Evaluates a Job's Expression on a Background Process.

Evaluates a Job's Expression on a Background Process.

Evaluates a Job's Expression on a Background Process.

Active bindings

hooks

A named list of currently registered callback hooks.

backlog

A list of Jobs waiting to run on this Worker.

job

The currently running Job.

r_session

The callr::r_session background process interface.

state

The Worker's state: 'starting', 'idle', 'busy', or 'stopped'.

loaded

A list of global variables and attached functions on this Worker.

uid

A short string, e.g. 'W11', that uniquely identifies this Worker.

Methods

Public methods

• Worker$new()

• Worker$print()

• Worker$start()

• Worker$stop()

• Worker$restart()

• Worker$on()

• Worker$run()

---

Method new()

Creates a background callr::r_session process for running Jobs.

Usage

Worker$new(
  globals = NULL,
  packages = NULL,
  init = NULL,
  hooks = NULL,
  options = callr::r_session_options()
)

Arguments

globals

A list or similar set of values that are added to the .GlobalEnv of workers.

packages

Character vector of package names to load on workers.

init

A call or R expression wrapped in curly braces to evaluate on each worker just once, immediately after start-up. Will have access to any variables defined by globals and assets from packages. Returned value is ignored.

hooks

A list of functions to run when the Worker state changes, of the form hooks = list(idle = function (worker) {...}, busy = ~{...}). The names of these functions should be starting, idle, busy, stopped, or '*'. '*' will be run every time the state changes, whereas the others will only be run when the Worker enters that state. Duplicate names are allowed.

options

Passed to callr::r_session$new()

Returns

A Worker object.

---

Method print()

Print method for a Worker.

Usage

Worker$print(...)

Arguments

...

Arguments are not used currently.

Returns

The Worker, invisibly.

---

Method start()

Starts a new background callr::r_session process using the configuration previously defined with Worker$new().

Usage

Worker$start()

Returns

The Worker, invisibly.

---

Method stop()

Stops a Worker by terminating the background callr::r_session process and calling <Job>$stop(reason) on any Jobs currently assigned to this Worker.

Usage

Worker$stop(reason = "worker stopped by user")

Arguments

reason

Passed to <Job>$stop(reason) for any Jobs currently assigned to this Worker.

Returns

The Worker, invisibly.

---

Method restart()

Restarts a Worker by calling <Worker>$stop(reason) and <Worker>$start() in succession.

Usage

Worker$restart(reason = "restarting worker")

Arguments

reason

Passed to <Job>$stop(reason) for any Jobs currently assigned to this Worker.

Returns

The Worker, invisibly.

---

Method on()

Attach a callback function.

Usage

Worker$on(state, func)

Arguments

state

The Worker state that will trigger this function. Typically one of:

'*' -

Every time the state changes.

'.next' -

Only one time, the next time the state changes.

'starting' -

After starting a new callr::r_session process.

'idle' -

Waiting on new Jobs to be added.

'busy' -

After a Job starts running.

'stopped' -

After <Worker>$stop() is called.

func

A function that accepts a Worker object as input. You can call <Worker>$stop() or edit its values and the changes will be persisted (since Workers are reference class objects). You can also edit/stop the active or backlogged jobs by modifying <Worker>$job or <Worker>$backlog. Return value is ignored.

Returns

A function that when called removes this callback from the Worker.

---

Method run()

Assigns a Job to this Worker for evaluation on its background callr::r_session process. Jobs can be assigned even when the Worker is in the 'starting' or 'busy' state. A backlog of jobs will be evaluated sequentially in the order they were added.

Usage

Worker$run(job)

Arguments

job

A Job object, as created by Job$new().

Returns

This Worker, invisibly.