Hi, I'm working with a client that wants to build a streaming analytic chart but with the option to switch mode to snap to historical data. Typically we can use a GW to stitch RDB and HDB data together but this use case is slightly different in that we need to stitch streaming data with HDB data.
We have a working POC using a rather unconventional approach, we utilize a lot of the QR APIs to make the HDB query a deferred request so that it doesn't block the streaming process. I'd like to reach out to see if there are other possible solutions and raise the challenges we're currently facing.
Current Solution (kdb 3.5, Dashboards V4.3.1)
- Delta Dashboards
- Simple canvas chart with a streaming data source
- Charts Process
- Dedicated RDB for real-time data
- Decides where to route the data too depending on subscription function params
- if HDB route to HDB process
- Snap Function
- A dedicated function that sets the function to be a deferred query
- Once the query is complete the callback function returns it to the dashboard via .sa.pub
Problems/Questions
- As the HDB query is async the dashboards don't know when it's going to be completed therefore there is no loading icon and the charts load layer by layer. Is there a way to force the chart loading icon?
- On dashboards, can we make the datasource a parameter (viewstate)? If we had this option then when we switch mode we can target the necessary process
Looking forward to see how we handle this with other projects/clients.
Thanks, Daniel
