Evaluate an R expression while collecting journals from completed futures

Usage

capture_journals(expr, substitute = TRUE, envir = parent.frame())

Arguments

expr: The R expression to evaluate
substitute: If TRUE, then expr is substituted, otherwise not.
envir: The environment where expr should be evaluated

Value

A list of FutureJournal:s.

Details

This function evaluates an R expression and capture the journals signaled by futures as they are completed. A future journal comprise a log of events appearing during the life-span of a future, e.g. the timestamps when the future was created, launched, queried, resolved, and its results are collected.

Examples

slow_fcn <- function(x) {
  Sys.sleep(x / 10)
  sqrt(x)
}

plan(multisession, workers = 2)
js <- capture_journals({
  fs <- lapply(3:1, FUN = function(x) future(slow_fcn(x)))
  value(fs)
})

## Summarize all journals
js_all <- Reduce(rbind, js)
print(summary(js_all), digits = 2L)
#> Number of futures: 3
#>   summary  evaluate evaluate_ratio   overhead overhead_ratio  duration
#> 1     min 0.10 secs           0.23 0.033 secs          0.073 0.45 secs
#> 2    mean 0.24 secs           0.45 0.167 secs          0.315 0.53 secs
#> 3  median 0.26 secs           0.47 0.035 secs          0.064 0.54 secs
#> 4     max 0.36 secs           0.60 0.432 secs          0.730 0.59 secs
#> 5   total 0.72 secs           0.45 0.500 secs          0.315 1.59 secs
#>    walltime
#> 1 0.45 secs
#> 2 0.53 secs
#> 3 0.54 secs
#> 4 0.59 secs
#> 5 1.59 secs

## Shut down parallel workers
plan(sequential)