purrr (version 1.0.2)

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

Description

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)

Value

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

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?

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.

See Also

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

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

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()

set.seed(3) # Failing seed
try(insistent_risky_runif())

# 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())

# 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()

set.seed(3)
possibly_insistent_risky_runif()