[PATCH] gcf2: improve error handling and do not ->fail on wbuf

[PATCH] gcf2: improve error handling and do not ->fail on wbuf

[Eric Wong]

For historical reasons, both Danga::Socket::write and
PublicInbox::DS::write will return 0 when data is buffered;
so we Gcf2Client must not call ->fail when DS::write returns 0.

We'll also improve robustness by recreating the entire
Gcf2Client object if it does die for other reasons, instead of
risking mismatched fields.

We also need to ensure we only get one EPOLLERR wakeup and
issue EPOLL_CTL_DEL if ->event_step is triggered by a dying
Gcf2 process.
---
 lib/PublicInbox/Daemon.pm      | 10 ++--------
 lib/PublicInbox/Gcf2Client.pm  | 31 +++++++++++++++++++------------
 lib/PublicInbox/GitAsyncCat.pm | 11 +++++++++--
 3 files changed, 30 insertions(+), 22 deletions(-)

diff --git a/lib/PublicInbox/Daemon.pm b/lib/PublicInbox/Daemon.pm
index 1520f8f2..155707e1 100644
--- a/lib/PublicInbox/Daemon.pm
+++ b/lib/PublicInbox/Daemon.pm
@@ -654,14 +654,8 @@ sub run ($$$;$) {
 	my $af_default = $default =~ /:8080\z/ ? 'httpready' : undef;
 	my $for_destroy = daemonize();
 
-	# this wastes a bit of memory for non-PublicInbox::WWW -httpd users
-	# oh well...
-	eval {
-		require PublicInbox::Gcf2;
-		require PublicInbox::Gcf2Client;
-	};
-	local $PublicInbox::GitAsyncCat::GCF2C =
-				PublicInbox::Gcf2Client::new() if !$@;
+	# localize GCF2C for tests:
+	local $PublicInbox::GitAsyncCat::GCF2C;
 
 	daemon_loop($refresh, $post_accept, $tlsd, $af_default);
 	PublicInbox::DS->Reset;
diff --git a/lib/PublicInbox/Gcf2Client.pm b/lib/PublicInbox/Gcf2Client.pm
index 42ff1bf3..ab486de5 100644
--- a/lib/PublicInbox/Gcf2Client.pm
+++ b/lib/PublicInbox/Gcf2Client.pm
@@ -8,27 +8,28 @@ use parent qw(PublicInbox::DS);
 use PublicInbox::Git;
 use PublicInbox::Spawn qw(popen_rd);
 use IO::Handle ();
-use PublicInbox::Syscall qw(EPOLLONESHOT EPOLLOUT);
+use PublicInbox::Syscall qw(EPOLLONESHOT);
 # fields:
 #	async_cat => GitAsyncCat ref (read-only pipe)
 #	sock => writable pipe to Gcf2::loop
 
-sub new { bless($_[0] // {}, __PACKAGE__) }
 
-sub gcf2c_begin ($) {
-	my ($self) = @_;
+sub new  {
+	my ($rdr) = @_;
+	my $self = bless {}, __PACKAGE__;
 	# ensure the child process has the same @INC we do:
 	my $env = { PERL5LIB => join(':', @INC) };
 	my ($out_r, $out_w);
 	pipe($out_r, $out_w) or die "pipe failed: $!";
-	my $rdr = { 0 => $out_r, 2 => $self->{2} };
+	$rdr //= {};
+	$rdr->{0} = $out_r;
 	my $cmd = [$^X, qw[-MPublicInbox::Gcf2 -e PublicInbox::Gcf2::loop()]];
 	@$self{qw(in pid)} = popen_rd($cmd, $env, $rdr);
 	fcntl($out_w, 1031, 4096) if $^O eq 'linux'; # 1031: F_SETPIPE_SZ
 	$out_w->autoflush(1);
 	$out_w->blocking(0);
-	$self->SUPER::new($out_w, 0); # EPOLL_CTL_ADD (a bit wasteful :x)
 	$self->{inflight} = [];
+	$self->SUPER::new($out_w, EPOLLONESHOT); # detect errors once
 }
 
 sub fail {
@@ -39,22 +40,28 @@ sub fail {
 
 sub cat_async ($$$;$) {
 	my ($self, $req, $cb, $arg) = @_;
-	my $inflight = $self->{inflight} // gcf2c_begin($self);
+	my $inflight = $self->{inflight};
 
-	# rare, I hope:
+	# {wbuf} is rare, I hope:
 	cat_async_step($self, $inflight) if $self->{wbuf};
 
-	$self->write(\"$req\n") or $self->fail("gcf2c write: $!");
+	if (!$self->write(\"$req\n")) {
+		$self->fail("gcf2c write: $!") if !$self->{sock};
+	}
 	push @$inflight, $req, $cb, $arg;
 }
 
 # ensure PublicInbox::Git::cat_async_step never calls cat_async_retry
 sub alternates_changed {}
 
-no warnings 'once';
-
 # this is the write-only end of a pipe, DS->EventLoop will call this
-*event_step = \&PublicInbox::DS::flush_write;
+sub event_step {
+	my ($self) = @_;
+	$self->flush_write;
+	$self->close if !$self->{in}; # process died
+}
+
+no warnings 'once';
 
 # used by GitAsyncCat
 *cat_async_step = \&PublicInbox::Git::cat_async_step;
diff --git a/lib/PublicInbox/GitAsyncCat.pm b/lib/PublicInbox/GitAsyncCat.pm
index b9dbe0cc..be51f673 100644
--- a/lib/PublicInbox/GitAsyncCat.pm
+++ b/lib/PublicInbox/GitAsyncCat.pm
@@ -53,14 +53,21 @@ sub event_step {
 
 sub git_async_cat ($$$$) {
 	my ($git, $oid, $cb, $arg) = @_;
-	my $gitish = $GCF2C;
-	if ($gitish) {
+	my $gitish = $GCF2C //= eval {
+		require PublicInbox::Gcf2;
+		require PublicInbox::Gcf2Client;
+		PublicInbox::Gcf2Client::new();
+	} // 0; # 0: do not retry if libgit2 or Inline::C are missing
+	if ($gitish) { # Gcf2 active, {inflight} may be unset due to errors
+		$GCF2C->{inflight} or
+			$gitish = $GCF2C = PublicInbox::Gcf2Client::new();
 		$oid .= " $git->{git_dir}";
 	} else {
 		$gitish = $git;
 	}
 	$gitish->cat_async($oid, $cb, $arg);
 	$gitish->{async_cat} //= do {
+		# read-only end of pipe (Gcf2Client is write-only end)
 		my $self = bless { gitish => $gitish }, __PACKAGE__;
 		$self->SUPER::new($gitish->{in}, EPOLLIN|EPOLLET);
 		\undef; # this is a true ref()

Re: [PATCH] gcf2: improve error handling and do not ->fail on wbuf

[Eric Wong]

Putting words together to write commit messages is hard
without enough sleep :<

Anyways, revised and pushed as
commit 8ba04f214bbadcbe106c94281a0c4c21dd50adb8

    gcf2: improve error handling and do not ->fail on wbuf
    
    For historical reasons, both Danga::Socket::write and
    PublicInbox::DS::write will return 0 when data is buffered;
    so Gcf2Client must not call ->fail when DS::write returns 0.
    
    We'll also improve robustness by recreating the entire
    Gcf2Client object if it does die for other reasons, instead of
    risking mismatched fields due to deferred close.
    
    We also need to ensure we only get one EPOLLERR wakeup and
    issue EPOLL_CTL_DEL if ->event_step is triggered by a dying
    Gcf2 process, so always register the FD with EPOLLONESHOT.