Good questions!
The predominant use of fixed interval (PHPfina/PHPfixa) feeds does mean that emoncms indirectly imposes a requirement to send data VERY regularly, the fixed interval is just that and if you are sending data at the same interval as the fixed interval then any network or server loading delays will cause some data to be discarded, this can be reduced by using pre-timestamped data and not using emoncms input stages to timestamp data.
Correct. and also if accuracy is a priority as every datapoint is recorded with PHPtimeseries and the datapoints retain their exact timestamp they do not get rounded to the time of the feeds fixed interval occurrence.
Correct again, they were fairly recently changed to only use PHPfina in line with discussions about the PHPfiwa engine potentially/possibly/probably being phased out.
For sometime now I have been storing all my incoming data in PHPtimeseries feeds for better accuracy and then also using PHPfina feeds where access speeds might be a concern (large or frequent data requests) and also because the webapps excluded the PHPtimeseries engines.
The recent issue (as discussed in your Latest Dev version (display ?) bug with calculated kwh (bar) graphs thread that was also seen in the web apps led me to add PHPtimeseries as an acceptable feed type and I am inclined not to go back, the android app can use either so I think I will continue to use PHPtimeseries and maybe look at stop duplicating data in PHPtimeseries and PHPfina feeds to use the apps, I will still check the server loading and speed implications of not using PHPfina before deleting all my PHPfina feeds, but duplicating feeds just for using the apps is no longer a requirement.
All I did was replace any occurance of "engine":"5", with "engine":"2,5", in these 3 files (16x)
/var/www/html/emoncms/Modules/app/myelectric/myelectric.js
https://github.com/emoncms/app/blob/9.0/myelectric/myelectric.js#L5-L6
/var/www/html/emoncms/Modules/app/mysolarpv/mysolarpv.js
https://github.com/emoncms/app/blob/9.0/mysolarpv/mysolarpv.js#L4-L9
/var/www/html/emoncms/Modules/app/mysolarpvdivert/mysolarpvdivert.js
https://github.com/emoncms/app/blob/9.0/mysolarpvdivert/mysolarpvdivert.js#L4-L13
Whilst it seems to work just fine, I have not tested thoroughly enough to be sure it’s trouble-free, but if it’s good enough for the androidapp it should be fine, it’s the same api’s as far as I know so the web apps should not notice any change.