worker_class: A Background Process (R6 Class)
In jobqueue: Run Interruptible Code Asynchronously
worker_class R Documentation
A Background Process (R6 Class)
Description
Where job expressions are evaluated.
Active bindings
hooksA named list of currently registered callback hooks.
jobThe currently running job.
psThe ps::ps_handle() object for the background process.
stateThe worker's state: 'starting', 'idle', 'busy',
or 'stopped'.
uidA short string, e.g. 'W11', that uniquely identifies this
worker.
tmpThe worker's temporary directory.
cndThe error that caused the worker to stop.
Methods
Public methods
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Method new()
Creates a background R process for running jobs.
Usage
worker_class$new(
globals = NULL,
packages = NULL,
namespace = NULL,
init = NULL,
hooks = NULL,
wait = TRUE,
timeout = Inf
)
Arguments
globalsA named list of variables that all <job>$exprs will have
access to. Alternatively, an object that can be coerced to a named
list with as.list(), e.g. named vector, data.frame, or environment.
packagesCharacter vector of package names to load on
workers.
namespaceThe name of a package to attach to the
worker's environment.
initA call or R expression wrapped in curly braces to evaluate on
each worker just once, immediately after start-up.
Will have access to variables defined by globals and assets from
packages and namespace. Returned value is ignored.
hooksA named list of functions to run when the
worker state changes, of the form
hooks = list(idle = function (worker) {...}). Names of
worker hooks are typically starting, idle,
busy, stopped, or '*' (duplicates okay).
See vignette('hooks').
waitIf TRUE, blocks until the worker is 'idle'.
If FALSE, the worker object is returned in the
'starting' state.
timeoutHow long to wait for the worker to finish
starting (in seconds). If NA, defaults to the worker_class$new()
argument.
Returns
A worker object.
Method print()
Print method for a worker.
Usage
worker_class$print(...)
Arguments
...Arguments are not used currently.
Returns
The worker, invisibly.
Method start()
Restarts a stopped worker.
Usage
worker_class$start(wait = TRUE, timeout = NA)
Arguments
waitIf TRUE, blocks until the worker is 'idle'.
If FALSE, the worker object is returned in the
'starting' state.
timeoutHow long to wait for the worker to finish
starting (in seconds). If NA, defaults to the worker_class$new()
argument.
Returns
The worker, invisibly.
Method stop()
Stops a worker by terminating the background process
and calling <job>$stop(reason) on any jobs currently
assigned to this worker.
Usage
worker_class$stop(reason = "worker stopped by user", cls = NULL)
Arguments
reasonPassed to <job>$stop() for any jobs
currently managed by this worker.
clsPassed to <job>$stop() for any jobs currently
managed by this worker.
Returns
The worker, invisibly.
Method restart()
Restarts a worker by calling <worker>$stop(reason)
and <worker>$start() in succession.
Usage
worker_class$restart(
wait = TRUE,
timeout = NA,
reason = "restarting worker",
cls = NULL
)
Arguments
waitIf TRUE, blocks until the worker is 'idle'.
If FALSE, the worker object is returned in the
'starting' state.
timeoutHow long to wait for the worker to finish
starting (in seconds). If NA, defaults to the worker_class$new()
argument.
reasonPassed to <job>$stop() for any jobs
currently managed by this worker.
clsPassed to <job>$stop() for any jobs currently
managed by this worker.
Returns
The worker, invisibly.
Method on()
Attach a callback function to execute when the worker
enters state.
Usage
worker_class$on(state, func)
Arguments
stateThe name of a worker state. Typically one of:
-
'*' - Every time the state changes.
-
'.next' - Only one time, the next time the state changes.
-
'starting' - Waiting for the background process to load.
-
'idle' - Waiting for jobs to be $run().
-
'busy' - While a job is running.
-
'stopped' - After <worker>$stop() is called.
funcA function that accepts a worker object as
input. You can call <worker>$stop() and other <worker>$ methods.
Returns
A function that when called removes this callback from the
worker.
Method wait()
Blocks until the worker enters the given state.
Usage
worker_class$wait(state = "idle", timeout = Inf, signal = TRUE)
Arguments
stateThe name of a worker state. Typically one of:
-
'*' - Every time the state changes.
-
'.next' - Only one time, the next time the state changes.
-
'starting' - Waiting for the background process to load.
-
'idle' - Waiting for jobs to be $run().
-
'busy' - While a job is running.
-
'stopped' - After <worker>$stop() is called.
timeoutStop the worker if it takes longer than
this number of seconds.
signalRaise an error if encountered (will also be recorded in
<worker>$cnd).
Returns
This worker, invisibly.
Method run()
Assigns a job to this worker for
evaluation on the background process.
Usage
worker_class$run(job)
Arguments
jobA job object, as created by job_class$new().
Returns
This worker, invisibly.
jobqueue documentation built on June 8, 2025, 12:45 p.m.
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| worker_class | R Documentation |
A Background Process (R6 Class)
Description
Where job expressions are evaluated.
Active bindings
hooksA named list of currently registered callback hooks.
jobThe currently running
job.psThe
ps::ps_handle()object for the background process.stateThe
worker'sstate:'starting','idle','busy', or'stopped'.uidA short string, e.g.
'W11', that uniquely identifies thisworker.tmpThe
worker'stemporary directory.cndThe error that caused the
workerto stop.
Methods
Public methods
Method new()
Creates a background R process for running jobs.
Usage
worker_class$new( globals = NULL, packages = NULL, namespace = NULL, init = NULL, hooks = NULL, wait = TRUE, timeout = Inf )
Arguments
globalsA named list of variables that all
<job>$exprs will have access to. Alternatively, an object that can be coerced to a named list withas.list(), e.g. named vector, data.frame, or environment.packagesCharacter vector of package names to load on
workers.namespaceThe name of a package to attach to the
worker'senvironment.initA call or R expression wrapped in curly braces to evaluate on each
workerjust once, immediately after start-up. Will have access to variables defined byglobalsand assets frompackagesandnamespace. Returned value is ignored.hooksA named list of functions to run when the
workerstate changes, of the formhooks = list(idle = function (worker) {...}). Names ofworkerhooks are typicallystarting,idle,busy,stopped, or'*'(duplicates okay). Seevignette('hooks').waitIf
TRUE, blocks until theworkeris 'idle'. IfFALSE, theworkerobject is returned in the 'starting' state.timeoutHow long to wait for the
workerto finish starting (in seconds). IfNA, defaults to theworker_class$new()argument.
Returns
A worker object.
Method print()
Print method for a worker.
Usage
worker_class$print(...)
Arguments
...Arguments are not used currently.
Returns
The worker, invisibly.
Method start()
Restarts a stopped worker.
Usage
worker_class$start(wait = TRUE, timeout = NA)
Arguments
waitIf
TRUE, blocks until theworkeris 'idle'. IfFALSE, theworkerobject is returned in the 'starting' state.timeoutHow long to wait for the
workerto finish starting (in seconds). IfNA, defaults to theworker_class$new()argument.
Returns
The worker, invisibly.
Method stop()
Stops a worker by terminating the background process
and calling <job>$stop(reason) on any jobs currently
assigned to this worker.
Usage
worker_class$stop(reason = "worker stopped by user", cls = NULL)
Arguments
reasonPassed to
<job>$stop()for anyjobscurrently managed by thisworker.clsPassed to
<job>$stop()for anyjobscurrently managed by thisworker.
Returns
The worker, invisibly.
Method restart()
Restarts a worker by calling <worker>$stop(reason)
and <worker>$start() in succession.
Usage
worker_class$restart( wait = TRUE, timeout = NA, reason = "restarting worker", cls = NULL )
Arguments
waitIf
TRUE, blocks until theworkeris 'idle'. IfFALSE, theworkerobject is returned in the 'starting' state.timeoutHow long to wait for the
workerto finish starting (in seconds). IfNA, defaults to theworker_class$new()argument.reasonPassed to
<job>$stop()for anyjobscurrently managed by thisworker.clsPassed to
<job>$stop()for anyjobscurrently managed by thisworker.
Returns
The worker, invisibly.
Method on()
Attach a callback function to execute when the worker
enters state.
Usage
worker_class$on(state, func)
Arguments
stateThe name of a
workerstate. Typically one of:-
'*'- Every time the state changes. -
'.next'- Only one time, the next time the state changes. -
'starting'- Waiting for the background process to load. -
'idle'- Waiting forjobsto be$run(). -
'busy'- While ajobis running. -
'stopped'- After<worker>$stop()is called.
-
funcA function that accepts a
workerobject as input. You can call<worker>$stop()and other<worker>$methods.
Returns
A function that when called removes this callback from the
worker.
Method wait()
Blocks until the worker enters the given state.
Usage
worker_class$wait(state = "idle", timeout = Inf, signal = TRUE)
Arguments
stateThe name of a
workerstate. Typically one of:-
'*'- Every time the state changes. -
'.next'- Only one time, the next time the state changes. -
'starting'- Waiting for the background process to load. -
'idle'- Waiting forjobsto be$run(). -
'busy'- While ajobis running. -
'stopped'- After<worker>$stop()is called.
-
timeoutStop the
workerif it takes longer than this number of seconds.signalRaise an error if encountered (will also be recorded in
<worker>$cnd).
Returns
This worker, invisibly.
Method run()
Assigns a job to this worker for
evaluation on the background process.
Usage
worker_class$run(job)
Arguments
jobA
jobobject, as created byjob_class$new().
Returns
This worker, invisibly.
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