1MooseX::Daemonize::CoreU(s3eprm)Contributed Perl DocumenMtoaotsieoXn::Daemonize::Core(3pm)
2
3
4

NAME

6       MooseX::Daemonize::Core - A Role with the core daemonization features
7

VERSION

9       version 0.22
10

SYNOPSIS

12         package My::Daemon;
13         use Moose;
14
15         with 'MooseX::Daemonize::Core';
16
17         sub start {
18             my $self = shift;
19             # daemonize me ...
20             $self->daemonize;
21             # return from the parent,...
22             return unless $self->is_daemon;
23             # but continue on in the child (daemon)
24         }
25

DESCRIPTION

27       This is the basic daemonization Role, it provides a few methods (see
28       below) and the minimum features needed to properly daemonize your code.
29
30   Important Notes
31       None of the methods in this role will exit the parent process for you,
32       it only forks and detaches your child (daemon) process. It is your
33       responsibility to exit the parent process in some way.
34
35       There is no PID or PID file management in this role, that is your
36       responsibility (see some of the other roles in this distro for that).
37

ATTRIBUTES

39       is_daemon (is = rw, isa => Bool)>
40           This attribute is used to signal if we are within the daemon
41           process or not.
42
43       no_double_fork (is = rw, isa => Bool)>
44           Setting this attribute to true will cause this method to not
45           perform the typical double-fork, which is extra added protection
46           from your process accidentally acquiring a controlling terminal.
47           More information can be found above, and by Googling "double fork
48           daemonize".
49
50           If you the double-fork behavior off, you might want to enable the
51           ignore_zombies.
52
53       ignore_zombies (is = rw, isa => Bool)>
54           Setting this attribute to a true value will result in setting the
55           $SIG{CHLD} handler to "IGNORE". This tells perl to clean up zombie
56           processes. By default, and for the most part you don't need it,
57           only when you turn off the double fork behavior (with the
58           no_double_fork attribute) do you sometimes want this behavior.
59
60       dont_close_all_files (is = rw, isa => Bool)>
61           Setting this attribute to true will cause it to skip closing all
62           the filehandles. This is useful if you are opening things like
63           sockets and such in the pre-fork.
64

METHODS

66       daemon_fork (?%options)
67           This forks off the child process to be daemonized. Just as with the
68           built in fork, it returns the child pid to the parent process, 0 to
69           the child process. It will also set the is_daemon flag
70           appropriately.
71
72           The %options argument remains for backwards compatibility, but it
73           is suggested that you use the attributes listed above instead.
74
75       daemon_detach (?%options)
76           This detaches the new child process from the terminal by doing the
77           following things.
78
79           The %options argument remains for backwards compatibility, but it
80           is suggested that you use the attributes listed above instead.
81
82           Becomes a session leader
83               This detaches the program from the controlling terminal, it is
84               accomplished by calling "POSIX::setsid".
85
86           Performing the double-fork
87               See below for information on how to change this part of the
88               process.
89
90           Changes the current working directory to "/"
91               This is standard daemon behavior, if you want a different
92               working directory then simply change it later in your daemons
93               code.
94
95           Clears the file creation mask.
96           Closes all open file descriptors.
97               See the dont_close_all_files attribute for information on how
98               to change this part of the process.
99
100           Reopen STDERR, STDOUT & STDIN to /dev/null
101               This behavior can be controlled slightly though the
102               "MX_DAEMON_STDERR" and "MX_DAEMON_STDOUT" environment
103               variables. It will look for a filename in either of these
104               variables and redirect "STDOUT" and/or "STDERR" to those files.
105               This is useful for debugging and/or testing purposes.
106
107               NOTE
108
109               If called from within the parent process (the "is_daemon" flag
110               is set to false), this method will simply return and do
111               nothing.
112
113           daemonize (?%options)
114               This will simply call "daemon_fork" followed by
115               "daemon_detach".
116
117               The %options argument remains for backwards compatibility, but
118               it is suggested that you use the attributes listed above
119               instead.
120
121           meta()
122               The "meta()" method from Class::MOP::Class
123

STUFF YOU SHOULD READ

125       Note about double fork
126           Taken from
127           <http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/66012> in
128           a comment entitled The second fork _is_ necessary by Jonathan
129           Bartlett, it is not the definitive statement on the issue, but it's
130           clear and well written enough so I decided to reproduce it here.
131
132             The first fork accomplishes two things - allow the shell to return,
133             and allow you to do a setsid().
134
135             The setsid() removes yourself from your controlling terminal. You
136             see, before, you were still listed as a job of your previous process,
137             and therefore the user might accidentally send you a signal. setsid()
138             gives you a new session, and removes the existing controlling terminal.
139
140             The problem is, you are now a session leader. As a session leader, if
141             you open a file descriptor that is a terminal, it will become your
142             controlling terminal (oops!). Therefore, the second fork makes you NOT
143             be a session leader. Only session leaders can acquire a controlling
144             terminal, so you can open up any file you wish without worrying that
145             it will make you a controlling terminal.
146
147             So - first fork - allow shell to return, and permit you to call setsid()
148
149             Second fork - prevent you from accidentally reacquiring a controlling
150             terminal.
151
152           That said, you don't always want this to be the behavior, so you
153           are free to specify otherwise using the no_double_fork attribute.
154
155       Note about zombies
156           Doing the double fork (see above) tends to get rid of your zombies
157           since by the time you have double forked your daemon process is
158           then owned by the init process. However, sometimes the double-fork
159           is more than you really need, and you want to keep your daemon
160           processes a little closer to you. In this case you have to watch
161           out for zombies, you can avoid then by just setting the
162           ignore_zombies attribute (see above).
163

ENVIRONMENT VARIABLES

165       These variables are best just used for debugging and/or testing, but
166       not used for actual logging. For that, you should reopen
167       "STDOUT"/"STDERR" on your own.
168
169       MX_DAEMON_STDOUT
170           A filename to redirect the daemon "STDOUT" to.
171
172       MX_DAEMON_STDERR
173           A filename to redirect the daemon "STDERR" to.
174

DEPENDENCIES

176       Moose::Role, POSIX
177

INCOMPATIBILITIES

SEE ALSO

180       Proc::Daemon
181
182       This code is based HEAVILY on Proc::Daemon, we originally depended on
183       it, but we needed some more flexibility, so instead we just stole the
184       code.
185

SUPPORT

187       Bugs may be submitted through the RT bug tracker
188       <https://rt.cpan.org/Public/Dist/Display.html?Name=MooseX-Daemonize>
189       (or bug-MooseX-Daemonize@rt.cpan.org <mailto:bug-MooseX-
190       Daemonize@rt.cpan.org>).
191
192       There is also a mailing list available for users of this distribution,
193       at <http://lists.perl.org/list/moose.html>.
194
195       There is also an irc channel available for users of this distribution,
196       at "#moose" on "irc.perl.org" <irc://irc.perl.org/#moose>.
197

AUTHORS

199       ·   Stevan Little <stevan.little@iinteractive.com>
200
201       ·   Chris Prather <chris@prather.org>
202
204       This software is copyright (c) 2007 by Chris Prather.
205
206       This is free software; you can redistribute it and/or modify it under
207       the same terms as the Perl 5 programming language system itself.
208
209       Portions heavily borrowed from Proc::Daemon which is copyright Earl
210       Hood.
211
212
213
214perl v5.32.0                      2020-07-28      MooseX::Daemonize::Core(3pm)
Impressum