Net::Server::PreFork(3) User Contributed Perl Documentation Net::Server::PreFork(3)
NAME
Net::Server::PreFork - Net::Server personality
SYNOPSIS
use base qw(Net::Server::PreFork);
sub process_request {
#...code...
}
__PACKAGE__->run();
DESCRIPTION
Please read the pod on Net::Server and Net::Server::PreForkSimple first. This module is a personality, or extension, or sub class, of the
Net::Server::PreForkSimple class which is a sub class of Net::Server. See Net::Server::PreForkSimple.
This personality binds to one or more ports and then forks "min_servers" child process. The server will make sure that at any given time
there are "min_spare_servers" available to receive a client request, up to "max_servers". Each of these children will process up to
"max_requests" client connections. This type is good for a heavily hit site, and should scale well for most applications. (Multi port
accept is accomplished 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 and the Net::Server::PreForkSimple parent class,
Net::Server::PreFork contains several other configurable parameters. You really should also see Net::Server::PreForkSimple.
Key Value Default
min_servers d+ 5
min_spare_servers d+ 2
max_spare_servers d+ 10
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
check_for_waiting d+ 10
max_dequeue d+ undef
check_for_dequeue d+ undef
child_communication 1 undef
min_servers
The minimum number of servers to keep running.
min_spare_servers
The minimum number of servers to have waiting for requests. Minimum and maximum numbers should not be set to close to each other or
the server will fork and kill children too often.
max_spare_servers
The maximum number of servers to have waiting for requests. See min_spare_servers.
max_servers
The maximum number of child servers to start. This does not apply to dequeue processes.
check_for_waiting
Seconds to wait before checking to see if we can kill off some waiting servers.
check_for_spawn
Seconds between checking to see if we need to spawn more children
min_child_ttl
Minimum number of seconds between starting children and killing a child process
child_communication
Enable child communication to parent via unix sockets. If set to true, will let children write to the socket contained in
$self->{'server'}->{'parent_sock'}. The parent will be notified through child_is_talking_hook where the first argument is the socket
to the child. The child's socket is stored in $self->{'server'}->{'children'}->{$child_pid}->{'sock'}.
serialize
See the documentation under Net::Server::PreForkSimple.
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
min_servers 20
max_servers 80
min_spare_servers 10
min_spare_servers 15
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
### enable child communication ?
# child_communication
#-------------- file test.conf --------------
PROCESS FLOW
Process flow follows Net::Server until the loop phase. At this point "min_servers" are forked and wait for connections. When a child
accepts a connection, finishs processing a client, or exits, it relays that information to the parent, which keeps track and makes sure
there are enough children to fulfill "min_servers", "min_spare_servers", "max_spare_servers", and "max_servers".
HOOKS
The PreFork server has the following hooks in addition to the hooks provided by PreForkSimple. See Net::Server::PreForkSimple.
"$self->run_n_children_hook()"
This hook occurs at the top of run_n_children which is called each time the server goes to start more child processes. This gives the
parent to do a little of its own accountting (as desired). Idea for this hook came from James FitzGibbon.
"$self->parent_read_hook()"
This hook occurs any time that the parent reads information from the child. The line from the child is sent as an argument.
"$self->child_is_talking_hook()"
This hook occurs if child_communication is true and the child has written to $self->{'server'}->{'parent_sock'}. The first argument
will be the open socket to the child.
"$self->idle_loop_hook()"
This hook is called in every pass through the main process wait loop, every "check_for_waiting" seconds. The first argument is a
reference to an array of file descriptors that can be read at the moment.
HOT DEPLOY
Since version 2.000, the PreFork server has accepted the TTIN and TTOU signals. When a TTIN is received, the min and max_servers are
increased by 1. If a TTOU signal is received the min max_servers are 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
SEE ALSO
Please see also Net::Server::Fork, Net::Server::INET, Net::Server::PreForkSimple, Net::Server::MultiType, Net::Server::Single
Net::Server::SIG Net::Server::Daemonize Net::Server::Proto
perl v5.18.2 2013-01-09 Net::Server::PreFork(3)