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package Munin::Common::Daemon;
use warnings;
use strict;
use English;
use IO::Socket;
sub emit_sd_notify_message {
eval {
my $socket_path = $ENV{NOTIFY_SOCKET};
if (defined $socket_path) {
# Prevent children from talking to the socket provided solely for us.
delete $ENV{NOTIFY_SOCKET};
# A socket path starting with "@" is interpreted as a Linux abstract namespace socket.
# This can be indicated by the socket path starting with a null byte.
# See "Address format: abstract" in "man 7 unix".
$socket_path =~ s/^@/\0/;
my $socket = IO::Socket::UNIX->new(Type => SOCK_DGRAM, Peer => $socket_path);
if (defined $socket) {
print($socket "READY=1\n");
close($socket);
}
}
}
}
1;
__END__
=head1 NAME
Munin::Common::Daemon - utilities for daemons.
=head1 SYNOPSIS
The following daemon-related features are supported:
=over
=item sd_notify: signal readiness of the daemon
=back
=head1 SUBROUTINES
=head2 emit_sd_notify_message
Example:
emit_sd_notify_message();
Send a "ready" signal according to the C<sd_notify> interface:
=over
=item 1. check whether the environment variable "NOTIFY_SOCKET" is defined
=item 2. remove this variable from the environment (this interface is not propagated to children)
=item 3. send the string "READY=1" to the socket
=back
The function returns silently, if something fails.
The function should be called as soon as the service is ready to accept
requests.
Calling this function is always safe - independent of the caller supporting the
C<sd_notify> interface or not.
Examples for callers supporting the C<sd_notify> interface:
=over
=item systemd: see C<Type=Notify> in L<systemd.exec/5>
=item start-stop-daemon: see C<--notify-await> in L<start-stop-daemon/8>
=back
See the L<specification of "sd_notify"|https://www.freedesktop.org/software/systemd/man/sd_notify.html>
for further details of this interface.
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