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Unikraft Cloud

Run a Go app

In this guide we create and deploy a simple Go-based HTTP web server. To run this example, follow these steps:

  1. Install the kraft CLI tool and a container runtime engine, e.g. Docker.

  2. Clone the examples repository and cd into the examples/http-go1.21/ directory:

Terminal window
git clone https://github.com/kraftcloud/examples
cd examples/http-go1.21/

Make sure to log into Unikraft Cloud by setting your token and a metro close to you. We use fra0 (Frankfurt, 🇩🇪) in this guide:

Terminal window
# Set Unikraft Cloud access token
export UKC_TOKEN=token
# Set metro to Frankfurt, DE
export UKC_METRO=fra0

When done, invoke the following command to deploy this application on Unikraft Cloud:

Terminal window
kraft cloud deploy -p 443:8080 .

The output shows the instance URL and other details:

Terminal window
[●] Deployed successfully!
 │
 ├────────── name: http-go121-9a2wv
 ├────────── uuid: 8bb34040-9434-4a28-bd1e-c24ee532e2da
 ├───────── state: running
 ├─────────── url: https://red-dew-jtk6yxk1.fra0.kraft.host
 ├───────── image: http-go121@sha256:b16d61bb7898e764d8c11ab5a0b995e8c25a25b5ff89e161fc994ebf25a75680
 ├───── boot time: 11.05 ms
 ├──────── memory: 128 MiB
 ├─────── service: red-dew-jtk6yxk1
 ├── private fqdn: http-go121-9a2wv.internal
 ├──── private ip: 172.16.3.3
 └────────── args: /server

In this case, the instance name is http-go121-9a2wv and the URL is https://red-dew-jtk6yxk1.fra0.kraft.host. They are different for each run.

Use curl to query the Unikraft Cloud instance of the Lua-based HTTP web server:

Terminal window
curl https://red-dew-jtk6yxk1.fra0.kraft.host
hello, world!

At any point in time, you can list information about the instance:

Terminal window
kraft cloud instance list
NAME              FQDN                               STATE    CREATED AT    IMAGE                                         MEMORY   ARGS  BOOT TIME
http-go121-9a2wv  red-dew-jtk6yxk1.fra0.kraft.host  running  1 minute ago  alex/http-go121@sha256:b16d61bb7898e764d...  128 MiB        9324us

When done, you can remove the instance:

Terminal window
kraft cloud instance delete http-go121-9a2wv

Customize your Application

To customize the application, update the files in the repository, listed below:

  • server.go: the actual Go HTTP server
  • Kraftfile: the Unikraft Cloud specification
  • Dockerfile: the Docker-specified application filesystem
package main


import (
  "fmt"
  "net/http"
)


func hello(w http.ResponseWriter, req *http.Request) {
  fmt.Fprintf(w, "hello, world!\n")
}


func main() {
  http.HandleFunc("/", hello)
  fmt.Println("Listening on :8080...")
  http.ListenAndServe(":8080", nil)
}

The following options are available for customizing the application:

  • If only updating the implementation in the server.go source file, no other change is required.

  • If new files are added, these have to be copied in the application filesystem, using the COPY command in the Dockerfile.

  • If new source code files are added, they have to be built using the corresponding go build command.

  • If a new executable is built, update the cmd line in the Kraftfile and replace /server with the path to the new executable.

  • More extensive changes may require expanding the Dockerfile with additional Dockerfile commands.

Learn More

Use the --help option for detailed information on using Unikraft Cloud:

Terminal window
kraft cloud --help

Or visit the CLI Reference.