Ubuntu Manpage: Net::Server::PreForkSimple

Provided by: libnet-server-perl_2.007-3_all

NAME

       Net::Server::PreForkSimple - Net::Server personality

SYNOPSIS

           use base qw(Net::Server::PreForkSimple);

           sub process_request {
               #...code...
           }

           __PACKAGE__->run();

DESCRIPTION

       Please read the pod on Net::Server first.  This module is a personality, or extension, or
       sub class, of the Net::Server module.

       This personality binds to one or more ports and then forks "max_servers" child processes.
       The server will make sure that at any given time there are always "max_servers" available
       to receive a client request.  Each of these children will process up to "max_requests"
       client connections.  This type is good for a heavily hit site that can keep "max_servers"
       processes dedicated to the serving.  (Multi port accept defaults to using flock to
       serialize the children).

       At this time, it does not appear that this module will pass tests on Win32 systems.  Any
       ideas or patches for making the tests pass would be welcome.

SAMPLE CODE

       Please see the sample listed in Net::Server.

COMMAND LINE ARGUMENTS

In addition to the command line arguments of the Net::Server base class,
Net::Server::PreFork contains several other configurable parameters.

Key Value Default
max_servers \d+ 50
max_requests \d+ 1000

serialize (flock|semaphore
|pipe|none) undef
# serialize defaults to flock on multi_port or on Solaris
lock_file "filename" File::Temp::tempfile or POSIX::tmpnam

check_for_dead \d+ 30

max_dequeue \d+ undef
check_for_dequeue \d+ undef

max_servers
The maximum number of child servers to start and maintain. This does not apply to
dequeue processes.

max_requests
The number of client connections to receive before a child terminates.

serialize
Determines whether the server serializes child connections. Options are undef, flock,
semaphore, pipe, or none. Default is undef. On multi_port servers or on servers
running on Solaris, the default is flock. The flock option uses blocking exclusive
flock on the file specified in lock_file (see below). The semaphore option uses
IPC::Semaphore (thanks to Bennett Todd) for giving some sample code. The pipe option
reads on a pipe to choose the next. the flock option should be the most bulletproof
while the pipe option should be the most portable. (Flock is able to relinquish the
block if the process dies between accept on the socket and reading of the client
connection - semaphore and pipe do not). An option of none will not perform any
serialization. If "none" is passed and there are multiple ports then a the default
serialization will be used instead of "none."

lock_file
Filename to use in flock serialized accept in order to serialize the accept sequence
between the children. This will default to a generated temporary filename. If
default value is used the lock_file will be removed when the server closes.

check_for_dead
Seconds to wait before checking to see if a child died without letting the parent
know.

max_dequeue
The maximum number of dequeue processes to start. If a value of zero or undef is
given, no dequeue processes will be started. The number of running dequeue processes
will be checked by the check_for_dead variable.

check_for_dequeue
Seconds to wait before forking off a dequeue process. The run_dequeue hook must be
defined when using this setting. It is intended to use the dequeue process to take
care of items such as mail queues. If a value of undef is given, no dequeue processes
will be started.

CONFIGURATION FILE

       "Net::Server::PreFork" allows for the use of a configuration file to read in server
       parameters.  The format of this conf file is simple key value pairs.  Comments and white
       space are ignored.

           #-------------- file test.conf --------------

           ### server information
           max_servers   80

           max_requests  1000

           ### user and group to become
           user        somebody
           group       everybody

           ### logging ?
           log_file    /var/log/server.log
           log_level   3
           pid_file    /tmp/server.pid

           ### access control
           allow       .+\.(net|com)
           allow       domain\.com
           deny        a.+

           ### background the process?
           background  1

           ### ports to bind
           host        127.0.0.1
           port        localhost:20204
           port        20205

           ### reverse lookups ?
           # reverse_lookups on

           #-------------- file test.conf --------------

PROCESS FLOW

       Process flow follows Net::Server until the loop phase.  At this point "max_servers" are
       forked and wait for connections.  When a child accepts a connection, finishes processing a
       client, or exits, it relays that information to the parent, which keeps track and makes
       sure there are always "max_servers" running.

HOOKS

       The PreForkSimple server has the following hooks in addition to the hooks provided by the
       Net::Server base class.  See Net::Server

       "$self->run_n_children_hook()"
           This hook occurs at the top of run_n_children which is called each time the server
           goes to start more child processes.  This gives the parent to do a little of its own
           accounting (as desired).  Idea for this hook came from James FitzGibbon.

       "$self->child_init_hook()"
           This hook takes place immediately after the child process forks from the parent and
           before the child begins accepting connections.  It is intended for any additional
           chrooting or other security measures.  It is suggested that all perl modules be used
           by this point, so that the most shared memory possible is used.

       "$self->child_finish_hook()"
           This hook takes place immediately before the child tells the parent that it is
           exiting.  It is intended for saving out logged information or other general cleanup.

       "$self->run_dequeue()"
           This hook only gets called in conjunction with the check_for_dequeue setting.

       "$self->idle_loop_hook()"
           This hook is called in every pass through the main process wait loop.

HOT DEPLOY

       Since version 2.000, the PreForkSimple server has accepted the TTIN and TTOU signals.
       When a TTIN is received, the max_servers is increased by 1.  If a TTOU signal is received
       the max_servers is decreased by 1.  This allows for adjusting the number of handling
       processes without having to restart the server.

BUGS

       Tests don't seem to work on Win32.  Any ideas or patches would be welcome.

TO DO

       See Net::Server

AUTHOR

       Paul T. Seamons paul@seamons.com

THANKS

       See Net::Server