task. rrqueue 0.1.4

Usage

task(obj, task_id, key_complete = NULL)

Arguments

obj: A queue or observer object.
task_id: Task identifier
key_complete: If known, specify the key_complete, otherwise we look it up on creation.

Description

Create a task handle object. This is a "pointer" to a task and can be used to retrieve information about status, running times, expression and the result of the task once complete. Generally you do not need to make a task object as they will be created for you by things like the task_get method of the observer and queue objects.

Details

Tasks have a unique identifier; these are unique within a queue and are implemented as an incrementing integer. However, this is an implementation detail and should not be relied on. The identifier is represented as a character string rather than an integer in most places.

Tasks exist in one of a number of statuses. See the status method below for a list of possible statuses and their interpretation.

Methods

status

Returns a scalar character indicating the task status.

Usage: status(follow_redirect = FALSE)

Arguments:

follow_redirect: should we follow redirects to get the status of any requeued task?

Value: Scalar character. Possible values are

PENDING: queued, but not run by a worker
RUNNING: being run on a worker, but not complete
COMPLETE: task completed successfully
ERROR: task completed with an error
ORPHAN: task orphaned due to loss of worker
REDIRECT: orphaned task has been redirected
MISSING: task not known (deleted, or never existed)

result

Fetch the result of a task, so long as it has completed.

Usage: result(follow_redirect = FALSE, sanitise = FALSE)

Arguments:

follow_redirect

should we follow redirects to get the status of any requeued task?

sanitise

If the task is not yet complete or is missing, return an UnfetchabmeTask object rather than throwing an error.

wait

Like result, but will wait until the task is complete. In order to preserve the key_complete for anything that might be listening for it (and to avoid collision with anything else writing to that key), this function repeatedly polls the database. Over a slow connection you may want to increase the every parameter.

Usage: wait(timeout = , every = 0.05)

Arguments:

timeout: Length of time, in seconds, to wait. A value of zero will not wait. Infinite times are possible and can be escaped by pressing Ctrl-C or Escape (depending on platform).
every: How often, in seconds, to poll for results

expr

returns the expression stored in the task

Usage: expr(locals = FALSE)

Arguments:

locals: Logical, indicating if the local variables associated with the expression should also be retuned. If TRUE, then local variables used in the expression will be returned in a attribute of the expression envir.

Value: A quoted expression (a language object). Turn this into a string with deparse. If locals was TRUE there will be an environment attribute with local variables included.

envir

returns the environment identifier for the task

Usage: envir()

times

returns a summar of times associated with this task.

Usage: times(unit_elapsed = "secs")

Arguments:

unit_elapsed: Unit to use in computing elapsed times. The default is to use "secs". This is passed through to difftime so the units there are available and are "auto", "secs", "mins", "hours", "days", "weeks".

Value: A one row data.frame with columns

submitted: Time the task was submitted
started: Time the task was started, or NA if waiting
finished: Time the task was completed, or NA if waiting or running
waiting: Elapsed time spent waiting
running: Elapsed time spent running, or NA if waiting
idle: Elapsed time since finished, or NA if waiting or running