[PATCH 35/57] ds: deal better with FS-related errors IO buffers

[Eric Wong <e@80x24.org>]

Instead of ENOMEM (or fragmentation/swap storms), using tempfile
buffers opens us up to filesystem and storage-related errors
(e.g. ENOSPC, EFBIG, EIO, EROFS).  Log these errors, drop the
particular client, and try to limp by with whateve we have left.
---
 lib/PublicInbox/DS.pm | 42 +++++++++++++++++++++++++-----------------
 1 file changed, 25 insertions(+), 17 deletions(-)

diff --git a/lib/PublicInbox/DS.pm b/lib/PublicInbox/DS.pm
index 486af40e..1a1ef7d3 100644
--- a/lib/PublicInbox/DS.pm
+++ b/lib/PublicInbox/DS.pm
@@ -33,7 +33,7 @@ use fields ('sock',              # underlying socket
             );
 
 use Errno  qw(EAGAIN EINVAL);
-use Carp   qw(croak confess);
+use Carp   qw(croak confess carp);
 use File::Temp qw(tempfile);
 
 our $HAVE_KQUEUE = eval { require IO::KQueue; IO::KQueue->import; 1 };
@@ -482,18 +482,27 @@ sub do_read ($$$$) {
     $! == EAGAIN ? $self->watch_in1 : $self->close;
 }
 
+# drop the socket if we hit unrecoverable errors on our system which
+# require BOFH attention: ENOSPC, EFBIG, EIO, EMFILE, ENFILE...
+sub drop {
+    my $self = shift;
+    carp(@_);
+    $self->close;
+}
+
 # n.b.: use ->write/->read for this buffer to allow compatibility with
 # PerlIO::mmap or PerlIO::scalar if needed
-sub tmpbuf ($$) {
-    my ($bref, $off) = @_;
+sub tmpio ($$$) {
+    my ($self, $bref, $off) = @_;
     # open(my $fh, '+>>', undef) doesn't set O_APPEND
-    my ($fh, $path) = tempfile('wbuf-XXXXXXX', TMPDIR => 1);
-    open $fh, '+>>', $path or die "open: $!";
+    my ($fh, $path) = eval { tempfile('wbuf-XXXXXXX', TMPDIR => 1) };
+    $fh or return drop($self, "tempfile: $@");
+    open($fh, '+>>', $path) or return drop($self, "open: $!");
     $fh->autoflush(1);
-    unlink $path;
-    my $to_write = bytes::length($$bref) - $off;
-    $fh->write($$bref, $to_write, $off) or die "write ($to_write): $!";
-    $fh;
+    unlink($path) or return drop($self, "unlink: $!");
+    my $len = bytes::length($$bref) - $off;
+    $fh->write($$bref, $len, $off) or return drop($self, "write ($len): $!");
+    $fh
 }
 
 =head2 C<< $obj->write( $data ) >>
@@ -523,12 +532,10 @@ sub write {
         } else {
             my $last = $wbuf->[-1];
             if (ref($last) eq 'GLOB') { # append to tmp file buffer
-                unless ($last->print($$bref)) {
-                    warn "error buffering: $!";
-                    return $self->close;
-                }
+                $last->print($$bref) or return drop($self, "print: $!");
             } else {
-                push @$wbuf, tmpbuf($bref, 0);
+                my $tmpio = tmpio($self, $bref, 0) or return 0;
+                push @$wbuf, $tmpio;
             }
         }
         return 0;
@@ -546,7 +553,8 @@ sub write {
         } else {
             return $self->close;
         }
-        $self->{wbuf} = [ tmpbuf($bref, $written) ];
+        my $tmpio = tmpio($self, $bref, $written) or return 0;
+        $self->{wbuf} = [ $tmpio ];
         watch($self, EPOLLOUT|EPOLLONESHOT);
         return 0;
     }
@@ -563,9 +571,9 @@ sub msg_more ($$) {
         if (defined $n) {
             my $nlen = bytes::length($_[1]) - $n;
             return 1 if $nlen == 0; # all done!
-
             # queue up the unwritten substring:
-            $self->{wbuf} = [ tmpbuf(\($_[1]), $n) ];
+            my $tmpio = tmpio($self, \($_[1]), $n) or return 0;
+            $self->{wbuf} = [ $tmpio ];
             watch($self, EPOLLOUT|EPOLLONESHOT);
             return 0;
         }
-- 
EW