Net::Server::PreFork - Net::Server personality

NAME SYNOPSIS DESCRIPTION SAMPLE CODE COMMAND LINE ARGUMENTS CONFIGURATION FILE PROCESS FLOW HOOKS HOT DEPLOY BUGS TO DO AUTHOR THANKS SEE ALSO

NAME

Net::Server::PreFork − Net::Server personality

SYNOPSIS

use base qw(Net::Server::PreFork);
sub process_request {
#...code...
}
__PACKAGE__−>run();

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−>new
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, finishes 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 accounting (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.

"$self−>cleanup_dead_child_hook( $child )"

This hook is called when a dead child is detected. A child is considered dead when the pid does no longer exist. This hook could be used to cleanup possible temporary files or locks left over by a dead child.

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.