Run a C++ app
In this guide we create and deploy a simple C++-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 example repository and
cd
into theexamples/http-cpp/
directory:
Make sure to log into KraftCloud by setting your token and a metro close to you.
We use fra0
(Frankfurt, 🇩🇪) in this guide:
When done, invoke the following command to deploy this application on KraftCloud:
The output shows the instance URL and other details:
In this case, the instance name is http-cpp-jzbuo
and the URL is https://throbbing-wave-grxjih4t.fra0.kraft.host
.
They are different for each run.
Use curl
to query the KraftCloud instance of the C++ HTTP web server:
At any point in time, you can list information about the instance:
When done, you can remove the instance:
Customize your Application
To customize the application, update the files in the repository, listed below:
http_server.cpp
: the actual C++ HTTP serverKraftfile
: the KraftCloud specificationDockerfile
: the Docker-specified application filesystem
Lines in the Kraftfile
have the following roles:
-
spec: v0.6
: The currentKraftfile
specification version is0.6
. -
runtime: base
: The Unikraft runtime kernel to use is its base one. -
rootfs: ./Dockerfile
: Build the application root filesystem using theDockerfile
. -
cmd: ["/http_server"]
: Use/http_server
as the starting command of the instance.
Lines in the Dockerfile
have the following roles:
-
FROM --platform=linux/x86_64 gcc:13.2.0-bookworm AS build
: Build the filesystem from thebookworm gcc
container image, to create a base image. -
COPY ./http_server.cpp /src/http_server.cpp
: Copy the server implementation file (http_server.cpp
) in the Docker filesystem (in/src/http_server.cpp
).
The following options are available for customizing the application:
-
If only updating the implementation in the
http_server.cpp
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 a new C++ source files is added, update the
cmd
line in theKraftfile
and replacehttp_server.cpp
to run that file when creating the instance. -
More extensive changes may require expanding the
Dockerfile
with additionalDockerfile
commands.
Learn More
Use the --help
option for detailed information on using KraftCloud:
Or visit the CLI Reference.