Multiple problems with live tiles and streaming data

[asthomas]

I have a streaming data set generated using the API.  The data represents a PID controller with three variables:  Mv, Pv and Sp.  Each variable is updated on an independent clock, so they are not transmitted as records but as individual values slightly offset from one another in time.  Mv and Pv update at 10Hz.  Sp updates at 0.2 Hz (once every 5 seconds).  The API application is sending the data in batches, once every 5 seconds.  In an ideal world that would be 101 values every 5 seconds, where each value is individually timestamped and the timestamps are not aligned.

I have created a dashboard that contains 3 card tiles, one for each variable, and a single chart tile that binds to all 3 variables.

* Both the tiles and chart are updating every 5 seconds.

* I confirmed that the data is intact.  I can see it all when I view the data as a table instead of a card or chart.

* I confirmed that the timestamps are in ISO UTC format, with 3 decimal places.

I see a few problems that I suspect are related:

* Only the Pv card shows a value.  The Sp and Mv cards are blank.

* The chart very occasionally shows the Sp line.  Most of the time the Sp line is absent from the chart.

* Only the Pv line in the chart displays at full resolution (10Hz data).  The Mv line is jagged and very low resolution, containing only a fraction of the points that it should.  The Sp line, when it is present, contains only a couple of points over a 5-minute window. 

If I were going to hazard a guess, it looks like the timestamp from the Pv data is being used as the index for addressing the data in Mv and Sp.  If, by chance, the Mv and Sp data have the same timestamp as the Pv point then they are rendered.  Otherwise they are not.  That could explain the chart behaviour, but does not explain why the cards are blank.

I would be happy to demonstrate over Teams if it would help.

[lbendlin]

Is this a "pure" streaming dataset or a hybrid one?

There is some ominous language here https://docs.microsoft.com/en-us/power-bi/connect-data/service-real-time-streaming

like " if a request exceeds the 15Kb size restriction " and "streaming tiles will fail to render"  that might be related to your issue.

You may need to look at other BI tools that are more suited for high speed streams (like Splunk).

[asthomas]

This is a hybrid data set.

You are right that that the language is ominous, but not clear.  What does it mean to temporarily fail?  In my case, one card works always, and the other two never work.  The chart works, but only one trace renders at full resolution.

I am not willing to give up on Power BI quite yet.  I do not think that data rate is the issue here...

I tried clearing all the data from the dataset by disabling and the re-enabling historic data analysis.  I then changed the data source to generate data at 1 value per second for Pv and Mv, leaving Sp at one value per 5 seconds.  That results in a payload of 1KB every 5 seconds, well below the ominous 15KB threshold.  The dashboard behaviour does not change:

* The Pv card updates normally

* The Sp and Mv cards are both blank, and never update

* The Pv trace on the chart renders at full resolution, about 300 values in a 5-minute window

* The Mv trace renders at a much reduced resolution, about 10 values where it should be 300

* The Sp trace sometimes renders, but only 2 or 3 values when it does.  It should render 60 points in a 5-minute window.

[asthomas]

After more playing around, I can add this information:

Only 1 of the 3 cards shows a value at any one time, but the card showing a value changes from time to time.  Most of the time there is a value in the Pv card, but sometimes Mv and Sp can get a value.  If any card gets a value the other two cards go blank.

If I pin a chart visual from a report to my dashboard, that visual updates properly.  All of the traces appear to be rendered at the full data resolution.  Adding this visual to a dashboard containing the 3 cards and one live chart does not change the behaviour of the cards and chart at all.  They continue to glitch as described earlier.