using `kubectl`: ```bash kubectl apply --filename service.yaml ``` 1. Now that your service is created, Knative performs the following steps: - Create a new immutable revision for this version of the app. - Network programming to create a route, ingress, service, and load balance for your app. - Automatically scale your pods up and down (including to zero active pods). 1. Run the following command to find the domain URL for your service: ```bash kubectl get ksvc helloworld-deno --output=custom-columns=NAME:.metadata.name,URL:.status.url ``` Example: ```bash NAME URL helloworld-deno http://helloworld-deno.default.1.2.3.4.sslip.io ``` 1. Now you can make a request to your app and see the result. Replace the URL below with the URL returned in the previous command. ```bash curl http://helloworld-deno.default.1.2.3.4.sslip.io ``` Example: ```bash curl http://helloworld-deno.default.1.2.3.4.sslip.io [1] "Hello R Sample v1!" ``` > Note: Add `-v` option to get more detail if the `curl` command failed. ## Removing the sample app deployment To remove the sample app from your cluster, delete the service record: ```bash kubectl delete --filename service.yaml ```