T M
role Scheduler
Error ReportCollection examples

Scheme for automatically assigning tasks to threads

role Scheduler {
    has &.uncaught_handler is rw
}

A scheduler is a piece of code that determines which resources to use to run which task, and when. This role contains code that will be the same for all kinds of schedulers.

Some operations for example on Proc::Async, Promise, Supply allow you to specify a scheduler explicitly; they generally expect those schedulers to follow the interface defined by Scheduler.

Methods

method uncaught_handler

method uncaught_handler() is rw

RW-Accessor for the handler that is caught for uncaught exceptions from the code that is being scheduled and run.

method cue

method cue(&codeInstant :$at:$in:$every:$times = 1:&catch --> Cancellation)

Schedules a callable (&code) for execution and returns an instantiated Cancellation object to cancel the scheduling of the code for execution (which is especially important if you specify the :every ( time ) named parameter). The adverbs control when and how the code is run:

  • $at can be an Instant before which the code won't be run. Alternatively $in is the number of seconds (possibly fractional) to wait before running the code. If $at is in the past or $in is negative, the delay is treated as zero. Implementations may equate to zero very small values (e.g. lower than 0.001s) of $in or result of $at - now.

  • If $every is specified, it is interpreted as the number of seconds (possibly fractional) to wait before re-executing the code. Implementations may treat too-small values as lowest resolution they support, possibly warning in such situations; e.g. treating 0.0001 as 0.001.

  • $times tells the scheduler how many times to run the code.

  • &catch is called with the Exception as its sole argument if &code dies.

  • If $at or $in are Inf, &code will never be run; if $every is Inf, &code will only be run once. If any of the three are -Inf, &code will be run immediately. If any of the three are NaN, an X::Scheduler::CueInNaNSeconds exception will be thrown. This only applies to releases 2019.05 and later.

One should call the cancel method on the returned Cancellation object to cancel the (possibly repeated) cueing of the code.

method loads

Defined as:

method loads()

This is a method stub, should be re-implemented when subclassing.