[PATCH 3/3] searchidx: release Xapian FDs before spawning git log

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

This will allow us to release and re-acquire Xapian locks
due to the lack of FD_CLOEXEC on some FDs.
---
 lib/PublicInbox/Import.pm    |   2 +-
 lib/PublicInbox/SearchIdx.pm | 138 ++++++++++++++++++++++++-------------------
 t/search.t                   |   9 +--
 3 files changed, 82 insertions(+), 67 deletions(-)

diff --git a/lib/PublicInbox/Import.pm b/lib/PublicInbox/Import.pm
index b3812a6..ff5b3f3 100644
--- a/lib/PublicInbox/Import.pm
+++ b/lib/PublicInbox/Import.pm
@@ -237,7 +237,7 @@ sub done {
 
 		eval {
 			require PublicInbox::SearchIdx;
-			my $s = PublicInbox::SearchIdx->new($git_dir, 2);
+			my $s = PublicInbox::SearchIdx->new($git_dir);
 			$s->index_sync({ ref => $self->{ref} });
 		};
 	}
diff --git a/lib/PublicInbox/SearchIdx.pm b/lib/PublicInbox/SearchIdx.pm
index 2c4e704..6efc1f3 100644
--- a/lib/PublicInbox/SearchIdx.pm
+++ b/lib/PublicInbox/SearchIdx.pm
@@ -16,6 +16,7 @@ $Email::MIME::ContentType::STRICT_PARAMS = 0;
 use base qw(PublicInbox::Search);
 use PublicInbox::MID qw/mid_clean id_compress mid_mime/;
 use PublicInbox::MsgIter;
+use Carp qw(croak);
 require PublicInbox::Git;
 *xpfx = *PublicInbox::Search::xpfx;
 
@@ -28,54 +29,47 @@ use constant {
 	PERM_EVERYBODY => 0664,
 };
 
-# XXX temporary hack...
-my $xap_ver = ((Search::Xapian::major_version << 16) |
-		 (Search::Xapian::minor_version << 8 ) |
-		  Search::Xapian::revision());
-our $XAP_LOCK_BROKEN = $xap_ver >= 0x010216; # >= 1.2.22
-
 sub new {
-	my ($class, $git_dir, $writable) = @_;
-	my $dir = PublicInbox::Search->xdir($git_dir);
+	my ($class, $git_dir, $creat) = @_;
 	require Search::Xapian::WritableDatabase;
-	my $flag = Search::Xapian::DB_OPEN;
 	my $self = bless { git_dir => $git_dir }, $class;
 	my $perm = $self->_git_config_perm;
 	my $umask = _umask_for($perm);
 	$self->{umask} = $umask;
 	$self->{lock_path} = "$git_dir/ssoma.lock";
 	$self->{git} = PublicInbox::Git->new($git_dir);
-	$self->{xdb} = $self->with_umask(sub {
-		if ($writable == 1) {
-			require File::Path;
-			File::Path::mkpath($dir);
-			$self->{batch_size} = 100 unless $XAP_LOCK_BROKEN;
-			$flag = Search::Xapian::DB_CREATE_OR_OPEN;
-			_lock_acquire($self);
-		}
-		Search::Xapian::WritableDatabase->new($dir, $flag);
-	});
+	$self->{creat} = ($creat || 0) == 1;
 	$self;
 }
 
 sub _xdb_release {
 	my ($self) = @_;
-	my $xdb = delete $self->{xdb};
-	$xdb->commit_transaction;
+	my $xdb = delete $self->{xdb} or croak 'not acquired';
 	$xdb->close;
+	_lock_release($self) if $self->{creat};
+	undef;
 }
 
 sub _xdb_acquire {
-	my ($self, $more) = @_;
+	my ($self) = @_;
+	croak 'already acquired' if $self->{xdb};
 	my $dir = PublicInbox::Search->xdir($self->{git_dir});
 	my $flag = Search::Xapian::DB_OPEN;
-	my $xdb = Search::Xapian::WritableDatabase->new($dir, $flag);
-	$xdb->begin_transaction if $more;
-	$self->{xdb} = $xdb;
+	if ($self->{creat}) {
+		require File::Path;
+		_lock_acquire($self);
+		File::Path::mkpath($dir);
+		$self->{batch_size} = 100;
+		$flag = Search::Xapian::DB_CREATE_OR_OPEN;
+	}
+	$self->{xdb} = Search::Xapian::WritableDatabase->new($dir, $flag);
 }
 
+# we only acquire the flock if creating or reindexing;
+# PublicInbox::Import already has the lock on its own.
 sub _lock_acquire {
 	my ($self) = @_;
+	croak 'already locked' if $self->{lockfh};
 	sysopen(my $lockfh, $self->{lock_path}, O_WRONLY|O_CREAT) or
 		die "failed to open lock $self->{lock_path}: $!\n";
 	flock($lockfh, LOCK_EX) or die "lock failed: $!\n";
@@ -84,7 +78,7 @@ sub _lock_acquire {
 
 sub _lock_release {
 	my ($self) = @_;
-	my $lockfh = delete $self->{lockfh};
+	my $lockfh = delete $self->{lockfh} or croak 'not locked';
 	flock($lockfh, LOCK_UN) or die "unlock failed: $!\n";
 	close $lockfh or die "close failed: $!\n";
 }
@@ -345,14 +339,12 @@ sub index_sync {
 }
 
 sub rlog {
-	my ($self, $range, $add_cb, $del_cb, $batch_cb) = @_;
+	my ($self, $log, $add_cb, $del_cb, $batch_cb) = @_;
 	my $hex = '[a-f0-9]';
 	my $h40 = $hex .'{40}';
 	my $addmsg = qr!^:000000 100644 \S+ ($h40) A\t${hex}{2}/${hex}{38}$!;
 	my $delmsg = qr!^:100644 000000 ($h40) \S+ D\t${hex}{2}/${hex}{38}$!;
 	my $git = $self->{git};
-	my $log = $git->popen(qw/log --reverse --no-notes --no-color
-				--raw -r --no-abbrev/, $range);
 	my $latest;
 	my $bytes;
 	my $max = $self->{batch_size}; # may be undef
@@ -378,56 +370,74 @@ sub rlog {
 	$batch_cb->($latest, 0);
 }
 
+sub _msgmap_init {
+	my ($self) = @_;
+	$self->{mm} = eval {
+		require PublicInbox::Msgmap;
+		PublicInbox::Msgmap->new($self->{git_dir}, 1);
+	};
+}
+
+sub _git_log {
+	my ($self, $range) = @_;
+	$self->{git}->popen(qw/log --reverse --no-notes --no-color
+				--raw -r --no-abbrev/, $range);
+}
+
 # indexes all unindexed messages
 sub _index_sync {
 	my ($self, $opts) = @_;
 	my $tip = $opts->{ref} || 'HEAD';
-	my $mm = $self->{mm} = eval {
-		require PublicInbox::Msgmap;
-		PublicInbox::Msgmap->new($self->{git_dir}, 1);
-	};
-	my $xdb = $self->{xdb};
-	$xdb->begin_transaction;
 	my $reindex = $opts->{reindex};
-	my $mkey = 'last_commit';
-	my $last_commit = $xdb->get_metadata($mkey);
-	my $lx = $last_commit;
-	if ($reindex) {
-		$lx = '';
-		$mkey = undef if $last_commit ne '';
-	}
-	my $dbh;
+	my ($mkey, $last_commit, $lx, $xlog);
+	my $xdb = _xdb_acquire($self);
+	$xdb->begin_transaction;
+	do {
+		$xlog = undef;
+		$mkey = 'last_commit';
+		$last_commit = $xdb->get_metadata('last_commit');
+		$lx = $last_commit;
+		if ($reindex) {
+			$lx = '';
+			$mkey = undef if $last_commit ne '';
+		}
+		$xdb->cancel_transaction;
+		$xdb = _xdb_release($self);
+
+		# ensure we leak no FDs to "git log"
+		my $range = $lx eq '' ? $tip : "$lx..$tip";
+		$xlog = _git_log($self, $range);
+
+		$xdb = _xdb_acquire($self);
+		$xdb->begin_transaction;
+	} while ($xdb->get_metadata('last_commit') ne $last_commit);
+
+	my $mm = _msgmap_init($self);
+	my $dbh = $mm->{dbh} if $mm;
 	my $cb = sub {
 		my ($commit, $more) = @_;
-		$xdb->set_metadata($mkey, $commit) if $mkey && $commit;
 		if ($dbh) {
 			$mm->last_commit($commit) if $commit;
 			$dbh->commit;
 		}
-		if ($XAP_LOCK_BROKEN) {
-			$xdb->commit_transaction if !$more;
-		} else {
-			$xdb = undef;
-			_xdb_release($self);
-			_lock_release($self);
-		}
-		# let another process do some work...
-		if (!$XAP_LOCK_BROKEN) {
-			_lock_acquire($self);
-			$dbh->begin_work if $dbh && $more;
-			$xdb = _xdb_acquire($self, $more);
+		$xdb->set_metadata($mkey, $commit) if $mkey && $commit;
+		$xdb->commit_transaction;
+		$xdb = _xdb_release($self);
+		# let another process do some work... <
+		if ($more) {
+			$xdb = _xdb_acquire($self);
+			$xdb->begin_transaction;
+			$dbh->begin_work if $dbh;
 		}
 	};
 
-	my $range = $lx eq '' ? $tip : "$lx..$tip";
 	if ($mm) {
-		$dbh = $mm->{dbh};
 		$dbh->begin_work;
 		my $lm = $mm->last_commit || '';
 		if ($lm eq $lx) {
 			# Common case is the indexes are synced,
 			# we only need to run git-log once:
-			rlog($self, $range, *index_both, *unindex_both, $cb);
+			rlog($self, $xlog, *index_both, *unindex_both, $cb);
 		} else {
 			# Uncommon case, msgmap and xapian are out-of-sync
 			# do not care for performance (but git is fast :>)
@@ -439,16 +449,20 @@ sub _index_sync {
 			# first, ensure msgmap is up-to-date:
 			my $mkey_prev = $mkey;
 			$mkey = undef; # ignore xapian, for now
-			rlog($self, $r, *index_mm, *unindex_mm, $cb);
+			my $mlog = _git_log($self, $r);
+			rlog($self, $mlog, *index_mm, *unindex_mm, $cb);
+			$mlog = undef;
 
 			# now deal with Xapian
 			$mkey = $mkey_prev;
 			$dbh = undef;
-			rlog($self, $range, *index_mm2, *unindex_mm2, $cb);
+			$xdb = _xdb_acquire($self);
+			$xdb->begin_transaction;
+			rlog($self, $xlog, *index_mm2, *unindex_mm2, $cb);
 		}
 	} else {
 		# user didn't install DBD::SQLite and DBI
-		rlog($self, $range, *index_blob, *unindex_blob, $cb);
+		rlog($self, $xlog, *index_blob, *unindex_blob, $cb);
 	}
 }
 
diff --git a/t/search.t b/t/search.t
index d5f9d95..2685348 100644
--- a/t/search.t
+++ b/t/search.t
@@ -33,13 +33,14 @@ ok($@, "exception raised on non-existent DB");
 }
 
 my $rw = PublicInbox::SearchIdx->new($git_dir, 1);
-my $ro = PublicInbox::Search->new($git_dir);
+$rw->_xdb_acquire;
+$rw->_xdb_release;
 $rw = undef;
+my $ro = PublicInbox::Search->new($git_dir);
 my $rw_commit = sub {
-	$rw->{xdb}->commit_transaction if $rw;
-	$rw = undef;
+	$rw->{xdb}->commit_transaction if $rw && $rw->{xdb};
 	$rw = PublicInbox::SearchIdx->new($git_dir, 1);
-	$rw->{xdb}->begin_transaction;
+	$rw->_xdb_acquire->begin_transaction;
 };
 
 {
-- 
EW