Proc::Daemon::Prefork - Create preforking, autoreloading daemon


This document describes version 0.711 of Proc::Daemon::Prefork (from Perl distribution Proc-Daemon-Prefork), released on 2019-07-08.




  • require_root => BOOL (default 0)

    If true, bails out if not running as root.

  • error_log_path => STR (required if daemonize=1)

    Or, alternatively, specify error_log_handle instead.

  • error_log_handle => OBJ

    An alternative to specifying error_log_path, to allow logging to a filehandle-like object, e.g. tied filehandle, instead of to a regular file.

  • access_log_path => STR (required if daemonize=1)

    Or, alternatively, specify access_log_handle instead.

  • access_log_handle => OBJ

    An alternative to specifying access_log_path, to allow logging to a filehandle-like object, e.g. tied filehandle, instead of to a regular file.

  • pid_path => STR (required if daemonize=1)

  • scoreboard_path => STR (default none)

    If not set, no scoreboard file will be created/updated. Scoreboard file is used to communicate between parent and child processes. Autoadjustment of number of processes, for example, requires this (see max_children for more details).

  • daemonize => BOOL (default 1)

  • prefork => INT (default 3, 0 means a nonforking/single-threaded daemon)

    This is like the StartServers setting in Apache webserver (the prefork MPM), the number of children processes to prefork.

  • max_children => INT (default 150)

    This is like the MaxClients setting in Apache webserver. Initially the number of children spawned will follow the 'prefork' setting. If while serving requests, all children are busy, parent will automatically increase the number of children gradually until 'max_children'. If afterwards these children are idle, they will be gradually killed off until there are 'prefork' number of children again.

    Note that for this to function, scoreboard_path must be defined since the parent needs to communicate with children.

  • auto_reload_check_every => INT (default undef, meaning never)

    In seconds.

  • auto_reload_handler => CODEREF (required if auto_reload_check_every is set)

  • before_daemonize => CODEREF (default none)

    Run code before daemonizing. If code returns false, will abort daemonizing and exit with non-zero status (1).

  • after_init => CODEREF (default none)

    Run after the daemon initializes itself (daemonizes, writes PID file, etc), before spawning children. You usually bind to sockets here (if your daemon is a network server).

  • on_client_disconnect => CODEREF

    Do something after socket connection between client and child process is closed. This requires scoreboard (see scoreboard_path argument) to record all the children's PIDs, and also the "netstat" command and Parse::Netstat module to check for connections.

    This can be used, for example, to kill child process (cancel job) on disconnect.

    Will be called for each child server being disconnected. Code will receive a hash containing: pid, proto, local_host, local_port, foreign_host, foreign_port.

    Note that monitoring connections is done every few seconds by the parent process, so this code will not be run immediately after closing of connection.

    Currently only works for TCP connections and not Unix connections, due to lack of information provided by "netstat" for Unix connections.

  • main_loop* => CODEREF

    Run at the beginning of each child process. This is the main loop for your daemon. You usually do this in your main loop routine:

     for(my $i=1; $i<=$MAX_REQUESTS_PER_CHILD; $i++) {
         # accept loop, or process job loop
  • before_shutdown => CODEREF (optional)

    Run before killing children and shutting down.


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Source repository is at


Please report any bugs or feature requests on the bugtracker website

When submitting a bug or request, please include a test-file or a patch to an existing test-file that illustrates the bug or desired feature.


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This software is copyright (c) 2019, 2014 by

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.