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What is the connector for OPC UA?

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Important

Azure IoT Operations Preview – enabled by Azure Arc is currently in PREVIEW. You shouldn't use this preview software in production environments.

You will need to deploy a new Azure IoT Operations installation when a generally available release is made available; you won't be able to upgrade a preview installation.

See the Supplemental Terms of Use for Microsoft Azure Previews for legal terms that apply to Azure features that are in beta, preview, or otherwise not yet released into general availability.

OPC UA (OPC Unified Architecture) is a standard developed by the OPC Foundation to enable the exchange of data between industrial components at the edge and with the cloud. OPC UA provides a consistent, secure, documented standard based on widely used data formats. Industrial components can implement the OPC UA standard to enable universal data exchange.

The connector for OPC UA is a part of Azure IoT Operations Preview. The connector for OPC UA connects to OPC UA servers to retrieve data that it publishes to topics in the MQTT broker. The connector for OPC UA enables your industrial OPC UA environment to ingress data into your local workloads running on a Kubernetes cluster, and into your cloud workloads.

The connector for OPC UA is a client application that runs as a middleware service in Azure IoT Operations. The connector for OPC UA connects to OPC UA servers, lets you browse the server address space, and monitor data changes and events in connected assets. Operations teams and developers use the connector for OPC UA to streamline the task of connecting OPC UA assets to their industrial solution at the edge.

Capabilities

As part of Azure IoT Operations, the connector for OPC UA is a native Kubernetes application that:

  • Connects existing OPC UA servers and assets to a native Kubernetes cluster at the edge.
  • Publishes JSON-encoded telemetry data from OPC UA servers in OPC UA PubSub format, using a JSON payload. By using this standard format for data exchange, you can reduce the risk of future compatibility issues.
  • Connects to Azure Arc-enabled services in the cloud.

The connector for OPC UA includes an OPC UA simulation server that you can use to test your applications. To learn more, see Configure an OPC PLC simulator to work with the connector for OPC UA.

Other features

The connector for OPC UA supports the following features as part of Azure IoT Operations:

  • Simultaneous connections to multiple OPC UA servers configured by using Kubernetes AssetEndpointProfile custom resources (CRs).
  • Publish OPC UA data value changes in OPC UA PubSub format with JSON encoding.
  • Publish message headers as user properties in the MQTT message. The headers in the messages published by the connector for OPC UA are based on the CloudEvents specification for OPC UA.
  • Publish OPC UA events with predefined event fields.
  • Asset definition by using Kubernetes Asset CRs
  • Payload compression including gzip and brotli.
  • Automatic reconnection to OPC UA servers.
  • Integrated OpenTelemetry compatible observability.
  • OPC UA transport encryption.
  • Anonymous authentication and authentication based on username and password.
  • AssetEndpointProfile and Asset CRs configurable by using Azure REST API and the operations experience web UI.
  • Akri-supported asset detection of OPC UA assets. The assets must be OPC UA Companion Specifications compliant.

How it works

The two main components of the connector for OPC UA are the application and the discovery handler.

The connector for OPC UA application:

  • Creates a session to the OPC UA server for each asset that you define.
  • All the tags of the asset are configured with the same publishing interval. This interval determines how frequently the connector publishes data to an MQTT broker topic.
  • Creates a separate subscription in the session for each 1,000 tags.
  • Creates a separate subscription for each event defined in the asset.
  • Implements retry logic to establish connections to endpoints that don't respond after a specified number of keep-alive requests. For example, there could be a nonresponsive endpoint in your environment when an OPC UA server stops responding because of a power outage.

The OPC UA discovery handler:

  • Uses the Akri configuration to connect to an OPC UA server. After the connection is made, the discovery handler inspects the OPC UA address space, and tries to detect assets that comply with the OPC UA Companion Specifications.
  • Creates Asset and AssetEndpointProfile CRs in the cluster.

Note

Asset detection by Akri only works for OPC UA servers that don't require user or transport authentication.

To learn more about Akri, see What are the Akri services?.