Autoplot shows possible issue with das2server waveform data then fftpower and caching

[jbfaden]

I noticed when Bill was navigating around a spectrogram produced by FFTPower of a waveform data from a Das2Server, that it would reload data when zooming in. I suspect there is an issue where the cache tag is lost, since it should have all the data loaded in memory already--it's waveform data.

In Autoplot:

1. plot 2 hours of waveform data: vap+das2server:https://planet.physics.uiowa.edu/das/das2Server?dataset=Juno/WAV/Burst_Waveforms&start_time=2021-07-21T07:00:00.000Z&end_time=2021-07-21T07:30:00.000Z
2. data tab, |fftPower(512,2,'Hanning') in Operations
3. zoom in to 2021-07-21T07:08Z to 2021-07-21T07:20Z

You can see it goes back to the server and loads the data again, even though it didn't need to. I think this is a client-side issue, and I'm going to look into it.

[jbfaden]

See https://sourceforge.net/p/autoplot/bugs/2818/ where I am resolving this as an Autoplot issue.

[jbfaden]

This issue is fixed. The problem is it's never been well-defined where the cache tag should go: on the dataset or on it's DEPEND_0 with time tags. There are codes that do it both ways*, and I now check both locations for the tags. I suspect this problem was introduced when I started using the straight-to-QDataSet Das2Stream parser, but I haven't gone back to look.

(* The best argument for having it attached to the dataset and not the xtags is joined datasets where DEPEND_0 is a join dimension which just connects datasets of different modes. To have the cache tag attached to all of the xtags would be tedious and prone to mistakes.)

[cpiker]

I think the das 2.2.2 ICD should be updated to document that:

• xCacheRange
• xCacheResolution

Are expected to be in the <stream> element. That's what all the readers I know of do, but I don't think it's written down as expected. I'll enter an issue for that.

[jbfaden]

Do you know if your server-side cache puts in the xCacheRange and xCacheResolution? That would be useful info.

[cpiker]

It's programmed to do so, see here:
https://github.com/das-developers/das2C/blob/cc6f2ef0fb372f49d9b69ea6128c963ac42e4897/utilities/das2_cache_rdr.c#L476
but I haven't run a comprehensive validation of all existing cached data sources.