man Event::RPC::Client (3): Client API to connect to Event::RPC Servers

SYNOPSIS

use Event::RPC::Client;
my $rpc_client = Event::RPC::Client->new (
#-- Required arguments
host => "localhost",
port => 5555,

#-- Optional arguments
classes => [ "Event::RPC::Test" ],
class_map => { "Event::RPC::Test" => "My::Event::RPC::Test" },
ssl => 1,
ssl_ca_file => "some/ca.crt",
ssl_ca_path => "some/ca/dir",
ssl_opts => { SSL_verifycn_name => 'server-hostname' },
timeout => 10,
auth_user => "fred",
auth_pass => Event::RPC->crypt("fred",$password),
insecure_msg_fmt_ok => 1,
error_cb => sub {
my ($client, $error) = @_;
print "An RPC error occured: $error\n";
$client->disconnect;
exit;
},
);
$rpc_client->set_max_packet_size(2*1024*1024*1024);
$rpc_client->connect;

#-- And now use classes and methods to which the
#-- server allows access via RPC, here My::TestModule
#-- from the Event::RPC::Server manpage SYNPOSIS.
my $obj = My::TestModule->new( data => "foobar" );
print "obj says hello: ".$obj->hello."\n";
$obj->set_data("new foobar");
print "updated data: ".$obj->get_data."\n";
$rpc_client->disconnect;

DESCRIPTION

Use this module to write clients accessing objects and methods exported by a Event::RPC driven server.

Just connect to the server over the network, optionally with SSL and user authentication, and then simply use the exported classes and methods like having them locally in the client.

General information about the architecture of Event::RPC driven applications is collected in the Event::RPC manpage.

The following documentation describes the client connection options in detail.

CONFIGURATION OPTIONS

You need to specify at least the server hostname and TCP port to connect a Event::RPC server instance. If the server requires a SSL connection or user authentication you need to supply the corresponding options as well, otherwise connecting will fail.

All options described here may be passed to the new() constructor of Event::RPC::Client. As well you may set or modify them using set_OPTION style mutators, but not after connect() was called! All options may be read using get_OPTION style accessors.

REQUIRED OPTIONS

These are necessary to connect the server:

server: This is the hostname of the server running Event::RPC::Server. Use a IP address or DNS name here.
port: This is the TCP port the server is listening to.

NETWORK OPTIONS

timeout: Specify a timeout (in seconds), which is applied when connecting the server.

CLASS IMPORT OPTION

classes

This is reference to a list of classes which should be imported into the client. You get a warning if you request a class which is not exported by the server.

By default all server classes are imported. Use this feature if your server exports a huge list of classes, but your client doesn't need all of them. This saves memory in the client and connect performance increases.

class_map

Optionally you can map the class names from the server to a different name on the local client using the class_map hash.

This is necessary if you like to use the same classes locally and remotely. Imported classes from the server are by default registered under the same name on the client, so this conflicts with local classes named identically.

On the client you access the remote classes under the name assigned in the class map. For example with this map

  class_map => { "Event::ExecFlow::Job" => "_srv::Event::ExecFlow::Job" }

you need to write this on the client, if you like to create an object remotely on the server:

  my $server_job = _srv::Event::ExecFlow::Job->new ( ... );

and this to create an object on the client:

  my $client_job = Event::ExecFlow::Job->new ( ... );

The server knows nothing of the renaming on client side, so you still write this on the server to create objects there:

  my $job = Event::ExecFlow::Job->new ( ... );

SSL OPTIONS

If the server accepts only SSL connections you need to enable ssl here in the client as well. By default the SSL connection will be established without any peer verification, which makes Man-in-the-Middle attacks possible. If you want to prevent that, you need to set either ssl_ca_file or ssl_ca_path option.

ssl: Set this option to 1 to encrypt the network connection using SSL.
ssl_ca_file: Path to the the Certificate Authority's certificate file (ca.crt), your server key was signed with.
ssl_ca_path: Path of a directory containing several trusted certificates with a proper index. Please refer to the OpenSSL documentation for details about setting up such a directory.
ssl_opts: This optional parameter takes a hash reference of options passed to IO::Socket::SSL->new(...) to have more control over the SSL connection. For example you can set the 'SSL_verifycn_name' here if the server certificate common name doesn't match to the hostname you use to resolve the server IP or use you have to use a static server IP address or something like that.

AUTHENTICATION OPTIONS

If the server requires user authentication you need to set the following options:

auth_user

A valid username.

auth_pass

The corresponding password, 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 wrapper around Perl's builtin crypt() function, but probably this changes someday, so better use this method:

  $crypted_pass = Event::RPC->crypt($user, $pass);

If the passed credentials are invalid the Event::RPC::Client->connect() method throws a correspondent exception.

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. The server sends a list of supported formats to the client which takes the first one which is available.

For the client there is one option to influence this format negotiation mechanism:

insecure_msg_fmt_ok: The Storable module is known to be insecure, so it should be taken as the last option only. By default the Client would do so. You can prevent that by setting this option explicitly to 0. It's enabled by default. Most likely the connection will fail in that case, because the server only will offer Storable if no other serialiser is available.

ERROR HANDLING

Any exceptions thrown on the server during execution of a remote method will result in a corresponding exception on the client. So you can use normal exception handling with eval {} when executing remote methods.

But besides this the network connection between your client and the server may break at any time. This raises an exception as well, but you can override this behaviour with the following attribute:

error_cb

This subroutine is called if any error occurs in the network communication between the client and the server. The actual Event::RPC::Client object and an error string are passed as arguments.

This is no generic exception handler for exceptions thrown from the executed methods on the server! If you like to catch such exceptions you need to put an eval {} around your method calls, as you would do for local method calls.

If you don't specify an error_cb an exception is thrown instead.

METHODS

$rpc_client->connect

This establishes the configured connection to the server. An exception is thrown if something goes wrong, e.g. server not available, credentials are invalid or something like this.

$rpc_client->disconnect

Closes the connection to the server. You may omit explicit disconnecting since it's done automatically once the Event::RPC::Client object gets destroyed.

$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.

READY ONLY ATTRIBUTES

$rpc_client->get_server_version: Returns the Event::RPC version number of the server after connecting.
$rpc_client->get_server_protocol: Returns the Event::RPC protocol number of the server after connecting.
$rpc_client->get_client_version: Returns the Event::RPC version number of the client.
$rpc_client->get_client_protocol: Returns the Event::RPC protocol number of the client.

AUTHORS

  Jo.rn Reder <joern AT zyn.de>

COPYRIGHT AND LICENSE

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