From: Eric Wong <e@80x24.org>
To: meta@public-inbox.org
Subject: [PATCH 08/13] lei: avoid racing on unlink + bind + listen
Date: Sun, 7 Feb 2021 23:05:16 -1000 [thread overview]
Message-ID: <20210208090521.28909-9-e@80x24.org> (raw)
In-Reply-To: <20210208090521.28909-1-e@80x24.org>
When multiple lei(1) processes are starting in parallel without
lei-daemon already running, it's possible for them to trample
each others' socket path trying to start lei-daemon. Lock
errors.log before unlink/bind/listen. We'll add an extra
connect(2) attempt to check if the starter lost the race.
Without this change, a stress script like the following could
easily cause problems:
lei q -o ~/tmp/a foo ... &
lei q -o ~/tmp/b bar ... &
lei q -o ~/tmp/c quux ... &
lei q -o ~/tmp/d baz ... &
---
lib/PublicInbox/LEI.pm | 37 +++++++++++++++++++++++--------------
1 file changed, 23 insertions(+), 14 deletions(-)
diff --git a/lib/PublicInbox/LEI.pm b/lib/PublicInbox/LEI.pm
index 2f370f52..cddb94e9 100644
--- a/lib/PublicInbox/LEI.pm
+++ b/lib/PublicInbox/LEI.pm
@@ -22,7 +22,7 @@ use PublicInbox::Syscall qw(SFD_NONBLOCK EPOLLIN EPOLLET);
use PublicInbox::Sigfd;
use PublicInbox::DS qw(now dwaitpid);
use PublicInbox::Spawn qw(spawn popen_rd);
-use PublicInbox::OnDestroy;
+use PublicInbox::Lock;
use Time::HiRes qw(stat); # ctime comparisons for config cache
use File::Path qw(mkpath);
use File::Spec;
@@ -828,17 +828,19 @@ sub accept_dispatch { # Listener {post_accept} callback
vec(my $rvec = '', fileno($sock), 1) = 1;
select($rvec, undef, undef, 60) or
return send($sock, 'timed out waiting to recv FDs', MSG_EOR);
- my @fds = $recv_cmd->($sock, my $buf, 4096 * 33); # >MAX_ARG_STRLEN
+ # (4096 * 33) >MAX_ARG_STRLEN
+ my @fds = $recv_cmd->($sock, my $buf, 4096 * 33) or return; # EOF
if (scalar(@fds) == 4) {
for my $i (0..3) {
my $fd = shift(@fds);
open($self->{$i}, '+<&=', $fd) and next;
send($sock, "open(+<&=$fd) (FD=$i): $!", MSG_EOR);
}
- } else {
- my $msg = "recv_cmd failed: $!";
- warn $msg;
+ } elsif (!defined($fds[0])) {
+ warn(my $msg = "recv_cmd failed: $!");
return send($sock, $msg, MSG_EOR);
+ } else {
+ return;
}
$self->{2}->autoflush(1); # keep stdout buffered until x_it|DESTROY
# $ENV_STR = join('', map { "\0$_=$ENV{$_}" } keys %ENV);
@@ -923,9 +925,19 @@ sub dump_and_clear_log {
# lei(1) calls this when it can't connect
sub lazy_start {
my ($path, $errno, $narg) = @_;
- if ($errno == ECONNREFUSED) {
- unlink($path) or die "unlink($path): $!";
- } elsif ($errno != ENOENT) {
+ local ($errors_log, $listener);
+ ($errors_log) = ($path =~ m!\A(.+?/)[^/]+\z!);
+ $errors_log .= 'errors.log';
+ my $addr = pack_sockaddr_un($path);
+ my $lk = bless { lock_path => $errors_log }, 'PublicInbox::Lock';
+ $lk->lock_acquire;
+ socket($listener, AF_UNIX, SOCK_SEQPACKET, 0) or die "socket: $!";
+ if ($errno == ECONNREFUSED || $errno == ENOENT) {
+ return if connect($listener, $addr); # another process won
+ if ($errno == ECONNREFUSED && -S $path) {
+ unlink($path) or die "unlink($path): $!";
+ }
+ } else {
$! = $errno; # allow interpolation to stringify in die
die "connect($path): $!";
}
@@ -935,10 +947,10 @@ sub lazy_start {
BSD::Resource::setrlimit($NOFILE, $h, $h) if $s < $h;
}
umask(077) // die("umask(077): $!");
- local $listener;
- socket($listener, AF_UNIX, SOCK_SEQPACKET, 0) or die "socket: $!";
- bind($listener, pack_sockaddr_un($path)) or die "bind($path): $!";
+ bind($listener, $addr) or die "bind($path): $!";
listen($listener, 1024) or die "listen: $!";
+ $lk->lock_release;
+ undef $lk;
my @st = stat($path) or die "stat($path): $!";
my $dev_ino_expect = pack('dd', $st[0], $st[1]); # dev+ino
local $oldset = PublicInbox::DS::block_signals();
@@ -956,9 +968,6 @@ sub lazy_start {
require PublicInbox::Listener;
require PublicInbox::EOFpipe;
(-p STDOUT) or die "E: stdout must be a pipe\n";
- local $errors_log;
- ($errors_log) = ($path =~ m!\A(.+?/)[^/]+\z!);
- $errors_log .= 'errors.log';
open(STDIN, '+>>', $errors_log) or die "open($errors_log): $!";
STDIN->autoflush(1);
dump_and_clear_log("from previous daemon process:\n");
next prev parent reply other threads:[~2021-02-08 9:05 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-08 9:05 [PATCH 00/13] lei approxidate, startup fix, --alert Eric Wong
2021-02-08 9:05 ` [PATCHv2 01/13] lei q: improve remote mboxrd UX + MUA Eric Wong
2021-02-08 9:05 ` [PATCH 02/13] lei_xsearch: quiet Eml warnings from remote mboxrds Eric Wong
2021-02-08 9:05 ` [PATCH 03/13] lei q: SIGWINCH process group with the terminal Eric Wong
2021-02-08 9:05 ` [PATCH 04/13] lei q: support --alert=CMD for early MUA users Eric Wong
2021-02-08 9:05 ` [PATCH 05/13] tests: favor IPv6 Eric Wong
2021-02-08 9:05 ` [PATCH 06/13] ds: improve add_timer usability Eric Wong
2021-02-08 9:05 ` [PATCH 07/13] lei: start_pager: drop COLUMNS default Eric Wong
2021-02-08 9:05 ` Eric Wong [this message]
2021-02-08 9:05 ` [PATCH 09/13] lei: drop BSD::Resource usage Eric Wong
2021-02-08 9:05 ` [PATCH 10/13] git: implement date_parse method Eric Wong
2021-02-08 9:05 ` [PATCH 11/13] lei q: use git approxidate with d:, dt: and rt: ranges Eric Wong
2021-02-10 9:59 ` [PATCH] search: fix argv handling of quoted phrases Eric Wong
2021-02-08 9:05 ` [PATCH 12/13] search: use one git-rev-parse process for all dates Eric Wong
2021-02-08 9:05 ` [PATCH 13/13] spawnpp: raise exception on E2BIG errors Eric Wong
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