Californium as k8s service

In the last years, k8s got very common to run applications in the cloud. Though at the begin UDP was rarely supported, this was changed and now many cloud-providers, not all, provide also support for UDP.

A k8s application is provided as containers and the maintained and orchestrated by k8s using REST APIs or kubectl.

Containers

Using Californium as Container requires some tools to build such a container. One common tool is docker. You find installation instructions here.

Each Container is described by a Dockerfile. Californium requires a java runtime to be executed, so the easiest way is to start with that in the Dockerfile:

FROM docker.io/openjdk:11-jre-slim

After that, prepare a folder and copy the Californium jar together with adjusted Californium3???.properties into the Container.

RUN mkdir /opt/app
COPY ./service/build ./CaliforniumReceivetest3.properties ./target/cf-extplugtest-server-3.0.0.jar /opt/app/

The define the network interface:

#EXPOSE 5683/udp
#EXPOSE 5683/tcp
#EXPOSE 5684/udp
#EXPOSE 5684/tcp
EXPOSE 5783/udp
#EXPOSE 5783/tcp
EXPOSE 5784/udp
#EXPOSE 5784/tcp
EXPOSE 5884/udp
EXPOSE 5884/tcp
EXPOSE 8080/tcp

CoAP uses 5683 and 5684 as default ports. The main protocol is UDP, TCP is only implemented experimental. The examples only exposes 5783/udp and 5784/udp, because the extended-plugtest-server is listening on these interfaces. 5884/udp is used for Californium internal CID cluster support, 5884/tcp to download credentials for dtls graceful restart. And 8080/tcp used by k8s for liveness and readiness checks.

Finally, the java process is started with

WORKDIR /opt/app
CMD ["java", "-XX:+UseContainerSupport", "-XX:MaxRAMPercentage=75", "-jar", "./cf-extplugtest-server-3.0.0.jar", "--no-plugtest", "--no-tcp", "--benchmark", "--k8s-dtls-cluster", ":5784;:5884;5884", "--k8s-monitor", ":8080", "--k8s-restore", ":5884"]

(See cf-extplugtest-server for further details.)

To create the container from that Dockerfile, execute

docker build . -f service/Dockerfile

assuming, the current directory contains the CaliforniumReceivetest3.properties a service folder with the Dockerfile, and a target folder with the Californium jar. If all works well, you now have a Container in your local docker installation.