Mojo::IOLoop(3)

NAME
Mojo::IOLoop - Minimalistic event loop

SYNOPSIS
  use Mojo::IOLoop;

  # Listen on port 3000
  Mojo::IOLoop->server({port => 3000} => sub {
    my ($loop, $stream) = @_;

    $stream->on(read => sub {
      my ($stream, $bytes) = @_;

      # Process input chunk
      say $bytes;

      # Write response
      $stream->write('HTTP/1.1 200 OK');
    });
  });

  # Connect to port 3000
  my $id = Mojo::IOLoop->client({port => 3000} => sub {
    my ($loop, $err, $stream) = @_;

    $stream->on(read => sub {
      my ($stream, $bytes) = @_;

      # Process input
      say "Input: $bytes";
    });

    # Write request
    $stream->write("GET / HTTP/1.1\x0d\x0a\x0d\x0a");
  });

  # Add a timer
  Mojo::IOLoop->timer(5 => sub {
    my $loop = shift;
    $loop->remove($id);
  });

  # Start event loop if necessary
  Mojo::IOLoop->start unless Mojo::IOLoop->is_running;

DESCRIPTION
Mojo::IOLoop is a very minimalistic event loop based on Mojo::Reactor, it has been reduced to the absolute minimal feature set required to build solid and scalable non-blocking clients and servers.

Depending on operating system, the default per-process and system-wide file descriptor limits are often very low and need to be tuned for better scalability. The "LIBEV_FLAGS" environment variable should also be used to select the best possible EV backend, which usually defaults to the not very scalable "select".

  LIBEV_FLAGS=1   # select
  LIBEV_FLAGS=2   # poll
  LIBEV_FLAGS=4   # epoll (Linux)
  LIBEV_FLAGS=8   # kqueue (*BSD, OS X)

The event loop will be resilient to time jumps if a monotonic clock is available through Time::HiRes. A TLS certificate and key are also built right in, to make writing test servers as easy as possible. Also note that for convenience the "PIPE" signal will be set to "IGNORE" when Mojo::IOLoop is loaded.

For better scalability (epoll, kqueue) and to provide non-blocking name resolution, SOCKS5 as well as TLS support, the optional modules EV (4.0+), Net::DNS::Native (0.15+), IO::Socket::Socks (0.64+) and IO::Socket::SSL (1.94+) will be used automatically if possible. Individual features can also be disabled with the "MOJO_NO_NNR", "MOJO_NO_SOCKS" and "MOJO_NO_TLS" environment variables.

See "REAL-TIME WEB" in Mojolicious::Guides::Cookbook for more.

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

  finish
  $loop->on(finish => sub {
    my $loop = shift;
    ...
  });

Emitted when the event loop wants to shut down gracefully and is just waiting for all existing connections to be closed.

ATTRIBUTES
Mojo::IOLoop implements the following attributes.

  max_accepts
  my $max = $loop->max_accepts;
  $loop   = $loop->max_accepts(1000);

The maximum number of connections this event loop is allowed to accept, before shutting down gracefully without interrupting existing connections, defaults to 0. Setting the value to 0 will allow this event loop to accept new connections indefinitely. Note that up to half of this value can be subtracted randomly to improve load balancing between multiple server processes, and to make sure that not all of them restart at the same time.

  max_connections
  my $max = $loop->max_connections;
  $loop   = $loop->max_connections(100);

The maximum number of accepted connections this event loop is allowed to handle concurrently, before stopping to accept new incoming connections, defaults to 1000.

  reactor
  my $reactor = $loop->reactor;
  $loop       = $loop->reactor(Mojo::Reactor->new);

Low-level event reactor, usually a Mojo::Reactor::Poll or Mojo::Reactor::EV object with a default subscriber to the event "error" in Mojo::Reactor.

  # Watch if handle becomes readable or writable
  Mojo::IOLoop->singleton->reactor->io($handle => sub {
    my ($reactor, $writable) = @_;
    say $writable ? 'Handle is writable' : 'Handle is readable';
  });

  # Change to watching only if handle becomes writable
  Mojo::IOLoop->singleton->reactor->watch($handle, 0, 1);

  # Remove handle again
  Mojo::IOLoop->singleton->reactor->remove($handle);

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

  acceptor
  my $server = Mojo::IOLoop->acceptor($id);
  my $server = $loop->acceptor($id);
  my $id     = $loop->acceptor(Mojo::IOLoop::Server->new);

Get Mojo::IOLoop::Server object for id or turn object into an acceptor.

  client
  my $id
    = Mojo::IOLoop->client(address => '127.0.0.1', port => 3000, sub {...});
  my $id = $loop->client(address => '127.0.0.1', port => 3000, sub {...});
  my $id = $loop->client({address => '127.0.0.1', port => 3000} => sub {...});

Open a TCP/IP or UNIX domain socket connection with Mojo::IOLoop::Client and create a Mojo::IOLoop::Stream object, takes the same arguments as "connect" in Mojo::IOLoop::Client.

  # Connect to 127.0.0.1 on port 3000
  Mojo::IOLoop->client({port => 3000} => sub {
    my ($loop, $err, $stream) = @_;
    ...
  });

  delay
  my $delay = Mojo::IOLoop->delay;
  my $delay = $loop->delay;
  my $delay = $loop->delay(sub {...});
  my $delay = $loop->delay(sub {...}, sub {...});

Build Mojo::IOLoop::Delay object to use as a promise and/or for flow-control. Callbacks will be passed along to "steps" in Mojo::IOLoop::Delay.

  # Wrap continuation-passing style APIs with promises
  my $ua = Mojo::UserAgent->new;
  sub get {
    my $promise = Mojo::IOLoop->delay;
    $ua->get(@_ => sub {
      my ($ua, $tx) = @_;
      my $err = $tx->error;
      $promise->resolve($tx) if !$err || $err->{code};
      $promise->reject($err->{message});
    });
    return $promise;
  }
  my $mojo = get('http://mojolicious.org');
  my $cpan = get('http://metacpan.org');
  Mojo::Promise->race($mojo, $cpan)->then(sub { say shift->req->url })->wait;

  # Synchronize multiple non-blocking operations
  my $delay = Mojo::IOLoop->delay(sub { say 'BOOM!' });
  for my $i (1 .. 10) {
    my $end = $delay->begin;
    Mojo::IOLoop->timer($i => sub {
      say 10 - $i;
      $end->();
    });
  }
  $delay->wait;

  # Sequentialize multiple non-blocking operations
  Mojo::IOLoop->delay(

    # First step (simple timer)
    sub {
      my $delay = shift;
      Mojo::IOLoop->timer(2 => $delay->begin);
      say 'Second step in 2 seconds.';
    },

    # Second step (concurrent timers)
    sub {
      my $delay = shift;
      Mojo::IOLoop->timer(1 => $delay->begin);
      Mojo::IOLoop->timer(3 => $delay->begin);
      say 'Third step in 3 seconds.';
    },

    # Third step (the end)
    sub { say 'And done after 5 seconds total.' }
  )->wait;

  is_running
  my $bool = Mojo::IOLoop->is_running;
  my $bool = $loop->is_running;

Check if event loop is running.

  exit unless Mojo::IOLoop->is_running;

  next_tick
  my $undef = Mojo::IOLoop->next_tick(sub {...});
  my $undef = $loop->next_tick(sub {...});

Execute callback as soon as possible, but not before returning or other callbacks that have been registered with this method, always returns "undef".

  # Perform operation on next reactor tick
  Mojo::IOLoop->next_tick(sub {
    my $loop = shift;
    ...
  });

  one_tick
  Mojo::IOLoop->one_tick;
  $loop->one_tick;

Run event loop until an event occurs.

  # Don't block longer than 0.5 seconds
  my $id = Mojo::IOLoop->timer(0.5 => sub {});
  Mojo::IOLoop->one_tick;
  Mojo::IOLoop->remove($id);

  recurring
  my $id = Mojo::IOLoop->recurring(3 => sub {...});
  my $id = $loop->recurring(0 => sub {...});
  my $id = $loop->recurring(0.25 => sub {...});

Create a new recurring timer, invoking the callback repeatedly after a given amount of time in seconds.

  # Perform operation every 5 seconds
  Mojo::IOLoop->recurring(5 => sub {
    my $loop = shift;
    ...
  });

  remove
  Mojo::IOLoop->remove($id);
  $loop->remove($id);

Remove anything with an id, connections will be dropped gracefully by allowing them to finish writing all data in their write buffers.

  reset
  Mojo::IOLoop->reset;
  $loop->reset;

Remove everything and stop the event loop.

  server
  my $id = Mojo::IOLoop->server(port => 3000, sub {...});
  my $id = $loop->server(port => 3000, sub {...});
  my $id = $loop->server({port => 3000} => sub {...});

Accept TCP/IP and UNIX domain socket connections with Mojo::IOLoop::Server and create Mojo::IOLoop::Stream objects, takes the same arguments as "listen" in Mojo::IOLoop::Server.

  # Listen on port 3000
  Mojo::IOLoop->server({port => 3000} => sub {
    my ($loop, $stream, $id) = @_;
    ...
  });

  # Listen on random port
  my $id = Mojo::IOLoop->server({address => '127.0.0.1'} => sub {
    my ($loop, $stream, $id) = @_;
    ...
  });
  my $port = Mojo::IOLoop->acceptor($id)->port;

  singleton
  my $loop = Mojo::IOLoop->singleton;

The global Mojo::IOLoop singleton, used to access a single shared event loop object from everywhere inside the process.

  # Many methods also allow you to take shortcuts
  Mojo::IOLoop->timer(2 => sub { Mojo::IOLoop->stop });
  Mojo::IOLoop->start;

  # Restart active timer
  my $id = Mojo::IOLoop->timer(3 => sub { say 'Timeout!' });
  Mojo::IOLoop->singleton->reactor->again($id);

  # Turn file descriptor into handle and watch if it becomes readable
  my $handle = IO::Handle->new_from_fd($fd, 'r');
  Mojo::IOLoop->singleton->reactor->io($handle => sub {
    my ($reactor, $writable) = @_;
    say $writable ? 'Handle is writable' : 'Handle is readable';
  })->watch($handle, 1, 0);

  start
  Mojo::IOLoop->start;
  $loop->start;

Start the event loop, this will block until "stop" is called. Note that some reactors stop automatically if there are no events being watched anymore.

  # Start event loop only if it is not running already
  Mojo::IOLoop->start unless Mojo::IOLoop->is_running;

  stop
  Mojo::IOLoop->stop;
  $loop->stop;

Stop the event loop, this will not interrupt any existing connections and the event loop can be restarted by running "start" again.

  stop_gracefully
  Mojo::IOLoop->stop_gracefully;
  $loop->stop_gracefully;

Stop accepting new connections and wait for already accepted connections to be closed, before stopping the event loop.

  stream
  my $stream = Mojo::IOLoop->stream($id);
  my $stream = $loop->stream($id);
  my $id     = $loop->stream(Mojo::IOLoop::Stream->new);

Get Mojo::IOLoop::Stream object for id or turn object into a connection.

  # Increase inactivity timeout for connection to 300 seconds
  Mojo::IOLoop->stream($id)->timeout(300);

  subprocess
  my $subprocess = Mojo::IOLoop->subprocess(sub {...}, sub {...});
  my $subprocess = $loop->subprocess;
  my $subprocess = $loop->subprocess(sub {...}, sub {...});

Build Mojo::IOLoop::Subprocess object to perform computationally expensive operations in subprocesses, without blocking the event loop. Callbacks will be passed along to "run" in Mojo::IOLoop::Subprocess.

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

  timer
  my $id = Mojo::IOLoop->timer(3 => sub {...});
  my $id = $loop->timer(0 => sub {...});
  my $id = $loop->timer(0.25 => sub {...});

Create a new timer, invoking the callback after a given amount of time in seconds.

  # Perform operation in 5 seconds
  Mojo::IOLoop->timer(5 => sub {
    my $loop = shift;
    ...
  });

DEBUGGING
You can set the "MOJO_IOLOOP_DEBUG" environment variable to get some advanced diagnostics information printed to "STDERR".

  MOJO_IOLOOP_DEBUG=1

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