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crew_class_controller: Controller class

crew_class_controller: Controller class
In crew: A Distributed Worker Launcher Framework

crew_class_controllerR Documentation

Controller class

Description

R6 class for controllers.

Details

See crew_controller().

Active bindings

profile

Character string, compute profile of the controller.

client

Client object.

launcher

Launcher object.

tasks

A list of mirai::mirai() task objects. The list of tasks is dynamically generated from an internal, dictionary, so it is not as fast as a simple lookup.

pushed

Number of tasks ever submitted to the mirai compute profile through the controller.

reset_globals

See crew_controller(). since the controller was started.

reset_packages

See crew_controller(). since the controller was started.

reset_options

See crew_controller(). since the controller was started.

garbage_collection

See crew_controller(). since the controller was started.

crashes_max

See crew_controller().

backup

See crew_controller().

error

Tibble of task results (with one result per row) from the last call to ⁠map(error = "stop)⁠.

loop

later loop if asynchronous auto-scaling is running, NULL otherwise.

queue_resolved

Queue of resolved tasks.

queue_backlog

Queue of explicitly backlogged tasks.

Methods

Public methods

Method new()

mirai controller constructor.

Usage
crew_class_controller$new(
  client = NULL,
  launcher = NULL,
  reset_globals = NULL,
  reset_packages = NULL,
  reset_options = NULL,
  garbage_collection = NULL,
  crashes_max = NULL,
  backup = NULL
)
Arguments
client

Client object. See crew_controller().

launcher

Launcher object. See crew_controller().

reset_globals

See crew_controller().

reset_packages

See crew_controller().

reset_options

See crew_controller().

garbage_collection

See crew_controller().

crashes_max

See crew_controller().

backup

See crew_controller().

Returns

An R6 controller object.

Examples
if (identical(Sys.getenv("CREW_EXAMPLES"), "true")) {
client <- crew_client()
launcher <- crew_launcher_local()
controller <- crew_controller(client = client, launcher = launcher)
controller$start()
controller$push(name = "task", command = sqrt(4))
controller$wait()
controller$pop()
controller$terminate()
}

Method validate()

Validate the controller.

Usage
crew_class_controller$validate()
Returns

NULL (invisibly).

Method size()

Number of tasks in the controller.

Usage
crew_class_controller$size(controllers = NULL)
Arguments
controllers

Not used. Included to ensure the signature is compatible with the analogous method of controller groups.

Returns

Non-negative integer, number of tasks in the controller.

Method empty()

Check if the controller is empty.

Usage
crew_class_controller$empty(controllers = NULL)
Arguments
controllers

Not used. Included to ensure the signature is compatible with the analogous method of controller groups.

Details

A controller is empty if it has no mirai::mirai() task objects in the controller. There may still be other tasks running on the workers of an empty controller, but those tasks were not submitted with push() or collect(), and they are not part of the controller task queue.

Returns

TRUE if the controller is empty, FALSE otherwise.

Method nonempty()

Check if the controller is nonempty.

Usage
crew_class_controller$nonempty(controllers = NULL)
Arguments
controllers

Not used. Included to ensure the signature is compatible with the analogous method of controller groups.

Details

A controller is empty if it has no mirai::mirai() task objects in the controller. There may still be other tasks running on the workers of an empty controller, but those tasks were not submitted with push() or collect(), and they are not part of the controller task queue.

Returns

TRUE if the controller is empty, FALSE otherwise.

Method resolved()

Cumulative number of resolved tasks.

Usage
crew_class_controller$resolved(controllers = NULL)
Arguments
controllers

Not used. Included to ensure the signature is compatible with the analogous method of controller groups.

Details

resolved() is cumulative: it counts all the resolved tasks over the entire lifetime of the controller session.

Returns

Non-negative integer of length 1, number of resolved tasks. The return value is 0 if the condition variable does not exist (i.e. if the client is not running).

Method unresolved()

Number of unresolved tasks.

Usage
crew_class_controller$unresolved(controllers = NULL)
Arguments
controllers

Not used. Included to ensure the signature is compatible with the analogous method of controller groups.

Returns

Non-negative integer of length 1, number of unresolved tasks.

Method saturated()

Check if the controller is saturated.

Usage
crew_class_controller$saturated(
  collect = NULL,
  throttle = NULL,
  controller = NULL
)
Arguments
collect

Deprecated in version 0.5.0.9003 (2023-10-02). Not used.

throttle

Deprecated in version 0.5.0.9003 (2023-10-02). Not used.

controller

Not used. Included to ensure the signature is compatible with the analogous method of controller groups.

Details

A controller is saturated if the number of uncollected tasks is greater than or equal to the maximum number of workers. You can still push tasks to a saturated controller, but tools that use crew such as targets may choose not to (for performance and user-friendliness).

Returns

TRUE if the controller is saturated, FALSE otherwise.

Method start()

Start the controller if it is not already started.

Usage
crew_class_controller$start(controllers = NULL)
Arguments
controllers

Not used. Included to ensure the signature is compatible with the analogous method of controller groups.

Details

Register the mirai client and register worker websockets with the launcher.

Returns

NULL (invisibly).

Method started()

Check whether the controller is started.

Usage
crew_class_controller$started(controllers = NULL)
Arguments
controllers

Not used. Included to ensure the signature is compatible with the analogous method of controller groups.

Details

Actually checks whether the client is started.

Returns

TRUE if the controller is started, FALSE otherwise.

Method launch()

Launch one or more workers.

Usage
crew_class_controller$launch(n = 1L, controllers = NULL)
Arguments
n

Number of workers to launch.

controllers

Not used. Included to ensure the signature is compatible with the analogous method of controller groups.

Returns

NULL (invisibly).

Method scale()

Auto-scale workers out to meet the demand of tasks.

Usage
crew_class_controller$scale(throttle = TRUE, controllers = NULL)
Arguments
throttle

TRUE to skip auto-scaling if it already happened within the last polling interval. FALSE to auto-scale every time scale() is called. Throttling avoids overburdening the local R process.

controllers

Not used. Included to ensure the signature is compatible with the analogous method of controller groups.

Details

The scale() method launches new workers to run tasks if needed.

Returns

Invisibly returns TRUE if auto-scaling was attempted (throttling can skip it) and there was any relevant auto-scaling activity (new worker launches or worker connection/disconnection events). FALSE otherwise.

Method autoscale()

Run worker auto-scaling in a later loop in polling intervals determined by exponential backoff.

Usage
crew_class_controller$autoscale(
  loop = later::global_loop(),
  controllers = NULL
)
Arguments
loop

A later loop to run auto-scaling.

controllers

Not used. Included to ensure the signature is compatible with the analogous method of controller groups.

Details

Call controller$descale() to terminate the auto-scaling loop.

Returns

NULL (invisibly).

Method descale()

Terminate the auto-scaling loop started by controller$autoscale().

Usage
crew_class_controller$descale(controllers = NULL)
Arguments
controllers

Not used. Included to ensure the signature is compatible with the analogous method of controller groups.

Returns

NULL (invisibly).

Method crashes()

Report the number of consecutive crashes of a task.

Usage
crew_class_controller$crashes(name, controllers = NULL)
Arguments
name

Character string, name of the task to check.

controllers

Not used. Included to ensure the signature is compatible with the analogous method of controller groups.

Details

See the crashes_max argument of crew_controller().

Returns

Non-negative integer, number of consecutive times the task crashed.

Method push()

Push a task to the head of the task list.

Usage
crew_class_controller$push(
  command,
  data = list(),
  globals = list(),
  substitute = TRUE,
  seed = NULL,
  algorithm = NULL,
  packages = character(0),
  library = NULL,
  seconds_timeout = NULL,
  scale = TRUE,
  throttle = TRUE,
  name = NULL,
  save_command = NULL,
  controller = NULL
)
Arguments
command

Language object with R code to run.

data

Named list of local data objects in the evaluation environment.

globals

Named list of objects to temporarily assign to the global environment for the task. This list should include any functions you previously defined in the global environment which are required to run tasks. See the reset_globals argument of crew_controller_local().

substitute

Logical of length 1, whether to call base::substitute() on the supplied value of the command argument. If TRUE (default) then command is quoted literally as you write it, e.g. push(command = your_function_call()). If FALSE, then crew assumes command is a language object and you are passing its value, e.g. push(command = quote(your_function_call())). substitute = TRUE is appropriate for interactive use, whereas substitute = FALSE is meant for automated R programs that invoke crew controllers.

seed

Integer of length 1 with the pseudo-random number generator seed to set for the evaluation of the task. Passed to the seed argument of set.seed() if not NULL. If seed and algorithm are both non-missing in the output of pop(), then you can recover the pseudo-random number generator state of the task using set.seed(seed = seed, kind = algorithm). Otherwise, if the algorithm and seed are both NULL (recommended), then the random number generator defaults to the widely spaced worker-specific L'Ecuyer streams as supported by mirai::nextstream(). See vignette("parallel", package = "parallel") for details.

algorithm

Integer of length 1 with the pseudo-random number generator algorithm to set for the evaluation of the task. Passed to the kind argument of RNGkind() if not NULL. If seed and algorithm are both non-missing in the output of pop(), then you can recover the pseudo-random number generator state of the task using set.seed(seed = seed, kind = algorithm). Otherwise, if the algorithm and seed are both NULL (recommended), then the random number generator defaults to the widely spaced worker-specific L'Ecuyer streams as supported by mirai::nextstream(). See vignette("parallel", package = "parallel") for details.

packages

Character vector of packages to load for the task.

library

Library path to load the packages. See the lib.loc argument of require().

seconds_timeout

Optional task timeout passed to the .timeout argument of mirai::mirai() (after converting to milliseconds).

scale

Logical, whether to automatically call scale() to auto-scale workers to meet the demand of the task load. Also see the throttle argument.

throttle

TRUE to skip auto-scaling if it already happened within the last polling interval. FALSE to auto-scale every time scale() is called. Throttling avoids overburdening the local R process.

name

Character string, name of the task. If NULL, then a random name is generated automatically. The name of the task must not conflict with the name of another task pushed to the controller. Any previous task with the same name must first be popped before a new task with that name can be pushed.

save_command

Deprecated on 2025-01-22 (crew version 0.10.2.9004) and no longer used.

controller

Not used. Included to ensure the signature is compatible with the analogous method of controller groups.

Returns

Invisibly return the mirai object of the pushed task. This allows you to interact with the task directly, e.g. to create a promise object with promises::as.promise().

Method synced()

Check if the controller is synced.

Usage
crew_class_controller$synced(controllers = NULL)
Arguments
controllers

Not used. Included to ensure the signature is compatible with the analogous method of controller groups.

Details

A controller is synced if all pushed tasks in the controller show up in the task counts in mirai::info().

Method walk()

Apply a single command to multiple inputs, and return control to the user without waiting for any task to complete.

Usage
crew_class_controller$walk(
  command,
  iterate,
  data = list(),
  globals = list(),
  substitute = TRUE,
  seed = NULL,
  algorithm = NULL,
  packages = character(0),
  library = NULL,
  seconds_timeout = NULL,
  names = NULL,
  save_command = NULL,
  verbose = interactive(),
  scale = TRUE,
  throttle = TRUE,
  controller = NULL
)
Arguments
command

Language object with R code to run.

iterate

Named list of vectors or lists to iterate over. For example, to run function calls f(x = 1, y = "a") and f(x = 2, y = "b"), set command to f(x, y), and set iterate to list(x = c(1, 2), y = c("a", "b")). The individual function calls are evaluated as f(x = iterate$x[[1]], y = iterate$y[[1]]) and f(x = iterate$x[[2]], y = iterate$y[[2]]). All the elements of iterate must have the same length. If there are any name conflicts between iterate and data, iterate takes precedence.

data

Named list of constant local data objects in the evaluation environment. Objects in this list are treated as single values and are held constant for each iteration of the map.

globals

Named list of constant objects to temporarily assign to the global environment for each task. This list should include any functions you previously defined in the global environment which are required to run tasks. See the reset_globals argument of crew_controller_local(). Objects in this list are treated as single values and are held constant for each iteration of the map.

substitute

Logical of length 1, whether to call base::substitute() on the supplied value of the command argument. If TRUE (default) then command is quoted literally as you write it, e.g. push(command = your_function_call()). If FALSE, then crew assumes command is a language object and you are passing its value, e.g. push(command = quote(your_function_call())). substitute = TRUE is appropriate for interactive use, whereas substitute = FALSE is meant for automated R programs that invoke crew controllers.

seed

Integer of length 1 with the pseudo-random number generator seed to set for the evaluation of the task. Passed to the seed argument of set.seed() if not NULL. If algorithm and seed are both NULL, then the random number generator defaults to the recommended widely spaced worker-specific L'Ecuyer streams as supported by mirai::nextstream(). See vignette("parallel", package = "parallel") for details.

algorithm

Integer of length 1 with the pseudo-random number generator algorithm to set for the evaluation of the task. Passed to the kind argument of RNGkind() if not NULL. If algorithm and seed are both NULL, then the random number generator defaults to the recommended widely spaced worker-specific L'Ecuyer streams as supported by mirai::nextstream(). See vignette("parallel", package = "parallel") for details.

packages

Character vector of packages to load for the task.

library

Library path to load the packages. See the lib.loc argument of require().

seconds_timeout

Optional task timeout passed to the .timeout argument of mirai::mirai() (after converting to milliseconds).

names

Optional character of length 1, name of the element of iterate with names for the tasks. If names is supplied, then iterate[[names]] must be a character vector.

save_command

Deprecated on 2025-01-22 (crew version 0.10.2.9004). The command is always saved now.

verbose

Logical of length 1, whether to print to a progress bar when pushing tasks.

scale

Logical, whether to automatically scale workers to meet demand. See also the throttle argument.

throttle

TRUE to skip auto-scaling if it already happened within the last polling interval. FALSE to auto-scale every time scale() is called. Throttling avoids overburdening the local R process.

controller

Not used. Included to ensure the signature is compatible with the analogous method of controller groups.

Details

In contrast to walk(), map() blocks the local R session and waits for all tasks to complete.

Returns

Invisibly returns a list of mirai task objects for the newly created tasks. The order of tasks in the list matches the order of data in the iterate argument.

Method map()

Apply a single command to multiple inputs, wait for all tasks to complete, and return the results of all tasks.

Usage
crew_class_controller$map(
  command,
  iterate,
  data = list(),
  globals = list(),
  substitute = TRUE,
  seed = NULL,
  algorithm = NULL,
  packages = character(0),
  library = NULL,
  seconds_interval = NULL,
  seconds_timeout = NULL,
  names = NULL,
  save_command = NULL,
  error = "stop",
  warnings = TRUE,
  verbose = interactive(),
  scale = TRUE,
  throttle = TRUE,
  controller = NULL
)
Arguments
command

Language object with R code to run.

iterate

Named list of vectors or lists to iterate over. For example, to run function calls f(x = 1, y = "a") and f(x = 2, y = "b"), set command to f(x, y), and set iterate to list(x = c(1, 2), y = c("a", "b")). The individual function calls are evaluated as f(x = iterate$x[[1]], y = iterate$y[[1]]) and f(x = iterate$x[[2]], y = iterate$y[[2]]). All the elements of iterate must have the same length. If there are any name conflicts between iterate and data, iterate takes precedence.

data

Named list of constant local data objects in the evaluation environment. Objects in this list are treated as single values and are held constant for each iteration of the map.

globals

Named list of constant objects to temporarily assign to the global environment for each task. This list should include any functions you previously defined in the global environment which are required to run tasks. See the reset_globals argument of crew_controller_local(). Objects in this list are treated as single values and are held constant for each iteration of the map.

substitute

Logical of length 1, whether to call base::substitute() on the supplied value of the command argument. If TRUE (default) then command is quoted literally as you write it, e.g. push(command = your_function_call()). If FALSE, then crew assumes command is a language object and you are passing its value, e.g. push(command = quote(your_function_call())). substitute = TRUE is appropriate for interactive use, whereas substitute = FALSE is meant for automated R programs that invoke crew controllers.

seed

Integer of length 1 with the pseudo-random number generator seed to set for the evaluation of the task. Passed to the seed argument of set.seed() if not NULL. If algorithm and seed are both NULL, then the random number generator defaults to the recommended widely spaced worker-specific L'Ecuyer streams as supported by mirai::nextstream(). See vignette("parallel", package = "parallel") for details.

algorithm

Integer of length 1 with the pseudo-random number generator algorithm to set for the evaluation of the task. Passed to the kind argument of RNGkind() if not NULL. If algorithm and seed are both NULL, then the random number generator defaults to the recommended widely spaced worker-specific L'Ecuyer streams as supported by mirai::nextstream(). See vignette("parallel", package = "parallel") for details.

packages

Character vector of packages to load for the task.

library

Library path to load the packages. See the lib.loc argument of require().

seconds_interval

Deprecated on 2025-01-17 (crew version 0.10.2.9003). Instead, the seconds_interval argument passed to crew_controller_group() is used as seconds_max in a crew_throttle() object which orchestrates exponential backoff.

seconds_timeout

Optional task timeout passed to the .timeout argument of mirai::mirai() (after converting to milliseconds).

names

Optional character string, name of the element of iterate with names for the tasks. If names is supplied, then iterate[[names]] must be a character vector.

save_command

Deprecated on 2025-01-22 (crew version 0.10.2.9004). The command is always saved now.

error

Character of length 1, choice of action if a task was not successful. Possible values:

  • "stop": throw an error in the main R session instead of returning a value. In case of an error, the results from the last errored map() are in the error field of the controller, e.g. controller_object$error. To reduce memory consumption, set controller_object$error <- NULL after you are finished troubleshooting.

  • "warn": throw a warning. This allows the return value with all the error messages and tracebacks to be generated.

  • "silent": do nothing special. NOTE: the only kinds of errors considered here are errors at the R level. A crashed tasks will return a status of "crash" in the output and not trigger an error in map() unless crashes_max is reached.

warnings

Logical of length 1, whether to throw a warning in the interactive session if at least one task encounters an error.

verbose

Logical of length 1, whether to print to a progress bar as tasks resolve.

scale

Logical, whether to automatically scale workers to meet demand. See also the throttle argument.

throttle

TRUE to skip auto-scaling if it already happened within the last polling interval. FALSE to auto-scale every time scale() is called. Throttling avoids overburdening the local R process.

controller

Not used. Included to ensure the signature is compatible with the analogous method of controller groups.

Details

map() cannot be used unless all prior tasks are completed and popped. You may need to wait and then pop them manually. Alternatively, you can start over: either call terminate() on the current controller object to reset it, or create a new controller object entirely.

Returns

A tibble of results and metadata: one row per task and columns corresponding to the output of pop().

Method pop()

Pop a completed task from the results data frame.

Usage
crew_class_controller$pop(
  scale = TRUE,
  collect = NULL,
  throttle = TRUE,
  error = NULL,
  controllers = NULL
)
Arguments
scale

Logical of length 1, whether to automatically call scale() to auto-scale workers to meet the demand of the task load. Scaling up on pop() may be important for transient or nearly transient workers that tend to drop off quickly after doing little work. See also the throttle argument.

collect

Deprecated in version 0.5.0.9003 (2023-10-02).

throttle

TRUE to skip auto-scaling if it already happened within the last polling interval. FALSE to auto-scale every time scale() is called. Throttling avoids overburdening the local R process.

error

NULL or character of length 1, choice of action if the popped task threw an error. Possible values:

  • "stop": throw an error in the main R session instead of returning a value.

  • "warn": throw a warning.

  • NULL or "silent": do not react to errors. NOTE: the only kinds of errors considered here are errors at the R level. A crashed tasks will return a status of "crash" in the output and not trigger an error in pop() unless crashes_max is reached.

controllers

Not used. Included to ensure the signature is compatible with the analogous method of controller groups.

Details

If not task is currently completed, pop() will attempt to auto-scale workers as needed.

Returns

If there is no task to collect, return NULL. Otherwise, return a one-row tibble with the following columns.

  • name: the task name.

  • command: a character string with the R command.

  • result: a list containing the return value of the R command. NA if the task failed.

  • status: a character string. "success" if the task succeeded, "cancel" if the task was canceled with the cancel() controller method, "crash" if the worker running the task exited before it could complete the task, or "error" for any other kind of error.

  • error: the first 2048 characters of the error message if the task status is not "success", NA otherwise. Messages for crashes and cancellations are captured here alongside ordinary R-level errors.

  • code: an integer code denoting the specific exit status: 0 for successful tasks, -1 for tasks with an error in the R command of the task, and another positive integer with an NNG status code if there is an error at the NNG/nanonext level. nanonext::nng_error() can interpret these codes.

  • trace: the first 2048 characters of the text of the traceback if the task threw an error, NA otherwise.

  • warnings: the first 2048 characters. of the text of warning messages that the task may have generated, NA otherwise.

  • seconds: number of seconds that the task ran.

  • seed: the single integer originally supplied to push(), NA otherwise. The pseudo-random number generator state just prior to the task can be restored using set.seed(seed = seed, kind = algorithm), where seed and algorithm are part of this output.

  • algorithm: name of the pseudo-random number generator algorithm originally supplied to push(), NA otherwise. The pseudo-random number generator state just prior to the task can be restored using set.seed(seed = seed, kind = algorithm), where seed and algorithm are part of this output.

  • controller: name of the crew controller where the task ran.

  • worker: name of the crew worker that ran the task.

Method collect()

Pop all available task results and return them in a tidy tibble.

Usage
crew_class_controller$collect(
  scale = TRUE,
  throttle = TRUE,
  error = NULL,
  controllers = NULL
)
Arguments
scale

Logical of length 1, whether to automatically call scale() to auto-scale workers to meet the demand of the task load.

throttle

TRUE to skip auto-scaling if it already happened within the last polling interval. FALSE to auto-scale every time scale() is called. Throttling avoids overburdening the local R process.

error

NULL or character of length 1, choice of action if the popped task threw an error. Possible values: * "stop": throw an error in the main R session instead of returning a value. * "warn": throw a warning. * NULL or "silent": do not react to errors. NOTE: the only kinds of errors considered here are errors at the R level. A crashed tasks will return a status of "crash" in the output and not trigger an error in collect() unless crashes_max is reached.

controllers

Not used. Included to ensure the signature is compatible with the analogous method of controller groups.

Returns

A tibble of results and metadata of all resolved tasks, with one row per task. Returns NULL if there are no tasks to collect. See pop() for details on the columns of the returned tibble.

Method wait()

Wait for tasks.

Usage
crew_class_controller$wait(
  mode = "all",
  seconds_interval = NULL,
  seconds_timeout = Inf,
  scale = TRUE,
  throttle = TRUE,
  controllers = NULL
)
Arguments
mode

Character string, name of the waiting condition. wait(mode = "all") waits until all tasks in the mirai compute profile resolve, and wait(mode = "one") waits until at least one task is available to push() or collect() from the controller. The former still works if the controller is not the only means of submitting tasks to the compute profile, whereas the latter assumes only the controller submits tasks.

seconds_interval

Deprecated on 2025-01-17 (crew version 0.10.2.9003). Instead, the seconds_interval argument passed to crew_controller_group() is used as seconds_max in a crew_throttle() object which orchestrates exponential backoff.

seconds_timeout

Timeout length in seconds waiting for tasks.

scale

Logical, whether to automatically call scale() to auto-scale workers to meet the demand of the task load. See also the throttle argument.

throttle

TRUE to skip auto-scaling if it already happened within the last polling interval. FALSE to auto-scale every time scale() is called. Throttling avoids overburdening the local R process.

controllers

Not used. Included to ensure the signature is compatible with the analogous method of controller groups.

Details

The wait() method blocks the calling R session and (optionally) auto-scales workers until the condition in the mode argument is met. NOTE: wait() may register a task as resolved a split second before the task handle is ready for pop() or collect(). If wait() returns but pop() returns NULL, simply retry pop() a short time later.

Returns

A logical of length 1, invisibly. wait(mode = "all") returns TRUE if all tasks in the mirai compute profile have resolved (FALSE otherwise). wait(mode = "one") returns TRUE if the controller is ready to pop or collect at least one resolved task (FALSE otherwise). wait(mode = "one") assumes all tasks were submitted through the controller and not by other means.

Method push_backlog()

Push the name of a task to the backlog.

Usage
crew_class_controller$push_backlog(name, controller = NULL)
Arguments
name

Character of length 1 with the task name to push to the backlog.

controller

Not used. Included to ensure the signature is compatible with the analogous method of controller groups.

Details

pop_backlog() pops the tasks that can be pushed without saturating the controller.

Returns

NULL (invisibly).

Method pop_backlog()

Pop the task names from the head of the backlog which can be pushed without saturating the controller.

Usage
crew_class_controller$pop_backlog(controllers = NULL)
Arguments
controllers

Not used. Included to ensure the signature is compatible with the analogous method of controller groups.

Returns

Character vector of task names which can be pushed to the controller without saturating it. If the controller is saturated, character(0L) is returned.

Method summary()

Summarize the collected tasks of the controller.

Usage
crew_class_controller$summary(controllers = NULL)
Arguments
controllers

Not used. Included to ensure the signature is compatible with the analogous method of controller groups.

Returns

A data frame of cumulative summary statistics on the tasks collected through pop() and collect(). It has one row and the following columns:

  • controller: name of the controller.

  • seconds: total number of runtime in seconds.

  • tasks: total number of tasks collected.

  • success: total number of collected tasks that did not crash or error.

  • error: total number of tasks with errors, either in the R code of the task or an NNG-level error that is not a cancellation or crash.

  • crash: total number of crashed tasks (where the worker exited unexpectedly while it was running the task).

  • cancel: total number of tasks interrupted with the cancel() controller method.

  • warning: total number of tasks with one or more warnings.

Method cancel()

Cancel one or more tasks.

Usage
crew_class_controller$cancel(names = character(0L), all = FALSE)
Arguments
names

Character vector of names of tasks to cancel. Those names must have been manually supplied by push().

all

TRUE to cancel all tasks, FALSE otherwise. all = TRUE supersedes the names argument.

Returns

NULL (invisibly).

Method pids()

Deprecated on 2025-08-26 in crew version 1.2.1.9005.

Usage
crew_class_controller$pids(controllers = NULL)
Arguments
controllers

Not used. Included to ensure the signature is compatible with the analogous method of controller groups.

Returns

The integer process ID of the current process.

Method terminate()

Terminate the workers and the mirai client.

Usage
crew_class_controller$terminate(controllers = NULL)
Arguments
controllers

Not used. Included to ensure the signature is compatible with the analogous method of controller groups.

Returns

NULL (invisibly).

See Also

Other controller: crew_controller()

Examples

if (identical(Sys.getenv("CREW_EXAMPLES"), "true")) {
client <- crew_client()
launcher <- crew_launcher_local()
controller <- crew_controller(client = client, launcher = launcher)
controller$start()
controller$push(name = "task", command = sqrt(4))
controller$wait()
controller$pop()
controller$terminate()
}

## ------------------------------------------------
## Method `crew_class_controller$new`
## ------------------------------------------------

if (identical(Sys.getenv("CREW_EXAMPLES"), "true")) {
client <- crew_client()
launcher <- crew_launcher_local()
controller <- crew_controller(client = client, launcher = launcher)
controller$start()
controller$push(name = "task", command = sqrt(4))
controller$wait()
controller$pop()
controller$terminate()
}

crew documentation built on Sept. 4, 2026, 9:07 a.m.

Related to crew_class_controller in crew...

crew index
Package overview Asynchronous Shiny apps Controller groups Introduction to crew Known risks of crew Launcher plugins Logging mirai workflows

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