Provided by: libevent-rpc-perl_1.08-2_all 
NAME
Event::RPC::Server - Simple API for event driven RPC servers
SYNOPSIS
use Event::RPC::Server;
use My::TestModule;
my $server = Event::RPC::Server->new (
#-- Required arguments
port => 8888,
classes => {
"My::TestModule" => {
new => "_constructor",
get_data => 1,
set_data => 1,
clone => "_object",
},
},
#-- Optional arguments
name => "Test server",
logger => Event::RPC::Logger->new(),
start_log_listener => 1,
ssl => 1
ssl_key_file => "server.key",
ssl_cert_file => "server.crt",
ssl_passwd_cb => sub { "topsecret" },
ssl_opts => { ... },
auth_required => 1,
auth_passwd_href => { $user => Event::RPC->crypt($user,$pass) },
auth_module => Your::Own::Auth::Module->new(...),
loop => Event::RPC::Loop::Event->new(),
host => "localhost",
load_modules => 1,
auto_reload_modules => 1,
connection_hook => sub { ... },
message_formats => [qw/ SERL CBOR JSON STOR /],
insecure_msg_fmt_ok => 1,
);
$server->set_max_packet_size(2*1024*1024*1024);
$server->start;
# and later from inside your server implementation
Event::RPC::Server->instance->stop;
DESCRIPTION
Use this module to add a simple to use RPC mechanism to your event driven server
application.
Just create an instance of the Event::RPC::Server class with a bunch of required settings.
Then enter the main event loop through it, or take control over the main loop on your own
if you like (refer to the MAINLOOP chapter for details).
General information about the architecture of Event::RPC driven applications is collected
in the Event::RPC manpage.
CONFIGURATION OPTIONS
All options described here may be passed to the new() constructor of Event::RPC::Server.
As well you may set or modify them using set_OPTION style mutators, but not after start()
or setup_listeners() was called! All options may be read using get_OPTION style
accessors.
REQUIRED OPTIONS
If you just pass the required options listed beyond you have a RPC server which listens to
a network port and allows everyone connecting to it to access a well defined list of
classes and methods resp. using the correspondent server objects.
There is no authentication or encryption active in this minimal configuration, so aware
that this may be a big security risk! Adding security is easy, refer to the chapters
about SSL and authentication.
These are the required options:
port
TCP port number of the RPC listener.
classes
This is a hash ref with the following structure:
classes => {
"Class1" => {
new => "_constructor",
simple_method => 1,
object_returner => "_object",
},
"Class2" => { ... },
...
},
Each class which should be accessible for clients needs to be listed here at the first
level, assigned a hash of methods allowed to be called. Event::RPC disuinguishes three
types of methods by classifying their return value:
Constructors
A constructor method creates a new object of the corresponding class and returns
it. You need to assign the string "_constructor" to the method entry to mark a
method as a constructor.
Singleton constructors
For singleton classes the method which returns the singleton instance should be
declared with "_singleton". This way the server takes care that references get
never destroyed on server side.
Simple methods
What's simple about these methods is their return value: it's a scalar, array,
hash or even any complex reference structure (Ok, not simple anymore ;), but in
particular it returns NO objects, because this needs to handled specially (see
below).
Declare simple methods by assigning 1 in the method declaration.
Object returners
Methods which return objects need to be declared by assigning "_object" to the
method name here. They're not bound to return just one scalar object reference and
may return an array or list reference with a bunch of objects as well.
SSL OPTIONS
The client/server protocol of Event::RPC is not encrypted by default, so everyone
listening on your network can read or even manipulate data. To prevent this efficiently
you can enable SSL encryption. Event::RPC uses the IO::Socket::SSL Perl module for this.
First you need to generate a server key and certificate for your server using the openssl
command which is part of the OpenSSL distribution, e.g. by issueing these commands (please
refer to the manpage of openssl for details - this is a very rough example, which works in
general, but probably you want to tweak some parameters):
% openssl genrsa -des3 -out server.key 1024
% openssl req -new -key server.key -out server.csr
% openssl x509 -req -days 3600 -in server.csr \
-signkey server.key -out server.crt
After executing these commands you have the following files
server.crt
server.key
server.csr
Event::RPC needs the first two of them to operate with SSL encryption.
To enable SSL encryption you need to pass the following options to the constructor:
ssl The ssl option needs to be set to 1.
ssl_key_file
This is the filename of the server.key you generated with the openssl command.
ssl_cert_file
This is the filename of the server.crt file you generated with the openssl command.
ssl_passwd_cb
Your server key is encrypted with a password you entered during the key creation
process described above. This callback must return it. Depending on how critical your
application is you probably must request the password from the user during server
startup or place it into a more or less secured file. For testing purposes you can
specify a simple anonymous sub here, which just returns the password, e.g.
ssl_passwd_cb => sub { return "topsecret" }
But note: having the password in plaintext in your program code is insecure!
ssl_opts
This optional parameter takes a hash reference of options passed to
IO::Socket::SSL->new(...) to have more control over the server SSL listener.
AUTHENTICATION OPTIONS
SSL encryption is fine, now it's really hard for an attacker to listen or modify your
network communication. But without any further configuration any user on your network is
able to connect to your server. To prevent this users resp. connections to your server
needs to be authenticated somehow.
Since version 0.87 Event::RPC has an API to delegate authentication tasks to a module,
which can be implemented outside Event::RPC. To be compatible with prior releases it
ships the module Event::RPC::AuthPasswdHash which implements the old behaviour
transparently.
This default implementation is a simple user/password based model. For now this controls
just the right to connect to your server, so knowing one valid user/password pair is
enough to access all exported methods of your server. Probably a more differentiated model
will be added later which allows granting access to a subset of exported methods only for
each user who is allowed to connect.
The following options control the authentication:
auth_required
Set this to 1 to enable authentication and nobody can connect your server until he
passes a valid user/password pair.
auth_passwd_href
If you like to use the builtin Event::RPC::AuthPasswdHash module simply set this
attribute. If you decide to use auth_module (explained beyound) it's not necessary.
auth_passwd_href is a hash of valid user/password pairs. The password stored here
needs to be encrypted using Perl's crypt() function, using the username as the salt.
Event::RPC has a convenience function for generating such a crypted password, although
it's currently just a 1:1 wrapper around Perl's builtin crypt() function, but probably
this changes someday, so better use this method:
$crypted_pass = Event::RPC->crypt($user, $pass);
This is a simple example of setting up a proper auth_passwd_href with two users:
auth_passwd_href => {
fred => Event::RPC->crypt("fred", $freds_password),
nick => Event::RPC->crypt("nick", $nicks_password),
},
auth_module
If you like to implement a more complex authentication method yourself you may set the
auth_module attribute to an instance of your class. For now your implementation just
needs to have this method:
$auth_module->check_credentials($user, $pass)
Aware that $pass is encrypted as explained above, so your original password needs to
by crypted using Event::RPC->crypt as well, at least for the comparison itself.
Note: you can use the authentication module without SSL but aware that an attacker
listening to the network connection will be able to grab the encrypted password token and
authenticate himself with it to the server (replay attack). Probably a more sophisticated
challenge/response mechanism will be added to Event::RPC to prevent this. But you
definitely should use SSL encryption in a critical environment anyway, which renders
grabbing the password from the net impossible.
LOGGING OPTIONS
Event::RPC has some logging abilities, primarily for debugging purposes. It uses a logger
for this, which is an object implementing the Event::RPC::Logger interface. The
documentation of Event::RPC::Logger describes this interface and Event::RPC's logging
facilities in general.
logger
To enable logging just pass such an Event::RPC::Logger object to the constructor.
start_log_listener
Additionally Event::RPC can start a log listener on the server's port number
incremented by 1. All clients connected to this port (e.g. by using telnet) get the
server's log output.
Note: currently the logging port supports neither SSL nor authentication, so be
careful enabling the log listener in critical environments.
MAINLOOP OPTIONS
Event::RPC derived it's name from the fact that it follows the event driven paradigm.
There are several toolkits for Perl which allow event driven software development.
Event::RPC has an abstraction layer for this and thus should be able to work with any
toolkit.
loop
This option takes an object of the loop abstraction layer you want to use. Currently
the following modules are implemented:
Event::RPC::Loop::AnyEvent Use the AnyEvent module
Event::RPC::Loop::Event Use the Event module
Event::RPC::Loop::Glib Use the Glib module
If loop isn't set, Event::RPC::Server tries all supported modules in a row and aborts
the program, if no module was found.
More modules will be added in the future. If you want to implement one just take a
look at the code in the modules above: it's really easy and I appreciate your patch.
The interface is roughly described in the documentation of Event::RPC::Loop.
If you use the Event::RPC->start() method as described in the SYNOPSIS Event::RPC will
enter the correspondent main loop for you. If you want to have full control over the main
loop, use this method to setup all necessary Event::RPC listeners:
$rpc_server->setup_listeners();
and manage the main loop stuff on your own.
MESSAGE FORMAT OPTIONS
Event::RPC supports different CPAN modules for data serialisation, named "message formats"
here:
SERL -- Sereal::Encoder, Sereal::Decoder
CBOR -- CBOR::XS
JSON -- JSON::XS
STOR -- Storable
Server and client negotiate automatically which format is best to use but you can
manipulate this behaviour with the following options:
message_formats
This takes an array of format identifiers from the list above. Event::RPC::Server will
only use / accept these formats.
insecure_msg_fmt_ok
The Storable module is known to be insecure. But for backward compatibility reasons
Event::RPC::Server accepts clients which can't offer anything but Storable. You can
prevent that by setting this option explicitly to 0. It's enabled by default.
MISCELLANEOUS OPTIONS
host
By default the network listeners are bound to all interfaces in the system. Use the
host option to bind to a specific interface, e.g. "localhost" if you efficiently want
to prevent network clients from accessing your server.
load_modules
Control whether the class module files should be loaded automatically when first
accesed by a client. This options defaults to true, for backward compatibility
reasons.
auto_reload_modules
If this option is set Event::RPC::Server will check on each method call if the
corresponding module changed on disk and reloads it automatically. Of course this has
an effect on performance, but it's very useful during development. You probably
shouldn't enable this in production environments.
connection_hook
This callback is called on each connection / disconnection with two arguments: the
Event::RPC::Connection object and a string containing either "connect" or "disconnect"
depending what's currently happening with this connection.
METHODS
The following methods are publically available:
Event::RPC::Server->instance
This returns the latest created Event::RPC::Server instance (usually you have only one
instance in one program).
$rpc_server->start
Start the mainloop of your Event::RPC::Server.
$rpc_server->stop
Stops the mainloop which usually means, that the server exits, as long you don't do
more sophisticated mainloop stuff by your own.
$rpc_server->setup_listeners
This method initializes all networking listeners needed for Event::RPC::Server to
work, using the configured loop module. Use this method if you don't use the start()
method but manage the mainloop on your own.
$rpc_server->log ( [$level,] $msg )
Convenience method for logging. It simply passes the arguments to the configured
logger's log() method.
$rpc_server->get_clients_connected
Returns the number of currently connected Event::RPC clients.
$rpc_server->get_log_clients_connected
Returns the number of currently connected logging clients.
$rpc_server->get_active_connection
This returns the currently active Event::RPC::Connection object representing the
connection resp. the client which currently requests method invocation. This is undef
if no client call is active.
$rpc_client->set_max_packet_size ( $bytes )
By default Event::RPC does not handle network packages which exceed 2 GB in size (was
4 MB with version 1.04 and earlier).
You can change this value using this method at any time, but 4 GB is the maximum. An
attempt of the server to send a bigger packet will be aborted and reported as an
exception on the client and logged as an error message on the server.
Note: you have to set the same value on client and server side!
$rpc_client->get_max_packet_size
Returns the currently active max packet size.
AUTHORS
Joern Reder <joern AT zyn.de>
COPYRIGHT AND LICENSE
Copyright (C) 2005-2015 by Joern Reder <joern AT zyn.de>.
This library is free software; you can redistribute it and/or modify it under the same
terms as Perl itself.