Transform a function to wait then retry after an error

insistently() takes a function and modifies it to retry after given amount of time whenever it errors.

Usage

insistently(f, rate = rate_backoff(), quiet = TRUE)

Arguments

f

A function to modify, specified in one of the following ways:

A named function, e.g. mean.
An anonymous function, e.g. \(x) x + 1 or function(x) x + 1.
A formula, e.g. ~ .x + 1. Only recommended if you require backward compatibility with older versions of R.

rate

A rate object. Defaults to jittered exponential backoff.

quiet

Hide errors (TRUE, the default), or display them as they occur?

Value

A function that takes the same arguments as .f, but returns a different value, as described above.

Adverbs

This function is called an adverb because it modifies the effect of a function (a verb). If you'd like to include a function created an adverb in a package, be sure to read faq-adverbs-export.

Examples

# For the purpose of this example, we first create a custom rate
# object with a low waiting time between attempts:
rate <- rate_delay(0.1)

# insistently() makes a function repeatedly try to work
risky_runif <- function(lo = 0, hi = 1) {
  y <- runif(1, lo, hi)
  if(y < 0.9) {
    stop(y, " is too small")
  }
  y
}

# Let's now create an exponential backoff rate with a low waiting
# time between attempts:
rate <- rate_backoff(pause_base = 0.1, pause_min = 0.005, max_times = 4)

# Modify your function to run insistently.
insistent_risky_runif <- insistently(risky_runif, rate, quiet = FALSE)

set.seed(6) # Succeeding seed
insistent_risky_runif()
#> Error: 0.606268297648057 is too small
#> Retrying in 0.19 seconds.
#> Error: 0.264352067606524 is too small
#> Retrying in 0.15 seconds.
#> Error: 0.807483389042318 is too small
#> Retrying in 0.78 seconds.
#> [1] 0.9579337

set.seed(3) # Failing seed
try(insistent_risky_runif())
#> Error: 0.168041526339948 is too small
#> Retrying in 0.16 seconds.
#> Error: 0.384942351374775 is too small
#> Retrying in 0.13 seconds.
#> Error: 0.602100674761459 is too small
#> Retrying in 0.48 seconds.
#> Error: 0.124633444240317 is too small
#> Error in rate_sleep(rate, quiet = quiet) : 
#>   Request failed after 4 attempts.

# You can also use other types of rate settings, like a delay rate
# that waits for a fixed amount of time. Be aware that a delay rate
# has an infinite amount of attempts by default:
rate <- rate_delay(0.2, max_times = 3)
insistent_risky_runif <- insistently(risky_runif, rate = rate, quiet = FALSE)
try(insistent_risky_runif())
#> Error: 0.294600924244151 is too small
#> Retrying in 0.2 seconds.
#> Error: 0.577609919011593 is too small
#> Retrying in 0.2 seconds.
#> Error: 0.630979274399579 is too small
#> Error in rate_sleep(rate, quiet = quiet) : 
#>   Request failed after 3 attempts.

# insistently() and possibly() are a useful combination
rate <- rate_backoff(pause_base = 0.1, pause_min = 0.005)
possibly_insistent_risky_runif <- possibly(insistent_risky_runif, otherwise = -99)

set.seed(6)
possibly_insistent_risky_runif()
#> Error: 0.606268297648057 is too small
#> Retrying in 0.2 seconds.
#> [1] 0.937642

set.seed(3)
possibly_insistent_risky_runif()
#> Error: 0.168041526339948 is too small
#> Retrying in 0.2 seconds.
#> Error: 0.807516399072483 is too small
#> Retrying in 0.2 seconds.
#> Error: 0.384942351374775 is too small
#> [1] -99