--- /dev/null
+# Copyright (C) 2020 all contributors <meta@public-inbox.org>
+# License: AGPL-3.0+ <https://www.gnu.org/licenses/agpl-3.0.txt>
+
+# 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 Socket qw(AF_UNIX SOCK_STREAM);
+use Carp qw(confess croak);
+use PublicInbox::Sigfd;
+
+sub _get_rec ($) {
+ my ($sock) = @_;
+ local $/ = "\n";
+ defined(my $len = <$sock>) or return;
+ chop($len) eq "\n" or croak "no LF byte in $len";
+ defined(my $r = read($sock, my $buf, $len)) or croak "read error: $!";
+ $r == $len or croak "short read: $r != $len";
+ thaw($buf);
+}
+
+sub _send_rec ($$) {
+ my ($sock, $ref) = @_;
+ my $buf = freeze($ref);
+ print $sock length($buf), "\n", $buf or croak "print: $!";
+}
+
+sub ipc_return ($$$) {
+ my ($s2, $ret, $exc) = @_;
+ _send_rec($s2, $exc ? bless(\$exc, 'PublicInbox::IPC::Die') : $ret);
+}
+
+sub ipc_worker_loop ($$) {
+ my ($self, $s2) = @_;
+ $self->ipc_atfork_child if $self->can('ipc_atfork_child');
+ $s2->autoflush(1);
+ while (my $rec = _get_rec($s2)) {
+ my ($wantarray, $sub, @args) = @$rec;
+ if (!defined($wantarray)) { # no waiting if client doesn't care
+ eval { $self->$sub(@args) };
+ eval { warn "die: $@ (from nowait $sub)\n" } if $@;
+ } elsif ($wantarray) {
+ my @ret = eval { $self->$sub(@args) };
+ ipc_return($s2, \@ret, $@);
+ } else {
+ my $ret = eval { $self->$sub(@args) };
+ ipc_return($s2, \$ret, $@);
+ }
+ }
+}
+
+sub ipc_worker_spawn ($$$) {
+ my ($self, $ident, $oldset) = @_;
+ eval { require Storable; Storable->import(qw(freeze thaw)); };
+ if ($@) {
+ state $w //= warn "Storable (part of Perl) missing: $@\n";
+ return;
+ }
+ my $pid = $self->{-ipc_worker_pid};
+ confess "BUG: already spawned PID:$pid" if $pid;
+ confess "BUG: already have worker socket" if $self->{-ipc_sock};
+ my ($s1, $s2);
+ socketpair($s1, $s2, AF_UNIX, SOCK_STREAM, 0) or die "socketpair: $!";
+ my $sigset = $oldset // PublicInbox::Sigfd::block_signals();
+ defined($pid = fork) or die "fork: $!";
+ if ($pid == 0) {
+ undef $s1;
+ local $0 = $ident;
+ $SIG{$_} = 'IGNORE' for (qw(TERM INT QUIT));
+ PublicInbox::Sigfd::sig_setmask($oldset);
+ eval { ipc_worker_loop($self, $s2) };
+ die "worker $ident died: $@\n" if $@;
+ $self->ipc_at_worker_exit if $self->can('ipc_at_worker_exit');
+ exit;
+ }
+ PublicInbox::Sigfd::sig_setmask($sigset) unless $oldset;
+ $s1->autoflush(1);
+ $self->{-ipc_sock} = $s1;
+ $self->{-ipc_worker_pid} = $pid;
+}
+
+sub ipc_reap_worker { # dwaitpid callback
+ my ($self, $pid) = @_;
+ warn "PID:$pid died with \$?=$?\n" if $?;
+}
+
+sub ipc_worker_stop {
+ my ($self) = @_;
+ my $pid;
+ if (delete $self->{-ipc_sock}) {
+ $pid = delete $self->{-ipc_worker_pid} or die "no PID?";
+ } else {
+ $pid = delete $self->{-ipc_worker_pid} and
+ die "unexpected PID:$pid";
+ }
+ return unless $pid;
+ eval { PublicInbox::DS::dwaitpid($pid, \&ipc_reap_worker, $self) };
+ if ($@) {
+ my $wp = waitpid($pid, 0);
+ $pid == $wp or die "waitpid($pid) returned $wp: \$?=$?";
+ ipc_reap_worker($self, $pid);
+ }
+}
+
+# use this if we have multiple readers reading curl or "pigz -dc"
+# and writing to the same store
+sub ipc_lock_init {
+ my ($self, $f) = @_;
+ require PublicInbox::Lock;
+ $self->{-ipc_lock} //= bless { lock_path => $f }, 'PublicInbox::Lock'
+}
+
+sub ipc_do {
+ my ($self, $sub, @args) = @_;
+ if (my $s1 = $self->{-ipc_sock}) {
+ my $ipc_lock = $self->{-ipc_lock};
+ my $lock = $ipc_lock ? $ipc_lock->lock_for_scope : undef;
+ _send_rec($s1, [ wantarray, $sub, @args ]);
+ return unless defined(wantarray);
+ my $ret = _get_rec($s1) // die "no response on $sub";
+ die $$ret if ref($ret) eq 'PublicInbox::IPC::Die';
+ wantarray ? @$ret : $$ret;
+ } else {
+ $self->$sub(@args);
+ }
+}
+
+1;
--- /dev/null
+#!perl -w
+# Copyright (C) 2020 all contributors <meta@public-inbox.org>
+# License: AGPL-3.0+ <https://www.gnu.org/licenses/agpl-3.0.txt>
+use strict;
+use v5.10.1;
+use Test::More;
+use PublicInbox::TestCommon;
+require_ok 'PublicInbox::IPC';
+state $once = eval <<'';
+package PublicInbox::IPC;
+use strict;
+sub test_array { qw(test array) }
+sub test_scalar { 'scalar' }
+sub test_scalarref { \'scalarref' }
+sub test_undef { undef }
+sub test_die { shift; die @_; 'unreachable' }
+sub test_pid { $$ }
+1;
+
+my $ipc = bless {}, 'PublicInbox::IPC';
+my @t = qw(array scalar scalarref undef);
+my $test = sub {
+ my $x = shift;
+ for my $type (@t) {
+ my $m = "test_$type";
+ my @ret = $ipc->ipc_do($m);
+ my @exp = $ipc->$m;
+ is_deeply(\@ret, \@exp, "wantarray $m $x");
+
+ $ipc->ipc_do($m);
+
+ my $ret = $ipc->ipc_do($m);
+ my $exp = $ipc->$m;
+ is_deeply($ret, $exp, "!wantarray $m $x");
+ }
+ my $ret = eval { $ipc->test_die('phail') };
+ my $exp = $@;
+ $ret = eval { $ipc->ipc_do('test_die', 'phail') };
+ my $err = $@;
+ my %lines;
+ for ($err, $exp) {
+ s/ line (\d+).*//s and $lines{$1}++;
+ }
+ is(scalar keys %lines, 1, 'line numbers match');
+ is((values %lines)[0], 2, '2 hits on same line number');
+ is($err, $exp, "$x die matches");
+ is($ret, undef, "$x die did not return");
+};
+$test->('local');
+
+SKIP: {
+ require_mods(qw(Storable), 16);
+ my $pid = $ipc->ipc_worker_spawn('test worker');
+ ok($pid > 0 && kill(0, $pid), 'worker spawned and running');
+ defined($pid) or BAIL_OUT 'no spawn, no test';
+ is($ipc->ipc_do('test_pid'), $pid, 'worker pid returned');
+ $test->('worker');
+ {
+ my ($tmp, $for_destroy) = tmpdir();
+ $ipc->ipc_lock_init("$tmp/lock");
+ is($ipc->ipc_do('test_pid'), $pid, 'worker pid returned');
+ }
+ $ipc->ipc_worker_stop;
+ ok(!kill(0, $pid) && $!{ESRCH}, 'worker stopped');
+}
+$ipc->ipc_worker_stop; # idempotent
+done_testing;