package Mojo::Server::Hypnotoad;
use Mojo::Base -base;

# "Bender: I was God once.
#  God: Yes, I saw. You were doing well, until everyone died."
use Config;
use Mojo::File 'path';
use Mojo::Server::Prefork;
use Mojo::Util 'steady_time';
use Scalar::Util 'weaken';

has prefork => sub { Mojo::Server::Prefork->new(listen => ['http://*:8080']) };
has upgrade_timeout => 180;

sub configure {
  my ($self, $name) = @_;

  # Hypnotoad settings
  my $prefork = $self->prefork;
  my $c       = $prefork->app->config($name) || {};
  $self->upgrade_timeout($c->{upgrade_timeout}) if $c->{upgrade_timeout};

  # Pre-fork settings
  $prefork->reverse_proxy($c->{proxy})   if defined $c->{proxy};
  $prefork->max_clients($c->{clients})   if $c->{clients};
  $prefork->max_requests($c->{requests}) if $c->{requests};
  defined $c->{$_} and $prefork->$_($c->{$_})
    for qw(accepts backlog graceful_timeout heartbeat_interval),
    qw(heartbeat_timeout inactivity_timeout listen pid_file spare workers);
}

sub run {
  my ($self, $app) = @_;

  # No fork emulation support
  _exit('Hypnotoad does not support fork emulation.') if $Config{d_pseudofork};

  # Remember executable and application for later
  $ENV{HYPNOTOAD_EXE} ||= $0;
  $0 = $ENV{HYPNOTOAD_APP} ||= path($app)->to_abs->to_string;

  # This is a production server
  $ENV{MOJO_MODE} ||= 'production';

  # Clean start (to make sure everything works)
  die "Can't exec: $!"
    if !$ENV{HYPNOTOAD_REV}++ && !exec $^X, $ENV{HYPNOTOAD_EXE};

  # Preload application and configure server
  my $prefork = $self->prefork->cleanup(0);
  $prefork->load_app($app)->config->{hypnotoad}{pid_file}
    //= path($ENV{HYPNOTOAD_APP})->sibling('hypnotoad.pid')->to_string;
  $self->configure('hypnotoad');
  weaken $self;
  $prefork->on(wait   => sub { $self->_manage });
  $prefork->on(reap   => sub { $self->_cleanup(pop) });
  $prefork->on(finish => sub { $self->_finish });

  # Testing
  _exit('Everything looks good!') if $ENV{HYPNOTOAD_TEST};

  # Stop running server
  $self->_stop if $ENV{HYPNOTOAD_STOP};

  # Initiate hot deployment
  $self->_hot_deploy unless $ENV{HYPNOTOAD_PID};

  # Daemonize as early as possible (but not for restarts)
  local $SIG{USR2} = sub { $self->{upgrade} ||= steady_time };
  $prefork->start;
  $prefork->daemonize if !$ENV{HYPNOTOAD_FOREGROUND} && $ENV{HYPNOTOAD_REV} < 3;

  # Start accepting connections
  $prefork->cleanup(1)->run;
}

sub _cleanup {
  my ($self, $pid) = @_;

  # Clean up failed upgrade
  return unless ($self->{new} || '') eq $pid;
  $self->prefork->app->log->error('Zero downtime software upgrade failed');
  delete @$self{qw(new upgrade)};
}

sub _exit { say shift and exit 0 }

sub _finish {
  my $self = shift;

  $self->{finish} = 1;
  return unless my $new = $self->{new};

  my $prefork = $self->prefork->cleanup(0);
  path($prefork->pid_file)->remove;
  $prefork->ensure_pid_file($new);
}

sub _hot_deploy {

  # Make sure server is running
  return unless my $pid = shift->prefork->check_pid;

  # Start hot deployment
  kill 'USR2', $pid;
  _exit("Starting hot deployment for Hypnotoad server $pid.");
}

sub _manage {
  my $self = shift;

  # Upgraded (wait for all workers to send a heartbeat)
  my $prefork = $self->prefork;
  my $log     = $prefork->app->log;
  if ($ENV{HYPNOTOAD_PID} && $ENV{HYPNOTOAD_PID} ne $$) {
    return unless $prefork->healthy == $prefork->workers;
    $log->info("Upgrade successful, stopping $ENV{HYPNOTOAD_PID}");
    kill 'QUIT', $ENV{HYPNOTOAD_PID};
  }
  $ENV{HYPNOTOAD_PID} = $$ unless ($ENV{HYPNOTOAD_PID} // '') eq $$;

  # Upgrade
  if ($self->{upgrade} && !$self->{finished}) {

    # Fresh start
    my $ut = $self->upgrade_timeout;
    unless ($self->{new}) {
      $log->info("Starting zero downtime software upgrade ($ut seconds)");
      die "Can't fork: $!" unless defined(my $pid = $self->{new} = fork);
      exec $^X, $ENV{HYPNOTOAD_EXE} or die "Can't exec: $!" unless $pid;
    }

    # Timeout
    kill 'KILL', $self->{new} if $self->{upgrade} + $ut <= steady_time;
  }
}

sub _stop {
  _exit('Hypnotoad server not running.')
    unless my $pid = shift->prefork->check_pid;
  kill 'QUIT', $pid;
  _exit("Stopping Hypnotoad server $pid gracefully.");
}

1;

=encoding utf8

=head1 NAME

Mojo::Server::Hypnotoad - A production web serv...ALL GLORY TO THE HYPNOTOAD!

=head1 SYNOPSIS

  use Mojo::Server::Hypnotoad;

  my $hypnotoad = Mojo::Server::Hypnotoad->new;
  $hypnotoad->run('/home/sri/myapp.pl');

=head1 DESCRIPTION

L<Mojo::Server::Hypnotoad> is a full featured, UNIX optimized, pre-forking
non-blocking I/O HTTP and WebSocket server, built around the very well tested
and reliable L<Mojo::Server::Prefork>, with IPv6, TLS, SNI, UNIX domain socket,
Comet (long polling), keep-alive, multiple event loop and hot deployment support
that just works. Note that the server uses signals for process management, so
you should avoid modifying signal handlers in your applications.

To start applications with it you can use the L<hypnotoad> script, which
listens on port C<8080>, automatically daemonizes the server process and
defaults to C<production> mode for L<Mojolicious> and L<Mojolicious::Lite>
applications.

  $ hypnotoad ./myapp.pl

You can run the same command again for automatic hot deployment.

  $ hypnotoad ./myapp.pl
  Starting hot deployment for Hypnotoad server 31841.

This second invocation will load the application again, detect the process id
file with it, and send a L</"USR2"> signal to the already running server.

For better scalability (epoll, kqueue) and to provide non-blocking name
resolution, SOCKS5 as well as TLS support, the optional modules L<EV> (4.0+),
L<Net::DNS::Native> (0.15+), L<IO::Socket::Socks> (0.64+) and
L<IO::Socket::SSL> (2.009+) will be used automatically if possible. Individual
features can also be disabled with the C<MOJO_NO_NNR>, C<MOJO_NO_SOCKS> and
C<MOJO_NO_TLS> environment variables.

See L<Mojolicious::Guides::Cookbook/"DEPLOYMENT"> for more.

=head1 MANAGER SIGNALS

The L<Mojo::Server::Hypnotoad> manager process can be controlled at runtime
with the following signals.

=head2 INT, TERM

Shut down server immediately.

=head2 QUIT

Shut down server gracefully.

=head2 TTIN

Increase worker pool by one.

=head2 TTOU

Decrease worker pool by one.

=head2 USR2

Attempt zero downtime software upgrade (hot deployment) without losing any
incoming connections.

  Manager (old)
  |- Worker [1]
  |- Worker [2]
  |- Worker [3]
  |- Worker [4]
  +- Manager (new)
     |- Worker [1]
     |- Worker [2]
     |- Worker [3]
     +- Worker [4]

The new manager will automatically send a L</"QUIT"> signal to the old manager
and take over serving requests after starting up successfully.

=head1 WORKER SIGNALS

L<Mojo::Server::Hypnotoad> worker processes can be controlled at runtime with
the following signals.

=head2 QUIT

Stop worker gracefully.

=head1 SETTINGS

L<Mojo::Server::Hypnotoad> can be configured with the following settings, see
L<Mojolicious::Guides::Cookbook/"Hypnotoad"> for examples.

=head2 accepts

  accepts => 100

Maximum number of connections a worker is allowed to accept, before stopping
gracefully and then getting replaced with a newly started worker, defaults to
the value of L<Mojo::Server::Prefork/"accepts">. Setting the value to C<0> will
allow workers to accept new connections indefinitely. Note that up to half of
this value can be subtracted randomly to improve load balancing, and to make
sure that not all workers restart at the same time.

=head2 backlog

  backlog => 128

Listen backlog size, defaults to the value of
L<Mojo::Server::Daemon/"backlog">.

=head2 clients

  clients => 100

Maximum number of accepted connections each worker process is allowed to handle
concurrently, before stopping to accept new incoming connections, defaults to
the value of L<Mojo::IOLoop/"max_connections">. Note that high concurrency works
best with applications that perform mostly non-blocking operations, to optimize
for blocking operations you can decrease this value and increase L</"workers">
instead for better performance.

=head2 graceful_timeout

  graceful_timeout => 15

Maximum amount of time in seconds stopping a worker gracefully may take before
being forced, defaults to the value of
L<Mojo::Server::Prefork/"graceful_timeout">. Note that this value should usually
be a little larger than the maximum amount of time you expect any one request to
take.

=head2 heartbeat_interval

  heartbeat_interval => 3

Heartbeat interval in seconds, defaults to the value of
L<Mojo::Server::Prefork/"heartbeat_interval">.

=head2 heartbeat_timeout

  heartbeat_timeout => 2

Maximum amount of time in seconds before a worker without a heartbeat will be
stopped gracefully, defaults to the value of
L<Mojo::Server::Prefork/"heartbeat_timeout">. Note that this value should
usually be a little larger than the maximum amount of time you expect any one
operation to block the event loop.

=head2 inactivity_timeout

  inactivity_timeout => 10

Maximum amount of time in seconds a connection can be inactive before getting
closed, defaults to the value of L<Mojo::Server::Daemon/"inactivity_timeout">.
Setting the value to C<0> will allow connections to be inactive indefinitely.

=head2 listen

  listen => ['http://*:80']

Array reference with one or more locations to listen on, defaults to
C<http://*:8080>. See also L<Mojo::Server::Daemon/"listen"> for more examples.

=head2 pid_file

  pid_file => '/var/run/hypnotoad.pid'

Full path to process id file, defaults to C<hypnotoad.pid> in the same
directory as the application. Note that this value can only be changed after
the server has been stopped.

=head2 proxy

  proxy => 1

Activate reverse proxy support, which allows for the C<X-Forwarded-For> and
C<X-Forwarded-Proto> headers to be picked up automatically, defaults to the
value of L<Mojo::Server/"reverse_proxy">.

=head2 requests

  requests => 50

Number of keep-alive requests per connection, defaults to the value of
L<Mojo::Server::Daemon/"max_requests">.

=head2 spare

  spare => 4

Temporarily spawn up to this number of additional workers if there is a need,
defaults to the value of L<Mojo::Server::Prefork/"spare">. This allows for new
workers to be started while old ones are still shutting down gracefully,
drastically reducing the performance cost of worker restarts.

=head2 upgrade_timeout

  upgrade_timeout => 45

Maximum amount of time in seconds a zero downtime software upgrade may take
before getting canceled, defaults to C<180>.

=head2 workers

  workers => 10

Number of worker processes, defaults to the value of
L<Mojo::Server::Prefork/"workers">. A good rule of thumb is two worker
processes per CPU core for applications that perform mostly non-blocking
operations, blocking operations often require more and benefit from decreasing
concurrency with L</"clients"> (often as low as C<1>). Note that during zero
downtime software upgrades there will be twice as many workers active for a
short amount of time.

=head1 ATTRIBUTES

L<Mojo::Server::Hypnotoad> implements the following attributes.

=head2 prefork

  my $prefork = $hypnotoad->prefork;
  $hypnotoad  = $hypnotoad->prefork(Mojo::Server::Prefork->new);

L<Mojo::Server::Prefork> object this server manages.

=head2 upgrade_timeout

  my $timeout = $hypnotoad->upgrade_timeout;
  $hypnotoad  = $hypnotoad->upgrade_timeout(15);

Maximum amount of time in seconds a zero downtime software upgrade may take
before getting canceled, defaults to C<180>.

=head1 METHODS

L<Mojo::Server::Hypnotoad> inherits all methods from L<Mojo::Base> and
implements the following new ones.

=head2 configure

  $hypnotoad->configure('hypnotoad');

Configure server from application settings.

=head2 run

  $hypnotoad->run('script/my_app');

Run server for application and wait for L</"MANAGER SIGNALS">.

=head1 SEE ALSO

L<Mojolicious>, L<Mojolicious::Guides>, L<https://mojolicious.org>.

=cut
