From @smls

The following code attempts to pipe a large Blob (larger than a pipe's
buffer size) through an external command.
However, it hangs on the `.in.close` line and never finishes​:

  my $proc = run «cat -», :in, :out, :bin;
  my $input = ("a" x 1000000).encode;
  my $promise = start {
  $proc.in.write​: $input;
  $proc.in.close;
  }
  say $proc.out.slurp-rest(​:close, :bin).bytes;
  await $promise;

More verbose version of the code with debug output showing where it blocks​:
https://gist.github.com/smls/75518c746ca65b3287482c491971eac0

IRC comments​:

  <timotimo> moar sometimes gets confused, i think
  <timotimo> or maybe it's libuv

  <RabidGravy> shouldn't that give an error as other handles across threads do?

  <gfldex> you get the same behaviour with
  https://rt.perl.org/Public/Bug/Display.html?id=129787

Note that without the `start` (i.e. when writing to `.in` and then
reading from `.out` in the same thread), it already hangs on the
`.in.write`, as geekosaur explains​:

  <geekosaur> it will block if the process is not reading, yes. pipes have
  finite buffer space
  <geekosaur> whether this block is happening at OS level or if libuv is
  supposed to be using non-blocking operations and return a "would
  block, try again" and some higher level is blocking based on
  that, I cannot say

From @jnthn

On Fri Oct 14 16​:40​:27 2016, smls75@​gmail.com wrote​:

The following code attempts to pipe a large Blob (larger than a pipe's
buffer size) through an external command.
However, it hangs on the `.in.close` line and never finishes​:

my $proc = run «cat -», :in, :out, :bin;
my $input = ("a" x 1000000).encode;
my $promise = start {
$proc.in.write​: $input;
$proc.in.close;
}
say $proc.out.slurp-rest(​:close, :bin).bytes;
await $promise;

For now, if using threads, stick with Proc​::Async (in the future, we'll probably re-implement Proc/run etc. in terms of Proc​::Async).

/jnthn

The RT System itself - Status changed from 'new' to 'open'

From @dogbert17

On Wed, 19 Oct 2016 05​:57​:04 -0700, jnthn@​jnthn.net wrote​:

On Fri Oct 14 16​:40​:27 2016, smls75@​gmail.com wrote​:

The following code attempts to pipe a large Blob (larger than a
pipe's
buffer size) through an external command.
However, it hangs on the `.in.close` line and never finishes​:

my $proc = run «cat -», :in, :out, :bin;
my $input = ("a" x 1000000).encode;
my $promise = start {
$proc.in.write​: $input;
$proc.in.close;
}
say $proc.out.slurp-rest(​:close, :bin).bytes;
await $promise;

For now, if using threads, stick with Proc​::Async (in the future,
we'll probably re-implement Proc/run etc. in terms of Proc​::Async).

/jnthn

jnthn recently made the above mentioned re-implementation so the code shown in the report now works.

Closing issue

@dogbert17 - Status changed from 'open' to 'resolved'

From @AlexDaniel

That's pretty good. But issues are not closed without tests, unless there's a good reason not to add a test. No reason was mentioned, therefore reopening this with “testneeded” tag.

On 2017-07-09 15​:49​:46, jan-olof.hendig@​bredband.net wrote​:

On Wed, 19 Oct 2016 05​:57​:04 -0700, jnthn@​jnthn.net wrote​:

On Fri Oct 14 16​:40​:27 2016, smls75@​gmail.com wrote​:

The following code attempts to pipe a large Blob (larger than a
pipe's
buffer size) through an external command.
However, it hangs on the `.in.close` line and never finishes​:

my $proc = run «cat -», :in, :out, :bin;
my $input = ("a" x 1000000).encode;
my $promise = start {
$proc.in.write​: $input;
$proc.in.close;
}
say $proc.out.slurp-rest(​:close, :bin).bytes;
await $promise;

For now, if using threads, stick with Proc​::Async (in the future,
we'll probably re-implement Proc/run etc. in terms of Proc​::Async).

/jnthn

jnthn recently made the above mentioned re-implementation so the code
shown in the report now works.

Closing issue

@AlexDaniel - Status changed from 'resolved' to 'open'

From @AlexDaniel

Test in Raku/roast@195227f

On 2017-07-09 19​:40​:57, alex.jakimenko@​gmail.com wrote​:

That's pretty good. But issues are not closed without tests, unless
there's a
good reason not to add a test. No reason was mentioned, therefore
reopening
this with “testneeded” tag.

On 2017-07-09 15​:49​:46, jan-olof.hendig@​bredband.net wrote​:

On Wed, 19 Oct 2016 05​:57​:04 -0700, jnthn@​jnthn.net wrote​:

On Fri Oct 14 16​:40​:27 2016, smls75@​gmail.com wrote​:

The following code attempts to pipe a large Blob (larger than a
pipe's
buffer size) through an external command.
However, it hangs on the `.in.close` line and never finishes​:

my $proc = run «cat -», :in, :out, :bin;
my $input = ("a" x 1000000).encode;
my $promise = start {
$proc.in.write​: $input;
$proc.in.close;
}
say $proc.out.slurp-rest(​:close, :bin).bytes;
await $promise;

For now, if using threads, stick with Proc​::Async (in the future,
we'll probably re-implement Proc/run etc. in terms of Proc​::Async).

/jnthn

jnthn recently made the above mentioned re-implementation so the code
shown in the report now works.

Closing issue

@AlexDaniel - Status changed from 'open' to 'resolved'