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| | # Copyright (C) 2016 all contributors <meta@public-inbox.org>
# License: AGPL-3.0+ <https://www.gnu.org/licenses/agpl-3.0.txt>
# Generic process management framework to limits the number of
# processes spawned in public-inbox-httpd, but has generic fallbacks
# to work on any PSGI server.
# This does not depend on Danga::Socket or any other external
# scheduling mechanism, you just need to call start and finish
# appropriately
package PublicInbox::Qspawn;
use strict;
use warnings;
use PublicInbox::Spawn qw(popen_rd);
require Plack::Util;
my $def_limiter;
sub new ($$$;) {
my ($class, $cmd, $env, $opt) = @_;
bless { args => [ $cmd, $env, $opt ] }, $class;
}
sub _do_spawn {
my ($self, $cb) = @_;
my $err;
($self->{rpipe}, $self->{pid}) = popen_rd(@{$self->{args}});
if (defined $self->{pid}) {
$self->{limiter}->{running}++;
} else {
$self->{err} = $!;
}
$cb->($self->{rpipe});
}
sub finish ($) {
my ($self) = @_;
my $limiter = $self->{limiter};
my $running;
if (delete $self->{rpipe}) {
my $pid = delete $self->{pid};
$self->{err} = $pid == waitpid($pid, 0) ? $? :
"PID:$pid still running?";
$running = --$limiter->{running};
}
# limiter->{max} may change dynamically
if (($running || $limiter->{running}) < $limiter->{max}) {
if (my $next = shift @{$limiter->{run_queue}}) {
_do_spawn(@$next);
}
}
$self->{err};
}
sub start {
my ($self, $limiter, $cb) = @_;
$self->{limiter} = $limiter;
if ($limiter->{running} < $limiter->{max}) {
_do_spawn($self, $cb);
} else {
push @{$limiter->{run_queue}}, [ $self, $cb ];
}
}
sub _psgi_finish ($$) {
my ($self, $env) = @_;
my $err = $self->finish;
if ($err && !$env->{'qspawn.quiet'}) {
$err = join(' ', @{$self->{args}->[0]}).": $err\n";
$env->{'psgi.errors'}->print($err);
}
}
sub psgi_qx {
my ($self, $env, $limiter, $qx_cb) = @_;
my $qx = PublicInbox::Qspawn::Qx->new;
my $end = sub {
_psgi_finish($self, $env);
eval { $qx_cb->($qx) };
$qx = undef;
};
my $rpipe;
my $async = $env->{'pi-httpd.async'};
my $cb = sub {
my $r = sysread($rpipe, my $buf, 8192);
if ($async) {
$async->async_pass($env->{'psgix.io'}, $qx, \$buf);
} elsif (defined $r) {
$r ? $qx->write($buf) : $end->();
} else {
return if $!{EAGAIN} || $!{EINTR}; # loop again
$end->();
}
};
$limiter ||= $def_limiter ||= PublicInbox::Qspawn::Limiter->new(32);
$self->start($limiter, sub { # may run later, much later...
($rpipe) = @_;
if ($async) {
# PublicInbox::HTTPD::Async->new($rpipe, $cb, $end)
$async = $async->($rpipe, $cb, $end);
} else { # generic PSGI
$cb->() while $qx;
}
});
}
# create a filter for "push"-based streaming PSGI writes used by HTTPD::Async
sub filter_fh ($$) {
my ($fh, $filter) = @_;
Plack::Util::inline_object(
close => sub {
$fh->write($filter->(undef));
$fh->close;
},
write => sub {
$fh->write($filter->($_[0]));
});
}
sub psgi_return {
my ($self, $env, $limiter, $parse_hdr) = @_;
my ($fh, $rpipe);
my $end = sub {
_psgi_finish($self, $env);
$fh->close if $fh; # async-only
};
my $buf = '';
my $rd_hdr = sub {
my $r = sysread($rpipe, $buf, 1024, length($buf));
return if !defined($r) && ($!{EINTR} || $!{EAGAIN});
$parse_hdr->($r, \$buf);
};
my $res = delete $env->{'qspawn.response'};
my $async = $env->{'pi-httpd.async'};
my $cb = sub {
my $r = $rd_hdr->() or return;
$rd_hdr = undef;
my $filter = delete $env->{'qspawn.filter'};
if (scalar(@$r) == 3) { # error
if ($async) {
$async->close; # calls rpipe->close and $end
} else {
$rpipe->close;
$end->();
}
$res->($r);
} elsif ($async) {
$fh = $res->($r); # scalar @$r == 2
$fh = filter_fh($fh, $filter) if $filter;
$async->async_pass($env->{'psgix.io'}, $fh, \$buf);
} else { # for synchronous PSGI servers
require PublicInbox::GetlineBody;
$r->[2] = PublicInbox::GetlineBody->new($rpipe, $end,
$buf, $filter);
$res->($r);
}
};
$limiter ||= $def_limiter ||= PublicInbox::Qspawn::Limiter->new(32);
my $start_cb = sub { # may run later, much later...
($rpipe) = @_;
if ($async) {
# PublicInbox::HTTPD::Async->new($rpipe, $cb, $end)
$async = $async->($rpipe, $cb, $end);
} else { # generic PSGI
$cb->() while $rd_hdr;
}
};
return $self->start($limiter, $start_cb) if $res;
sub {
($res) = @_;
$self->start($limiter, $start_cb);
};
}
package PublicInbox::Qspawn::Limiter;
use strict;
use warnings;
sub new {
my ($class, $max) = @_;
bless {
# 32 is same as the git-daemon connection limit
max => $max || 32,
running => 0,
run_queue => [],
}, $class;
}
# captures everything into a buffer and executes a callback when done
package PublicInbox::Qspawn::Qx;
use strict;
use warnings;
sub new {
my ($class) = @_;
my $buf = '';
bless \$buf, $class;
}
# called by PublicInbox::HTTPD::Async ($fh->write)
sub write {
${$_[0]} .= $_[1];
undef;
}
1;
|