Fetch single task result

Get the result for a single task (see rrq_task_results for a method for efficiently getting multiple results at once). Returns the value of running the task if it is complete, and an error otherwise.

Usage

rrq_task_result(task_id, error = FALSE, follow = NULL, controller = NULL)

Arguments

task_id

The single id for which the result is wanted.

error

Logical, indicating if we should throw an error if a task was not successful. By default (error = FALSE), in the case of the task result returning an error we return an object of class rrq_task_error, which contains information about the error. Passing error = TRUE calls stop() on this error if it is returned.

follow

Optional logical, indicating if we should follow any redirects set up by doing rrq_task_retry. If not given, falls back on the value passed into the controller, the global option rrq.follow, and finally TRUE. Set to FALSE if you want to return information about the original task, even if it has been subsequently retried.

controller

The controller to use. If not given (or NULL) we'll use the controller registered with rrq_default_controller_set().

Value

The result of your task. This may be an error (an object with class rrq_task_error) if your task has failed.

Examples

obj <- rrq_controller("rrq:example")

# Create a task, wait for it to finish and fetch its result
t <- rrq_task_create_expr(runif(1), controller = obj)
rrq_task_wait(t, controller = obj)
#> [1] TRUE
rrq_task_result(t, controller = obj)
#> [1] 0.7242312

# Tasks that fail do not fail on result, but instead return an
# object with the class "rrq_task_error"
t <- rrq_task_create_expr(readRDS("somefile.rds"), controller = obj)
rrq_task_wait(t, controller = obj)
#> [1] FALSE
rrq_task_result(t, controller = obj)
#> <rrq_task_error>
#>   from:   gzfile(file, "rb")
#>   error:  cannot open the connection
#>   queue:  rrq:example
#>   task:   e4abc6863a5ab63b5fa8e693ba7600f7
#>   status: ERROR
#>   * To throw this error, use stop() with it
#>   * This error has a stack trace, use '$trace' to see it
#>   * This error has warnings, use '$warnings' to see them