insistently: Transform a function to wait then retry after an error

View source: R/adverb-insistently.R

insistentlyR Documentation

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.


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



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.


A rate object. Defaults to jittered exponential backoff.


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


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


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.

See Also

httr::RETRY() is a special case of insistently() for HTTP verbs.

Other adverbs: auto_browse(), compose(), negate(), partial(), possibly(), quietly(), safely(), slowly()


# 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")

# 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

set.seed(3) # Failing seed

# 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)

# 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)



purrr documentation built on Jan. 10, 2023, 5:15 p.m.