################################################################################
## File:
## Daemon.pm
## Authors:
## Earl Hood earl@earlhood.com
## Detlef Pilzecker deti@cpan.org
## Pavel Denisov akreal@cpan.org
## Description:
## Run Perl program(s) as a daemon process, see docs in the Daemon.pod file
################################################################################
## Copyright (C) 1997-2015 by Earl Hood, Detlef Pilzecker and Pavel Denisov.
##
## All rights reserved.
##
## This module is free software. It may be used, redistributed and/or modified
## under the same terms as Perl itself.
################################################################################
package Proc::Daemon;
use strict;
use POSIX();
$Proc::Daemon::VERSION = '0.19';
################################################################################
# Create the Daemon object:
# my $daemon = Proc::Daemon->new( [ %Daemon_Settings ] )
#
# %Daemon_Settings are hash key=>values and can be:
# work_dir => '/working/daemon/directory' -> defaults to '/'
# setgid => 12345 -> defaults to <undef>
# setuid => 12345 -> defaults to <undef>
# child_STDIN => '/path/to/daemon/STDIN.file' -> defautls to '</dev/null'
# child_STDOUT => '/path/to/daemon/STDOUT.file' -> defaults to '+>/dev/null'
# child_STDERR => '/path/to/daemon/STDERR.file' -> defaults to '+>/dev/null'
# dont_close_fh => [ 'main::DATA', 'PackageName::DATA', 'STDOUT', ... ]
# -> arrayref with file handles you do not want to be closed in the daemon.
# dont_close_fd => [ 5, 8, ... ] -> arrayref with file
# descriptors you do not want to be closed in the daemon.
# pid_file => '/path/to/pid/file.txt' -> defaults to
# undef (= write no file).
# file_umask => 022 -> defaults to 066
# exec_command => 'perl /home/script.pl' -> execute a system command
# via Perls *exec PROGRAM* at the end of the Init routine and never return.
# Must be an arrayref if you want to create several daemons at once.
#
# Returns: the blessed object.
################################################################################
sub new {
my ( $class, %args ) = @_;
my $self = \%args;
bless( $self, $class );
$self->{memory} = {};
return $self;
}
################################################################################
# Become a daemon:
# $daemon->Init
#
# or, for more daemons with other settings in the same script:
# Use a hash as below. The argument must (!) now be a hashref: {...}
# even if you don't modify the initial settings (=> use empty hashref).
# $daemon->Init( { [ %Daemon_Settings ] } )
#
# or, if no Daemon->new() object was created and for backward compatibility:
# Proc::Daemon::Init( [ { %Daemon_Settings } ] )
# In this case the argument must be <undef> or a hashref!
#
# %Daemon_Settings see &new.
#
# Returns to the parent:
# - nothing (parent does exit) if the context is looking for no return value.
# - the PID(s) of the daemon(s) created.
# Returns to the child (daemon):
# its PID (= 0) | never returns if used with 'exec_command'.
################################################################################
sub Init {
my Proc::Daemon $self = shift;
my $settings_ref = shift;
# Check if $self has been blessed into the package, otherwise do it now.
unless ( ref( $self ) && eval{ $self->isa( 'Proc::Daemon' ) } ) {
$self = ref( $self ) eq 'HASH' ? Proc::Daemon->new( %$self ) : Proc::Daemon->new();
}
# If $daemon->Init is used again in the same script,
# update to the new arguments.
elsif ( ref( $settings_ref ) eq 'HASH' ) {
map { $self->{ $_ } = $$settings_ref{ $_ } } keys %$settings_ref;
}
# Open a filehandle to an anonymous temporary pid file. If this is not
# possible (some environments do not allow all users to use anonymous
# temporary files), use the pid_file(s) to retrieve the PIDs for the parent.
my $FH_MEMORY;
unless ( open( $FH_MEMORY, "+>", undef ) || $self->{pid_file} ) {
die "Can not <open> anonymous temporary pidfile ('$!'), therefore you must add 'pid_file' as an Init() argument, e.g. to: '/tmp/proc_daemon_pids'";
}
# Get the file descriptors the user does not want to close.
my %dont_close_fd;
if ( defined $self->{dont_close_fd} ) {
die "The argument 'dont_close_fd' must be arrayref!"
if ref( $self->{dont_close_fd} ) ne 'ARRAY';
foreach ( @{ $self->{dont_close_fd} } ) {
die "All entries in 'dont_close_fd' must be numeric ('$_')!" if $_ =~ /\D/;
$dont_close_fd{ $_ } = 1;
}
}
# Get the file descriptors of the handles the user does not want to close.
if ( defined $self->{dont_close_fh} ) {
die "The argument 'dont_close_fh' must be arrayref!"
if ref( $self->{dont_close_fh} ) ne 'ARRAY';
foreach ( @{ $self->{dont_close_fh} } ) {
if ( defined ( my $fn = fileno $_ ) ) {
$dont_close_fd{ $fn } = 1;
}
}
}
# If system commands are to be executed, put them in a list.
my @exec_command = ref( $self->{exec_command} ) eq 'ARRAY' ? @{ $self->{exec_command} } : ( $self->{exec_command} );
$#exec_command = 0 if $#exec_command < 0;
# Create a daemon for every system command.
foreach my $exec_command ( @exec_command ) {
# The first parent is running here.
# Using this subroutine or loop multiple times we must modify the filenames:
# 'child_STDIN', 'child_STDOUT', 'child_STDERR' and 'pid_file' for every
# daemon (a higher number will be appended to the filenames).
$self->adjust_settings();
# First fork.
my $pid = Fork();
if ( defined $pid && $pid == 0 ) {
# The first child runs here.
# Set the new working directory.
die "Can't <chdir> to $self->{work_dir}: $!" unless chdir $self->{work_dir};
# Set the file creation mask.
$self->{_orig_umask} = umask;
umask($self->{file_umask});
# Detach the child from the terminal (no controlling tty), make it the
# session-leader and the process-group-leader of a new process group.
die "Cannot detach from controlling terminal" if POSIX::setsid() < 0;
# "Is ignoring SIGHUP necessary?
#
# It's often suggested that the SIGHUP signal should be ignored before
# the second fork to avoid premature termination of the process. The
# reason is that when the first child terminates, all processes, e.g.
# the second child, in the orphaned group will be sent a SIGHUP.
#
# 'However, as part of the session management system, there are exactly
# two cases where SIGHUP is sent on the death of a process:
#
# 1) When the process that dies is the session leader of a session that
# is attached to a terminal device, SIGHUP is sent to all processes
# in the foreground process group of that terminal device.
# 2) When the death of a process causes a process group to become
# orphaned, and one or more processes in the orphaned group are
# stopped, then SIGHUP and SIGCONT are sent to all members of the
# orphaned group.' [2]
#
# The first case can be ignored since the child is guaranteed not to have
# a controlling terminal. The second case isn't so easy to dismiss.
# The process group is orphaned when the first child terminates and
# POSIX.1 requires that every STOPPED process in an orphaned process
# group be sent a SIGHUP signal followed by a SIGCONT signal. Since the
# second child is not STOPPED though, we can safely forego ignoring the
# SIGHUP signal. In any case, there are no ill-effects if it is ignored."
# Source: http://code.activestate.com/recipes/278731/
#
# local $SIG{'HUP'} = 'IGNORE';
# Second fork.
# This second fork is not absolutely necessary, it is more a precaution.
# 1. Prevent possibility of reacquiring a controlling terminal.
# Without this fork the daemon would remain a session-leader. In
# this case there is a potential possibility that the process could
# reacquire a controlling terminal. E.g. if it opens a terminal device,
# without using the O_NOCTTY flag. In Perl this is normally the case
# when you use <open> on this kind of device, instead of <sysopen>
# with the O_NOCTTY flag set.
# Note: Because of the second fork the daemon will not be a session-
# leader and therefore Signals will not be send to other members of
# his process group. If you need the functionality of a session-leader
# you may want to call POSIX::setsid() manually on your daemon.
# 2. Detach the daemon completely from the parent.
# The double-fork prevents the daemon from becoming a zombie. It is
# needed in this module because the grandparent process can continue.
# Without the second fork and if a child exits before the parent
# and you forget to call <wait> in the parent you will get a zombie
# until the parent also terminates. Using the second fork we can be
# sure that the parent of the daemon is finished near by or before
# the daemon exits.
$pid = Fork();
if ( defined $pid && $pid == 0 ) {
# Here the second child is running.
# Close all file handles and descriptors the user does not want
# to preserve.
my $hc_fd; # highest closed file descriptor
close $FH_MEMORY;
foreach ( 0 .. OpenMax() ) {
unless ( $dont_close_fd{ $_ } ) {
if ( $_ == 0 ) { close STDIN }
elsif ( $_ == 1 ) { close STDOUT }
elsif ( $_ == 2 ) { close STDERR }
else { $hc_fd = $_ if POSIX::close( $_ ) }
}
}
# Sets the real group identifier and the effective group
# identifier for the daemon process before opening files.
# Must set group first because you cannot change group
# once you have changed user
POSIX::setgid( $self->{setgid} ) if defined $self->{setgid};
# Sets the real user identifier and the effective user
# identifier for the daemon process before opening files.
POSIX::setuid( $self->{setuid} ) if defined $self->{setuid};
# Reopen STDIN, STDOUT and STDERR to 'child_STD...'-path or to
# /dev/null. Data written on a null special file is discarded.
# Reads from the null special file always return end of file.
open( STDIN, $self->{child_STDIN} || "</dev/null" ) unless $dont_close_fd{ 0 };
open( STDOUT, $self->{child_STDOUT} || "+>/dev/null" ) unless $dont_close_fd{ 1 };
open( STDERR, $self->{child_STDERR} || "+>/dev/null" ) unless $dont_close_fd{ 2 };
# Since <POSIX::close(FD)> is in some cases "secretly" closing
# file descriptors without telling it to perl, we need to
# re<open> and <CORE::close(FH)> as many files as we closed with
# <POSIX::close(FD)>. Otherwise it can happen (especially with
# FH opened by __DATA__ or __END__) that there will be two perl
# handles associated with one file, what can cause some
# confusion. :-)
# see: http://rt.perl.org/rt3/Ticket/Display.html?id=72526
if ( $hc_fd ) {
my @fh;
foreach ( 3 .. $hc_fd ) { open $fh[ $_ ], "</dev/null" }
# Perl will try to close all handles when @fh leaves scope
# here, but the rude ones will sacrifice themselves to avoid
# potential damage later.
}
# Restore the original file creation mask.
umask $self->{_orig_umask};
# Execute a system command and never return.
if ( $exec_command ) {
exec ($exec_command) or die "couldn't exec $exec_command: $!";
exit; # Not a real exit, but needed since Perl warns you if
# there is no statement like <die>, <warn>, or <exit>
# following <exec>. The <exec> function executes a system
# command and never returns.
}
# Return the childs own PID (= 0)
return $pid;
}
# First child (= second parent) runs here.
# Print the PID of the second child into ...
$pid ||= '';
# ... the anonymous temporary pid file.
if ( $FH_MEMORY ) {
print $FH_MEMORY "$pid\n";
close $FH_MEMORY;
}
# ... the real 'pid_file'.
if ( $self->{pid_file} ) {
open( my $FH_PIDFILE, "+>", $self->{pid_file} ) ||
die "Can not open pidfile (pid_file => '$self->{pid_file}'): $!";
print $FH_PIDFILE $pid;
close $FH_PIDFILE;
}
# Don't <wait> for the second child to exit,
# even if we don't have a value in $exec_command.
# The second child will become orphan by <exit> here, but then it
# will be adopted by init(8), which automatically performs a <wait>
# to remove the zombie when the child exits.
POSIX::_exit(0);
}
# Only first parent runs here.
# A child that terminates, but has not been waited for becomes
# a zombie. So we wait for the first child to exit.
waitpid( $pid, 0 );
}
# Only first parent runs here.
# Exit if the context is looking for no value (void context).
exit 0 unless defined wantarray;
# Get the daemon PIDs out of the anonymous temporary pid file
# or out of the real pid-file(s)
my @pid;
if ( $FH_MEMORY ) {
seek( $FH_MEMORY, 0, 0 );
@pid = map { chomp $_; $_ eq '' ? undef : $_ } <$FH_MEMORY>;
$_ = (/^(\d+)$/)[0] foreach @pid; # untaint
close $FH_MEMORY;
}
elsif ( $self->{memory}{pid_file} ) {
foreach ( keys %{ $self->{memory}{pid_file} } ) {
open( $FH_MEMORY, "<", $_ ) || die "Can not open pid_file '<$_': $!";
push( @pid, <$FH_MEMORY> );
close $FH_MEMORY;
}
}
# Return the daemon PIDs (from second child/ren) to the first parent.
return ( wantarray ? @pid : $pid[0] );
}
# For backward capability:
*init = \&Init;
################################################################################
# Set some defaults and adjust some settings.
# Args: ( $self )
# Returns: nothing
################################################################################
sub adjust_settings {
my Proc::Daemon $self = shift;
# Set default 'work_dir' if needed.
$self->{work_dir} ||= '/';
$self->fix_filename( 'child_STDIN', 1 ) if $self->{child_STDIN};
$self->fix_filename( 'child_STDOUT', 1 ) if $self->{child_STDOUT};
$self->fix_filename( 'child_STDERR', 1 ) if $self->{child_STDERR};
# Check 'pid_file's name
if ( $self->{pid_file} ) {
die "Pidfile (pid_file => '$self->{pid_file}') can not be only a number. I must be able to distinguish it from a PID number in &get_pid('...')." if $self->{pid_file} =~ /^\d+$/;
$self->fix_filename( 'pid_file' );
}
$self->{file_umask} ||= 066;
return;
}
################################################################################
# - If the keys value is only a filename add the path of 'work_dir'.
# - If we have already set a file for this key with the same "path/name",
# add a number to the file.
# Args: ( $self, $key, $extract_mode )
# key: one of 'child_STDIN', 'child_STDOUT', 'child_STDERR', 'pid_file'
# extract_mode: true = separate <open> MODE form filename before checking
# path/filename; false = no MODE to check
# Returns: nothing
################################################################################
sub fix_filename {
my Proc::Daemon $self = shift;
my $key = shift;
my $var = $self->{ $key };
my $mode = ( shift ) ? ( $var =~ s/^([\+\<\>\-\|]+)// ? $1 : ( $key eq 'child_STDIN' ? '<' : '+>' ) ) : '';
# add path to filename
if ( $var =~ s/^\.\/// || $var !~ /\// ) {
$var = $self->{work_dir} =~ /\/$/ ?
$self->{work_dir} . $var : $self->{work_dir} . '/' . $var;
}
# If the file was already in use, modify it with '_number':
# filename_X | filename_X.ext
if ( $self->{memory}{ $key }{ $var } ) {
$var =~ s/([^\/]+)$//;
my @i = split( /\./, $1 );
my $j = $#i ? $#i - 1 : 0;
$self->{memory}{ "$key\_num" } ||= 0;
$i[ $j ] =~ s/_$self->{memory}{ "$key\_num" }$//;
$self->{memory}{ "$key\_num" }++;
$i[ $j ] .= '_' . $self->{memory}{ "$key\_num" };
$var .= join( '.', @i );
}
$self->{memory}{ $key }{ $var } = 1;
$self->{ $key } = $mode . $var;
return;
}
################################################################################
# Fork(): Retries to fork over 30 seconds if possible to fork at all and
# if necessary.
# Returns the child PID to the parent process and 0 to the child process.
# If the fork is unsuccessful it C<warn>s and returns C<undef>.
################################################################################
sub Fork {
my $pid;
my $loop = 0;
FORK: {
if ( defined( $pid = fork ) ) {
return $pid;
}
# EAGAIN - fork cannot allocate sufficient memory to copy the parent's
# page tables and allocate a task structure for the child.
# ENOMEM - fork failed to allocate the necessary kernel structures
# because memory is tight.
# Last the loop after 30 seconds
if ( $loop < 6 && ( $! == POSIX::EAGAIN() || $! == POSIX::ENOMEM() ) ) {
$loop++; sleep 5; redo FORK;
}
}
warn "Can't fork: $!";
return undef;
}
################################################################################
# OpenMax( [ NUMBER ] )
# Returns the maximum number of possible file descriptors. If sysconf()
# does not give me a valid value, I return NUMBER (default is 64).
################################################################################
sub OpenMax {
my $openmax = POSIX::sysconf( &POSIX::_SC_OPEN_MAX );
return ( ! defined( $openmax ) || $openmax < 0 ) ?
( shift || 64 ) : $openmax;
}
################################################################################
# Check if the (daemon) process is alive:
# Status( [ number or string ] )
#
# Examples:
# $object->Status() - Tries to get the PID out of the settings in new() and checks it.
# $object->Status( 12345 ) - Number of PID to check.
# $object->Status( './pid.txt' ) - Path to file containing one PID to check.
# $object->Status( 'perl /home/my_perl_daemon.pl' ) - Command line entry of the
# running program to check. Requires Proc::ProcessTable to work.
#
# Returns the PID (alive) or 0 (dead).
################################################################################
sub Status {
my Proc::Daemon $self = shift;
my $pid = shift;
# Get the process ID.
( $pid, undef ) = $self->get_pid( $pid );
# Return if no PID was found.
return 0 if ! $pid;
# The kill(2) system call will check whether it's possible to send
# a signal to the pid (that means, to be brief, that the process
# is owned by the same user, or we are the super-user). This is a
# useful way to check that a child process is alive (even if only
# as a zombie) and hasn't changed its UID.
return ( kill( 0, $pid ) ? $pid : 0 );
}
################################################################################
# Kill the (daemon) process:
# Kill_Daemon( [ number or string [, SIGNAL ] ] )
#
# Examples:
# $object->Kill_Daemon() - Tries to get the PID out of the settings in new() and kill it.
# $object->Kill_Daemon( 12345, 'TERM' ) - Number of PID to kill with signal 'TERM'. The
# names or numbers of the signals are the ones listed out by kill -l on your system.
# $object->Kill_Daemon( './pid.txt' ) - Path to file containing one PID to kill.
# $object->Kill_Daemon( 'perl /home/my_perl_daemon.pl' ) - Command line entry of the
# running program to kill. Requires Proc::ProcessTable to work.
#
# Returns the number of processes successfully killed,
# which mostly is not the same as the PID number.
################################################################################
sub Kill_Daemon {
my Proc::Daemon $self = shift;
my $pid = shift;
my $signal = shift || 'KILL';
my $pidfile;
# Get the process ID.
( $pid, $pidfile ) = $self->get_pid( $pid );
# Return if no PID was found.
return 0 if ! $pid;
# Kill the process.
my $killed = kill( $signal, $pid );
if ( $killed && $pidfile ) {
# Set PID in pid file to '0'.
if ( open( my $FH_PIDFILE, "+>", $pidfile ) ) {
print $FH_PIDFILE '0';
close $FH_PIDFILE;
}
else { warn "Can not open pidfile (pid_file => '$pidfile'): $!" }
}
return $killed;
}
################################################################################
# Return the PID of a process:
# get_pid( number or string )
#
# Examples:
# $object->get_pid() - Tries to get the PID out of the settings in new().
# $object->get_pid( 12345 ) - Number of PID to return.
# $object->get_pid( './pid.txt' ) - Path to file containing the PID.
# $object->get_pid( 'perl /home/my_perl_daemon.pl' ) - Command line entry of
# the running program. Requires Proc::ProcessTable to work.
#
# Returns an array with ( 'the PID | <undef>', 'the pid_file | <undef>' )
################################################################################
sub get_pid {
my Proc::Daemon $self = shift;
my $string = shift || '';
my ( $pid, $pidfile );
if ( $string ) {
# $string is already a PID.
if ( $string =~ /^(\d+)$/ ) {
$pid = $1; # untaint
}
# Open the pidfile and get the PID from it.
elsif ( open( my $FH_MEMORY, "<", $string ) ) {
$pid = <$FH_MEMORY>;
close $FH_MEMORY;
die "I found no valid PID ('$pid') in the pidfile: '$string'" if $pid =~ /\D/s;
$pid = ($pid =~ /^(\d+)$/)[0]; # untaint
$pidfile = $string;
}
# Get the PID by the system process table.
else {
$pid = $self->get_pid_by_proc_table_attr( 'cmndline', $string );
}
}
# Try to get the PID out of the new() settings.
if ( ! $pid ) {
# Try to get the PID out of the 'pid_file' setting.
if ( $self->{pid_file} && open( my $FH_MEMORY, "<", $self->{pid_file} ) ) {
$pid = <$FH_MEMORY>;
close $FH_MEMORY;
if ($pid && $pid =~ /^(\d+)$/) {
$pid = $1; # untaint
$pidfile = $self->{pid_file};
} else {
$pid = undef;
}
}
# Try to get the PID out of the system process
# table by the 'exec_command' setting.
if ( ! $pid && $self->{exec_command} ) {
$pid = $self->get_pid_by_proc_table_attr( 'cmndline', $self->{exec_command} );
}
}
return ( $pid, $pidfile );
}
################################################################################
# This sub requires the Proc::ProcessTable module to be installed!!!
#
# Search for the PID of a process in the process table:
# $object->get_pid_by_proc_table_attr( 'unix_process_table_attribute', 'string that must match' )
#
# unix_process_table_attribute examples:
# For more see the README.... files at http://search.cpan.org/~durist/Proc-ProcessTable/
# uid - UID of process
# pid - process ID
# ppid - parent process ID
# fname - file name
# state - state of process
# cmndline - full command line of process
# cwd - current directory of process
#
# Example:
# get_pid_by_proc_table_attr( 'cmndline', 'perl /home/my_perl_daemon.pl' )
#
# Returns the process PID on success, otherwise <undef>.
################################################################################
sub get_pid_by_proc_table_attr {
my Proc::Daemon $self = shift;
my ( $command, $match ) = @_;
my $pid;
# eval - Module may not be installed
eval {
require Proc::ProcessTable;
my $table = Proc::ProcessTable->new()->table;
foreach ( @$table ) {
# fix for Proc::ProcessTable: under some conditions $_->cmndline
# returns with space and/or other characters at the end
next unless $_->$command =~ /^$match\s*$/;
$pid = $_->pid;
last;
}
};
warn "- Problem in get_pid_by_proc_table_attr( '$command', '$match' ):\n $@ You may not use a command line entry to get the PID of your process.\n This function requires Proc::ProcessTable (http://search.cpan.org/~durist/Proc-ProcessTable/) to work.\n" if $@;
return $pid;
}
1;