From 5a27f82749d723625848c8d1cf216a0f4de73597 Mon Sep 17 00:00:00 2001
From: Eric Wong <e@80x24.org>
Date: Tue, 24 Aug 2021 13:06:39 +0000
Subject: lei: non-blocking lei/store->done in lei-daemon

This allows client sockets to wait for "done" commits to
lei/store while the daemon reacts asynchronously.  The goal
of this change is to keep the script/lei client alive until
lei/store commits changes to the filesystem, but without
blocking the lei-daemon event loop.  It depends on Perl
refcounting to close the socket.

This change also highlighted our over-use of "done" requests to
lei/store processes, which is now corrected so we only issue it
on collective socket EOF rather than upon reaping every single
worker.

This also fixes "lei forget-mail-sync" when it is the initial
command.

This took several iterations and much debugging to arrive at the
current implementation:

1. The initial iteration of this change utilized socket passing
   from lei-daemon to lei/store, which necessitated switching
   from faster pipes to slower Unix sockets.

2. The second iteration switched to registering notification sockets
   independently of "done" requests, but that could lead to early
   wakeups when "done" was requested by other workers.  This
   appeared to work most of the time, but suffered races under
   high load which were difficult to track down.

Finally, this iteration passes the stringified socket GLOB ref
to lei/store which is echoed back to lei-daemon upon completion
of that particular "done" request.
---
 lib/PublicInbox/LeiNoteEvent.pm | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

(limited to 'lib/PublicInbox/LeiNoteEvent.pm')

diff --git a/lib/PublicInbox/LeiNoteEvent.pm b/lib/PublicInbox/LeiNoteEvent.pm
index 1cd15296..6a40ba39 100644
--- a/lib/PublicInbox/LeiNoteEvent.pm
+++ b/lib/PublicInbox/LeiNoteEvent.pm
@@ -15,7 +15,7 @@ sub flush_lei ($) {
 	if (my $lne = delete $lei->{cfg}->{-lei_note_event}) {
 		$lne->wq_close(1, undef, $lei); # runs _lei_wq_eof;
 	} elsif ($lei->{sto}) { # lms_clear_src calls only:
-		my $wait = $lei->{sto}->ipc_do('done');
+		$lei->sto_done_request;
 	}
 }
 
@@ -117,7 +117,7 @@ sub lne_done_wait {
 sub _lei_wq_eof { # EOF callback for main lei daemon
 	my ($lei) = @_;
 	my $lne = delete $lei->{lne} or return $lei->fail;
-	my $wait = $lei->{sto}->ipc_do('done');
+	$lei->sto_done_request;
 	$lne->wq_wait_old(\&lne_done_wait, $lei);
 }
 
-- 
cgit v1.2.3-24-ge0c7