crew_launcher {crew}

Create an abstract launcher.

Description

This function is useful for inheriting argument documentation in functions that create custom third-party launchers. See ⁠@inheritParams crew::crew_launcher⁠ in the source code file of crew_launcher_local().

Usage

crew_launcher(
  name = NULL,
  seconds_interval = 0.5,
  seconds_timeout = 60,
  seconds_launch = 30,
  seconds_idle = Inf,
  seconds_wall = Inf,
  seconds_exit = NULL,
  tasks_max = Inf,
  tasks_timers = 0L,
  reset_globals = TRUE,
  reset_packages = FALSE,
  reset_options = FALSE,
  garbage_collection = FALSE,
  launch_max = 5L,
  tls = crew::crew_tls(),
  processes = NULL
)

Arguments

name

Name of the launcher.

seconds_interval

Number of seconds between polling intervals waiting for certain internal synchronous operations to complete, such as checking mirai::status().

seconds_timeout

Number of seconds until timing out while waiting for certain synchronous operations to complete, such as checking mirai::status().

seconds_launch

Seconds of startup time to allow. A worker is unconditionally assumed to be alive from the moment of its launch until seconds_launch seconds later. After seconds_launch seconds, the worker is only considered alive if it is actively connected to its assign websocket.

seconds_idle

Maximum number of seconds that a worker can idle since the completion of the last task. If exceeded, the worker exits. But the timer does not launch until tasks_timers tasks have completed. See the idletime argument of mirai::daemon(). crew does not excel with perfectly transient workers because it does not micromanage the assignment of tasks to workers, so please allow enough idle time for a new worker to be delegated a new task.

seconds_wall

Soft wall time in seconds. The timer does not launch until tasks_timers tasks have completed. See the walltime argument of mirai::daemon().

seconds_exit

Deprecated on 2023-09-21 in version 0.5.0.9002. No longer necessary.

tasks_max

Maximum number of tasks that a worker will do before exiting. See the maxtasks argument of mirai::daemon(). crew does not excel with perfectly transient workers because it does not micromanage the assignment of tasks to workers, it is recommended to set tasks_max to a value greater than 1.

tasks_timers

Number of tasks to do before activating the timers for seconds_idle and seconds_wall. See the timerstart argument of mirai::daemon().

reset_globals

TRUE to reset global environment variables between tasks, FALSE to leave them alone.

reset_packages

TRUE to unload any packages loaded during a task (runs between each task), FALSE to leave packages alone.

reset_options

TRUE to reset global options to their original state between each task, FALSE otherwise. It is recommended to only set reset_options = TRUE if reset_packages is also TRUE because packages sometimes rely on options they set at loading time.

garbage_collection

TRUE to run garbage collection between tasks, FALSE to skip.

launch_max

Positive integer of length 1, maximum allowed consecutive launch attempts which do not complete any tasks. Enforced on a worker-by-worker basis. The futile launch count resets to back 0 for each worker that completes a task. It is recommended to set launch_max above 0 because sometimes workers are unproductive under perfectly ordinary circumstances. But launch_max should still be small enough to detect errors in the underlying platform.

tls

A TLS configuration object from crew_tls().

processes

NULL or positive integer of length 1, number of local processes to launch to allow worker launches to happen asynchronously. If NULL, then no local processes are launched. If 1 or greater, then the launcher starts the processes on start() and ends them on terminate(). Plugins that may use these processes should run asynchronous calls using launcher$async$eval() and expect a mirai task object as the return value.

See Also

Other launcher: crew_class_launcher

Examples

if (identical(Sys.getenv("CREW_EXAMPLES"), "true")) {
client <- crew_client()
client$start()
launcher <- crew_launcher_local(name = client$name)
launcher$start(sockets = client$summary()$socket)
launcher$launch(index = 1L)
task <- mirai::mirai("result", .compute = client$name)
mirai::call_mirai_(task)
task$data
client$terminate()
}