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lib/DBIx/QuickDB/Watcher.pm  view on Meta::CPAN

package DBIx::QuickDB::Watcher;
use strict;
use warnings;

our $VERSION = '0.000041';

use Carp qw/croak/;
use POSIX qw/:sys_wait_h/;
use Time::HiRes qw/sleep time/;
use Scalar::Util qw/weaken/;
use File::Path qw/remove_tree/;

use DBIx::QuickDB::Util::HashBase qw{
    <db <args
    <server_pid
    <watcher_pid
    <master_pid
    <log_file

    <stopped
    <eliminated
    <detached

    <delete_data
};

sub init {
    my $self = shift;

    $self->{+MASTER_PID} ||= $$;

    $self->{+LOG_FILE} = $self->{+DB}->gen_log;

    $self->start();

    weaken($self->{+DB}) if $self->{+MASTER_PID} == $$;
}

sub start {
    my $self = shift;
    return if $self->{+SERVER_PID};

    my ($rh, $wh);
    pipe($rh, $wh) or die "Could not open pipe: $!";

    my $pid = fork;
    die "Could not fork: $!" unless defined $pid;

    if ($pid) {
        close($wh);
        waitpid($pid, 0);
        chomp($self->{+WATCHER_PID} = <$rh>);
        chomp($self->{+SERVER_PID}  = <$rh>);
        close($rh);
        die "Did not get watcher pid!" unless $self->{+WATCHER_PID};
        die "Did not get server pid!"  unless $self->{+SERVER_PID};
        return;
    }

    close($rh);
    POSIX::setsid();
    setpgrp(0, 0);
    $pid = fork;
    die "Could not fork: $!" unless defined $pid;
    POSIX::_exit(0) if $pid;

    $wh->autoflush(1);
    print $wh "$$\n";

    # In watcher now
    eval { $self->watch($wh); 1 } or POSIX::_exit(1);
    POSIX::_exit(0);
}

sub watch {
    my $self = shift;
    my ($wh) = @_;

    $0 = 'db-quick-watcher';

    my $kill = '';
    my $hup = 0;
    local $SIG{TERM} = sub { $kill = 'TERM' };
    local $SIG{INT}  = sub { $kill = 'INT' };
    local $SIG{HUP} = sub { $hup = 1 };

    my $start_pid = $$;
    my $pid = $self->spawn();
    print $wh "$pid\n";
    close($wh);

    my $mpid = $self->{+MASTER_PID};
    my $spid = $self->{+SERVER_PID} or die "No server pid";

    my $ddir = $self->{+DB}->dir;
    my $ssig = $self->{+DB}->stop_sig // 'TERM';