[PATCH 2/3] nntpd+imapd: detect unlinked msgmap

[Eric Wong <e@yhbt.net>]

While it's even less common to experience a replaced
msgmap.sqlite3 file, BOFHs may do the darndest things.  This is
another step towards reducing the number of needless wakeups
we need to do in long-lived read-only daemons.
---
 lib/PublicInbox/Inbox.pm  |  7 ++---
 lib/PublicInbox/Msgmap.pm | 59 ++++++++++++++++++++-------------------
 t/nntpd.t                 |  8 ++++++
 3 files changed, 42 insertions(+), 32 deletions(-)

diff --git a/lib/PublicInbox/Inbox.pm b/lib/PublicInbox/Inbox.pm
index 02186dac..3d9754dc 100644
--- a/lib/PublicInbox/Inbox.pm
+++ b/lib/PublicInbox/Inbox.pm
@@ -31,7 +31,7 @@ sub cleanup_task () {
 	for my $ibx (values %$CLEANUP) {
 		my $again;
 		if ($have_devel_peek) {
-			foreach my $f (qw(mm search)) {
+			foreach my $f (qw(search)) {
 				# we bump refcnt by assigning tmp, here:
 				my $tmp = $ibx->{$f} or next;
 				next if Devel::Peek::SvREFCNT($tmp) > 2;
@@ -47,7 +47,7 @@ sub cleanup_task () {
 		}
 		check_inodes($ibx);
 		if ($have_devel_peek) {
-			$again ||= !!($ibx->{mm} || $ibx->{search});
+			$again ||= !!$ibx->{search};
 		}
 		$next->{"$ibx"} = $ibx if $again;
 	}
@@ -182,7 +182,6 @@ sub mm {
 	my ($self) = @_;
 	$self->{mm} ||= eval {
 		require PublicInbox::Msgmap;
-		_cleanup_later($self);
 		my $dir = $self->{inboxdir};
 		if ($self->version >= 2) {
 			PublicInbox::Msgmap->new_file("$dir/msgmap.sqlite3");
@@ -409,7 +408,7 @@ sub unsubscribe_unlock {
 
 sub check_inodes ($) {
 	my ($self) = @_;
-	for (qw(over)) { # TODO: search, mm
+	for (qw(over mm)) { # TODO: search
 		$self->{$_}->check_inodes if $self->{$_};
 	}
 }
diff --git a/lib/PublicInbox/Msgmap.pm b/lib/PublicInbox/Msgmap.pm
index aa07e344..e86fb854 100644
--- a/lib/PublicInbox/Msgmap.pm
+++ b/lib/PublicInbox/Msgmap.pm
@@ -13,6 +13,7 @@ use warnings;
 use DBI;
 use DBD::SQLite;
 use File::Temp qw(tempfile);
+use PublicInbox::Over;
 
 sub new {
 	my ($class, $git_dir, $writable) = @_;
@@ -24,29 +25,13 @@ sub new {
 	new_file($class, "$d/msgmap.sqlite3", $writable);
 }
 
-sub dbh_new {
-	my ($f, $writable) = @_;
-	if ($writable && !-f $f) { # SQLite defaults mode to 0644, we want 0666
-		open my $fh, '+>>', $f or die "failed to open $f: $!";
-	}
-	my $dbh = DBI->connect("dbi:SQLite:dbname=$f",'','', {
-		AutoCommit => 1,
-		RaiseError => 1,
-		PrintError => 0,
-		ReadOnly => !$writable,
-		sqlite_use_immediate_transaction => 1,
-	});
-	$dbh;
-}
-
 sub new_file {
-	my ($class, $f, $writable) = @_;
-	return if !$writable && !-r $f;
+	my ($class, $f, $rw) = @_;
+	return if !$rw && !-r $f;
 
-	my $dbh = dbh_new($f, $writable);
-	my $self = bless { dbh => $dbh }, $class;
-
-	if ($writable) {
+	my $self = bless { filename => $f }, $class;
+	my $dbh = $self->{dbh} = PublicInbox::Over::dbh_new($self, $rw);
+	if ($rw) {
 		create_tables($dbh);
 
 		# TRUNCATE reduces I/O compared to the default (DELETE)
@@ -70,7 +55,6 @@ sub tmp_clone {
 	my $tmp = ref($self)->new_file($fn, 1);
 	$tmp->{dbh}->do('PRAGMA synchronous = OFF');
 	$tmp->{dbh}->do('PRAGMA journal_mode = MEMORY');
-	$tmp->{tmp_name} = $fn; # SQLite won't work if unlinked, apparently
 	$tmp->{pid} = $$;
 	close $fh or die "failed to close $fn: $!";
 	$tmp;
@@ -246,28 +230,28 @@ sub mid_set {
 sub DESTROY {
 	my ($self) = @_;
 	delete $self->{dbh};
-	my $f = delete $self->{tmp_name};
-	if (defined $f && $self->{pid} == $$) {
+	my $f = $self->{filename};
+	if (($self->{pid} // 0) == $$) {
 		unlink $f or warn "failed to unlink $f: $!\n";
 	}
 }
 
 sub atfork_parent {
 	my ($self) = @_;
-	my $f = $self->{tmp_name} or die "not a temporary clone\n";
+	$self->{pid} or die "not a temporary clone\n";
 	delete $self->{dbh} and die "tmp_clone dbh not prepared for parent";
-	my $dbh = $self->{dbh} = dbh_new($f, 1);
+	my $dbh = $self->{dbh} = PublicInbox::Over::dbh_new($self, 1);
 	$dbh->do('PRAGMA synchronous = OFF');
 }
 
 sub atfork_prepare {
 	my ($self) = @_;
-	my $f = $self->{tmp_name} or die "not a temporary clone\n";
+	$self->{pid} or die "not a temporary clone\n";
 	$self->{pid} == $$ or
 		die "BUG: atfork_prepare not called from $self->{pid}\n";
 	$self->{dbh} or die "temporary clone not open\n";
 	# must clobber prepared statements
-	%$self = (tmp_name => $f, pid => $$);
+	%$self = (filename => $self->{filename}, pid => $$);
 }
 
 sub skip_artnum {
@@ -296,4 +280,23 @@ sub skip_artnum {
 	}
 }
 
+sub check_inodes {
+	my ($self) = @_;
+	# no filename if in-:memory:
+	my $f = $self->{dbh}->sqlite_db_filename // return;
+	if (my @st = stat($f)) { # did st_dev, st_ino change?
+		my $st = pack('dd', $st[0], $st[1]);
+		if ($st ne ($self->{st} // $st)) {
+			my $tmp = eval { ref($self)->new_file($f) };
+			if ($@) {
+				warn "E: DBI->connect($f): $@\n";
+			} else {
+				%$self = %$tmp;
+			}
+		}
+	} else {
+		warn "W: stat $f: $!\n";
+	}
+}
+
 1;
diff --git a/t/nntpd.t b/t/nntpd.t
index 28008ec1..954e6e75 100644
--- a/t/nntpd.t
+++ b/t/nntpd.t
@@ -14,6 +14,7 @@ use Net::NNTP;
 use Sys::Hostname;
 use POSIX qw(_exit);
 use Digest::SHA;
+use_ok 'PublicInbox::Msgmap';
 
 # FIXME: make easier to test both versions
 my $version = $ENV{PI_TEST_VERSION} || 1;
@@ -341,6 +342,13 @@ Date: Fri, 02 Oct 1993 00:00:00 +0000
 			'article did not exist');
 		$im->add($ex);
 		$im->done;
+		{
+			my $f = $ibx->mm->{filename};
+			my $tmp = "$tmpdir/tmp.sqlite3";
+			$ibx->mm->{dbh}->sqlite_backup_to_file($tmp);
+			delete $ibx->{mm};
+			rename($tmp, $f) or BAIL_OUT "rename($tmp, $f): $!";
+		}
 		ok(run_script([qw(-index --reindex -c), $ibx->{inboxdir}],
 				undef, $noerr), '-compacted');
 		select(undef, undef, undef, $fast_idle ? 0.1 : 2.1);