imap: IDLE: avoid extraneous wakeups, keep-alive

We should not waste memory for IDLE unless it's used on the most
recent inbox slice.  We also need to keep the IDLE connection
alive regardless of $PublicInbox::DS::EXPTIME.

1 files changed, 47 insertions, 9 deletions

diff --git a/lib/PublicInbox/IMAP.pm b/lib/PublicInbox/IMAP.pm
index 0d553da9..77e8af12 100644
--- a/lib/PublicInbox/IMAP.pm
+++ b/lib/PublicInbox/IMAP.pm
@@ -151,7 +151,7 @@ sub cmd_close ($$) {
 
 sub cmd_logout ($$) {
         my ($self, $tag) = @_;
-        delete $self->{logged_in};
+        delete @$self{qw(logged_in -idle_tag)};
         $self->write(\"* BYE logging out\r\n$tag OK Logout done\r\n");
         $self->shutdn; # PublicInbox::DS::shutdn
         undef;
@@ -174,23 +174,63 @@ sub cmd_noop ($$) { "$_[1] OK Noop done\r\n" }
 sub on_inbox_unlock {
         my ($self, $ibx) = @_;
         my $new = $ibx->mm->max;
+        my $uid_end = ($self->{uid_min} // 1) - 1 + UID_BLOCK;
         defined(my $old = $self->{-idle_max}) or die 'BUG: -idle_max unset';
+        $new = $uid_end if $new > $uid_end;
         if ($new > $old) {
                 $self->{-idle_max} = $new;
                 $self->msg_more("* $_ EXISTS\r\n") for (($old + 1)..($new - 1));
                 $self->write(\"* $new EXISTS\r\n");
+        } elsif ($new == $uid_end) { # max exceeded $uid_end
+                # continue idling w/o inotify
+                delete $self->{-idle_max};
+                my $sock = $self->{sock} or return;
+                $ibx->unsubscribe_unlock(fileno($sock));
         }
 }
 
+# called every X minute(s) or so by PublicInbox::DS::later
+my $IDLERS = {};
+my $idle_timer;
+sub idle_tick_all {
+        my $old = $IDLERS;
+        $IDLERS = {};
+        for my $i (values %$old) {
+                next if ($i->{wbuf} || !exists($i->{-idle_tag}));
+                $i->update_idle_time or next;
+                $IDLERS->{fileno($i->{sock})} = $i;
+                $i->write(\"* OK Still here\r\n");
+        }
+        $idle_timer = scalar keys %$IDLERS ?
+                        PublicInbox::DS::later(\&idle_tick_all) : undef;
+}
+
 sub cmd_idle ($$) {
         my ($self, $tag) = @_;
         # IDLE seems allowed by dovecot w/o a mailbox selected *shrug*
         my $ibx = $self->{ibx} or return "$tag BAD no mailbox selected\r\n";
-        $ibx->subscribe_unlock(fileno($self->{sock}), $self);
-        $self->{imapd}->idler_start;
         $self->{-idle_tag} = $tag;
-        $self->{-idle_max} = $ibx->mm->max // 0;
-        "+ idling\r\n"
+        my $max = $ibx->mm->max // 0;
+        my $uid_end = ($self->{uid_min} // 1) - 1 + UID_BLOCK;
+        my $sock = $self->{sock} or return;
+        my $fd = fileno($sock);
+        # only do inotify on most recent slice
+        if ($max < $uid_end) {
+                $ibx->subscribe_unlock($fd, $self);
+                $self->{imapd}->idler_start;
+                $self->{-idle_max} = $max;
+        }
+        $idle_timer //= PublicInbox::DS::later(\&idle_tick_all);
+        $IDLERS->{$fd} = $self;
+        \"+ idling\r\n"
+}
+
+sub stop_idle ($$) {
+        my ($self, $ibx);
+        my $sock = $self->{sock} or return;
+        my $fd = fileno($sock);
+        delete $IDLERS->{$fd};
+        $ibx->unsubscribe_unlock($fd);
 }
 
 sub cmd_done ($$) {
@@ -201,7 +241,7 @@ sub cmd_done ($$) {
                 warn "BUG: idle_tag set w/o inbox";
                 return "$tag BAD internal bug\r\n";
         };
-        $ibx->unsubscribe_unlock(fileno($self->{sock}));
+        stop_idle($self, $ibx);
         "$idle_tag OK Idle done\r\n";
 }
 
@@ -1185,9 +1225,7 @@ sub busy {
 sub close {
         my ($self) = @_;
         if (my $ibx = delete $self->{ibx}) {
-                if (my $sock = $self->{sock}) {;
-                        $ibx->unsubscribe_unlock(fileno($sock));
-                }
+                stop_idle($self, $ibx);
         }
         $self->SUPER::close; # PublicInbox::DS::close
 }