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From: Eric Wong <e@80x24.org>
To: meta@public-inbox.org
Subject: [PATCH 16/22] ipc: fix IO::FDPass use with a worker limit of 1
Date: Sun, 10 Jan 2021 12:15:13 +0000	[thread overview]
Message-ID: <20210110121519.17044-17-e@80x24.org> (raw)
In-Reply-To: <20210110121519.17044-1-e@80x24.org>

IO::FDPass is our last choice for implementing the workqueue
because its lack of atomicity makes it impossible to guarantee
all requests of a single group hit a single worker out of many.

So the only way to use IO::FDPass for workqueues it to only have
a single worker.  A single worker still buys us a small amount
of parallelism because of the parent process.
---
 lib/PublicInbox/IPC.pm | 34 +++++++++++++++++++++++++++++++---
 t/ipc.t                | 18 +++++++++++-------
 2 files changed, 42 insertions(+), 10 deletions(-)

diff --git a/lib/PublicInbox/IPC.pm b/lib/PublicInbox/IPC.pm
index b0a0bfb5..e6a1082c 100644
--- a/lib/PublicInbox/IPC.pm
+++ b/lib/PublicInbox/IPC.pm
@@ -12,6 +12,7 @@ use POSIX qw(WNOHANG);
 use Socket qw(AF_UNIX MSG_EOR);
 my $SEQPACKET = eval { Socket::SOCK_SEQPACKET() }; # portable enough?
 use constant PIPE_BUF => $^O eq 'linux' ? 4096 : POSIX::_POSIX_PIPE_BUF();
+my $WQ_MAX_WORKERS = 4096;
 my ($enc, $dec);
 # ->imports at BEGIN turns sereal_*_with_object into custom ops on 5.14+
 # and eliminate method call overhead
@@ -36,17 +37,39 @@ if ($enc && $dec) { # should be custom ops
 	} // warn("Storable (part of Perl) missing: $@\n");
 }
 
+my $recv_cmd1; # PublicInbox::CmdIPC1::recv_cmd1;
 my $recv_cmd = PublicInbox::Spawn->can('recv_cmd4');
 my $send_cmd = PublicInbox::Spawn->can('send_cmd4') // do {
 	require PublicInbox::CmdIPC4;
 	$recv_cmd //= PublicInbox::CmdIPC4->can('recv_cmd4');
 	PublicInbox::CmdIPC4->can('send_cmd4');
 } // do {
+	# IO::FDPass only allows sending a single FD at-a-time, which
+	# means we can't guarantee all packets end up on the same worker,
+	# so we cap WQ_MAX_WORKERS
 	require PublicInbox::CmdIPC1;
-	$recv_cmd = PublicInbox::CmdIPC1->can('recv_cmd1');
+	$recv_cmd1 = PublicInbox::CmdIPC1->can('recv_cmd1');
+	$WQ_MAX_WORKERS = 1 if $recv_cmd1;
+	wq_set_recv_fds(3);
 	PublicInbox::CmdIPC1->can('send_cmd1');
 };
 
+# needed to tell recv_cmd1 how many times to loop IO::FDPass::recv
+sub wq_set_recv_fds {
+	return unless $recv_cmd1;
+	my $nfds = pop;
+	my $sub = sub {
+		my ($sock, $fds, undef, $flags) = @_;
+		$recv_cmd1->($sock, $fds, $_[2], $flags, $nfds);
+	};
+	my $self = pop;
+	if (ref $self) {
+		$self->{-wq_recv_cmd} = $sub;
+	} else {
+		$recv_cmd = $sub;
+	}
+}
+
 sub _get_rec ($) {
 	my ($r) = @_;
 	defined(my $len = <$r>) or return;
@@ -237,8 +260,9 @@ sub wq_worker_loop ($) {
 	local $SIG{PIPE} = sub {
 		die(bless(\"$_[0]", __PACKAGE__.'::PIPE')) if $sub;
 	};
+	my $rcv = $self->{-wq_recv_cmd} // $recv_cmd;
 	until ($self->{-wq_quit}) {
-		my (@fds) = $recv_cmd->($s2, $buf, $len) or return; # EOF
+		my (@fds) = $rcv->($s2, $buf, $len) or return; # EOF
 		my $i = 0;
 		my @m = @{$self->{wq_open_modes} // [qw( +<&= >&= >&= )]};
 		for my $fd (@fds) {
@@ -305,6 +329,7 @@ sub wq_workers_start {
 	socketpair($s1, $s2, AF_UNIX, $SEQPACKET, 0) or die "socketpair: $!";
 	$self->ipc_atfork_parent;
 	$nr_workers //= 4;
+	$nr_workers = $WQ_MAX_WORKERS if $nr_workers > $WQ_MAX_WORKERS;
 	my $sigset = $oldset // PublicInbox::DS::block_signals();
 	$self->{-wq_workers} = {};
 	$self->{-wq_ident} = $ident;
@@ -318,6 +343,7 @@ sub wq_workers_start {
 sub wq_worker_incr { # SIGTTIN handler
 	my ($self, $oldset) = @_;
 	$self->{-wq_s2} or return;
+	return if wq_workers($self) >= $WQ_MAX_WORKERS;
 	$self->ipc_atfork_parent;
 	my $sigset = $oldset // PublicInbox::DS::block_signals();
 	_wq_worker_start($self, $sigset);
@@ -331,7 +357,7 @@ sub wq_exit { # wakes up wq_worker_decr_wait
 
 sub wq_worker_decr { # SIGTTOU handler, kills first idle worker
 	my ($self) = @_;
-	my $workers = $self->{-wq_workers} or return;
+	return unless wq_workers($self);
 	my $s2 = $self->{-wq_s2} // die 'BUG: no wq_s2';
 	$self->wq_do('wq_exit', [ $s2, $s2, $s2 ]);
 	$self->{-wq_exit_pending}++;
@@ -377,6 +403,8 @@ sub wq_close {
 	}
 }
 
+sub WQ_MAX_WORKERS { $WQ_MAX_WORKERS }
+
 sub DESTROY {
 	wq_close($_[0]);
 	ipc_worker_stop($_[0]);
diff --git a/t/ipc.t b/t/ipc.t
index d2b6ad4f..fd290809 100644
--- a/t/ipc.t
+++ b/t/ipc.t
@@ -171,13 +171,17 @@ is($warn[2], $warn[1], 'worker did not die');
 $SIG{__WARN__} = 'DEFAULT';
 is($ipc->wq_workers_start('wq', 1), $$, 'workers started again');
 is($ipc->wq_workers, 1, '1 worker started');
-$ipc->wq_worker_incr;
-is($ipc->wq_workers, 2, 'worker count bumped');
-$ipc->wq_worker_decr;
-$ipc->wq_worker_decr_wait(10);
-is($ipc->wq_workers, 1, 'worker count lowered');
-is($ipc->wq_workers(2), 2, 'worker count set');
-is($ipc->wq_workers, 2, 'worker count stayed set');
+SKIP: {
+	$ipc->WQ_MAX_WORKERS > 1 or
+		skip 'Inline::C or Socket::MsgHdr not available', 4;
+	$ipc->wq_worker_incr;
+	is($ipc->wq_workers, 2, 'worker count bumped');
+	$ipc->wq_worker_decr;
+	$ipc->wq_worker_decr_wait(10);
+	is($ipc->wq_workers, 1, 'worker count lowered');
+	is($ipc->wq_workers(2), 2, 'worker count set');
+	is($ipc->wq_workers, 2, 'worker count stayed set');
+}
 $ipc->wq_close;
 is($ipc->wq_workers, undef, 'workers undef after close');
 

  parent reply	other threads:[~2021-01-10 12:15 UTC|newest]

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-01-10 12:14 [PATCH 00/22] lei query overview views Eric Wong
2021-01-10 12:14 ` [PATCH 01/22] lei query + pagination sorta working Eric Wong
2021-01-10 12:14 ` [PATCH 02/22] lei q: deduplicate smsg Eric Wong
2021-01-10 12:15 ` [PATCH 03/22] ds: block signals when reaping Eric Wong
2021-01-10 12:15 ` [PATCH 04/22] ipc: add support for asynchronous callbacks Eric Wong
2021-01-10 12:15 ` [PATCH 05/22] cmd_ipc: send FDs with buffer payload Eric Wong
2021-01-10 12:15 ` [PATCH 06/22] ipc: avoid excessive evals Eric Wong
2021-01-10 12:15 ` [PATCH 07/22] ipc: work queue support via SOCK_SEQPACKET Eric Wong
2021-01-10 12:15 ` [PATCH 08/22] ipc: eliminate ipc_worker_stop method Eric Wong
2021-01-10 12:15 ` [PATCH 09/22] ipc: wq: support dynamic worker count change Eric Wong
2021-01-10 12:15 ` [PATCH 10/22] ipc: drop -ipc_parent_pid field Eric Wong
2021-01-10 12:15 ` [PATCH 11/22] ipc: DESTROY and wq_workers methods Eric Wong
2021-01-10 12:15 ` [PATCH 12/22] lei: rename $w to $wpager for warning message Eric Wong
2021-01-10 12:15 ` [PATCH 13/22] lei: fix oneshot TTY detection by passing STD*{GLOB} Eric Wong
2021-01-10 12:15 ` [PATCH 14/22] lei: query: ensure pager exit is instantaneous Eric Wong
2021-01-10 12:15 ` [PATCH 15/22] ipc: start supporting sending/receiving more than 3 FDs Eric Wong
2021-01-10 12:15 ` Eric Wong [this message]
2021-01-10 12:15 ` [PATCH 17/22] ipc: drop unused fields, default sighandlers for wq Eric Wong
2021-01-10 12:15 ` [PATCH 18/22] lei: get rid of client {pid} field Eric Wong
2021-01-10 12:15 ` [PATCH 19/22] lei: fork + FD cleanup Eric Wong
2021-01-10 12:15 ` [PATCH 20/22] lei: run pager in client script Eric Wong
2021-01-10 12:15 ` [PATCH 21/22] lei_xsearch: transfer 4 FDs internally, drop IO::FDPass Eric Wong
2021-01-10 12:15 ` [PATCH 22/22] lei: query: restore JSON output overview Eric Wong

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