docs/doc/source/developer_resources/stx_opcua.rst

Enable OPC UA on StarlingX

This guide describes how to enable OPC UA (Open Platform Communications Unified Architecture) on StarlingX.

Background

As a cloud infrastructure software stack for the edge, Industrial IoT (IIoT) is an important use case for StarlingX.

OPC UA (Open Platform Communications Unified Architecture) is a data exchange standard for industrial communication, which integrates all functionalities from the existing OPC Classic specifications. It is an indispensable part of Industry 4.0. For StarlingX, it is very valuable to support OPC UA.

In this article, we'd like to share our practice of enabling OPC UA on StarlingX.

Build a container image with OPC UA server/client

There are quite a few open source OPC UA implementations available. Our work in this article is based on the project open62541, which is a popular and free OPC UA implementation written in C&C++ language.

The example below shows the dockerfile used to build the container image. The latest open62541 binary release v1.1 was installed.

From ubuntu:18.04

RUN apt-get update
RUN apt-get install -y wget

WORKDIR /opt

# install open62541 release package
RUN mkdir temp
RUN wget -qO- https://github.com/open62541/open62541/releases/download/v1.1/open62541-linux64.tar.gz | tar -xvz -C temp
RUN mv ./temp/open62541-linux64/bin/* /usr/bin/
RUN mv ./temp/open62541-linux64/include/* /usr/local/include/
RUN mv ./temp/open62541-linux64/lib/* /usr/lib/
RUN mv ./temp/open62541-linux64/share/open62541/tools .
RUN rm -r temp

ENV OPCUA_SERVER_IP "opcua-service.kube-system"
ENV OPCUA_SERVER_PORT "4840"

COPY run_ua_client.sh .
COPY run_ua_server.sh .
COPY ua_client .

run_ua_client.sh and run_ua_server.sh are two simple scripts to launch OPC UA server and OPC UA client. The objective of this work is to enable and verify OPC UA on StarlingX platform. For simplicity, we chose the sample OPC UA server provided by the open62541 release instead of developing our own OPC UA server. The sample client of open62541 hardcoded the server address and port as localhost:4840. We made some changes so it will accept two arguments: server address and server port.

The content of run_ua_server.sh:

#! /bin/sh
echo "start opc ua server ..."
ua_server_ctt.exe

The content of run_ua_client.sh:

#! /bin/sh
n=1
while true
do
    sleep 5
    echo "start opc ua client for the $n time ..."
    ./ua_client $OPCUA_SERVER_IP $OPCUA_SERVER_PORT
    n=$((n+1))
done

Deploy OPC UA server/client

In this step, we will demonstrate how to deploy OPC UA server and client with the container image built in the previous step on StarlingX platform.

Here we assume the container image with the name stx-opcua-base has been already pulled from a registry which StarlingX can access and uploaded into StarlingX local registry.

We have two yaml files shown below for OPC UA server and client respectively.

apiVersion: v1
kind: Pod
metadata:
  name: opcua-server
  labels:
    app: opcua-server
  namespace: kube-system
spec:
  hostNetwork: false
  imagePullSecrets:
    - name: registry-local-secret
  containers:
  - name: opcua-server
    image: registry.local:9001/stx-opcua-base
    command: ["/opt/run_ua_server.sh"]

---

apiVersion: v1
kind: Service
metadata:
  name: opcua-service
  namespace: kube-system
spec:
  selector:
    app: opcua-server
  ports:
    - protocol: TCP
      port: 4840
      targetPort: 4840

apiVersion: v1
kind: Pod
metadata:
  name: opcua-client
  labels:
    app: opcua-client
  namespace: kube-system
spec:
  hostNetwork: false
  imagePullSecrets:
    - name: registry-local-secret
  containers:
  - name: opcua-client
    image: registry.local:9001/stx-opcua-base
    command: ["/opt/run_ua_client.sh"]

Once applied the two yaml files by the Kubernetes command kubectl apply -f opcua-server.yaml and kubectl apply -f opcua-client.yaml, two pods will be created. Then we can check the status of the two pods.

controller-1:~$ kubectl -n kube-system get po | grep opcua
opcua-client                     1/1     Running       0          15m
opcua-server                     1/1     Running       0          15m

We also can use below commands to check the output of OPC UA server and client. The client was repeatedly reading some information from the server.

kubectl -n kube-system logs opcua-server
kubectl -n kube-system logs opcua-client

Summary

In this work, we took open62541 as an example to show how to enable OPC UA server and clients on StarlingX platform. In the future, we may explore how to operate more efficiently with OPC UA on StarlingX platform.