An experiment running http4s as native image with Graal (+ Substrate)
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http4s + Graal

http4s-graal is an experiment to get http4s web service running as native image with Graal (+ Substrate).


Develop and Compile Dependencies

The following binaries / libraries need to be installed in order to compile the web service (including converting it to native image). The version numbers denotes the specific version used to develop the web service, it may not work under other minor versions:

Setup Steps

  1. Install and configure Graal:
    1. Download Graal (CE / EE) and extract to a folder of your choice
    2. Add Graal binaries folder (bin) to PATH, e.g. export PATH=~/graalvm-ce-1.0.0-rc9/bin:$PATH
  2. Install SBT:
  3. Create the uber-jar by running sbt assembly on the project root
  4. Create the native image by running native-image -H:+ReportUnsupportedElementsAtRuntime -jar target/scala-2.12/http4s-graal-assembly-0.0.1-SNAPSHOT.jar
  5. Start the web service with ./http4s-graal-assembly-0.0.1-SNAPSHOT

Now you can visit localhost:8080 from your browser.


  1. Run ./scripts/graal/bin/ to download and setup Graal.
  2. Run ./scripts/graal/bin/ to create a native image distribution under the /dist directory.

Docker Images

Several Dockerfiles have been provided to allow project compilation and packaging, targeting multiple runtime environments. It utilises multi-stage Docker builds, so no other dependency is required apart from Docker itself. All containers by default will be accessible at port 9080, e.g. localhost:9080.

Run ./scripts/graal/bin/ -i <image> where image is one of the following:

  • zulu8 (default) Azul Zulu 8 on Ubuntu 18.04
  • zulu11 Azul Zulu 11 on Ubuntu 18.04
  • graal GraalVM on Oracle Linux 7 (slim)
  • native Graal + Substrate native image on Oracle Linux 7 (slim)

NOTE: http4s Docker containers will be constrained to 1 CPU and 4GB of memory.

Container Management and Monitoring

Portainer is an open-source web-based Docker management UI. It allows viewing of container stats in realtime: CPU and memory usage, networking, and processes running in the container.

  1. Run ./scripts/portainer/bin/ to pull the latest Portainer image and create the data volume.
  2. Run ./scripts/portainer/bin/ to start the Portainer container:

Gatling Load Testing

Gatling is an open-source load and performance testing framework based on Scala, Akka and Netty.

  1. Run sbt gatling:test to download, setup, and run Gatling load testing simulation(s).


We follow the "feature-branch" Git workflow.

  1. Commit changes to a branch in your fork (use snake_case convention):
    • For technical chores, use chore/ prefix followed by the short description, e.g. chore/do_this_chore
    • For new features, use feature/ prefix followed by the feature name, e.g. feature/feature_name
    • For bug fixes, use bug/ prefix followed by the short description, e.g. bug/fix_this_bug
  2. Rebase or merge from "upstream"
  3. Submit a PR "upstream" to develop branch with your changes

Please read CONTRIBUTING for more details.


    Copyright (c) 2018 Herdy Handoko

    Licensed under the Apache License, Version 2.0 (the "License");
    you may not use this file except in compliance with the License.
    You may obtain a copy of the License at

    Unless required by applicable law or agreed to in writing, software
    distributed under the License is distributed on an "AS IS" BASIS,
    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    See the License for the specific language governing permissions and
    limitations under the License.

http4s-graal is released under the Apache Version 2.0 License. See the LICENSE file for further details.