ipc: wq: support dynamic worker count change

Increasing/decreasing workers count will be useful in
some situations.

diff --git a/lib/PublicInbox/IPC.pm b/lib/PublicInbox/IPC.pm
index 0c5205c12c6561c1c8960f36c1044ddef410f9c3..5bca362788d629b438b757d9c624ae7603d29e41 100644 (file)
--- a/lib/PublicInbox/IPC.pm
+++ b/lib/PublicInbox/IPC.pm
@@ -8,7 +8,7 @@ use v5.10.1;
 use Carp qw(confess croak);
 use PublicInbox::DS qw(dwaitpid);
 use PublicInbox::Spawn;
-use POSIX ();
+use POSIX qw(WNOHANG);
 use Socket qw(AF_UNIX MSG_EOR);
 my $SEQPACKET = eval { Socket::SOCK_SEQPACKET() }; # portable enough?
 use constant PIPE_BUF => $^O eq 'linux' ? 4096 : POSIX::_POSIX_PIPE_BUF();
@@ -112,7 +112,7 @@ sub ipc_worker_spawn {
                $w_res->autoflush(1);
                $SIG{$_} = 'IGNORE' for (qw(TERM INT QUIT));
                local $0 = $ident;
-               PublicInbox::DS::sig_setmask($oldset);
+               PublicInbox::DS::sig_setmask($sigset);
                my $on_destroy = $self->ipc_atfork_child;
                eval { ipc_worker_loop($self, $r_req, $w_res) };
                die "worker $ident PID:$$ died: $@\n" if $@;
@@ -229,12 +229,13 @@ sub ipc_sibling_atfork_child {
        $pid == $$ and die "BUG: $$ ipc_atfork_child called on itself";
 }
 
-sub wq_worker_loop ($$) {
-       my ($self, $s2) = @_;
+sub wq_worker_loop ($) {
+       my ($self) = @_;
        my $buf;
        my $len = $self->{wq_req_len} // (4096 * 33);
        my ($rec, $sub, @args);
-       while (1) {
+       my $s2 = $self->{-wq_s2} // die 'BUG: no -wq_s2';
+       until ($self->{-wq_quit}) {
                my (@fds) = $recv_cmd->($s2, $buf, $len) or return; # EOF
                my $i = 0;
                my @m = @{$self->{wq_open_modes} // [qw( +<&= >&= >&= )]};
@@ -258,7 +259,7 @@ sub wq_worker_loop ($$) {
 
 sub wq_do { # always async
        my ($self, $sub, $in, $out, $err, @args) = @_;
-       if (my $s1 = $self->{-wq_seq}) { # run in worker
+       if (my $s1 = $self->{-wq_s1}) { # run in worker
                $_ = fileno($_) for ($in, $out, $err);
                $send_cmd->($s1, $in, $out, $err,
                                freeze([$sub, @args]), MSG_EOR);
@@ -270,42 +271,86 @@ sub wq_do { # always async
        }
 }
 
+sub _wq_worker_start ($$) {
+       my ($self, $oldset) = @_;
+       my $pid = fork // die "fork: $!";
+       if ($pid == 0) {
+               eval { PublicInbox::DS->Reset };
+               close(delete $self->{-wq_s1});
+               delete $self->{qw(-wq_workers -wq_quit)};
+               my $quit = sub { $self->{-wq_quit} = 1 };
+               $SIG{$_} = $quit for (qw(TERM INT QUIT));
+               $SIG{$_} = 'IGNORE' for (qw(TTOU TTIN));
+               local $0 = $self->{-wq_ident};
+               PublicInbox::DS::sig_setmask($oldset);
+               my $on_destroy = $self->ipc_atfork_child;
+               eval { wq_worker_loop($self) };
+               die "worker $self->{-wq_ident} PID:$$ died: $@\n" if $@;
+               exit;
+       } else {
+               $self->{-wq_workers}->{$pid} = \undef;
+       }
+}
+
 # starts workqueue workers if Sereal or Storable is installed
 sub wq_workers_start {
        my ($self, $ident, $nr_workers, $oldset) = @_;
        ($enc && $send_cmd && $recv_cmd && defined($SEQPACKET)) or return;
-       return if $self->{-wq_seq}; # idempotent
+       return if $self->{-wq_s1}; # idempotent
        my ($s1, $s2);
        socketpair($s1, $s2, AF_UNIX, $SEQPACKET, 0) or die "socketpair: $!";
-       my $sigset = $oldset // PublicInbox::DS::block_signals();
        $self->ipc_atfork_parent;
        $nr_workers //= 4;
+       my $sigset = $oldset // PublicInbox::DS::block_signals();
        $self->{-wq_workers} = {};
-       for my $i (0..($nr_workers - 1)) {
-               defined(my $pid = fork) or die "fork: $!";
-               if ($pid == 0) {
-                       eval { PublicInbox::DS->Reset };
-                       $s1 = undef;
-                       $SIG{$_} = 'IGNORE' for (qw(TERM INT QUIT));
-                       local $0 = $ident."[$i]";
-                       PublicInbox::DS::sig_setmask($oldset);
-                       my $on_destroy = $self->ipc_atfork_child;
-                       eval { wq_worker_loop($self, $s2) };
-                       die "worker $ident PID:$$ died: $@\n" if $@;
-                       exit;
-               } else {
-                       $self->{-wq_workers}->{$pid} = $i;
-               }
-       }
+       $self->{-wq_ident} = $ident;
+       $self->{-wq_s1} = $s1;
+       $self->{-wq_s2} = $s2;
+       _wq_worker_start($self, $sigset) for (1..$nr_workers);
        PublicInbox::DS::sig_setmask($sigset) unless $oldset;
-       $s2 = undef;
-       $self->{-wq_seq} = $s1;
        $self->{-wq_ppid} = $$;
 }
 
+sub wq_worker_incr { # SIGTTIN handler
+       my ($self, $oldset) = @_;
+       $self->{-wq_s2} or return;
+       $self->ipc_atfork_parent;
+       my $sigset = $oldset // PublicInbox::DS::block_signals();
+       _wq_worker_start($self, $sigset);
+       PublicInbox::DS::sig_setmask($sigset) unless $oldset;
+}
+
+sub wq_exit { # wakes up wq_worker_decr_wait
+       send($_[0]->{-wq_s2}, $$, MSG_EOR) // die "$$ send: $!";
+       exit;
+}
+
+sub wq_worker_decr { # SIGTTOU handler, kills first idle worker
+       my ($self) = @_;
+       my $workers = $self->{-wq_workers} or return;
+       my $s2 = $self->{-wq_s2} // die 'BUG: no wq_s2';
+       $self->wq_do('wq_exit', $s2, $s2, $s2);
+       $self->{-wq_exit_pending}++;
+       # caller must call wq_worker_decr_wait in main loop
+}
+
+sub wq_worker_decr_wait {
+       my ($self, $timeout) = @_;
+       return if $self->{-wq_ppid} != $$; # can't reap siblings or parents
+       my $s1 = $self->{-wq_s1} // croak 'BUG: no wq_s1';
+       vec(my $rin = '', fileno($s1), 1) = 1;
+       select(my $rout = $rin, undef, undef, $timeout) or
+               croak 'timed out waiting for wq_exit';
+       recv($s1, my $pid, 64, 0) // croak "recv: $!";
+       my $workers = $self->{-wq_workers} // croak 'BUG: no wq_workers';
+       delete $workers->{$pid} // croak "BUG: PID:$pid invalid";
+       $self->{-wq_exit_pending}--;
+       dwaitpid($pid, \&ipc_worker_reap, $self);
+}
+
 sub wq_close {
        my ($self) = @_;
-       delete $self->{-wq_seq} or return;
+       delete @$self{qw(-wq_s1 -wq_s2)} or return;
        my $ppid = delete $self->{-wq_ppid} // die 'BUG: no wq_ppid';
        my $workers = delete $self->{-wq_workers} // die 'BUG: no wq_workers';
        return if $ppid != $$; # can't reap siblings or parents

diff --git a/t/ipc.t b/t/ipc.t
index f09f76ef740434b8b02c35a5640c890a91e5a127..51e347c68860fa5e1819358bac499e574ac36d5a 100644 (file)
--- a/t/ipc.t
+++ b/t/ipc.t
@@ -168,4 +168,13 @@ like($warn[0], qr/ wq_do: /, '1st warned from wq_do');
 like($warn[1], qr/ wq_worker: /, '2nd warned from wq_worker');
 is($warn[2], $warn[1], 'worker did not die');
 
+$SIG{__WARN__} = 'DEFAULT';
+is($ipc->wq_workers_start('wq', 1), $$, 'workers started again');
+is(scalar(keys %{$ipc->{-wq_workers}}), 1, '1 worker started');
+$ipc->wq_worker_incr;
+is(scalar(keys %{$ipc->{-wq_workers}}), 2, 'worker count bumped');
+$ipc->wq_worker_decr;
+$ipc->wq_worker_decr_wait(10);
+is(scalar(keys %{$ipc->{-wq_workers}}), 1, 'worker count lowered');
+
 done_testing;