Preamble
Inspired by the presentation by Barret Schloerke at studio::global(2021) (I will add the link as soon as it becomes available), I tried to implement an app to see the differences between using {future}, {plumber}, both or none into a Shiny app running a sequence of fast-slow-slow-fast computations (both on distinct output and in a sequence within the same one).
Gist
You can find here my attempt, including the app.R Shiny app and the plumber.R APIs.
Results
| execution selected (5 s for "slow") | result | expectation | comments |
|---|---|---|---|
| Standard run | ~20 seconds before anything appear, next everything appears in the same moment | ~20 seconds, appearing sequentially somehow | Why did not appear sequentially? |
{future} only |
~5 seconds before anything appear, next everything appears in the same moment | ~20 with "first fast" and "second fast" appearing almost immediatly and next (~5) "first slow" or "second slow," next (~10) the other, and finally (~20) "Sequential") | I would expect that something similar to what happened here for the combined type of run... how is possible that "sequential" completed in 5 seconds??? |
{plumber} only |
same as the standard run (r should remain busy until each API call would be resolved, right?) | same time (~20) but appearing sequentially some how | why shiny rendered everything the same time? |
{future} and {plumber} |
same as the standard run | I do not expect this at all!, What I expected here is to have "_fast"s appearing immediately, "_slow"s quite the same time after ~5 seconds, and "sequential" after ~10 seconds from the start (i.e., ~10 seconds overall) | I am totally confused here :-( |
Doubts
One of the main things I did not understand is why when activating {future} (both with or without {plumber}), "first fast" does not appear immediately. And in general, why the output does not appear in a single sequence when {future} is not involved. And how is it possible that with {future} alone, "sequential" stay ~5 seconds?
So, clearly, I made something the wrong way, and I do not understand something correctly.
Questions
Can someone help me understand where/what (and maybe try to infer "why") I made the app wrong, and/or the API wrong, or their interaction wrong?
Thank you, Corrado.