future (version 1.40.0)

reset: Reset a finished, failed, or interrupted future to a lazy future

Description

A future that has successfully completed, has been interrupted, or failed due to an error, can be relaunched after resetting it.

Usage

reset(x, ...)

Value

reset() returns a lazy, vanilla Future that can be relaunched. Resetting a running future results in a FutureError.

Arguments

x

A Future.

...

Not used.

Details

A lazy, vanilla Future can be reused in another R session. For instance, if we do:

library(future)
a <- 2
f <- future(42 * a, lazy = TRUE)
saveRDS(f, "myfuture.rds")

Then we can read and evaluate the future in another R session using:

library(future)
f <- readRDS("myfuture.rds")
v <- value(f)
print(v)
#> [1] 84

Examples

## Like mean(), but fails 90% of the time
shaky_mean <- function(x) {
  if (as.double(Sys.time()) %% 1 < 0.90) stop("boom")
  mean(x)
}

x <- rnorm(100)

## Calculate the mean of 'x' with a risk of failing randomly
f <- future({ shaky_mean(x) })

## Relaunch until success
repeat({
  v <- tryCatch(value(f), error = identity)
  if (!inherits(v, "error")) break
  message("Resetting failed future, and retry in 0.1 seconds")
  f <- reset(f)
  Sys.sleep(0.1)
})
cat("mean:", v, "\n")