ipc: add support for asynchronous callbacks

Similar to git->cat_async, this will let us deal with responses
asynchronously, as well as being able to mix synchronous and
asynchronous code transparently (though perhaps not optimally).

1 files changed, 50 insertions, 3 deletions

diff --git a/lib/PublicInbox/IPC.pm b/lib/PublicInbox/IPC.pm
index 81623fc0..7dc8ec6a 100644
--- a/lib/PublicInbox/IPC.pm
+++ b/lib/PublicInbox/IPC.pm
@@ -8,6 +8,8 @@ use strict;
 use v5.10.1;
 use Carp qw(confess croak);
 use PublicInbox::Sigfd;
+use POSIX ();
+use constant PIPE_BUF => $^O eq 'linux' ? 4096 : POSIX::_POSIX_PIPE_BUF();
 my ($enc, $dec);
 # ->imports at BEGIN turns sereal_*_with_object into custom ops on 5.14+
 # and eliminate method call overhead
@@ -41,10 +43,15 @@ sub _get_rec ($) {
         thaw($buf);
 }
 
+sub _pack_rec ($) {
+        my ($ref) = @_;
+        my $buf = freeze($ref);
+        length($buf) . "\n" . $buf;
+}
+
 sub _send_rec ($$) {
         my ($w, $ref) = @_;
-        my $buf = freeze($ref);
-        print $w length($buf), "\n", $buf or croak "print: $!";
+        print $w _pack_rec($ref) or croak "print: $!";
 }
 
 sub ipc_return ($$$) {
@@ -156,6 +163,21 @@ sub ipc_lock_init {
         $self->{-ipc_lock} //= bless { lock_path => $f }, 'PublicInbox::Lock'
 }
 
+sub ipc_async_wait ($$) {
+        my ($self, $max) = @_; # max == -1 to wait for all
+        my $aif = $self->{-async_inflight} or return;
+        my $r_res = $self->{-ipc_res} or die 'BUG: no ipc_res';
+        while (my ($sub, $bytes, $cb, $cb_arg) = splice(@$aif, 0, 4)) {
+                my $ret = _get_rec($r_res) //
+                        die "no response on $sub (req.size=$bytes)";
+                $self->{-async_inflight_bytes} -= $bytes;
+
+                eval { $cb->($cb_arg, $ret) };
+                warn "E: $sub callback error: $@\n" if $@;
+                return if --$max == 0;
+        }
+}
+
 # call $self->$sub(@args), on a worker if ipc_worker_spawn was used
 sub ipc_do {
         my ($self, $sub, @args) = @_;
@@ -163,7 +185,8 @@ sub ipc_do {
                 my $ipc_lock = $self->{-ipc_lock};
                 my $lock = $ipc_lock ? $ipc_lock->lock_for_scope : undef;
                 if (defined(wantarray)) {
-                        my $r_res = $self->{-ipc_res} or die 'no ipc_res';
+                        my $r_res = $self->{-ipc_res} or die 'BUG: no ipc_res';
+                        ipc_async_wait($self, -1);
                         _send_rec($w_req, [ wantarray, $sub, @args ]);
                         my $ret = _get_rec($r_res) // die "no response on $sub";
                         die $$ret if ref($ret) eq 'PublicInbox::IPC::Die';
@@ -176,6 +199,30 @@ sub ipc_do {
         }
 }
 
+sub ipc_async {
+        my ($self, $sub, $sub_args, $cb, $cb_arg) = @_;
+        if (my $w_req = $self->{-ipc_req}) { # run in worker
+                my $rec = _pack_rec([ 1, $sub, @$sub_args ]);
+                my $cur_bytes = \($self->{-async_inflight_bytes} //= 0);
+                while (($$cur_bytes + length($rec)) > PIPE_BUF) {
+                        ipc_async_wait($self, 1);
+                }
+                my $ipc_lock = $self->{-ipc_lock};
+                my $lock = $ipc_lock ? $ipc_lock->lock_for_scope : undef;
+                print $w_req $rec or croak "print: $!";
+                $$cur_bytes += length($rec);
+                push @{$self->{-async_inflight}},
+                                $sub, length($rec), $cb, $cb_arg;
+        } else {
+                my $ret = [ eval { $self->$sub(@$sub_args) } ];
+                if (my $exc = $@) {
+                        $ret = ( bless(\$exc, 'PublicInbox::IPC::Die') );
+                }
+                eval { $cb->($cb_arg, $ret) };
+                warn "E: $sub callback error: $@\n" if $@;
+        }
+}
+
 # needed when there's multiple IPC workers and the parent forking
 # causes newer siblings to inherit older siblings sockets
 sub ipc_sibling_atfork_child {