client |
An R6 client object created by crew_client() .
|
launcher |
An R6 launcher object created by one of the
crew_launcher_*() functions such as crew_launcher_local() .
|
reset_globals |
TRUE to reset global environment
variables between tasks, FALSE to leave them alone.
|
reset_packages |
TRUE to detach any packages loaded during
a task (runs between each task), FALSE to leave packages alone.
In either case, the namespaces are not detached.
|
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.
for this and other reasons, reset_options only resets options
that were nonempty at the beginning of the task.
If your task sets an entirely new option not already in options() ,
then reset_options = TRUE does not delete the option.
|
garbage_collection |
TRUE to run garbage collection after each task
task, FALSE to skip.
|
crashes_max |
In rare cases, a worker may exit unexpectedly
before it completes its current task. If this happens, pop()
returns a status of "crash" instead of "error" for the task.
The controller does not automatically retry the task, but
you can retry it manually by calling push() again and using the same
task name as before. (However, targets pipelines running crew
do automatically retry tasks whose workers crashed.)
crashes_max is a non-negative integer, and it sets the maximum number of
allowable consecutive crashes for a given task.
If a task's worker crashes more than crashes_max times in a row,
then pop() throws an error when it tries to return the results
of the task.
|
backup |
An optional crew controller object, or NULL to omit.
If supplied, the backup controller runs any pushed tasks that have
already reached crashes_max consecutive crashes.
Using backup , you can create
a chain of controllers with different levels of resources
(such as worker memory and CPUs) so that a task that fails on
one controller can retry using incrementally more powerful workers.
All controllers in a backup chain should be part of the same
controller group (see crew_controller_group() ) so you can call the
group-level pop() and collect() methods to make sure you get results
regardless of which controller actually ended up running the task.
Limitations of backup :
* crashes_max needs to be positive in order for backup to be used.
Otherwise, every task would always skip the current controller and
go to backup .
* backup cannot be a controller group. It must be an ordinary
controller.
|
auto_scale |
Deprecated. Use the scale argument of push() ,
pop() , and wait() instead.
|