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authorEric Wong <e@80x24.org>2016-06-15 00:14:28 +0000
committerEric Wong <e@80x24.org>2016-06-15 00:15:12 +0000
commitc1abb946e53e4179666ebb290e31c2d9ddc40711 (patch)
treecd3fcfeefb12e7a0a5858a841826788d2a2e1a07
parent61f05bf5869c3f471a16926b1a837ab0d95fb095 (diff)
downloadpublic-inbox-c1abb946e53e4179666ebb290e31c2d9ddc40711.tar.gz
This is transactional and hopefully safer in case we hit SIGSEGV
or SIGKILL during processing, as the tmp/ copy will remain on
the FS even if DESTROY/END handlers are not called.
-rw-r--r--lib/PublicInbox/Emergency.pm96
-rw-r--r--t/emergency.t53
2 files changed, 149 insertions, 0 deletions
diff --git a/lib/PublicInbox/Emergency.pm b/lib/PublicInbox/Emergency.pm
new file mode 100644
index 00000000..e402d30f
--- /dev/null
+++ b/lib/PublicInbox/Emergency.pm
@@ -0,0 +1,96 @@
+# Copyright (C) 2016 all contributors <meta@public-inbox.org>
+# License: AGPL-3.0+ <https://www.gnu.org/licenses/agpl-3.0.txt>
+#
+# Emergency Maildir delivery for MDA
+package PublicInbox::Emergency;
+use strict;
+use warnings;
+use Fcntl qw(:DEFAULT SEEK_SET);
+use Sys::Hostname qw(hostname);
+use IO::Handle;
+
+sub new {
+        my ($class, $dir) = @_;
+
+        foreach (qw(new tmp cur)) {
+                my $d = "$dir/$_";
+                next if -d $d;
+                require File::Path;
+                File::Path::mkpath($d); # croaks on fatal errors
+        }
+        bless { dir => $dir, files => {}, t => 0, cnt => 0 }, $class;
+}
+
+sub _fn_in {
+        my ($self, $dir) = @_;
+        my @host = split(/\./, hostname);
+        my $now = time;
+        if ($self->{t} != $now) {
+                $self->{t} = $now;
+                $self->{cnt} = 0;
+        } else {
+                $self->{cnt}++;
+        }
+
+        my $f;
+        do {
+                $f = "$self->{dir}/$dir/$self->{t}.$$"."_$self->{cnt}.$host[0]";
+                $self->{cnt}++;
+        } while (-e $f);
+        $f;
+}
+
+sub prepare {
+        my ($self, $strref) = @_;
+
+        die "already in transaction: $self->{tmp}" if $self->{tmp};
+        my ($tmp, $fh);
+        do {
+                $tmp = _fn_in($self, 'tmp');
+                $! = undef;
+        } while (!sysopen($fh, $tmp, O_CREAT|O_EXCL|O_RDWR) && $!{EEXIST});
+        print $fh $$strref or die "write failed: $!";
+        $fh->flush or die "flush failed: $!";
+        $fh->autoflush(1);
+        $self->{fh} = $fh;
+        $self->{tmp} = $tmp;
+}
+
+sub abort {
+        my ($self) = @_;
+        delete $self->{fh};
+        my $tmp = delete $self->{tmp} or return;
+
+        unlink($tmp) or warn "Failed to unlink $tmp: $!";
+        undef;
+}
+
+sub fh {
+        my ($self) = @_;
+        my $fh = $self->{fh} or die "{fh} not open!\n";
+        seek($fh, 0, SEEK_SET) or die "seek(fh) failed: $!";
+        sysseek($fh, 0, SEEK_SET) or die "sysseek(fh) failed: $!";
+        $fh;
+}
+
+sub commit {
+        my ($self) = @_;
+
+        delete $self->{fh};
+        my $tmp = delete $self->{tmp} or return;
+        my $new;
+        do {
+                $new = _fn_in($self, 'new');
+        } while (!link($tmp, $new) && $!{EEXIST});
+        my @sn = stat($new) or die "stat $new failed: $!";
+        my @st = stat($tmp) or die "stat $tmp failed: $!";
+        if ($st[0] == $sn[0] && $st[1] == $sn[1]) {
+                unlink($tmp) or warn "Failed to unlink $tmp: $!";
+        } else {
+                warn "stat($new) and stat($tmp) differ";
+        }
+}
+
+sub DESTROY { commit($_[0]) }
+
+1;
diff --git a/t/emergency.t b/t/emergency.t
new file mode 100644
index 00000000..e480338d
--- /dev/null
+++ b/t/emergency.t
@@ -0,0 +1,53 @@
+# Copyright (C) 2016 all contributors <meta@public-inbox.org>
+# License: AGPL-3.0+ <https://www.gnu.org/licenses/agpl-3.0.txt>
+use strict;
+use warnings;
+use Test::More;
+use File::Temp qw/tempdir/;
+my $tmpdir = tempdir('emergency-XXXXXX', TMPDIR => 1, CLEANUP => 1);
+use_ok 'PublicInbox::Emergency';
+
+{
+        my $md = "$tmpdir/a";
+        my $em = PublicInbox::Emergency->new($md);
+        ok(-d $md, 'Maildir a auto-created');
+        my @tmp = <$md/tmp/*>;
+        is(scalar @tmp, 0, 'no temporary files exist, yet');
+        $em->prepare(\"BLAH");
+        @tmp = <$md/tmp/*>;
+        is(scalar @tmp, 1, 'globbed one temporary file');
+        open my $fh, '<', $tmp[0] or die "failed to open: $!";
+        is("BLAH", <$fh>, 'wrote contents to temporary location');
+        my @new = <$md/new/*>;
+        is(scalar @new, 0, 'no new files exist, yet');
+        $em = undef;
+        @tmp = <$md/tmp/*>;
+        is(scalar @tmp, 0, 'temporary file no longer exists');
+        @new = <$md/new/*>;
+        is(scalar @new, 1, 'globbed one new file');
+        open $fh, '<', $new[0] or die "failed to open: $!";
+        is("BLAH", <$fh>, 'wrote contents to new location');
+}
+{
+        my $md = "$tmpdir/b";
+        my $em = PublicInbox::Emergency->new($md);
+        ok(-d $md, 'Maildir b auto-created');
+        my @tmp = <$md/tmp/*>;
+        is(scalar @tmp, 0, 'no temporary files exist, yet');
+        $em->prepare(\"BLAH");
+        @tmp = <$md/tmp/*>;
+        is(scalar @tmp, 1, 'globbed one temporary file');
+        open my $fh, '<', $tmp[0] or die "failed to open: $!";
+        is("BLAH", <$fh>, 'wrote contents to temporary location');
+        my @new = <$md/new/*>;
+        is(scalar @new, 0, 'no new files exist, yet');
+        is(sysread($em->fh, my $buf, 9), 4, 'read file handle exposed');
+        is($buf, 'BLAH', 'got expected data');
+        $em->abort;
+        @tmp = <$md/tmp/*>;
+        is(scalar @tmp, 0, 'temporary file no longer exists');
+        @new = <$md/new/*>;
+        is(scalar @new , 0, 'new file no longer exists');
+}
+
+done_testing();