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crew_class_controller_group: Controller group class

crew_class_controller_group: Controller group class
In crew: A Distributed Worker Launcher Framework

crew_class_controller_groupR Documentation

Controller group class

Description

R6 class for controller groups.

Details

See crew_controller_group().

Active bindings

controllers

List of R6 controller objects.

relay

Relay object for event-driven programming on a downstream condition variable.

throttle

crew_throttle() object to orchestrate exponential backoff in the relay and auto-scaling.

Methods

Public methods

Method new()

Multi-controller constructor.

Usage
crew_class_controller_group$new(
  controllers = NULL,
  relay = NULL,
  throttle = NULL
)
Arguments
controllers

List of R6 controller objects.

relay

Relay object for event-driven programming on a downstream condition variable.

throttle

crew_throttle() object to orchestrate exponential backoff in the relay and auto-scaling.

Returns

An R6 object with the controller group object.

Examples
if (identical(Sys.getenv("CREW_EXAMPLES"), "true")) {
persistent <- crew_controller_local(name = "persistent")
transient <- crew_controller_local(
  name = "transient",
  tasks_max = 1L
)
group <- crew_controller_group(persistent, transient)
group$start()
group$push(name = "task", command = sqrt(4), controller = "transient")
group$wait()
group$pop()
group$terminate()
}

Method validate()

Validate the client.

Usage
crew_class_controller_group$validate()
Returns

NULL (invisibly).

Method empty()

See if the controllers are empty.

Usage
crew_class_controller_group$empty(controllers = NULL)
Arguments
controllers

Character vector of controller names. Set to NULL to select all controllers.

Details

A controller is empty if it has no running tasks or completed tasks waiting to be retrieved with push().

Returns

TRUE if all the selected controllers are empty, FALSE otherwise.

Method nonempty()

Check if the controller group is nonempty.

Usage
crew_class_controller_group$nonempty(controllers = NULL)
Arguments
controllers

Character vector of controller names. Set to NULL to select all controllers.

Details

A controller is empty if it has no running tasks or completed tasks waiting to be retrieved with push().

Returns

TRUE if the controller is empty, FALSE otherwise.

Method resolved()

Number of resolved mirai() tasks.

Usage
crew_class_controller_group$resolved(controllers = NULL)
Arguments
controllers

Character vector of controller names. Set to NULL to select all controllers.

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 mirai() 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 mirai() tasks.

Usage
crew_class_controller_group$unresolved(controllers = NULL)
Arguments
controllers

Character vector of controller names. Set to NULL to select all controllers.

Returns

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

Method unpopped()

Number of resolved mirai() tasks available via pop().

Usage
crew_class_controller_group$unpopped(controllers = NULL)
Arguments
controllers

Character vector of controller names. Set to NULL to select all controllers.

Returns

Non-negative integer of length 1, number of resolved mirai() tasks available via pop().

Method saturated()

Check if a controller is saturated.

Usage
crew_class_controller_group$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

Character vector of length 1 with the controller name. Set to NULL to select the default controller that push() would choose.

Details

A controller is saturated if the number of unresolved tasks is greater than or equal to the maximum number of workers. In other words, in a saturated controller, every available worker has a task. You can still push tasks to a saturated controller, but tools that use crew such as targets may choose not to.

Returns

TRUE if all the selected controllers are saturated, FALSE otherwise.

Method start()

Start one or more controllers.

Usage
crew_class_controller_group$start(controllers = NULL)
Arguments
controllers

Character vector of controller names. Set to NULL to select all controllers.

Returns

NULL (invisibly).

Method started()

Check whether all the given controllers are started.

Usage
crew_class_controller_group$started(controllers = NULL)
Arguments
controllers

Character vector of controller names. Set to NULL to select all controllers.

Details

Actually checks whether all the given clients are started.

Returns

TRUE if the controllers are started, FALSE if any are not.

Method launch()

Launch one or more workers on one or more controllers.

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

Number of workers to launch in each controller selected.

controllers

Character vector of controller names. Set to NULL to select all controllers.

Returns

NULL (invisibly).

Method scale()

Automatically scale up the number of workers if needed in one or more controller objects.

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

TRUE to skip auto-scaling if it already happened within the last seconds_interval seconds. FALSE to auto-scale every time scale() is called. Throttling avoids overburdening the mirai dispatcher and other resources.

controllers

Character vector of controller names. Set to NULL to select all controllers.

Details

See the scale() method in individual controller classes.

Returns

Invisibly returns TRUE if 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 private later loop every controller$client$seconds_interval seconds.

Usage
crew_class_controller_group$autoscale(controllers = NULL)
Arguments
controllers

Character vector of controller names. Set to NULL to select all controllers.

Returns

NULL (invisibly).

Method descale()

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

Usage
crew_class_controller_group$descale(controllers = NULL)
Arguments
controllers

Character vector of controller names. Set to NULL to select all controllers.

Returns

NULL (invisibly).

Method crashes()

Report the number of consecutive crashes of a task, summed over all selected controllers in the group.

Usage
crew_class_controller_group$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

Number of consecutive crashes of the named task, summed over all the controllers in the group.

Method push()

Push a task to the head of the task list.

Usage
crew_class_controller_group$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. 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 algorithm and seed are both NULL, 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 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).

scale

Logical, whether to automatically scale workers to meet demand. See the scale argument of the push() method of ordinary single controllers.

throttle

TRUE to skip auto-scaling if it already happened within the last seconds_interval seconds. FALSE to auto-scale every time scale() is called. Throttling avoids overburdening the mirai dispatcher and other resources.

name

Character string, name of the task. If NULL, a random name is automatically generated. The task name must not conflict with an existing task in the controller where it is submitted. To reuse the name, wait for the existing task to finish, then either pop() or collect() it to remove it from its controller.

save_command

Deprecated on 2025-01-22 (crew version 0.10.2.9004).

controller

Character of length 1, name of the controller to submit the task. If NULL, the controller defaults to the first controller in the list.

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 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_group$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).

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 seconds_interval seconds. FALSE to auto-scale every time scale() is called. Throttling avoids overburdening the mirai dispatcher and other resources.

controller

Character of length 1, name of the controller to submit the tasks. If NULL, the controller defaults to the first controller in the list.

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.

Usage
crew_class_controller_group$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 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).

error

Character vector of length 1, choice of action if a task has an error. 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.

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 progress messages.

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 seconds_interval seconds. FALSE to auto-scale every time scale() is called. Throttling avoids overburdening the mirai dispatcher and other resources.

controller

Character of length 1, name of the controller to submit the tasks. If NULL, the controller defaults to the first controller in the list.

Details

The idea comes from functional programming: for example, the map() function from the purrr package.

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

Logical, whether to automatically scale workers to meet demand. See the scale argument of the pop() method of ordinary single controllers.

collect

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

throttle

TRUE to skip auto-scaling if it already happened within the last seconds_interval seconds. FALSE to auto-scale every time scale() is called. Throttling avoids overburdening the mirai dispatcher and other resources.

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.

controllers

Character vector of controller names. Set to NULL to select all controllers.

Returns

If there is no task to collect, return NULL. Otherwise, return a one-row tibble with the same columns as pop() for ordinary controllers.

Method collect()

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

Usage
crew_class_controller_group$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 seconds_interval seconds. FALSE to auto-scale every time scale() is called. Throttling avoids overburdening the mirai dispatcher and other resources.

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.

controllers

Character vector of controller names. Set to NULL to select all controllers.

Returns

A tibble of results and metadata of all resolved tasks, with one row per task. Returns NULL if there are no available results.

Method promise()

Create a promises::promise() object to asynchronously pop or collect one or more tasks.

Usage
crew_class_controller_group$promise(
  mode = "one",
  seconds_interval = 0.1,
  scale = NULL,
  throttle = NULL,
  controllers = NULL
)
Arguments
mode

Character of length 1, what kind of promise to create. mode must be "one" or "all". Details:

  • If mode is "one", then the promise is fulfilled (or rejected) when at least one task is resolved and available to pop(). When that happens, pop() runs asynchronously, pops a result off the task list, and returns a value. If the task succeeded, then the promise is fulfilled and its value is the result of pop() (a one-row tibble with the result and metadata). If the task threw an error, the error message of the task is forwarded to any error callbacks registered with the promise.

  • If mode is "all", then the promise is fulfilled (or rejected) when there are no unresolved tasks left in the controller. (Be careful: this condition is trivially met in the moment if the controller is empty and you have not submitted any tasks, so it is best to create this kind of promise only after you submit tasks.) When there are no unresolved tasks left, collect() runs asynchronously, pops all available results off the task list, and returns a value. If the task succeeded, then the promise is fulfilled and its value is the result of collect() (a tibble with one row per task result). If any of the tasks threw an error, then the first error message detected is forwarded to any error callbacks registered with the promise.

seconds_interval

Positive numeric of length 1, delay in the later::later() polling interval to asynchronously check if the promise can be resolved.

scale

Deprecated on 2024-04-10 (version 0.9.1.9003) and no longer used. Now, promise() always turns on auto-scaling in a private later loop (if not already activated).

throttle

Deprecated on 2024-04-10 (version 0.9.1.9003) and no longer used. Now, promise() always turns on auto-scaling in a private later loop (if not already activated).

controllers

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

Details

Please be aware that pop() or collect() will happen asynchronously at a some unpredictable time after the promise object is created, even if your local R process appears to be doing something completely different. This behavior is highly desirable in a Shiny reactive context, but please be careful as it may be surprising in other situations.

Returns

A promises::promise() object whose eventual value will be a tibble with results from one or more popped tasks. If mode = "one", only one task is popped and returned (one row). If mode = "all", then all the tasks are returned in a tibble with one row per task (or NULL is returned if there are no tasks to pop).

Method wait()

Wait for tasks.

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

Character of length 1: "all" to wait for all tasks in all controllers to complete, "one" to wait for a single task in a single controller to complete. In this scheme, the timeout limit is applied to each controller sequentially, and a timeout is treated the same as a completed controller.

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 results to become available.

scale

Logical of length 1, whether to call scale_later() on each selected controller to schedule auto-scaling. See the scale argument of the wait() method of ordinary single controllers.

throttle

TRUE to skip auto-scaling if it already happened within the last seconds_interval seconds. FALSE to auto-scale every time scale() is called. Throttling avoids overburdening the mirai dispatcher and other resources.

controllers

Character vector of controller names. Set to NULL to select all controllers.

Details

The wait() method blocks the calling R session and repeatedly auto-scales workers for tasks that need them. The function runs until it either times out or the condition in mode is met.

Returns

A logical of length 1, invisibly. TRUE if the condition in mode was met, FALSE otherwise.

Method push_backlog()

Push the name of a task to the backlog.

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

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

controller

Character vector of length 1 with the controller name. Set to NULL to select the default controller that push_backlog() would choose.

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_group$pop_backlog(controllers = NULL)
Arguments
controllers

Character vector of controller names. Set to NULL to select all controllers.

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 workers of one or more controllers.

Usage
crew_class_controller_group$summary(controllers = NULL)
Arguments
controllers

Character vector of controller names. Set to NULL to select all controllers.

Returns

A data frame of aggregated worker summary statistics of all the selected controllers. It has one row per worker, and the rows are grouped by controller. See the documentation of the summary() method of the controller class for specific information about the columns in the output.

Method pids()

Get the process IDs of the local process and the mirai dispatchers (if started).

Usage
crew_class_controller_group$pids(controllers = NULL)
Arguments
controllers

Character vector of controller names. Set to NULL to select all controllers.

Returns

An integer vector of process IDs of the local process and the mirai dispatcher (if started).

Method terminate()

Terminate the workers and disconnect the client for one or more controllers.

Usage
crew_class_controller_group$terminate(controllers = NULL)
Arguments
controllers

Character vector of controller names. Set to NULL to select all controllers.

Returns

NULL (invisibly).

See Also

Other controller_group: crew_controller_group()

Examples

if (identical(Sys.getenv("CREW_EXAMPLES"), "true")) {
persistent <- crew_controller_local(name = "persistent")
transient <- crew_controller_local(
  name = "transient",
  tasks_max = 1L
)
group <- crew_controller_group(persistent, transient)
group$start()
group$push(name = "task", command = sqrt(4), controller = "transient")
group$wait()
group$pop()
group$terminate()
}

## ------------------------------------------------
## Method `crew_class_controller_group$new`
## ------------------------------------------------

if (identical(Sys.getenv("CREW_EXAMPLES"), "true")) {
persistent <- crew_controller_local(name = "persistent")
transient <- crew_controller_local(
  name = "transient",
  tasks_max = 1L
)
group <- crew_controller_group(persistent, transient)
group$start()
group$push(name = "task", command = sqrt(4), controller = "transient")
group$wait()
group$pop()
group$terminate()
}

crew documentation built on June 9, 2025, 5:09 p.m.

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