1 files changed, 35 insertions, 13 deletions

diff --git a/lib/PublicInbox/LeiStoreErr.pm b/lib/PublicInbox/LeiStoreErr.pm
index cc085fdc..c8bc72b6 100644
--- a/lib/PublicInbox/LeiStoreErr.pm
+++ b/lib/PublicInbox/LeiStoreErr.pm
@@ -1,38 +1,60 @@
-# Copyright (C) 2021 all contributors <meta@public-inbox.org>
+# Copyright (C) all contributors <meta@public-inbox.org>
 # License: AGPL-3.0+ <https://www.gnu.org/licenses/agpl-3.0.txt>
 
 # forwards stderr from lei/store process to any lei clients using
 # the same store, falls back to syslog if no matching clients exist.
 package PublicInbox::LeiStoreErr;
-use strict;
-use v5.10.1;
+use v5.12;
 use parent qw(PublicInbox::DS);
-use PublicInbox::Syscall qw(EPOLLIN EPOLLONESHOT);
+use PublicInbox::Syscall qw(EPOLLIN);
 use Sys::Syslog qw(openlog syslog closelog);
 use IO::Handle (); # ->blocking
+use Time::HiRes ();
+use autodie qw(open);
+our $err_wr;
+
+# We don't want blocked stderr on clients to block lei/store or lei-daemon.
+# We can't make stderr non-blocking since it can break MUAs or anything
+# lei might spawn.  So we setup a timer to wake us up after a second if
+# printing to a user's stderr hasn't completed, yet.  Unfortunately,
+# EINTR alone isn't enough since Perl auto-restarts writes on signals,
+# so to interrupt writes to clients with blocked stderr, we dup the
+# error output to $err_wr ahead-of-time and close $err_wr in the
+# SIGALRM handler to ensure `print' gets aborted:
+
+sub abort_err_wr { close($err_wr) if $err_wr; undef $err_wr }
+
+sub emit ($@) {
+        my ($efh, @msg) = @_;
+        open(local $err_wr, '>&', $efh); # fdopen(dup(fileno($efh)), "w")
+        local $SIG{ALRM} = \&abort_err_wr;
+        Time::HiRes::alarm(1.0, 0.1);
+        my $ret = print $err_wr @msg;
+        Time::HiRes::alarm(0);
+        $ret;
+}
 
 sub new {
         my ($cls, $rd, $lei) = @_;
         my $self = bless { sock => $rd, store_path => $lei->store_path }, $cls;
         $rd->blocking(0);
-        $self->SUPER::new($rd, EPOLLIN | EPOLLONESHOT);
+        $self->SUPER::new($rd, EPOLLIN); # level-trigger
 }
 
 sub event_step {
         my ($self) = @_;
-        my $rbuf = $self->{rbuf} // \(my $x = '');
-        $self->do_read($rbuf, 8192, length($$rbuf)) or return;
-        my $cb;
+        my $n = sysread($self->{sock}, my $buf, 8192);
+        return ($!{EAGAIN} ? 0 : $self->close) if !defined($n);
+        return $self->close if !$n;
         my $printed;
-        for my $lei (values %PublicInbox::DS::DescriptorMap) {
-                $cb = $lei->can('store_path') // next;
+        for my $lei (grep defined, @PublicInbox::DS::FD_MAP) {
+                my $cb = $lei->can('store_path') // next;
                 next if $cb->($lei) ne $self->{store_path};
-                my $err = $lei->{2} // next;
-                print $err $$rbuf and $printed = 1;
+                emit($lei->{2} // next, $buf) and $printed = 1;
         }
         if (!$printed) {
                 openlog('lei/store', 'pid,nowait,nofatal,ndelay', 'user');
-                for my $l (split(/\n/, $$rbuf)) { syslog('warning', '%s', $l) }
+                for my $l (split(/\n/, $buf)) { syslog('warning', '%s', $l) }
                 closelog(); # don't share across fork
         }
 }