This guide explains how to create and deploy a Spring Boot web server. To run this example, follow these steps:

1. Install the CLI. Use the unikraft CLI or the legacy kraft CLI. You need a BuildKit builder. The easiest way to get one is via Docker. Alternatively, you can also directly set up and use BuildKit, see the quick start.

   Note: The unikraft CLI is the current standard, while kraft is the legacy version. Choose one of the CLIs below and only run the commands associated with it for the rest of this guide.

2. Clone the examples repository and cd into the examples/httpserver-java17-springboot/ directory:

   git clone https://github.com/unikraft-cloud/examples
   cd examples/httpserver-java17-springboot/

Make sure to log into Unikraft Cloud and pick a metro close to you. This guide uses fra (Frankfurt, 🇩🇪):

Using the unikraft CLI (Recommended)

unikraft login

or

Using the legacy kraft CLI

# Set Unikraft Cloud access token
export UKC_TOKEN=token
# Set metro to Frankfurt, DE
export UKC_METRO=fra

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

Using the unikraft CLI (Recommended)

unikraft build . --output <my-org>/httpserver-java17-springboot:latest
unikraft run --metro fra \
  -m 1G \
  -p 443:8080/tls+http \
  --scale-to-zero policy=idle,cooldown-time=1000,stateful=true \
  --image <my-org>/httpserver-java17-springboot:latest

or

Using the legacy kraft CLI

kraft cloud deploy \
  -M 1Gi \
  -p 443:8080/tls+http \
  --scale-to-zero idle \
  --scale-to-zero-stateful \
  --scale-to-zero-cooldown 1s \
  .

The output shows the instance address and other details:

Using the unikraft CLI (Recommended)

metro:        fra
name:         httpserver-java17-springboot-qseeo
uuid:         b081166d-a2a0-43af-982d-1aa17f06b5c4
state:        starting
image:        <my-org>/httpserver-java17-springboot
resources:
  memory:     1024MiB
  vcpus:      1
service:
  uuid:       04f5b3ce-0aae-a50a-9d58-e6fa618b2cdc
  name:       long-dust-si7xsngk
  domains:
  - fqdn:     long-dust-si7xsngk.fra.unikraft.app
networks:
- uuid:       4bde3abf-faf8-3a14-ceb9-bc05e646dfac
  private-ip: 10.0.6.2
  mac:        12:b0:eb:ad:60:a2
timestamps:
  created:    just now

or

Using the legacy kraft CLI

[●] Deployed successfully!
 │
 ├───────── name: httpserver-java17-springboot-qseeo
 ├───────── uuid: b081166d-a2a0-43af-982d-1aa17f06b5c4
 ├──────── metro: https://api.fra.unikraft.cloud/v1
 ├──────── state: starting
 ├─────── domain: https://long-dust-si7xsngk.fra.unikraft.app
 ├──────── image: oci://unikraft.io/<my-org>/httpserver-java17-springboot@sha256:cc2f2ad18ce8e36b8e8f4debee096fef7b0bb8b47762575a2ba5a9de8199c64a
 ├─────── memory: 1024 MiB
 ├────── service: long-dust-si7xsngk
 ├─ private fqdn: httpserver-java17-springboot-qseeo.internal
 └─── private ip: 10.0.6.2

In this case, the instance name is httpserver-java17-springboot-qseeo and the address is https://long-dust-si7xsngk.fra.unikraft.app. They're different for each run.

Use curl to query the Spring Boot server's hello endpoint:

curl https://long-dust-si7xsngk.fra.unikraft.app/hello

Hello World!

When done, you can remove the instance:

Using the unikraft CLI (Recommended)

unikraft instances delete httpserver-java17-springboot-qseeo

or

Using the legacy kraft CLI

kraft cloud instance remove httpserver-java17-springboot-qseeo

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

• DemoApplication.java: the server
• Kraftfile: the Unikraft Cloud specification
• Dockerfile: the Docker-specified app filesystem

Lines in the Kraftfile have the following roles:

• spec: v0.7: The current Kraftfile specification version is 0.7.

• runtime: base-compat:latest: The runtime kernel to use is the base compatibility kernel.

• rootfs: Build the app root filesystem. source: ./Dockerfile means the filesystem is built using the Dockerfile. format: erofs means the filesystem type is EROFS.

• cmd: ["/usr/lib/jvm/java-17-openjdk-amd64/bin/java", "-jar", "/usr/src/demo-0.0.1-SNAPSHOT.jar"]: Use as the starting command of the instance.

Lines in the Dockerfile have the following roles:

• FROM scratch: Build the filesystem from the scratch container image, to create a base image.

• COPY DemoApplication.java src/main/java/com/example/demo/: Copy the server implementation file in the Docker filesystem.

The following options are available for customizing the app:

• If you only update the implementation in the DemoApplication.java source file, you don't need to make any other changes.

• If you create any new source files, copy them into the app filesystem by using the COPY command in the Dockerfile.

• More extensive changes may require extending the Dockerfile (see Dockerfile syntax reference).

You can list information about the instance by running:

Using the unikraft CLI (Recommended)

unikraft instances list

METRO  NAME                                   STATE    IMAGE                                     ARGS  MEMORY   VCPUS  FQDN                                 CREATED
fra    httpserver-java17-springboot-qseeo     running  <my-org>/httpserver-java17-springboot           1024MiB  1      long-dust-si7xsngk.fra.unikraft.app  2 minutes ago

or

Using the legacy kraft CLI

kraft cloud instance list

NAME                                   FQDN                                 STATE    STATUS        IMAGE                                                                  MEMORY   VCPUS  ARGS  BOOT TIME
httpserver-java17-springboot-qseeo     long-dust-si7xsngk.fra.unikraft.app  running  1 minute ago  oci://unikraft.io/<my-org>/httpserver-java17-springboot@sha256:...     1.0 GiB  1            421.30 ms

When done, you can remove the instance:

Using the unikraft CLI (Recommended)

unikraft instances delete httpserver-java17-springboot-qseeo

or

Using the legacy kraft CLI

kraft cloud instance remove httpserver-java17-springboot-qseeo

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

Using the unikraft CLI (Recommended)

unikraft --help

or

Using the legacy kraft CLI

kraft cloud --help

Or visit the CLI Reference or the legacy CLI Reference.