library(rush)
branin = function(x1, x2) {
(x2 - 5.1 / (4 * pi^2) * x1^2 + 5 / pi * x1 - 6)^2 + 10 * (1 - 1 / (8 * pi)) * cos(x1) + 10
}
wl_random_search = function(rush, branin) {
while (rush$n_finished_tasks < 100) {
xs = list(x1 = runif(1, -5, 10), x2 = runif(1, 0, 15))
key = rush$push_running_tasks(xss = list(xs))
tryCatch({
if (runif(1) < 0.5) stop("Random Error")
ys = list(y = branin(xs$x1, xs$x2))
rush$finish_tasks(key, yss = list(ys))
}, error = function(e) {
condition = list(message = e$message)
rush$fail_tasks(key, conditions = list(condition))
})
}
}rush provides error-handling mechanisms for two failure modes: standard R errors during task evaluation and unexpected worker failures such as crashes or lost connections. If errors cannot be caught automatically, the worker loop can be debugged locally.
Simple R Errors
We use the random search example from the tutorial and introduce a random error with 50% probability. Within the worker loop, users are responsible for catching errors and marking the corresponding task as "failed" using the $fail_tasks() method.
We initialize the network and start the workers.
rush = rsh(
network = "test-simple-error",
config = redux::redis_config())
mirai::daemons(4)
rush$start_workers(
worker_loop = wl_random_search,
n_workers = 4,
branin = branin)When an error occurs, the task is marked as "failed" and the error message is stored in the "message" column. This ensures that errors do not interrupt the overall execution and allows subsequent inspection and reevaluation of failed tasks.
rush$fetch_failed_tasks() x1 x2 worker_id condition keys
<num> <num> <char> <list> <char>
1: 6.1096317 3.93761416 untrigonom... <list[1]> 355e1613-5...
2: -4.4327314 5.86245464 minimal_qu... <list[1]> a8c8a19f-8...
3: -0.1031148 1.51799123 untrigonom... <list[1]> 94981c3e-2...
4: 9.7425715 3.15865981 undiseased... <list[1]> 624723b0-5...
5: -2.6452990 0.05437061 undiseased... <list[1]> b9d55cd0-8...
---
98: -0.8020474 11.64074808 minimal_qu... <list[1]> d41e8182-e...
99: 9.8105506 1.77926947 undiseased... <list[1]> 81251758-7...
100: 1.3482679 12.25978688 depreciabl... <list[1]> 0b90ca18-3...
101: 0.4910896 8.40321348 untrigonom... <list[1]> 11508a23-7...
102: 3.0261641 6.19577205 undiseased... <list[1]> 73d3212c-2...Handling Failing Workers
When a worker fails due to a crash or lost connection, its tasks may remain in the "running" state indefinitely. We simulate a segmentation fault by terminating the worker process.
wl_failed_worker = function(rush) {
xs = list(x1 = runif(1, -5, 10), x2 = runif(1, 0, 15))
key = rush$push_running_tasks(xss = list(xs))
tools::pskill(Sys.getpid(), tools::SIGKILL)
}
rush = rsh(
network = "test-failed-workers",
config = redux::redis_config())
mirai::daemons(2)
worker_ids = rush$start_workers(
worker_loop = wl_failed_worker,
n_workers = 2)The $detect_lost_workers() method identifies such workers and updates their state to "terminated". For workers started with $start_local_workers() or $start_workers(), lost worker detection works automatically by checking process status. Workers started via $worker_script() require an additional heartbeat mechanism (see the manager vignette).
rush$detect_lost_workers()[1] "subsequent_slug_e8fd7c6c" "sickening_wattlebird_ecdc8ad9"When a worker fails, the state of any task it was evaluating is set to "failed".
rush$fetch_failed_tasks() x1 x2 worker_id condition keys
<num> <num> <char> <list> <char>
1: 2.904121 14.40359 subsequent... <list[1]> 3eef9e48-e...
2: 5.124074 0.56857 sickening_... <list[1]> 4ea3d550-c...Debugging
When the worker loop fails due to an uncaught error, the loop can be executed locally to reproduce and inspect the failure. Consider the following worker loop, which generates an error for large values of x1.
To debug the worker loop locally, a RushWorker instance is instantiated manually and passed as argument to the worker loop.
rush_worker = RushWorker$new(network_id = "test-error")
wl_error(rush_worker)Error in `wl_error()`:
! Unexpected errorWhen an error is raised in the main process, traceback() can be called to examine the stack trace and breakpoints can be set within the worker loop to inspect the program state. Note that certain errors such as missing packages may not be reproducible locally but can be identified by running the worker loop in a separate process and using $detect_lost_workers().
rush = rsh(
network = "test-error",
config = redux::redis_config())
mirai::daemons(1)
rush$start_workers(
worker_loop = wl_error,
n_workers = 1)
rush$detect_lost_workers()[1] "communicatory_thrush_c5f3f784"Output and message logs can be written to files via the message_log and output_log arguments.
rush = rsh(
network = "test-error",
config = redux::redis_config())
message_log = tempdir()
output_log = tempdir()
mirai::daemons(1)
worker_ids = rush$start_workers(
worker_loop = wl_error,
n_workers = 1,
message_log = message_log,
output_log = output_log)
Sys.sleep(5)
readLines(file.path(message_log, sprintf("message_%s.log", worker_ids[1])))[1] "Debug message logging on worker kleptomaniac_shorebird_1cac4371 started"[1] "[1] \"Debug output logging on worker kleptomaniac_shorebird_1cac4371 started\""