Lock: new base class for writable lockers

This reduces code duplication needed for locking and
and hopefully makes things easier to understand.

1 files changed, 31 insertions, 0 deletions

diff --git a/lib/PublicInbox/Lock.pm b/lib/PublicInbox/Lock.pm
new file mode 100644
index 00000000..ca6b33f2
--- /dev/null
+++ b/lib/PublicInbox/Lock.pm
@@ -0,0 +1,31 @@
+# Copyright (C) 2018 all contributors <meta@public-inbox.org>
+# License: AGPL-3.0+ <https://www.gnu.org/licenses/agpl-3.0.txt>
+
+# Base class for per-inbox locking
+package PublicInbox::Lock;
+use strict;
+use warnings;
+use Fcntl qw(:flock :DEFAULT);
+use Carp qw(croak);
+
+# 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};
+        my $lock_path = $self->{lock_path} or return;
+        sysopen(my $lockfh, $lock_path, O_WRONLY|O_CREAT) or
+                die "failed to open lock $lock_path: $!\n";
+        flock($lockfh, LOCK_EX) or die "lock failed: $!\n";
+        $self->{lockfh} = $lockfh;
+}
+
+sub lock_release {
+        my ($self) = @_;
+        return unless $self->{lock_path};
+        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";
+}
+
+1;