mirror of https://github.com/knative/docs.git
214 lines
6.2 KiB
Markdown
214 lines
6.2 KiB
Markdown
# Hello World - Go
|
|
|
|
This guide describes the steps required to to create the `helloworld-go` sample app
|
|
and deploy it to your cluster.
|
|
The sample app reads a `TARGET` environment variable, and prints `Hello ${TARGET}!`.
|
|
If `TARGET` is not specified, `World` is used as the default value.
|
|
|
|
## Prerequisites
|
|
|
|
You will need:
|
|
|
|
- A Kubernetes cluster with Knative installed and DNS configured. See
|
|
[Install Knative Serving](https://knative.dev/docs/install/serving/install-serving-with-yaml).
|
|
- [Docker](https://www.docker.com) installed and running on your local machine, and a Docker Hub account configured.
|
|
- Optional: You can use the Knative CLI client [`kn`](https://github.com/knative/client/releases) to simplify resource creation and deployment. Alternatively, you can use `kubectl` to apply resource files directly.
|
|
|
|
## Building
|
|
|
|
Create a basic web server which listens on port 8080, by copying the following code into a new file named `helloworld.go`:
|
|
|
|
```go
|
|
package main
|
|
|
|
import (
|
|
"fmt"
|
|
"log"
|
|
"net/http"
|
|
"os"
|
|
)
|
|
|
|
func handler(w http.ResponseWriter, r *http.Request) {
|
|
log.Print("helloworld: received a request")
|
|
target := os.Getenv("TARGET")
|
|
if target == "" {
|
|
target = "World"
|
|
}
|
|
fmt.Fprintf(w, "Hello %s!\n", target)
|
|
}
|
|
|
|
func main() {
|
|
log.Print("helloworld: starting server...")
|
|
|
|
http.HandleFunc("/", handler)
|
|
|
|
port := os.Getenv("PORT")
|
|
if port == "" {
|
|
port = "8080"
|
|
}
|
|
|
|
log.Printf("helloworld: listening on port %s", port)
|
|
log.Fatal(http.ListenAndServe(fmt.Sprintf(":%s", port), nil))
|
|
}
|
|
```
|
|
|
|
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/serving/hello-world/helloworld-go
|
|
```
|
|
|
|
|
|
Navigate to your project directory and copy the following code into a new file named `Dockerfile`:
|
|
|
|
```dockerfile
|
|
# Use the official Golang image to create a build artifact.
|
|
# This is based on Debian and sets the GOPATH to /go.
|
|
FROM golang:latest AS builder
|
|
|
|
ARG TARGETOS
|
|
ARG TARGETARCH
|
|
|
|
# Create and change to the app directory.
|
|
WORKDIR /app
|
|
|
|
# Copy local code to the container image.
|
|
COPY . ./
|
|
|
|
# Install dependencies and tidy up the go.mod and go.sum files.
|
|
RUN go mod tidy
|
|
|
|
# Build the binary.
|
|
# -mod=readonly ensures immutable go.mod and go.sum in container builds.
|
|
RUN CGO_ENABLED=0 GOOS=${TARGETOS} GOARCH=${TARGETARCH} go build -mod=readonly -v -o server
|
|
|
|
# Use the official Alpine image for a lean production container.
|
|
# https://hub.docker.com/_/alpine
|
|
# https://docs.docker.com/develop/develop-images/multistage-build/#use-multi-stage-builds
|
|
FROM alpine:3
|
|
RUN apk add --no-cache ca-certificates
|
|
|
|
# Copy the binary to the production image from the builder stage.
|
|
COPY --from=builder /app/server /server
|
|
|
|
# Run the web service on container startup.
|
|
CMD ["/server"]
|
|
```
|
|
|
|
Use the Go tool to create a [`go.mod`](https://github.com/golang/go/wiki/Modules#gomod) manifest.
|
|
|
|
```bash
|
|
go mod init github.com/knative/docs/code-samples/serving/hello-world/helloworld-go
|
|
```
|
|
|
|
## Deploying
|
|
|
|
### Build and Push the docker image
|
|
|
|
To build the sample code into a container, and push using Docker Hub, enter the following commands and replace `{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-go" --push .
|
|
```
|
|
|
|
### Deploying to knative
|
|
After the build has completed and the container is pushed to docker hub, you can deploy the app into your cluster. Choose one of the following methods:
|
|
|
|
### yaml
|
|
|
|
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-go
|
|
namespace: default
|
|
spec:
|
|
template:
|
|
spec:
|
|
containers:
|
|
- image: docker.io/{username}/helloworld-go
|
|
env:
|
|
- name: TARGET
|
|
value: "Go Sample v1"
|
|
```
|
|
|
|
1. Check that the container image value in the `service.yaml` file matches the container you built in the previous step.
|
|
|
|
1. Apply the configuration using `kubectl`:
|
|
|
|
```bash
|
|
kubectl apply --filename service.yaml
|
|
```
|
|
After your service is created, Knative will perform 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-go --output=custom-columns=NAME:.metadata.name,URL:.status.url
|
|
```
|
|
|
|
Example:
|
|
```bash
|
|
NAME URL
|
|
helloworld-go http://helloworld-go.default.1.2.3.4.xip.io
|
|
```
|
|
|
|
|
|
### kn
|
|
|
|
1. Use `kn` to deploy the service:
|
|
|
|
```bash
|
|
kn service create helloworld-go --image=docker.io/{username}/helloworld-go --env TARGET="Go Sample v1"
|
|
```
|
|
|
|
You should see output like this:
|
|
```bash
|
|
Creating service 'helloworld-go' in namespace 'default':
|
|
0.031s The Configuration is still working to reflect the latest desired specification.
|
|
0.051s The Route is still working to reflect the latest desired specification.
|
|
0.076s Configuration "helloworld-go" is waiting for a Revision to become ready.
|
|
15.694s ...
|
|
15.738s Ingress has not yet been reconciled.
|
|
15.784s Waiting for Envoys to receive Endpoints data.
|
|
16.066s Waiting for load balancer to be ready
|
|
16.237s Ready to serve.
|
|
|
|
Service 'helloworld-go' created to latest revision 'helloworld-go-jjzgd-1' is available at URL: http://helloworld-go.default.1.2.3.4.xip.io
|
|
```
|
|
|
|
1. You can then access your service through the resulting URL.
|
|
|
|
|
|
|
|
## Verification
|
|
|
|
Now you can make a request to your app and see the result. Replace the following URL with the URL returned in the previous command.
|
|
|
|
```bash
|
|
curl http://helloworld-go.default.1.2.3.4.sslip.io
|
|
Hello Go Sample v1!
|
|
```
|
|
|
|
> Note: Add `-v` option to get more detail if the `curl` command failed.
|
|
|
|
## Removing
|
|
|
|
To remove the sample app from your cluster, delete the service record:
|
|
|
|
### kubectl
|
|
```bash
|
|
kubectl delete --filename service.yaml
|
|
```
|
|
|
|
### kn
|
|
```bash
|
|
kn service delete helloworld-go
|
|
```
|