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:
-
Install the
kraft
CLI tool and a container runtime engine, e.g. Docker. -
Clone the
examples
repository andcd
into theexamples/http-go1.21/
directory:
git clone https://github.com/kraftcloud/examplescd 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:
# Set Unikraft Cloud access tokenexport UKC_TOKEN=token# Set metro to Frankfurt, DEexport UKC_METRO=fra0
When done, invoke the following command to deploy this application on Unikraft Cloud:
kraft cloud deploy -p 443:8080 .
The output shows the instance URL and other details:
[●] 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:
curl https://red-dew-jtk6yxk1.fra0.kraft.host
hello, world!
At any point in time, you can list information about the instance:
kraft cloud instance list
NAME FQDN STATE CREATED AT IMAGE MEMORY ARGS BOOT TIMEhttp-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:
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 serverKraftfile
: the Unikraft Cloud specificationDockerfile
: 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)}
spec: v0.6
runtime: base:latest
rootfs: ./Dockerfile
cmd: ["/server"]
FROM golang:1.21.3-bookworm AS build
WORKDIR /src
COPY ./server.go /src/server.go
RUN set -xe; \ go build \ -buildmode=pie \ -ldflags "-linkmode external -extldflags -static-pie" \ -tags netgo \ -o /server \ server.go \ ;
# This stage is optional but reduces overall image sizeFROM scratchCOPY --from=build /server /serverCOPY --from=build /lib/x86_64-linux-gnu/libc.so.6 /lib/x86_64-linux-gnu/COPY --from=build /lib64/ld-linux-x86-64.so.2 /lib64/
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 theDockerfile
. -
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 theKraftfile
and replace/server
with the path to the new executable. -
More extensive changes may require expanding the
Dockerfile
with additionalDockerfile
commands.
Learn More
Use the --help
option for detailed information on using Unikraft Cloud:
kraft cloud --help
Or visit the CLI Reference.