[PATCH 1/9] lei q: limit concurrency to 4 remote connections

[Eric Wong <e@80x24.org>]

Unfortunately, this isn't a per-host limit, yet; but
nevertheless reduces load on existing PublicInbox::WWW
instances, since requesting a mboxrd is one of the more
expensive operations.
---
 lib/PublicInbox/LeiQuery.pm   |  2 +-
 lib/PublicInbox/LeiXSearch.pm | 82 +++++++++++++++++++++--------------
 2 files changed, 51 insertions(+), 33 deletions(-)

diff --git a/lib/PublicInbox/LeiQuery.pm b/lib/PublicInbox/LeiQuery.pm
index acab3c2c..a7938e8b 100644
--- a/lib/PublicInbox/LeiQuery.pm
+++ b/lib/PublicInbox/LeiQuery.pm
@@ -26,7 +26,7 @@ sub lei_q {
 		my $cb = $lxs->can('prepare_external');
 		$self->_externals_each($cb, $lxs);
 	}
-	my $xj = $opt->{thread} ? $lxs->locals : ($lxs->remotes + 1);
+	my $xj = $lxs->concurrency($opt);
 	my $ovv = PublicInbox::LeiOverview->new($self) or return;
 	$self->atfork_prepare_wq($lxs);
 	$lxs->wq_workers_start('lei_xsearch', $xj, $self->oldset);
diff --git a/lib/PublicInbox/LeiXSearch.pm b/lib/PublicInbox/LeiXSearch.pm
index defe5e67..1c093a94 100644
--- a/lib/PublicInbox/LeiXSearch.pm
+++ b/lib/PublicInbox/LeiXSearch.pm
@@ -182,25 +182,16 @@ sub each_eml { # callback for MboxReader->mboxrd
 }
 
 sub query_remote_mboxrd {
-	my ($self, $lei, $uri) = @_;
+	my ($self, $lei, $uris) = @_;
 	local $0 = "$0 query_remote_mboxrd";
 	my %sig = $lei->atfork_child_wq($self); # keep $self->{5} startq
 	local @SIG{keys %sig} = values %sig;
-	my $opt = $lei->{opt};
-	$uri->query_form(q => $lei->{mset_opt}->{qstr}, x => 'm',
-			$opt->{thread} ? (t => 1) : ());
-	my $each_smsg = $lei->{ovv}->ovv_each_smsg_cb($lei, $uri);
+	my ($opt, $env) = @$lei{qw(opt env)};
+	my @qform = (q => $lei->{mset_opt}->{qstr}, x => 'm');
+	push(@qform, t => 1) if $opt->{thread};
 	my $dedupe = $lei->{dedupe} // die 'BUG: {dedupe} missing';
 	$dedupe->prepare_dedupe;
 	my @cmd = qw(curl -XPOST -sSf);
-	$opt->{torsocks} = 'false' if $opt->{'no-torsocks'};
-	my $tor = $opt->{torsocks} //= 'auto';
-	if ($tor eq 'auto' && substr($uri->host, -6) eq '.onion' &&
-			(($lei->{env}->{LD_PRELOAD}//'') !~ /torsocks/)) {
-		unshift @cmd, 'torsocks';
-	} elsif (PublicInbox::Config::git_bool($tor)) {
-		unshift @cmd, 'torsocks';
-	}
 	my $verbose = $opt->{verbose};
 	push @cmd, '-v' if $verbose;
 	for my $o ($lei->curl_opt) {
@@ -215,25 +206,36 @@ sub query_remote_mboxrd {
 			push @cmd, "--$o";
 		}
 	}
-	push @cmd, $uri->as_string;
-	$lei->err("# @cmd") if $verbose;
-	$? = 0;
-	my $fh = popen_rd(\@cmd, $lei->{env}, { 2 => $lei->{2} });
-	$fh = IO::Uncompress::Gunzip->new($fh);
-	eval {
-		PublicInbox::MboxReader->mboxrd($fh, \&each_eml,
-						$self, $lei, $each_smsg);
-	};
-	return $lei->fail("E: @cmd: $@") if $@;
-	if (($? >> 8) == 22) { # HTTP 404 from curl(1)
-		$uri->query_form(q => $lei->{mset_opt}->{qstr});
-		$lei->err('# no results from '.$uri->as_string);
-	} elsif ($?) {
-		$uri->query_form(q => $lei->{mset_opt}->{qstr});
-		$lei->err('E: '.$uri->as_string);
-		$lei->child_error($?);
+	$opt->{torsocks} = 'false' if $opt->{'no-torsocks'};
+	my $tor = $opt->{torsocks} //= 'auto';
+	for my $uri (@$uris) {
+		$uri->query_form(@qform);
+		my $each_smsg = $lei->{ovv}->ovv_each_smsg_cb($lei, $uri);
+		my $cmd = [ @cmd, $uri->as_string ];
+		if ($tor eq 'auto' && substr($uri->host, -6) eq '.onion' &&
+				(($env->{LD_PRELOAD}//'') !~ /torsocks/)) {
+			unshift @$cmd, 'torsocks';
+		} elsif (PublicInbox::Config::git_bool($tor)) {
+			unshift @$cmd, 'torsocks';
+		}
+		$lei->err("# @$cmd") if $verbose;
+		$? = 0;
+		my $fh = popen_rd($cmd, $env, { 2 => $lei->{2} });
+		$fh = IO::Uncompress::Gunzip->new($fh);
+		eval {
+			PublicInbox::MboxReader->mboxrd($fh, \&each_eml, $self,
+							$lei, $each_smsg);
+		};
+		return $lei->fail("E: @$cmd: $@") if $@;
+		if (($? >> 8) == 22) { # HTTP 404 from curl(1)
+			$uri->query_form(q => $lei->{mset_opt}->{qstr});
+			$lei->err('# no results from '.$uri->as_string);
+		} elsif ($?) {
+			$uri->query_form(q => $lei->{mset_opt}->{qstr});
+			$lei->err('E: '.$uri->as_string);
+			$lei->child_error($?);
+		}
 	}
-	undef $each_smsg;
 	$lei->{ovv}->ovv_atexit_child($lei);
 }
 
@@ -292,6 +294,17 @@ sub do_post_augment {
 	close $au_done; # triggers wait_startq
 }
 
+my $MAX_PER_HOST = 4;
+sub MAX_PER_HOST { $MAX_PER_HOST }
+
+sub concurrency {
+	my ($self, $opt) = @_;
+	my $nl = $opt->{thread} ? locals($self) : 1;
+	my $nr = remotes($self);
+	$nr = $MAX_PER_HOST if $nr > $MAX_PER_HOST;
+	$nl + $nr;
+}
+
 sub start_query { # always runs in main (lei-daemon) process
 	my ($self, $io, $lei) = @_;
 	if ($lei->{opt}->{thread}) {
@@ -301,8 +314,13 @@ sub start_query { # always runs in main (lei-daemon) process
 	} else {
 		$self->wq_do('query_mset', $io, $lei);
 	}
+	my $i = 0;
+	my $q = [];
 	for my $uri (remotes($self)) {
-		$self->wq_do('query_remote_mboxrd', $io, $lei, $uri);
+		push @{$q->[$i++ % $MAX_PER_HOST]}, $uri;
+	}
+	for my $uris (@$q) {
+		$self->wq_do('query_remote_mboxrd', $io, $lei, $uris);
 	}
 	@$io = ();
 }