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.\" ========================================================================
.\"
.IX Title "Mojo::IOLoop 3pm"
.TH Mojo::IOLoop 3pm "2019-02-05" "perl v5.28.1" "User Contributed Perl Documentation"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
.if n .ad l
.nh
.SH "NAME"
Mojo::IOLoop \- Minimalistic event loop
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 1
\&  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(\*(AqHTTP/1.1 200 OK\*(Aq);
\&    });
\&  });
\&
\&  # 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\ex0d\ex0a\ex0d\ex0a");
\&  });
\&
\&  # 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;
.Ve
.SH "DESCRIPTION"
.IX Header "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.
.PP
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 \f(CW\*(C`LIBEV_FLAGS\*(C'\fR environment variable should also be used to
select the best possible \s-1EV\s0 backend, which usually defaults to the not very
scalable \f(CW\*(C`select\*(C'\fR.
.PP
.Vb 4
\&  LIBEV_FLAGS=1   # select
\&  LIBEV_FLAGS=2   # poll
\&  LIBEV_FLAGS=4   # epoll (Linux)
\&  LIBEV_FLAGS=8   # kqueue (*BSD, OS X)
.Ve
.PP
The event loop will be resilient to time jumps if a monotonic clock is
available through Time::HiRes. A \s-1TLS\s0 certificate and key are also built
right in, to make writing test servers as easy as possible. Also note that for
convenience the \f(CW\*(C`PIPE\*(C'\fR signal will be set to \f(CW\*(C`IGNORE\*(C'\fR when Mojo::IOLoop is
loaded.
.PP
For better scalability (epoll, kqueue) and to provide non-blocking name
resolution, \s-1SOCKS5\s0 as well as \s-1TLS\s0 support, the optional modules \s-1EV\s0 (4.0+),
Net::DNS::Native (0.15+), IO::Socket::Socks (0.64+) and
IO::Socket::SSL (2.009+) will be used automatically if possible. Individual
features can also be disabled with the \f(CW\*(C`MOJO_NO_NNR\*(C'\fR, \f(CW\*(C`MOJO_NO_SOCKS\*(C'\fR and
\&\f(CW\*(C`MOJO_NO_TLS\*(C'\fR environment variables.
.PP
See \*(L"REAL-TIME \s-1WEB\*(R"\s0 in Mojolicious::Guides::Cookbook for more.
.SH "EVENTS"
.IX Header "EVENTS"
Mojo::IOLoop inherits all events from Mojo::EventEmitter and can emit the
following new ones.
.SS "finish"
.IX Subsection "finish"
.Vb 4
\&  $loop\->on(finish => sub {
\&    my $loop = shift;
\&    ...
\&  });
.Ve
.PP
Emitted when the event loop wants to shut down gracefully and is just waiting
for all existing connections to be closed.
.SS "reset"
.IX Subsection "reset"
.Vb 4
\&  $loop\->on(reset => sub {
\&    my $loop = shift;
\&    ...
\&  });
.Ve
.PP
Emitted when the event loop is reset, this usually happens after the process is
forked to clean up resources that cannot be shared.
.SH "ATTRIBUTES"
.IX Header "ATTRIBUTES"
Mojo::IOLoop implements the following attributes.
.SS "max_accepts"
.IX Subsection "max_accepts"
.Vb 2
\&  my $max = $loop\->max_accepts;
\&  $loop   = $loop\->max_accepts(1000);
.Ve
.PP
The maximum number of connections this event loop is allowed to accept, before
shutting down gracefully without interrupting existing connections, defaults to
\&\f(CW0\fR. Setting the value to \f(CW0\fR 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.
.SS "max_connections"
.IX Subsection "max_connections"
.Vb 2
\&  my $max = $loop\->max_connections;
\&  $loop   = $loop\->max_connections(100);
.Ve
.PP
The maximum number of accepted connections this event loop is allowed to handle
concurrently, before stopping to accept new incoming connections, defaults to
\&\f(CW1000\fR.
.SS "reactor"
.IX Subsection "reactor"
.Vb 2
\&  my $reactor = $loop\->reactor;
\&  $loop       = $loop\->reactor(Mojo::Reactor\->new);
.Ve
.PP
Low-level event reactor, usually a Mojo::Reactor::Poll or
Mojo::Reactor::EV object with a default subscriber to the event
\&\*(L"error\*(R" in Mojo::Reactor.
.PP
.Vb 5
\&  # Watch if handle becomes readable or writable
\&  Mojo::IOLoop\->singleton\->reactor\->io($handle => sub {
\&    my ($reactor, $writable) = @_;
\&    say $writable ? \*(AqHandle is writable\*(Aq : \*(AqHandle is readable\*(Aq;
\&  });
\&
\&  # Change to watching only if handle becomes writable
\&  Mojo::IOLoop\->singleton\->reactor\->watch($handle, 0, 1);
\&
\&  # Remove handle again
\&  Mojo::IOLoop\->singleton\->reactor\->remove($handle);
.Ve
.SH "METHODS"
.IX Header "METHODS"
Mojo::IOLoop inherits all methods from Mojo::EventEmitter and implements
the following new ones.
.SS "acceptor"
.IX Subsection "acceptor"
.Vb 3
\&  my $server = Mojo::IOLoop\->acceptor($id);
\&  my $server = $loop\->acceptor($id);
\&  my $id     = $loop\->acceptor(Mojo::IOLoop::Server\->new);
.Ve
.PP
Get Mojo::IOLoop::Server object for id or turn object into an acceptor.
.SS "client"
.IX Subsection "client"
.Vb 4
\&  my $id
\&    = Mojo::IOLoop\->client(address => \*(Aq127.0.0.1\*(Aq, port => 3000, sub {...});
\&  my $id = $loop\->client(address => \*(Aq127.0.0.1\*(Aq, port => 3000, sub {...});
\&  my $id = $loop\->client({address => \*(Aq127.0.0.1\*(Aq, port => 3000} => sub {...});
.Ve
.PP
Open a \s-1TCP/IP\s0 or \s-1UNIX\s0 domain socket connection with Mojo::IOLoop::Client and
create a stream object (usually Mojo::IOLoop::Stream), takes the same
arguments as \*(L"connect\*(R" in Mojo::IOLoop::Client.
.SS "delay"
.IX Subsection "delay"
.Vb 4
\&  my $delay = Mojo::IOLoop\->delay;
\&  my $delay = $loop\->delay;
\&  my $delay = $loop\->delay(sub {...});
\&  my $delay = $loop\->delay(sub {...}, sub {...});
.Ve
.PP
Build Mojo::IOLoop::Delay object to use as a promise and/or for flow-control.
Callbacks will be passed along to \*(L"steps\*(R" in Mojo::IOLoop::Delay.
.PP
.Vb 10
\&  # 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 = $tx\->error;
\&      if   (!$err || $err\->{code}) { $promise\->resolve($tx) }
\&      else                         { $promise\->reject($err\->{message}) }
\&    });
\&    return $promise;
\&  }
\&  my $mojo = get(\*(Aqhttps://mojolicious.org\*(Aq);
\&  my $cpan = get(\*(Aqhttps://metacpan.org\*(Aq);
\&  Mojo::Promise\->race($mojo, $cpan)\->then(sub { say shift\->req\->url })\->wait;
\&
\&  # Synchronize multiple non\-blocking operations
\&  my $delay = Mojo::IOLoop\->delay(sub { say \*(AqBOOM!\*(Aq });
\&  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 \*(AqSecond step in 2 seconds.\*(Aq;
\&    },
\&
\&    # Second step (concurrent timers)
\&    sub {
\&      my $delay = shift;
\&      Mojo::IOLoop\->timer(1 => $delay\->begin);
\&      Mojo::IOLoop\->timer(3 => $delay\->begin);
\&      say \*(AqThird step in 3 seconds.\*(Aq;
\&    },
\&
\&    # Third step (the end)
\&    sub { say \*(AqAnd done after 5 seconds total.\*(Aq }
\&  )\->wait;
.Ve
.SS "is_running"
.IX Subsection "is_running"
.Vb 2
\&  my $bool = Mojo::IOLoop\->is_running;
\&  my $bool = $loop\->is_running;
.Ve
.PP
Check if event loop is running.
.SS "next_tick"
.IX Subsection "next_tick"
.Vb 2
\&  my $undef = Mojo::IOLoop\->next_tick(sub {...});
\&  my $undef = $loop\->next_tick(sub {...});
.Ve
.PP
Execute callback as soon as possible, but not before returning or other
callbacks that have been registered with this method, always returns \f(CW\*(C`undef\*(C'\fR.
.PP
.Vb 5
\&  # Perform operation on next reactor tick
\&  Mojo::IOLoop\->next_tick(sub {
\&    my $loop = shift;
\&    ...
\&  });
.Ve
.SS "one_tick"
.IX Subsection "one_tick"
.Vb 2
\&  Mojo::IOLoop\->one_tick;
\&  $loop\->one_tick;
.Ve
.PP
Run event loop until an event occurs.
.PP
.Vb 4
\&  # Don\*(Aqt block longer than 0.5 seconds
\&  my $id = Mojo::IOLoop\->timer(0.5 => sub {});
\&  Mojo::IOLoop\->one_tick;
\&  Mojo::IOLoop\->remove($id);
.Ve
.SS "recurring"
.IX Subsection "recurring"
.Vb 3
\&  my $id = Mojo::IOLoop\->recurring(3 => sub {...});
\&  my $id = $loop\->recurring(0 => sub {...});
\&  my $id = $loop\->recurring(0.25 => sub {...});
.Ve
.PP
Create a new recurring timer, invoking the callback repeatedly after a given
amount of time in seconds.
.PP
.Vb 5
\&  # Perform operation every 5 seconds
\&  Mojo::IOLoop\->recurring(5 => sub {
\&    my $loop = shift;
\&    ...
\&  });
.Ve
.SS "remove"
.IX Subsection "remove"
.Vb 2
\&  Mojo::IOLoop\->remove($id);
\&  $loop\->remove($id);
.Ve
.PP
Remove anything with an id, connections will be dropped gracefully by allowing
them to finish writing all data in their write buffers.
.SS "reset"
.IX Subsection "reset"
.Vb 2
\&  Mojo::IOLoop\->reset;
\&  $loop\->reset;
.Ve
.PP
Remove everything and stop the event loop.
.SS "server"
.IX Subsection "server"
.Vb 3
\&  my $id = Mojo::IOLoop\->server(port => 3000, sub {...});
\&  my $id = $loop\->server(port => 3000, sub {...});
\&  my $id = $loop\->server({port => 3000} => sub {...});
.Ve
.PP
Accept \s-1TCP/IP\s0 and \s-1UNIX\s0 domain socket connections with Mojo::IOLoop::Server
and create stream objects (usually Mojo::IOLoop::Stream, takes the same
arguments as \*(L"listen\*(R" in Mojo::IOLoop::Server.
.PP
.Vb 6
\&  # Listen on random port
\&  my $id = Mojo::IOLoop\->server({address => \*(Aq127.0.0.1\*(Aq} => sub {
\&    my ($loop, $stream, $id) = @_;
\&    ...
\&  });
\&  my $port = Mojo::IOLoop\->acceptor($id)\->port;
.Ve
.SS "singleton"
.IX Subsection "singleton"
.Vb 1
\&  my $loop = Mojo::IOLoop\->singleton;
.Ve
.PP
The global Mojo::IOLoop singleton, used to access a single shared event loop
object from everywhere inside the process.
.PP
.Vb 3
\&  # Many methods also allow you to take shortcuts
\&  Mojo::IOLoop\->timer(2 => sub { Mojo::IOLoop\->stop });
\&  Mojo::IOLoop\->start;
\&
\&  # Restart active timer
\&  my $id = Mojo::IOLoop\->timer(3 => sub { say \*(AqTimeout!\*(Aq });
\&  Mojo::IOLoop\->singleton\->reactor\->again($id);
\&
\&  # Turn file descriptor into handle and watch if it becomes readable
\&  my $handle = IO::Handle\->new_from_fd($fd, \*(Aqr\*(Aq);
\&  Mojo::IOLoop\->singleton\->reactor\->io($handle => sub {
\&    my ($reactor, $writable) = @_;
\&    say $writable ? \*(AqHandle is writable\*(Aq : \*(AqHandle is readable\*(Aq;
\&  })\->watch($handle, 1, 0);
.Ve
.SS "start"
.IX Subsection "start"
.Vb 2
\&  Mojo::IOLoop\->start;
\&  $loop\->start;
.Ve
.PP
Start the event loop, this will block until \*(L"stop\*(R" is called. Note that
some reactors stop automatically if there are no events being watched anymore.
.PP
.Vb 2
\&  # Start event loop only if it is not running already
\&  Mojo::IOLoop\->start unless Mojo::IOLoop\->is_running;
.Ve
.SS "stop"
.IX Subsection "stop"
.Vb 2
\&  Mojo::IOLoop\->stop;
\&  $loop\->stop;
.Ve
.PP
Stop the event loop, this will not interrupt any existing connections and the
event loop can be restarted by running \*(L"start\*(R" again.
.SS "stop_gracefully"
.IX Subsection "stop_gracefully"
.Vb 2
\&  Mojo::IOLoop\->stop_gracefully;
\&  $loop\->stop_gracefully;
.Ve
.PP
Stop accepting new connections and wait for already accepted connections to be
closed, before stopping the event loop.
.SS "stream"
.IX Subsection "stream"
.Vb 3
\&  my $stream = Mojo::IOLoop\->stream($id);
\&  my $stream = $loop\->stream($id);
\&  my $id     = $loop\->stream(Mojo::IOLoop::Stream\->new);
.Ve
.PP
Get Mojo::IOLoop::Stream object for id or turn object into a connection.
.PP
.Vb 2
\&  # Increase inactivity timeout for connection to 300 seconds
\&  Mojo::IOLoop\->stream($id)\->timeout(300);
.Ve
.SS "subprocess"
.IX Subsection "subprocess"
.Vb 3
\&  my $subprocess = Mojo::IOLoop\->subprocess(sub {...}, sub {...});
\&  my $subprocess = $loop\->subprocess;
\&  my $subprocess = $loop\->subprocess(sub {...}, sub {...});
.Ve
.PP
Build Mojo::IOLoop::Subprocess object to perform computationally expensive
operations in subprocesses, without blocking the event loop. Callbacks will be
passed along to \*(L"run\*(R" in Mojo::IOLoop::Subprocess.
.PP
.Vb 10
\&  # Operation that would block the event loop for 5 seconds
\&  Mojo::IOLoop\->subprocess(
\&    sub {
\&      my $subprocess = shift;
\&      sleep 5;
\&      return \*(Aq♥\*(Aq, \*(AqMojolicious\*(Aq;
\&    },
\&    sub {
\&      my ($subprocess, $err, @results) = @_;
\&      say "Subprocess error: $err" and return if $err;
\&      say "I $results[0] $results[1]!";
\&    }
\&  );
.Ve
.SS "timer"
.IX Subsection "timer"
.Vb 3
\&  my $id = Mojo::IOLoop\->timer(3 => sub {...});
\&  my $id = $loop\->timer(0 => sub {...});
\&  my $id = $loop\->timer(0.25 => sub {...});
.Ve
.PP
Create a new timer, invoking the callback after a given amount of time in
seconds.
.PP
.Vb 5
\&  # Perform operation in 5 seconds
\&  Mojo::IOLoop\->timer(5 => sub {
\&    my $loop = shift;
\&    ...
\&  });
.Ve
.SH "DEBUGGING"
.IX Header "DEBUGGING"
You can set the \f(CW\*(C`MOJO_IOLOOP_DEBUG\*(C'\fR environment variable to get some advanced
diagnostics information printed to \f(CW\*(C`STDERR\*(C'\fR.
.PP
.Vb 1
\&  MOJO_IOLOOP_DEBUG=1
.Ve
.SH "SEE ALSO"
.IX Header "SEE ALSO"
Mojolicious, Mojolicious::Guides, <https://mojolicious.org>.