http: avoid corking on "Content-Length: 0" response

We must use a normal write instead of send(.., MSG_MORE)
when writing responses of "Content-Length: 0" to avoid
the corking effect MSG_MORE provides.  We only want to
cork headers if we will send a non-empty body.

Fixes: c3eeaf664cf0 ("http: clarify intent for persistence")
This needs a proper test.

diff --git a/lib/PublicInbox/HTTP.pm b/lib/PublicInbox/HTTP.pm
index 393451221112478d832c82142d37e7c3faf57757..c7fb954ebd6c0f0b472dce57bf1a07601a01866c 100644 (file)
--- a/lib/PublicInbox/HTTP.pm
+++ b/lib/PublicInbox/HTTP.pm
@@ -151,7 +151,7 @@ sub response_header_write {
        my $proto = $env->{SERVER_PROTOCOL} or return; # HTTP/0.9 :P
        my $status = $res->[0];
        my $h = "$proto $status " . status_message($status) . "\r\n";
-       my $term;
+       my ($len, $chunked);
        my $headers = $res->[1];
 
        for (my $i = 0; $i < @$headers; $i += 2) {
@@ -159,14 +159,15 @@ sub response_header_write {
                my $v = $headers->[$i + 1];
                next if $k =~ /\A(?:Connection|Date)\z/i;
 
-               if ($k =~ /\AContent-Length\z/ ||
-                   ($k =~ /\ATransfer-Encoding\z/i && $v =~ /\bchunked\b/i)) {
-                       $term = 1;
+               $len = $v if $k =~ /\AContent-Length\z/i;
+               if ($k =~ /\ATransfer-Encoding\z/i && $v =~ /\bchunked\b/i) {
+                       $chunked = 1;
                }
                $h .= "$k: $v\r\n";
        }
 
        my $conn = $env->{HTTP_CONNECTION} || '';
+       my $term = defined($len) || $chunked;
        my $alive = $term &&
                        (($proto eq 'HTTP/1.1' && $conn !~ /\bclose\b/i) ||
                         ($conn =~ /\bkeep-alive\b/i));
@@ -174,7 +175,7 @@ sub response_header_write {
        $h .= 'Connection: ' . ($alive ? 'keep-alive' : 'close');
        $h .= "\r\nDate: " . http_date() . "\r\n\r\n";
 
-       if ($term && $env->{REQUEST_METHOD} ne 'HEAD') {
+       if (($len || $chunked) && $env->{REQUEST_METHOD} ne 'HEAD') {
                more($self, $h);
        } else {
                $self->write($h);

diff --git a/t/httpd-corner.psgi b/t/httpd-corner.psgi
index da8a2ee8b646ef7b9937c9d72ab9616e924f4fd3..2f7be8320eaf518cb2772e7a53519df6f245f7c2 100644 (file)
--- a/t/httpd-corner.psgi
+++ b/t/httpd-corner.psgi
@@ -56,6 +56,8 @@ my $app = sub {
                        $fh->write($buf);
                        $fh->close;
                }
+       } elsif ($path eq '/empty') {
+               $code = 200;
        }
 
        [ $code, $h, $body ]

diff --git a/t/httpd-corner.t b/t/httpd-corner.t
index b64f334ab94627acadc140b87c1ebc940978f1fb..b9eaa6fbec46bd3ea377ad8b5ac0b810a74fa437 100644 (file)
--- a/t/httpd-corner.t
+++ b/t/httpd-corner.t
@@ -5,6 +5,7 @@
 use strict;
 use warnings;
 use Test::More;
+use Time::HiRes qw(gettimeofday tv_interval);
 
 foreach my $mod (qw(Plack::Util Plack::Request Plack::Builder Danga::Socket
                        HTTP::Date HTTP::Status)) {
@@ -274,6 +275,18 @@ SKIP: {
        }
 }
 
+{
+       my $conn = conn_for($sock, 'no TCP_CORK on empty body');
+       $conn->write("GET /empty HTTP/1.1\r\nHost:example.com\r\n\r\n");
+       my $buf = '';
+       my $t0 = [ gettimeofday ];
+       until ($buf =~ /\r\n\r\n/s) {
+               $conn->sysread($buf, 4096, length($buf));
+       }
+       my $elapsed = tv_interval($t0, [ gettimeofday ]);
+       ok($elapsed < 0.190, 'no 200ms TCP cork delay on empty body');
+}
+
 {
        my $conn = conn_for($sock, 'graceful termination during slow request');
        $conn->write("PUT /sha1 HTTP/1.0\r\n");