Transform a function to make it run insistently or slowly
insistently() takes a function and modifies it to retry a given
amount of time on error.
slowly() takes a function and modifies it to wait a given
amount of time between each call.
The number and rate of attempts is determined by a
rate object (by default a jittered exponential
backoff rate for insistently(), and a constant rate for
slowly()).
If you would like to include a function created with safely, slowly, or
insistently in a package, see faq-adverbs-export.
insistently(f, rate = rate_backoff(), quiet = TRUE) slowly(f, rate = rate_delay(), quiet = TRUE)
f |
A function to modify. |
rate |
A rate object determining the waiting time. |
quiet |
If |
httr::RETRY() is a special case of insistently() for
HTTP verbs. rate_backoff() and rate_delay() for creating
custom backoff rates. rate_sleep() for the function powering
insistently() and slowly(). safely() for another useful
function operator.
# 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)
# slowly() causes a function to sleep for a given time between calls:
slow_runif <- slowly(~ runif(1), rate = rate, quiet = FALSE)
map(1:5, slow_runif)
# 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()Please choose more modern alternatives, such as Google Chrome or Mozilla Firefox.