taskqueue (version 0.2.0)

worker: Execute Tasks as a Worker

Description

Runs as a worker process that continuously fetches and executes tasks from a project until no tasks remain or the project is stopped.

Usage

worker(project, fun, ...)

Value

Does not return normally. Stops when: no more tasks are available, the project is stopped, or runtime limit is reached (SLURM only).

Arguments

project

Character string specifying the project name.

fun

Function to execute for each task. Must accept the task ID as its first argument. The function should save its results to disk and is not expected to return a value.

...

Additional arguments passed to fun for every task.

Details

This function implements the worker loop:

1. Request a task from the database (atomically)

2. Update task status to "working"

3. Execute fun(task_id, ...)

4. Update task status to "finished" (or "failed" if error)

5. Repeat until no more tasks or stopping condition

Workers automatically:

• Add random delays to reduce database contention

• Track runtime to respect SLURM walltime limits

• Reconnect to database on connection failures

• Log progress and errors to console

Your worker function should:

• Check if output already exists (idempotent)

• Save results to disk (not return them)

• Handle errors gracefully or let them propagate

For SLURM resources, set the TASKQUEUE_RESOURCE environment variable to enable automatic walltime management.

See Also

worker_slurm, task_add, project_start, tq_apply

Examples

if (FALSE) {
# Not run:
# Define worker function
my_task <- function(task_id, param1, param2) {
  out_file <- sprintf("results/task_%04d.Rds", task_id)
  if (file.exists(out_file)) return()  # Skip if done
 
  result <- expensive_computation(task_id, param1, param2)
  saveRDS(result, out_file)
}

# Run worker locally (for testing)
worker("test_project", my_task, param1 = 10, param2 = "value")
}