From: Eric Wong <e@80x24.org>
Date: Mon, 16 Jun 2025 20:05:13 +0000 (+0000)
Subject: daemon: reopen log files atomically
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=62b462a9845cacd3e7f45386cf12502d6456e01c;p=thirdparty%2Fpublic-inbox.git

daemon: reopen log files atomically

Ensuring there is no window for a Perl IO (file handle) to be
invalid is useful in case some code ever gets used in a
multithreaded environment.  The FD stability would also be less
confusing for users using `lsof(8)' or similar to track FDs.
---

diff --git a/lib/PublicInbox/Daemon.pm b/lib/PublicInbox/Daemon.pm
index c5af83677..c52ac0a11 100644
--- a/lib/PublicInbox/Daemon.pm
+++ b/lib/PublicInbox/Daemon.pm
@@ -110,7 +110,12 @@ sub do_chown ($) {
 }
 
 sub open_log_path ($$) { # my ($fh, $path) = @_; # $_[0] is modified
-	open $_[0], '>>', $_[1];
+	if (defined $_[0]) {
+		open my $tmp_fh, '>>', $_[1];
+		POSIX::dup2(fileno($tmp_fh), fileno($_[0])) or die "dup2: $!";
+	} else {
+		open $_[0], '>>', $_[1];
+	}
 	$_[0]->autoflush(1);
 	do_chown($_[1]);
 	$_[0];