cmd_ipc4: retry sendmsg on ENOBUFS/ENOMEM/ETOOMANYREFS

[public-inbox.git] / lib / PublicInbox / CmdIPC4.pm

diff --git a/lib/PublicInbox/CmdIPC4.pm b/lib/PublicInbox/CmdIPC4.pm
index c4fcb0d679d9256319ab6f5b45e86d72772256e4..c3a7f56ec7e3f356243d270447402aa3217c499a 100644 (file)
--- a/lib/PublicInbox/CmdIPC4.pm
+++ b/lib/PublicInbox/CmdIPC4.pm
@@ -3,7 +3,7 @@
 
 # callers should use PublicInbox::CmdIPC4->can('send_cmd4') (or recv_cmd4)
 # first choice for script/lei front-end and 2nd choice for lei backend
-# libsocket-msghdr-perl is in Debian but many other distros as of 2021.
+# libsocket-msghdr-perl is in Debian but not many other distros as of 2021.
 package PublicInbox::CmdIPC4;
 use strict;
 use v5.10.1;
@@ -12,23 +12,31 @@ BEGIN { eval {
 require Socket::MsgHdr; # XS
 no warnings 'once';
 
-# 3 FDs per-sendmsg(2) + buffer
+# any number of FDs per-sendmsg(2) + buffer
 *send_cmd4 = sub ($$$$) { # (sock, fds, buf, flags) = @_;
        my ($sock, $fds, undef, $flags) = @_;
        my $mh = Socket::MsgHdr->new(buf => $_[2]);
-       $mh->cmsghdr(SOL_SOCKET, SCM_RIGHTS,
-                       pack('i' x scalar(@$fds), @$fds));
-       Socket::MsgHdr::sendmsg($sock, $mh, $flags) or die "sendmsg: $!";
+       $mh->cmsghdr(SOL_SOCKET, SCM_RIGHTS, pack('i' x scalar(@$fds), @$fds));
+       my $s;
+       my $try = 0;
+       do {
+               $s = Socket::MsgHdr::sendmsg($sock, $mh, $flags);
+       } while (!defined($s) &&
+                       ($!{ENOBUFS} || $!{ENOMEM} || $!{ETOOMANYREFS}) &&
+                       (++$try < 50) &&
+                       warn "sleeping on sendmsg: $! (#$try)\n" &&
+                       select(undef, undef, undef, 0.1) == 0);
+       $s;
 };
 
 *recv_cmd4 = sub ($$$) {
        my ($s, undef, $len) = @_; # $_[1] = destination buffer
        my $mh = Socket::MsgHdr->new(buflen => $len, controllen => 256);
-       my $r = Socket::MsgHdr::recvmsg($s, $mh, 0) // die "recvmsg: $!";
+       my $r = Socket::MsgHdr::recvmsg($s, $mh, 0) // return ($_[1] = undef);
        $_[1] = $mh->buf;
        return () if $r == 0;
        my (undef, undef, $data) = $mh->cmsghdr;
-       unpack('i' x (length($data) / 4), $data);
+       defined($data) ? unpack('i' x (length($data) / 4), $data) : ();
 };
 
 } } # /eval /BEGIN