Allow a value of 0 with :vent-at

[lizmat]

Hopefully fixing #5358

[lizmat]

@amano-kenji @AlexDaniel could you check this out the coming days so that it can make the 2023.10 release due this Thursday?

[amano-kenji]

I will test this next morning.

[amano-kenji]

I tried to test it. I built it with

perl Configure.pl --gen-moar --gen-nqp --backend=moar

But, I can't find rakudo executable anywhere.

When I call

multi method throttle(Supply:D:
      Int()  $elems,
      Callable:D $process,
      Real() $delay = 0,
      :$scheduler   = $*SCHEDULER,
      :$control,
      :$status,
      :$bleed,
      :$vent-at,
    )

I want only one process to be executed at a time, and while the process is being executed, I want the supply to drop all incoming messages. Does vent-at(0) do that?

[lizmat]

That's the idea. If you also specify :bleed of course?

[amano-kenji]

If I also specify :bleed, while process is busy, I want the supply to send everything to bleed which will get rid of excess.

[amano-kenji]

If that works properly as expected, then I think it should be okay to merge it without us.

[lizmat]

If that works properly as expected, then I think it should be okay to merge it without us.

That's it: I didn't test it, as I don't really have an easy test case.

Anyway, it is too late for the 2023.10 release, which will be today.

[amano-kenji]

How can I test this without installing rakudo?

[ab5tract]

@amano-kenji You have to use this git repo checked out to the branch of this PR (lizmat-vet-0). First you run perl Configure.pl --gen-moar --gen-nqp --backends=moar and then run make. This will create executables in the directory. No installation necessary.

[amano-kenji]

I got rakudo-m executable which seemed to be what I wanted.

I executed this.

my $supplier = Supplier.new;

my $chan = $supplier.Supply.throttle(1, -> $a { sleep 5; $a; }, :bleed(Supplier.new), :vent-at(0)).Channel;

start {
  for [1..*] {
    sleep 0.1;
    $supplier.emit($_);
  }
}

react {
  whenever $chan {
    say $_.result;
  }
}

The output was

1
51
101
151
...

It seems to do what I want, but I will have to see whether this is performant.

[ab5tract]

FWIW I was unable to achieve the behavior that @amano-kenji reported when using this branch on macOS 14.

[ab5tract]

I've rebased this against current main and still unfortunately do not get the expected results:

~/c/r/z/rakudo ((6435e28b))
> ./rakudo-m ~/code/raku/scripts/ventatzeroraku/vent-at-zero.raku
1
49
97
145
194
242
291