Mojo::IOLoop::Subprocess(3pm)

NAME
Mojo::IOLoop::Subprocess - Subprocesses

SYNOPSIS
  use Mojo::IOLoop::Subprocess;

  # Operation that would block the event loop for 5 seconds
  my $subprocess = Mojo::IOLoop::Subprocess->new;
  $subprocess->run(
    sub ($subprocess) {
      sleep 5;
      return '♥', 'Mojolicious';
    },
    sub ($subprocess, $err, @results) {
      say "Subprocess error: $err" and return if $err;
      say "I $results[0] $results[1]!";
    }
  );

  # Operation that would block the event loop for 5 seconds (with promise)
  $subprocess->run_p(sub {
    sleep 5;
    return '♥', 'Mojolicious';
  })->then(sub (@results) {
    say "I $results[0] $results[1]!";
  })->catch(sub  {
    my $err = shift;
    say "Subprocess error: $err";
  });

  # Start event loop if necessary
  $subprocess->ioloop->start unless $subprocess->ioloop->is_running;

DESCRIPTION
Mojo::IOLoop::Subprocess allows Mojo::IOLoop to perform computationally expensive operations in subprocesses, without blocking the event loop.

EVENTS
Mojo::IOLoop::Subprocess inherits all events from Mojo::EventEmitter and can emit the following new ones.

  cleanup
  $subprocess->on(cleanup => sub ($subprocess) {...});

Emitted in the subprocess right before the process will exit.

  $subprocess->on(cleanup => sub ($subprocess) { say "Process $$ is about to exit" });

  progress
  $subprocess->on(progress => sub ($subprocess, @data) {...});

Emitted in the parent process when the subprocess calls the progress method.

  spawn
  $subprocess->on(spawn => sub ($subprocess) {...});

Emitted in the parent process when the subprocess has been spawned.

  $subprocess->on(spawn => sub ($subprocess) {
    my $pid = $subprocess->pid;
    say "Performing work in process $pid";
  });

ATTRIBUTES
Mojo::IOLoop::Subprocess implements the following attributes.

  deserialize
  my $cb      = $subprocess->deserialize;
  $subprocess = $subprocess->deserialize(sub {...});

A callback used to deserialize subprocess return values, defaults to using Mojo::JSON.

  $subprocess->deserialize(sub ($bytes) { return [] });

  ioloop
  my $loop    = $subprocess->ioloop;
  $subprocess = $subprocess->ioloop(Mojo::IOLoop->new);

Event loop object to control, defaults to the global Mojo::IOLoop singleton. Note that this attribute is weakened.

  serialize
  my $cb      = $subprocess->serialize;
  $subprocess = $subprocess->serialize(sub {...});

A callback used to serialize subprocess return values, defaults to using Mojo::JSON.

  $subprocess->serialize(sub ($array) { return '' });

METHODS
Mojo::IOLoop::Subprocess inherits all methods from Mojo::EventEmitter and implements the following new ones.

  exit_code
  my $code = $subprocess->exit_code;

Returns the subprocess exit code, or "undef" if the subprocess is still running.

  pid
  my $pid = $subprocess->pid;

Process id of the spawned subprocess if available.

  progress
  $subprocess->progress(@data);

Send data serialized with Mojo::JSON to the parent process at any time during the subprocess's execution. Must be called by the subprocess and emits the "progress" event in the parent process with the data.

  # Send progress information to the parent process
  $subprocess->run(
    sub ($subprocess) {
      $subprocess->progress('0%');
      sleep 5;
      $subprocess->progress('50%');
      sleep 5;
      return 'Hello Mojo!';
    },
    sub ($subprocess, $err, @results) {
      say 'Progress is 100%';
      say $results[0];
    }
  );
  $subprocess->on(progress => sub ($subprocess, @data) { say "Progress is $data[0]" });

  run
  $subprocess = $subprocess->run(sub {...}, sub {...});

Execute the first callback in a child process and wait for it to return one or more values, without blocking "ioloop" in the parent process. Then execute the second callback in the parent process with the results. The return values of the first callback and exceptions thrown by it, will be serialized with Mojo::JSON, so they can be shared between processes.

  run_p
  my $promise = $subprocess->run_p(sub {...});

Same as "run", but returns a Mojo::Promise object instead of accepting a second callback.

  $subprocess->run_p(sub {
    sleep 5;
    return '♥', 'Mojolicious';
  })->then(sub (@results) {
    say "I $results[0] $results[1]!";
  })->catch(sub ($err) {
    say "Subprocess error: $err";
  })->wait;

SEE ALSO
Mojolicious, Mojolicious::Guides, <https://mojolicious.org>.