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From: Eric Wong <e@80x24.org>
To: meta@public-inbox.org
Subject: [PATCH 2/2] lei: fix output race in client/daemon mode
Date: Sun,  3 Jan 2021 11:24:51 +0000	[thread overview]
Message-ID: <20210103112451.75313-3-e@80x24.org> (raw)
In-Reply-To: <20210103112451.75313-1-e@80x24.org>

The daemon needs to flush stdout before disconnecting or killing
clients, otherwise they may reread empty data on redirected
outputs.  We also don't want to unbuffer stdout too early in
case we have lots of small chunks of data to output.

The received ($self->{2}) will always have autoflush, matching normal
STDERR behavior.
---
 lib/PublicInbox/LEI.pm | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/lib/PublicInbox/LEI.pm b/lib/PublicInbox/LEI.pm
index 3ad5e01a..6f21da35 100644
--- a/lib/PublicInbox/LEI.pm
+++ b/lib/PublicInbox/LEI.pm
@@ -236,6 +236,7 @@ my %CONFIG_KEYS = (
 
 sub x_it ($$) { # pronounced "exit"
 	my ($self, $code) = @_;
+	$self->{1}->autoflush(1); # make sure client sees stdout before exit
 	if (my $sig = ($code & 127)) {
 		kill($sig, $self->{pid} // $$);
 	} else {
@@ -635,6 +636,7 @@ sub accept_dispatch { # Listener {post_accept} callback
 		say $sock "timed out waiting to recv FDs";
 		return;
 	}
+	$self->{2}->autoflush(1); # keep stdout buffered until x_it|DESTROY
 	# $ARGV_STR = join("]\0[", @ARGV);
 	# $ENV_STR = join('', map { "$_=$ENV{$_}\0" } keys %ENV);
 	# $line = "$$\0\0>$ARGV_STR\0\0>$ENV_STR\0\0";
@@ -773,4 +775,8 @@ sub oneshot {
 	}, __PACKAGE__), @ARGV);
 }
 
+# ensures stdout hits the FS before sock disconnects so a client
+# can immediately reread it
+sub DESTROY { $_[0]->{1}->autoflush(1) }
+
 1;

      parent reply	other threads:[~2021-01-03 11:24 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-01-03  9:48 [PATCH 0/3] lei-related test fixes Eric Wong
2021-01-03  9:48 ` [PATCH 1/3] t/lei: use $lei->() callback wrapper Eric Wong
2021-01-03  9:48 ` [PATCH 2/3] testcommon: prepare_redirects: fix error message Eric Wong
2021-01-03  9:48 ` [PATCH 3/3] spawn: support send_fd+recv_fd w/o IO::FDPass Eric Wong
2021-01-03 11:24 ` [PATCH 0/2] fix race from stdout buffering in FD pass exit Eric Wong
2021-01-03 11:24   ` [PATCH 1/2] send and receive all 3 FDs at once Eric Wong
2021-01-03 11:24   ` Eric Wong [this message]

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