# Copyright (C) 2020-2021 all contributors
# License: AGPL-3.0+
# base class for remote IPC calls, requires Storable
# TODO: this ought to be usable in SearchIdxShard
package PublicInbox::IPC;
use strict;
use v5.10.1;
use Carp qw(confess croak);
use PublicInbox::Sigfd;
my ($enc, $dec);
# ->imports at BEGIN turns sereal_*_with_object into custom ops on 5.14+
# and eliminate method call overhead
BEGIN {
eval {
require Sereal::Encoder;
require Sereal::Decoder;
Sereal::Encoder->import('sereal_encode_with_object');
Sereal::Decoder->import('sereal_decode_with_object');
($enc, $dec) = (Sereal::Encoder->new, Sereal::Decoder->new);
};
};
if ($enc && $dec) { # should be custom ops
*freeze = sub ($) { sereal_encode_with_object $enc, $_[0] };
*thaw = sub ($) { sereal_decode_with_object $dec, $_[0], my $ret };
} else {
eval { # some distros have Storable as a separate package from Perl
require Storable;
Storable->import(qw(freeze thaw));
$enc = 1;
} // warn("Storable (part of Perl) missing: $@\n");
}
sub _get_rec ($) {
my ($r) = @_;
defined(my $len = <$r>) or return;
chop($len) eq "\n" or croak "no LF byte in $len";
defined(my $n = read($r, my $buf, $len)) or croak "read error: $!";
$n == $len or croak "short read: $n != $len";
thaw($buf);
}
sub _send_rec ($$) {
my ($w, $ref) = @_;
my $buf = freeze($ref);
print $w length($buf), "\n", $buf or croak "print: $!";
}
sub ipc_return ($$$) {
my ($w, $ret, $exc) = @_;
_send_rec($w, $exc ? bless(\$exc, 'PublicInbox::IPC::Die') : $ret);
}
sub ipc_worker_loop ($$$) {
my ($self, $r_req, $w_res) = @_;
my ($rec, $wantarray, $sub, @args);
local $/ = "\n";
while ($rec = _get_rec($r_req)) {
($wantarray, $sub, @args) = @$rec;
# no waiting if client doesn't care,
# this is the overwhelmingly likely case
if (!defined($wantarray)) {
eval { $self->$sub(@args) };
eval { warn "$$ die: $@ (from nowait $sub)\n" } if $@;
} elsif ($wantarray) {
my @ret = eval { $self->$sub(@args) };
ipc_return($w_res, \@ret, $@);
} else { # '' => wantscalar
my $ret = eval { $self->$sub(@args) };
ipc_return($w_res, \$ret, $@);
}
}
}
# starts a worker if Sereal or Storable is installed
sub ipc_worker_spawn {
my ($self, $ident, $oldset) = @_;
return unless $enc; # no Sereal or Storable
return if ($self->{-ipc_ppid} // -1) == $$; # idempotent
delete(@$self{qw(-ipc_req -ipc_res -ipc_ppid -ipc_pid)});
pipe(my ($r_req, $w_req)) or die "pipe: $!";
pipe(my ($r_res, $w_res)) or die "pipe: $!";
my $sigset = $oldset // PublicInbox::Sigfd::block_signals();
my $parent = $$;
$self->ipc_atfork_parent;
defined(my $pid = fork) or die "fork: $!";
if ($pid == 0) {
eval { PublicInbox::DS->Reset };
$self->{-ipc_parent_pid} = $parent;
$w_req = $r_res = undef;
$w_res->autoflush(1);
$SIG{$_} = 'IGNORE' for (qw(TERM INT QUIT));
local $0 = $ident;
PublicInbox::Sigfd::sig_setmask($oldset);
my $on_destroy = $self->ipc_atfork_child;
eval { ipc_worker_loop($self, $r_req, $w_res) };
die "worker $ident PID:$$ died: $@\n" if $@;
exit;
}
PublicInbox::Sigfd::sig_setmask($sigset) unless $oldset;
$r_req = $w_res = undef;
$w_req->autoflush(1);
$self->{-ipc_req} = $w_req;
$self->{-ipc_res} = $r_res;
$self->{-ipc_ppid} = $$;
$self->{-ipc_pid} = $pid;
}
sub ipc_worker_reap { # dwaitpid callback
my ($self, $pid) = @_;
warn "PID:$pid died with \$?=$?\n" if $?;
}
# for base class, override in sub classes
sub ipc_atfork_parent {}
sub ipc_atfork_child {}
# should only be called inside the worker process
sub ipc_worker_exit {
my (undef, $code) = @_;
exit($code);
}
# idempotent, can be called regardless of whether worker is active or not
sub ipc_worker_stop {
my ($self) = @_;
my ($pid, $ppid) = delete(@$self{qw(-ipc_pid -ipc_ppid)});
my ($w_req, $r_res) = delete(@$self{qw(-ipc_req -ipc_res)});
if (!$w_req && !$r_res) {
die "unexpected PID:$pid without IPC pipes" if $pid;
return; # idempotent
}
die 'no PID with IPC pipes' unless $pid;
_send_rec($w_req, [ undef, 'ipc_worker_exit', 0 ]);
$w_req = $r_res = undef;
# allow any sibling to send ipc_worker_exit, but siblings can't wait
return if $$ != $ppid;
eval {
my $reap = $self->can('ipc_worker_reap');
PublicInbox::DS::dwaitpid($pid, $reap, $self);
};
if ($@) {
my $wp = waitpid($pid, 0);
$pid == $wp or die "waitpid($pid) returned $wp: \$?=$?";
$self->ipc_worker_reap($pid);
}
}
# use this if we have multiple readers reading curl or "pigz -dc"
# and writing to the same store
sub ipc_lock_init {
my ($self, $f) = @_;
require PublicInbox::Lock;
$self->{-ipc_lock} //= bless { lock_path => $f }, 'PublicInbox::Lock'
}
# call $self->$sub(@args), on a worker if ipc_worker_spawn was used
sub ipc_do {
my ($self, $sub, @args) = @_;
if (my $w_req = $self->{-ipc_req}) { # run in worker
my $ipc_lock = $self->{-ipc_lock};
my $lock = $ipc_lock ? $ipc_lock->lock_for_scope : undef;
if (defined(wantarray)) {
my $r_res = $self->{-ipc_res} or die 'no ipc_res';
_send_rec($w_req, [ wantarray, $sub, @args ]);
my $ret = _get_rec($r_res) // die "no response on $sub";
die $$ret if ref($ret) eq 'PublicInbox::IPC::Die';
wantarray ? @$ret : $$ret;
} else { # likely, fire-and-forget into pipe
_send_rec($w_req, [ undef , $sub, @args ]);
}
} else { # run locally
$self->$sub(@args);
}
}
# needed when there's multiple IPC workers and the parent forking
# causes newer siblings to inherit older siblings sockets
sub ipc_sibling_atfork_child {
my ($self) = @_;
my ($pid, undef) = delete(@$self{qw(-ipc_pid -ipc_ppid)});
delete(@$self{qw(-ipc_req -ipc_res)});
$pid == $$ and die "BUG: $$ ipc_atfork_child called on itself";
}
1;