NAME RPC::Serialized - Subroutine calls over the network using common serialization VERSION This document refers to version 0.0602 of RPC::Serialized SYNOPSIS # for the RPC server... # choose one of the supplied server types (NetServer is Net::Server) use RPC::Serialized::Server::NetServer; my $s = RPC::Serialized::Server::NetServer->new; $s->run; # server process is now looping and waiting for RPC (like Apache prefork) # the default port number for Net::Server is 20203 # and so for the RPC client... use RPC::Serialized::Client::INET; my $c = RPC::Serialized::Client::INET->new({ io_socket_inet => {PeerPort => 20203}, }); my $result = $c->remote_sub_name(qw/ some data /); # remote_sub_name gets mapped to an invocation on the RPC server # it's best to wrap this in an eval{} block DESCRIPTION This module allows you to call a Perl subroutine in another process, possibly on another machine, using a very simple and extensible interface which ties together the features of other good modules from the CPAN. There are lots of uses for RPC (remote procedure calls), so here are a couple of examples just to give you an idea: Priveledge separation If you have a web interface which is used to control a critical backend system, perhaps a key database or the settings on a firewall, you can use RPC to prevent security flaws on the web service from affecting the backend service. Only procedure calls which are permitted will be accepted from the web host, and it also offers a nice interface separation for your systems. File or data access To avoid sharing of filesystems over the network (SAMBA, NFS, etc), you can provide a restricted interface using RPC. For example a web service to search log files could send an RPC request with the search string to the log server, and display the results. There would be no need to run a network filesystem. What makes this module different from another RPC implementation? Data Serialization This module uses Data::Serializer to construct its "on the wire" protocol. This means any Perl data structure can be sent or received, even Perl code itself in the case of some of the serialization modules (e.g. YAML supports this). You can also encrypt and compress data; all options to Data::Serializer are easily available through the configuration of this module. Simple deployment Each remote procedure is simply a perl subroutine in a module which is loaded by the server. You can let the server autoload everything as it is called, or specify each "handler" subroutine individually (or combine both!). Adding and modifying the available handlers is simple, meaning you think less about the RPC subsystem and more about your code and service provision. Flexible configuration All the modules used by "RPC::Serialized" can be fully configured as you wish, from one configuration file, or via options to "new()". You saw an example of this in the "SYNOPSIS" section, above, for the IO::Socket::INET module. The following sections take you through setting up an RPC server and client. GENERAL CONFIGURATION Both the client and server parts of this module share the same configuration system. There is a file, RPC::Serialized::Config, which contains the basic defaults suitable for most situations. Then, you can also specify the name of a configuration file as a parameter to any call to "new()". Finally, a hash reference of options can be supplied directly to any call to "new()". Let's go through these cases by example: # this is for a server, but the example applies equally to a client use RPC::Serialized::Server::NetServer; # no configuration at all - use the built in defaults $s = RPC::Serialized::Server::NetServer->new; If you are happy with the settings in the source code of RPC::Serialized::Config, then no options are required. In the case of some types of server and client this is enough to get you going. # load a configuration file, using Config::Any $s = RPC::Serialized::Server::NetServer->new('/path/to/config/file'); Alternatively, specify a file with configuration. We use Config::Any to load the file, and so it should contain a data structure in one of the formats supported by that module. *Tip*: make sure there is a filename suffix, e.g. ".yml", to help "Config::Any" load the data. For details of the required structure of that data, read on... # pass some options directly $s = RPC::Serialized::Server::NetServer->new({ net_server => {log_file => undef, port => 5233}, rpc_serialized => {handler_namespaces => 'RPC::Serialized::Handler'}, }); You can pass a hash reference to "new()". Each key in this hash is the name of a module to configure. The module names are converted to lowercase, and the "::" separator is replaced by an underscore. In the example above we are providing some options to Net::Server and this module, RPC::Serialized. The value of each key is another anonymous hash, this time with any options as specified by that module's own manual page. Of course, this only works for modules which use key/value options themselves, but thankfully that is the case for each module used by "RPC::Serialized". Remember, in all of the examples in this manual page which show passing configuration settings to "new()", you can also achieve the same thing using a configuration file by passing its name to "new()" instead. As a final note on this topic, you can provide both a configuration filename, and an hash reference of options to the "new()" call. In fact, whatever and however many of these you provide, they will be read in with the later ones taking prescedent. SETTING UP A SERVER You do not have to know too much about internet servers to use this module. As well as providing a standard TCP and UDP server, there are also UNIX socket and Standard Input/Output servers that you might use for communicating with clients on the same host system. In the main, we are dealing with a UNIX world here, so most of the description will make assumptions about that. If you get this module running on Windows, please let the author know! A small perl script which starts the server running is all you need. This can be copied verbatim from the "SYNOPSIS" section above. For guidance on providing configuration to the server, see "GENERAL CONFIGURATION", above. When running a server process, it can either stay in the foreground, or detach from your shell. The default is to stay in the foreground, for two reasons. First, when you are developing you probably want to start the server and see what is happening on "STDERR". Second, many people use Dan Bernstein's "daemontools" package to manage persistent servers, and this requires a process which does not detach from its parent process. If you are using the "NetServer" server, then it is easy to make it detach: $s = RPC::Serialized::Server::NetServer->new({ net_server => { background => 1, setsid => 1 }, }); To stop the server you will then have to issue a kill to the detached process. There is a handful of alternative servers shipped with this module. For more details, please see the manual pages for each of them: RPC::Serialized::Server::NetServer This is a full-blown pre-forking internet server, with many many good features. You will have to install the Net::Server Perl module and dependencies to use this server. It supports TCP and UDP INET sockets, as well as UNIX domain sockets. RPC::Serialized::Server::STDIO This is a very simple server which processes one request at a time, accepting data on Standard Input and sending responses to Standard Output. RPC::Serialized::Server::UCSPI::TCP If you use Dan Bernstein's "tcpserver" (a.k.a. "ucspi-tcp") then this is the option for you. It is based upon the "STDIO" server, above, and is designed to be fired up by "tcpserver" whenever an incoming connection is handled. There is an example script for this in the Perl distribution for this module. RPC::Serialized::Server::UCSPI::IPC This is similar to the option above, but for UNIX (i.e. local filesystem) sockets rather than INET sockets. It is designed for "ucspi-ipc", producted by *SuperScript Technology, Inc.*, and you can find more details by searching on *Google*. How the server works Each RPC message which comes in "over the wire" is really just a Perl data structure, a hash. There is a "CALL" key, which has the name of the RPC method to invoke, and some "ARGS" to pass to it as arguments. The server looks at the CALL and tries to load and execute the handler which maps to that CALL. If it fails it raises an Exception, and fires that back to the client. If the invocation is successful, then the RESPONSE is sent back to the client, again in a Perl data structure. It is all quite elegant and simple (i.e. not my design, see "AUTHOR" below for the acknowledgement!). On the wire, if we switch off most of the Data::Serializer magic and set the Serializer to YAML, then it looks like this: --- CALL: localtime ARGS: [] ... --- RESPONSE: Sun Jul 8 21:57:28 2007 ... Note that "..." is the record separator which tells the server when it can process the incoming request. In this example, the CALL was for a method called "localtime", and there were no arguments so I passed an empty list. The RESPONSE was just the scalar output of Perl's "localtime" function. You might find it interesting to note that, inside of "RPC::Serialized", the methods used to send and receive data at the client and server *are identical*. In the example above, I entered the YAML document and trailing "..." to make the method call, and the server responded with another YAML document and "..." record terminator. Using one of the "RPC::Serialized::Client" family, it would look just the same. How to write RPC Handlers First, know that there are three example handlers included in this distribution, so you can just go and look at them if you prefer reading code to documentation! See the modules under "RPC::Serialized::Handler::". So you might have guessed that the first step is to choose your package name for the handler. Each package contains one handler, or put another way, each handler lives in its own package. You can either have the handler's name be derived from the package's name, or set it manually. Using the "localtime" example from above, this is what the handler looks like: package RPC::Serialized::Handler::Localtime; use strict; use warnings FATAL => 'all'; use base 'RPC::Serialized::Handler'; sub invoke { my $self = shift; my $time = shift; $time = time unless defined $time; return scalar localtime($time); } 1; There is a "magic" method in the package, called "invoke()", and it is this which is called by the RPC server to handle the incoming request. By default all the servers will take the name of the requested method CALL, convert underscores to "::" separators, convert initial letters to uppercase, and try to load a module in the "RPC::Serialized::Handler::" namespace. For example, if I called the "$c->frobnits_goo" handler from a client, the server would try to load a package called "RPC::Serialized::Handler::Frobnits::Goo" and then call the method within that. Alternatively you can see the "OPTIONS FOR THIS MODULE" section below to change that default namespace, or have your own mappings between client calls and loaded handler packages (or a mixture of both). You should expect all arguments passed to your "invoke()" method to be in a plain perl list (i.e. @_); items in the list may be references to complex data structures. You should return a single scalar value from that method, and nothing else. The scalar value can, however, be a reference to an arbitrarily complex data structure. SETTING UP A CLIENT As with the server, you don't need to know a lot about how networked services operate in order to set up the client. However you probably do need to know where your server is listening, to make contact with it! Therefore, you will need to use the client which corresponds to your server. Please read the manual page for the appropriate module: RPC::Serialized::Client::INET Use this client package to communicate with either a "NetServer" server, or the "UCSPI/TCP" server. RPC::Serialized::Client::UNIX This client will make UNIX domain socket (i.e. local filesystem) connections to the "NetServer" or "UCSPI/IPC" servers. RPC::Serialized::Client::STDIO For testing purposes you can use this client, which communicates on Standard Input and Standard Output. Alternatively, use this package as a base to implement a new kind of client. The basis of the client set-up is given in "SYNOPSIS", above, but we will show another example here for completeness: #!/usr/bin/perl use strict; use warnings FATAL => 'all'; use Readonly; use RPC::Serialized::Client::UNIX; Readonly my $SOCKET => '/var/run/rpc-serialized-example.socket'; my $c = RPC::Serialized::Client::UNIX->new({ io_socket_unix => { Peer => $SOCKET } }); eval { my $response = $c->echo(qw/ a b c d /); print "echo: " . join( ":", @$res ) . "\n"; }; warn "$@\n" if $@; eval { my $now = $c->localtime; print "Localtime on the server is: $now\n"; }; warn "$@\n" if $@; The above code uses the UNIX domain socket client to contact a server which is listening on the file mentioned in $SOCKET. Once the client object is set up, we can make a call to any method we wish on the remote server, just by specifying its name. Here, we call the "echo" and the "localtime" handlers. For each call, you should specify the arguments as a plain perl list, although that list can include references to complex data structures. There is a single (scalar) return value from each call you make, although again this may be a reference to a data structure if you wish. This example also shows how you should use "eval{}" constructs around the RPC calls. This is good practice for most network programming, as all kinds of things can go wrong. See the section "ERROR HANDLING" below for more information. Timeouts You should be aware that "RPC::Serialized" operates timeouts on all handler calls. By default, you get 30 seconds to make your request (i.e. make the call and pass any data to the server), another 30 seconds for the server to handle the call, and 30 seconds to transfer the response back to your client. If any of this fails or times out, an exception will be raised and passed back to you if possible. Exceptions can be passed through RPC, but you don't need to know about how that works, only that you should be prepared to handle "die" using "eval". To alter the timeout setting, see the next section "OPTIONS FOR THIS MODULE". To see examples of the "eval" construct see "ERROR HANDLING", below. OPTIONS FOR THIS MODULE There is actually only a small number of options for this module, as most of the heavy lifting within is done by other modules on the CPAN. In particular, we use Data::Serializer, and there is a section below which explains how to customize your serializer set-up. Options are passed to the "new()" method in a hash reference. To see how this is done, take a look at the "GENERAL CONFIGURATION" or "SYNOPSIS" sections above, although here is a quick example: my $s = RPC::Serialized::Server::NetServer->new({ rpc_serialized => { timeout => 15, trace => 1 }, }); "handler_namespaces" As explained above in "How the server works", the server will try to auto-load the handler for a call, based on some naming conventions. This value sets the Perl package namespaces which are searched. You can set this either to a scalar string, the name of a single namespace, or an array reference containing a list of such namespaces. The default setting is "RPC::Serialized::Handler", into which we supply the "echo", "localtime", and "sleep" handlers as examples. Setting this value to an array reference containing an empty list will disable auto-loading. "handlers" An alternative to "handler_namespaces", this value allows you to map individual CALLs to a given package name. In this way you can alias or alter the "published" name of handlers, or restrict calls. It can be used in addition to "handler_namespaces", but will take priority where both can be used to invoke an RPC handler. Set this value to an anonymous hash, where keys are calls made by the client (e.g. "echo") and values are package names containing the handler (e.g. "RPC::Serialized::Handler::Echo"). No handlers are specified by default. "timeout" This is a scalar value which sets how long "RPC::Serializer" servers wait before timing out their connections. As explained above, it is used when receiving an RPC call, when dispatching to the handler of that call, and when replying to the client. Each phase is given the "timeout" in seconds to do its work. The default value is 30 seconds. "trace" This is a boolean (scalar) which sets whether logging of the content of RPC traffic is made using UNIX syslog. For more details see the section "SERVER LOGGING", below. If set to a true value, logging will be enabled. The default value is false. "debug" This is a boolean (scalar) which disables the "RPC::Serializer" magic, meaning just the raw serialized data structures are sent between client and server. Normally, "RPC::Serializer" will perform compression, encryption, ASCII-armoring and hashing of the data it sends, if so configured. If set to a true value, "debug" prevents this. It can be very useful when combined with the "STDIO" client and server, to test operations, as you can type CALLs in by hand at the console. The default value is false. CONFIGURING Data::Serializer The defaults for Data::Serializer, which is used to encode and decode your method calls and responses, are quite sane so you can safely leave this alone. However you might prefer to override this and use a particular serialization format, or enable encryption, and this is quite straightforward to do. Passing a hash of options within the call to "new()" at either the client or server will do this, like so: my $c = RPC::Serialized::Client::STDIO->new({ data_serializer => { serializer => 'YAML::Syck', encoding => 'b64' }, }); The only option which you cannot alter is "portable", and this is forced to true, meaning that "Data::Serializer" will ASCII-armor the a data structure (i.e. encode it in hexadecimal or base64). Of course, if you have enabled the "debug" option to "RPC::Serialized" then "portable" is ignored. In most cases, the "Data::Serializer" module at the RPC server will auto-detect the settings used, and reply with a packet with the same settings. Where this might not work is in two cases: First make sure that the serializer used on the client is installed on the server. Second, make sure any keys and modules used for encryption on the client are available on the server. With a standard install of "RPC::Serialized" there should be no concern here, as it uses only core Perl modules, and encryption is not enabled. For further details please see the Data::Serializer manual page. CONFIGURING Net::Server The Net::Server binding shipped with this module has some defaults set, although none are enforced so you can override all options to that module. The chosen *personality* is "PreFork". If you want to use something else just copy the bundled binding module ("RPC::Serialized::Server::NetServer") and modify as appropriate. Default settings which differ from those in the native "Net::Server" are as follows: "log_level" is set to 4 "syslog_facility" is set to "local1" "background" is set to "undef" "setsid" is set to "undef" This means that logging goes to STDERR from the parent server, but to send it to Syslog instead just do the following (after reading the Net::Server manual page): my $s = RPC::Serialized::Server::NetServer->new({ net_server => { log_file => 'Sys::Syslog' }, }); In addition the server does not fork or detach from the shell and go into the background. For further details please see the Net::Server manual page. AUTHORIZATION The system from which "RPC::Serialized" derives supports user-based authorization based on a calling username, the called handler, and the arguments passed to that handler. In addition, "Net::Server" supports IP-based access control lists. Both of these systems are available although by default disabled. Looking in the examples folder with this distribution you should find some sample ACLs for "RPC::Serialized". You can also consult the Net::Server manual page for its options. For the time being the authorization is not documented here, but it is hoped this will be remedied before too long! If you want help with authorization configuration, feel free to email the module author. SERVER LOGGING If you have enabled RPC server logging, using the "trace" option to "new()", then output is sent via UNIX Syslog. The server will write out a serialized dump of the data sent and received, using whichever serializer you have set the server to use. This might not be the same serializer used in the transaction, however, as explained in the section "CONFIGURING Data::Serializer", above. You will see the CALL, ARGS, RESPONSE and any EXCEPTIONs raised, in the log. Logging uses the excellent Log::Dispatch module from CPAN, with its "Syslog" personality. The default settings are as follows: "name" is set to "rpc-serialized" "min_level" is set to "info" "facility" is set to "local0" "callbacks" is set to add a newline to each log message You can override these settings in the configuration file, or the call to "new()", like this: my $s = RPC::Serialized::Server::STDIO->new({ log_dispatch_syslog => { facility => 'local7' }, }); Log messages will be dispatched to your syslog subsystem at the level set in "min_level". Note that the hash key used is "log_dispatch_syslog", as above. ERROR HANDLING This module makes use of Exception::Class when it needs to raise a critical error, but don't fret if this makes no sense to you. The essential concept is that calls to this module might die, and you need to be able to deal with that. The usual way is to wrap calls in an "eval{}" block to trap errors, like so: eval { my $now = $c->localtime; print "Localtime on the server is: $now\n"; }; warn "Remote procedure call failed: $@\n" if $@; A nifty part of this module (courtesy of the original authors of the code) is that an exception can be raised in the server and delivered to the client. The exceptions are "RPC::Serialized::X" objects, derived from "Class::Exception", of the following types: "RPC::Serialized::X::Protocol" is for an RPC protocol error "RPC::Serialized::X::Parse" is for a Data::Serializer parser failure "RPC::Serialized::X::Validation" is for a data validation error "RPC::Serialized::X::System" is for any system error "RPC::Serialized::X::Application" is for application programming errors "RPC::Serialized::X::Authorization" is for an authorization failure Typically you want to check if it was "RPC::Serialized" having a problem, or some other issue: eval { my $num = $c->cabbages; print "Number of cabbages is: $num\n"; }; if ($@ and $@->isa('RPC::Serialized::X')) { print $@->message, "\n"; # "no handler for cabbages" } else { die $@ } # rethrow the exception For further details please see the Class::Exception manual page. DIAGNOSTICS Here is a list of the common error messages and exception types raised by this module, and probable causes: "Failed to create socket: ..." in an "X::System" The "INET" or "UNIX" client has failed to set up an IO::Socket::INET or IO::Socket::UNIX socket respectively. "Invalid or missing CALL" in an "X::Protocol" After de-serializing the incoming data message from the client, there appears to be no CALL parameter. "Invalid or missing ARGS" in an "X::Protocol" After de-serializing the incoming data message from the client, there appears to be no ARGS list. "Failed to load ..." in an "X::System" The server has attempted to load the handler specified for the current call, but failed. Did you specify the correct handler? "No handler for ..." in an "X::Application" After searching any manual handler mappings, or the auto-load namespaces, no suitable handler package was found for the current call. "... not a RPC::Serialized::Handler" in an "X::Application" Having found a package to load for the current call from the handler specification, it does not inherit from "RPC::Serialized::Handler". "Cannot search for invalid name: ..." in an "X::Application" You are attempting to auto-load a handler whose package name would not be valid in perl. It must be letters, digits and underscores only. "Invalid or missing CLASS" in an "X::Protocol" An Exception class rasied by the server is not known to the client, so this exception is raised instead. "Object method called on class" in an "X::Application" You are attempting to invoke a call on the client module directly, rather than instantiating a new client object from it and then making the call on that. "Missing or invalid input handle" in an "X::Application" The server has not been passed a valid "IO::Handle" upon which to read data. The handle is passed in the call to "new()" or via the "ifh" accessor method on the server object. "Missing or invalid output handle" in an "X::Application" The server has not been passed a valid "IO::Handle" upon which to write data. The handle is passed in the call to "new()" or via the "ofh" accessor method on the server object. "Failed to load Log::Dispatch but trace is on: ..." in an "X::Application" You have enabled server logging using the "trace" option, but the Log::Dispatch or Log::Dispatch::Syslog module has failed to load. "Data not a hash reference" in an "X::Protocol" After de-serializing some data (from the client or server), the data structure appears not to be a hash reference. "Failed to send data: ..." in an "X::System" A system error has ocurred when sending data through the handle to the client or server. "Failed to read data: ..." in an "X::System" A system error has ocurred when reading data from the handle to the client or server. "Data::Serializer error: ..." in an "X::Protocol" An error has been thrown by the Data::Serializer module when initializing. "Serializer parse error" in an "X::Protocol" An error has been thrown by the "Data::Serializer" module when attempting to serialize or de-serialize data to or from the client or server. DEPENDENCIES In addition to the contents of the standard Perl 5.8.4 distribution, this module requires the following: Data::Serializer Exception::Class Module::MultiConf Readonly Class::Accessor::Fast::Contained To use some optional features, you may require the following: Net::Server Log::Dispatch GDBM_File AUTHOR Oliver Gorwits "" This module is a derivative of "YAML::RPC", written by "pod" and Ray Miller, at the University of Oxford Computing Services. Without their brilliant creation this system would not exist. COPYRIGHT & LICENSE Copyright (c) The University of Oxford 2007. All Rights Reserved. This program is free software; you can redistribute it and/or modify it under the terms of version 2 of the GNU General Public License as published by the Free Software Foundation. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA