From 2a717d13f10fcdc69921d80cf94c47a694a175d4 Mon Sep 17 00:00:00 2001
From: Eric Wong <e@80x24.org>
Date: Thu, 11 Jun 2020 00:57:53 +0000
Subject: nntpd+imapd: detect replaced over.sqlite3

For v1 inboxes (and possibly v2 in the future, for VACUUM),
public-inbox-compact replaces over.sqlite3 with a new file.

This currently doesn't need an extra inotify watch descriptor
(or FD for kevent) at the moment, so it can coexist nicely for
systems w/o IO::KQueue or Linux::Inotify2.
---
 lib/PublicInbox/Over.pm | 36 +++++++++++++++++++++++++++++-------
 1 file changed, 29 insertions(+), 7 deletions(-)

(limited to 'lib/PublicInbox/Over.pm')

diff --git a/lib/PublicInbox/Over.pm b/lib/PublicInbox/Over.pm
index e32104f0..74c8fb86 100644
--- a/lib/PublicInbox/Over.pm
+++ b/lib/PublicInbox/Over.pm
@@ -19,13 +19,23 @@ sub dbh_new {
 	if ($rw && !-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 => !$rw,
-		sqlite_use_immediate_transaction => 1,
-	});
+	my (@st, $st, $dbh);
+	my $tries = 0;
+	do {
+		@st = stat($f) or die "failed to stat $f: $!";
+		$st = pack('dd', $st[0], $st[1]); # 0: dev, 1: inode
+		$dbh = DBI->connect("dbi:SQLite:dbname=$f",'','', {
+			AutoCommit => 1,
+			RaiseError => 1,
+			PrintError => 0,
+			ReadOnly => !$rw,
+			sqlite_use_immediate_transaction => 1,
+		});
+		$self->{st} = $st;
+		@st = stat($f) or die "failed to stat $f: $!";
+		$st = pack('dd', $st[0], $st[1]);
+	} while ($st ne $self->{st} && $tries++ < 3);
+	warn "W: $f: .st_dev, .st_ino unstable\n" if $st ne $self->{st};
 	$dbh->{sqlite_unicode} = 1;
 	$dbh;
 }
@@ -259,4 +269,16 @@ SELECT MAX(num) FROM over WHERE num > 0
 	($exists, $uidnext, $sth->fetchrow_array // 0);
 }
 
+sub check_inodes {
+	my ($self) = @_;
+	if (my @st = stat($self->{filename})) { # did st_dev, st_ino change?
+		my $st = pack('dd', $st[0], $st[1]);
+
+		# don't actually reopen, just let {dbh} be recreated later
+		delete($self->{dbh}) if ($st ne ($self->{st} // $st));
+	} else {
+		warn "W: stat $self->{filename}: $!\n";
+	}
+}
+
 1;
-- 
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