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Crosser + UNS - Expose data via HTTP

Using MQTT as the foundation for your UNS provides a robust publish/subscribe model for data exchange. However, if a client or application needs to query specific data points on demand, Crosser can act as a ‘wrapper’ around your UNS. This setup allows you to send HTTP requests to Crosser, which then retrieves the requested data from the UNS.

To achieve this you first have to make sure that the data which you want to expose via HTTP is available in memory (Key/Value Store). You can subscribe via wildcard to all topics on the UNS, use the string replace to replace ‘ / ’ with ‘ . ‘ . The Key/Value store modules can nowadays deal with hierarchical information like ‘stockholm.packaging.line1.cellA.Conveyor1’ and can therefore store and query nested objects.

Once that is done use the HTTP Listener module in combination with the HTTP Response module to build and end-to-end flow that fetches data from the Key/Value store based on the query (GET), checks if the query was successful, maps the data into proper response body and sends it back to the requester client.

Crosser Example

As a result you can use regular HTTP applications to query data from your UNS.

Crosser Example

About the author

David Nienhaus | Senior Solution Engineer

David is a Senior Solution Engineer at Crosser. He has over 15 years experience working with software integration and digitization projects for critical infrastructure.
His engineering background gives him the understanding and focus needed to solve customer use cases in the most efficient and successful way.