Using OPC-UA-Subscriber node

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Publish/subscribe, also known as Pub/Sub, is a style of messaging application in which the providers of information (publishers) have no direct link to specific consumers of that information (subscribers), but the interactions between publishers and subscribers are controlled by pub/sub brokers.

Overview

The Pub/Sub model is an asynchronous service-to-service communication method that is used in server-less and micro services architectures. The model basically involves,
  • A publisher who sends a message.
  • A subscriber who receives the message through a message broker.

For more information, see the following links. OPC UA PubSub overview and OPC UA PubSub concepts.

In IBM App Connect for Manufacturing, publish/subscribe functions are provided by the OPC-UA-Subscriber message flow node, which is used to notify applications of significant events that occur in integration nodes.

A built-in OPC-UA-Subscriber manufacturing node is provided with IBM App Connect for Manufacturing Version 13.0.

Limitations

Reconnect scenario in case of MQTT-based PubSub connection.
Symptoms: If user is using MQTT based PubSub connection, and Broker stops in between for some time, the OPC-UA-Subscriber node flow stops subscribing and requires restart of flow to start subscribing again.
Resolving the problem: Restart the flow to start subscribing again.
Integration Server stops when wrong metadata is provided
Symptoms: If data types of field in the metadata file are different than that of the data types published by the publisher, the Integration Server stops. The sequence of the data types is also important.
Resolving the problem: Correct the metadata file as mentioned and restart Integration Server.
Release 13.0.0.1

These limitations were fixed with IBM App Connect for Manufacturing Release 13.0.0.1.