From 1dacadf3328241e7c4a378c4566c497d1e33326b Mon Sep 17 00:00:00 2001
From: Eric Wong <e@yhbt.net>
Date: Wed, 10 Jun 2020 07:04:23 +0000
Subject: [PATCH] git: idle rbuf for async

We do this for the C10K-oriented HTTP/NNTP/IMAP processes, and
we may support thousands of git-cat-file processes in the
future.
---
 lib/PublicInbox/Git.pm         | 47 ++++++++++++++++++----------------
 lib/PublicInbox/GitAsyncCat.pm |  2 +-
 2 files changed, 26 insertions(+), 23 deletions(-)

diff --git a/lib/PublicInbox/Git.pm b/lib/PublicInbox/Git.pm
index c5a3fa46..1c148086 100644
--- a/lib/PublicInbox/Git.pm
+++ b/lib/PublicInbox/Git.pm
@@ -123,7 +123,6 @@ sub _bidi_pipe {
 		fcntl($out_w, 1031, 4096);
 		fcntl($in_r, 1031, 4096) if $batch eq '--batch-check';
 	}
-	$self->{$batch} = \(my $rbuf = '');
 	$self->{$out} = $out_w;
 	$self->{$in} = $in_r;
 }
@@ -160,18 +159,20 @@ sub cat_async_step ($$) {
 	my ($self, $inflight) = @_;
 	die 'BUG: inflight empty or odd' if scalar(@$inflight) < 2;
 	my ($cb, $arg) = splice(@$inflight, 0, 2);
-	my $head = my_readline($self->{in}, $self->{'--batch'});
-	$head =~ / missing$/ and return
-		eval { $cb->(undef, undef, undef, undef, $arg) };
-
-	$head =~ /^([0-9a-f]{40}) (\S+) ([0-9]+)$/ or
+	my $rbuf = delete($self->{cat_rbuf}) // \(my $new = '');
+	my ($bref, $oid, $type, $size);
+	my $head = my_readline($self->{in}, $rbuf);
+	if ($head =~ /^([0-9a-f]{40}) (\S+) ([0-9]+)$/) {
+		($oid, $type, $size) = ($1, $2, $3 + 0);
+		$bref = my_read($self->{in}, $rbuf, $size + 1) or
+			fail($self, defined($bref) ? 'read EOF' : "read: $!");
+		chop($$bref) eq "\n" or fail($self, 'LF missing after blob');
+	} elsif ($head !~ / missing$/) {
 		fail($self, "Unexpected result from async git cat-file: $head");
-	my ($oid_hex, $type, $size) = ($1, $2, $3 + 0);
-	my $ret = my_read($self->{in}, $self->{'--batch'}, $size + 1);
-	fail($self, defined($ret) ? 'read EOF' : "read: $!") if !$ret;
-	chop($$ret) eq "\n" or fail($self, 'newline missing after blob');
-	eval { $cb->($ret, $oid_hex, $type, $size, $arg) };
-	warn "E: $oid_hex $@\n" if $@;
+	}
+	eval { $cb->($bref, $oid, $type, $size, $arg) };
+	$self->{cat_rbuf} = $rbuf if $$rbuf ne '';
+	warn "E: $oid: $@\n" if $@;
 }
 
 sub cat_async_wait ($) {
@@ -188,12 +189,13 @@ sub batch_prepare ($) {
 
 sub cat_file {
 	my ($self, $obj, $sizeref) = @_;
-	my ($retried, $head);
+	my ($retried, $head, $rbuf);
 	cat_async_wait($self);
 again:
 	batch_prepare($self);
+	$rbuf = delete($self->{cat_rbuf}) // \(my $new = '');
 	print { $self->{out} } $obj, "\n" or fail($self, "write error: $!");
-	$head = my_readline($self->{in}, $self->{'--batch'});
+	$head = my_readline($self->{in}, $rbuf);
 	if ($head =~ / missing$/) {
 		if (!$retried && alternates_changed($self)) {
 			$retried = 1;
@@ -207,7 +209,8 @@ again:
 
 	my $size = $1 + 0;
 	$$sizeref = $size if $sizeref;
-	my $ret = my_read($self->{in}, $self->{'--batch'}, $size + 1);
+	my $ret = my_read($self->{in}, $rbuf, $size + 1);
+	$self->{cat_rbuf} = $rbuf if $$rbuf ne '';
 	fail($self, defined($ret) ? 'read EOF' : "read: $!") if !$ret;
 	chop($$ret) eq "\n" or fail($self, 'newline missing after blob');
 	$ret;
@@ -217,7 +220,8 @@ sub check {
 	my ($self, $obj) = @_;
 	_bidi_pipe($self, qw(--batch-check in_c out_c pid_c err_c));
 	print { $self->{out_c} } $obj, "\n" or fail($self, "write error: $!");
-	chomp(my $line = my_readline($self->{in_c}, $self->{'--batch-check'}));
+	my $rbuf = ''; # TODO: async + {chk_rbuf}
+	chomp(my $line = my_readline($self->{in_c}, \$rbuf));
 	my ($hex, $type, $size) = split(' ', $line);
 
 	# Future versions of git.git may show 'ambiguous', but for now,
@@ -227,8 +231,7 @@ sub check {
 	return if $type eq 'missing' || $type eq 'ambiguous';
 
 	if ($hex eq 'dangling' || $hex eq 'notdir' || $hex eq 'loop') {
-		my $ret = my_read($self->{in_c}, $self->{'--batch-check'},
-				$type + 1);
+		my $ret = my_read($self->{in_c}, \$rbuf, $type + 1);
 		fail($self, defined($ret) ? 'read EOF' : "read: $!") if !$ret;
 		return;
 	}
@@ -237,9 +240,9 @@ sub check {
 }
 
 sub _destroy {
-	my ($self, $batch, $in, $out, $pid, $err) = @_;
+	my ($self, $rbuf, $in, $out, $pid, $err) = @_;
 	my $p = delete $self->{$pid} or return;
-	delete @$self{($batch, $in, $out)};
+	delete @$self{($rbuf, $in, $out)};
 	delete $self->{$err} if $err; # `err_c'
 
 	# PublicInbox::DS may not be loaded
@@ -278,8 +281,8 @@ sub qx {
 sub cleanup {
 	my ($self) = @_;
 	cat_async_wait($self);
-	_destroy($self, qw(--batch in out pid));
-	_destroy($self, qw(--batch-check in_c out_c pid_c err_c));
+	_destroy($self, qw(cat_rbuf in out pid));
+	_destroy($self, qw(chk_rbuf in_c out_c pid_c err_c));
 	!!($self->{pid} || $self->{pid_c});
 }
 
diff --git a/lib/PublicInbox/GitAsyncCat.pm b/lib/PublicInbox/GitAsyncCat.pm
index f168169f..65e16121 100644
--- a/lib/PublicInbox/GitAsyncCat.pm
+++ b/lib/PublicInbox/GitAsyncCat.pm
@@ -30,7 +30,7 @@ sub event_step {
 	my $inflight = $git->{inflight};
 	if (@$inflight) {
 		$git->cat_async_step($inflight);
-		$self->requeue if @$inflight || length(${$git->{'--batch'}});
+		$self->requeue if @$inflight || exists $git->{cat_rbuf};
 	}
 }
 
-- 
2.44.0