insistently {purrr}

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)

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.

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()