[Feature]: Track inputs exclusively via JS to optimize perfomance

[averissimo]

Guidelines

• I agree to follow this project's Contributing Guidelines.

Description

🏹 Goal: Add option to track inputs via JavaScript.

How?

• Shiny javascript events allow to detect input changing via JS (see snipped below)
• This could replace existing logic in Telemetry$.log_all_inputs
  • Sending a message to R Shiny and processed by Telemetry class
  • Or see "Taking one step further"

$(document).on('shiny:inputchanged', function(event) {
  if (event.name === 'foo') {
    event.value *= 2;
  }
});

Benefits:

1. Performance improvements as the Shiny R session wouldn't be monitoring the input changes

Taking one step further

🏹 Goal: Delegate write operations to external API via JS

In other words, bypass using the DataStorage backend on the current R Shiny session and send the data to a deployment of the existing PlumberAPI

In turn, the Plumber API would write to the correct backend (LogFile, SQLite, SQL, ...)

Benefits:

1. Performance improvements as write operations would be done asynchronously in JS only
   • without blocking Shiny R session

Cons:

• Less guarantees that data is being written as process becomes asynchronous
• Requirement to have a Plumber API instance running

Additional work:

• Need additional check to verify availability of Plumber API
  • Implement fallback to write data locally
  • Add documentation on how to reconcile data storages
• Plumber API needs to be optimized to handle more queries per second (using {future})

Diagram

Alternatives Considered

1. Using a queue system that allows to group together multiple events Use event queue to send messages to data storage #148

[averissimo]

Alternative:

• Use async writes to DataStorage so it doesn't bottleneck the App (from @WahiduzzamanKhan)

note: Creating a future call has its own overhead. One way to minimize it is to define the globals argument manually and it might be as slow as the write operation.

A benchmark should be done to assess the performance benefits.