[PATCH 3/3] git: fatalize async callback errors by default

[Eric Wong <e@80x24.org>]

This should help us catch BUG: errors (and then some) in
-extindex and other read-write code paths.  Only read-only
daemons should warn on async callback failures, since those
aren't capable of causing data loss.
---
 lib/PublicInbox/Daemon.pm |  2 ++
 lib/PublicInbox/Git.pm    | 13 ++++++++++---
 t/git.t                   | 24 ++++++++++++++++++++++++
 3 files changed, 36 insertions(+), 3 deletions(-)

diff --git a/lib/PublicInbox/Daemon.pm b/lib/PublicInbox/Daemon.pm
index 5be474fa8754..0acd4ee9946c 100644
--- a/lib/PublicInbox/Daemon.pm
+++ b/lib/PublicInbox/Daemon.pm
@@ -18,6 +18,7 @@ use PublicInbox::DS qw(now);
 require PublicInbox::Listener;
 use PublicInbox::EOFpipe;
 use PublicInbox::Sigfd;
+use PublicInbox::Git;
 use PublicInbox::GitAsyncCat;
 our $SO_ACCEPTFILTER = 0x1000;
 my @CMD;
@@ -640,6 +641,7 @@ sub run ($$$;$) {
 
 	# localize GCF2C for tests:
 	local $PublicInbox::GitAsyncCat::GCF2C;
+	local $PublicInbox::Git::async_warn = 1;
 
 	daemon_loop($refresh, $post_accept, $tlsd, $af_default);
 	PublicInbox::DS->Reset;
diff --git a/lib/PublicInbox/Git.pm b/lib/PublicInbox/Git.pm
index f15ace1a3d62..7c08be47bbe4 100644
--- a/lib/PublicInbox/Git.pm
+++ b/lib/PublicInbox/Git.pm
@@ -26,6 +26,7 @@ our @EXPORT_OK = qw(git_unquote git_quote);
 our $PIPE_BUFSIZ = 65536; # Linux default
 our $in_cleanup;
 our $RDTIMEO = 60_000; # milliseconds
+our $async_warn; # true in read-only daemons
 
 use constant MAX_INFLIGHT => (POSIX::PIPE_BUF * 3) /
 	65; # SHA-256 hex size + "\n" in preparation for git using non-SHA1
@@ -227,7 +228,7 @@ sub cat_async_step ($$) {
 	}
 	$self->{rbuf} = $rbuf if $$rbuf ne '';
 	eval { $cb->($bref, $oid, $type, $size, $arg) };
-	warn "E: $oid: $@\n" if $@;
+	async_err($self, "E: cat $req ($oid) $@") if $@;
 }
 
 sub cat_async_wait ($) {
@@ -273,7 +274,7 @@ sub check_async_step ($$) {
 	}
 	$self->{rbuf_c} = $rbuf if $$rbuf ne '';
 	eval { $cb->($hex, $type, $size, $arg, $self) };
-	warn "E: check($req) $@\n" if $@;
+	async_err($self, "E: check $req ($hex) $@") if $@;
 }
 
 sub check_async_wait ($) {
@@ -343,7 +344,7 @@ sub async_abort ($) {
 				my ($req, $cb, $arg) = splice(@$q, 0, 3);
 				$req =~ s/ .*//; # drop git_dir for Gcf2Client
 				eval { $cb->(undef, $req, undef, undef, $arg) };
-				warn "E: $req: $@ (in abort)\n" if $@;
+				warn "E: (in abort) $req: $@" if $@;
 			}
 			delete $self->{"inflight$c"};
 			delete $self->{"rbuf$c"};
@@ -358,6 +359,12 @@ sub fail { # may be augmented in subclasses
 	croak(ref($self) . ' ' . ($self->{git_dir} // '') . ": $msg");
 }
 
+sub async_err ($$) {
+	my ($self, $msg) = @_;
+	return warn($msg) if $async_warn;
+	$self->fail($msg);
+}
+
 # $git->popen(qw(show f00)); # or
 # $git->popen(qw(show f00), { GIT_CONFIG => ... }, { 2 => ... });
 sub popen {
diff --git a/t/git.t b/t/git.t
index 2a189eac6c40..8a02021103ff 100644
--- a/t/git.t
+++ b/t/git.t
@@ -68,6 +68,30 @@ use_ok 'PublicInbox::Git';
 	is_deeply($raw, $bref, 'blob result matches');
 	is_deeply($missing, [ undef, 'non-existent', 'missing', undef, $arg],
 		'non-existent blob gives expected result');
+
+	$res = [];
+	$gcf->cat_async($oid, sub { push @$res, \@_ });
+	$gcf->cat_async($oid, sub { die 'HI' });
+	$gcf->cat_async($oid, sub { push @$res, \@_ });
+	eval { $gcf->async_wait_all };
+	like($@, qr/\bHI\b/, 'die in callback propagates');
+	is(scalar(@$res), 2, 'two results');
+	is_deeply($res->[0], [ $raw, @x, undef ], '1st cb result');
+	is_deeply($res->[1], [ undef, $oid, undef, undef, undef ],
+		'2nd cb aborted ');
+
+	my @w;
+	local $PublicInbox::Git::async_warn = 1;
+	local $SIG{__WARN__} = sub { push @w, @_ };
+	$res = [];
+	$gcf->cat_async($oid, sub { push @$res, \@_ });
+	$gcf->cat_async($oid, sub { die 'HI' });
+	$gcf->cat_async($oid, sub { push @$res, \@_ });
+	eval { $gcf->async_wait_all };
+	is(scalar(@$res), 2, 'two results');
+	is_deeply($res->[0], [ $raw, @x, undef ], '1st cb result');
+	is_deeply($res->[1], [ $raw, @x, undef ], '2st cb result');
+	like("@w", qr/\bHI\b/, 'die turned to warning');
 }
 
 if (1) {