NAME AtomMQ - An atompub server that supports the message queue/bus model. VERSION version 1.0200 SYNOPSIS use AtomMQ; my $db_info = { dsn => 'dbi:SQLite:dbname=/path/to/foo.db' }; my $server = AtomMQ->new(db_info => $db_info); $server->run; DESCRIPTION AtomMQ is an atompub server that supports the message queue/bus model. Throughout this document, I will use the term message when referring to an atom feed entry, since the point of this module is to use atompub for messaging. The idea is that atom feeds correspond to conceptual queues (or buses) and atom entries correspond to messages. AtomMQ extends Inoue's Atompub::Server which extends Miyagawa's XML::Atom::Server. Can you feel the love already? To create an AtomMQ server, just copy the code from the "SYNOPSIS". Make sure to change the dsn to something valid. You can run it via CGI or as a mod_perl handler. To run in a FastCGI or PSGI environment, see the "FastCGI" and "PSGI" sections in this document. This is highly recommended because it will run considerably faster. These examples assume that you have configured your web server to point http requests starting with /atommq to the script you just created. To publish a message, make a HTTP POST request: $ curl -d ' allo
an important message
' http://localhost/atommq/feed=widgets That adds a new message to a feed titled widgets. If that feed didn't exist before, it will be created for you. To retrieve messages from the widgets feed, make a HTTP GET request: $ curl http://localhost/atommq/feed=widgets That will get all the messages since the feed was created. Lets say you are running a client that polls the feed and processes messages. If this client dies, you will not want it to process all the messages again when it comes back up. So clients are responsible for maintaining and persisting the id of the last message they processed. This allows a client to request only messages that came after the message with the given id. They can do this by passing a Xlastid header: $ curl -H 'Xlastid: urn:uuid:4018425e-f747-11df-b990-b7043ee4d39e' http://localhost/atommq/feed=widgets METHODS new Arguments: \%db_info, $auto_create_db, $max_msgs_per_request This is the AtomMQ constructor. Only $db_info is required. $db_info is a hashref containing the database connection info as described in "connect_info" in DBIx::Class::Storage::DBI. It must at least contain a dsn entry. $auto_create_db defaults to 1. Set it to 0 if you don't want AtomMQ to attempt to create the db tables for you. You can leave it set to 1 even if the db tables already exist. Setting it to 0 improves performance slightly. $max_msgs_per_request defaults to 100. This default value may change in future versions, so you may want to set it explicitly. It determines the maximum number of messages returned by the server for a GET request. So if there were 1000 messages, a GET request will return messages 1 - 100. To get messages 101 - 200, you should provide the id of message 100 in the next GET request via the Xlastid header, as shown above. See "DATABASE" for more info. Example: my $server = AtomMQ->new( auto_create_db => 0, max_msgs_per_request => 100, db_info => { dsn => 'dbi:SQLite:dbname=/path/to/foo.db', user => 'joe', password => 'momma', } ); run Arguments: None Call this method to start the server. DATABASE AtomMQ uses a database to store its data. The db_info you pass to the constructor must point to a database which you have write privileges to. The tables will be created automagically for you if they don't already exist. Of course for that to work, you will need create table privileges. All databases supported by DBIx::Class are supported, which are most major databases including postgresql, sqlite, mysql and oracle. FastCGI CGI can be very slow. Not to worry, AtomMQ can be run via FastCGI. This requires that you have the FCGI module installed. #!/usr/bin/perl use AtomMQ; use FCGI; my $db_info = { dsn => "dbi:SQLite:dbname=/path/to/foo.db" }; my $request = FCGI::Request(); while($request->Accept() >= 0) { my $server = AtomMQ->new(db_info => $db_info); $server->run; } Here is an example lighttpd config. It assumes you named the above file atommq.fcgi. Make sure you chmod +x atommq.fcgi. fastcgi.server += ( "/atommq" => (( "socket" => "/tmp/fcgi.sock", "check-local" => "disable", "bin-path" => "/path/to/atommq.fcgi", )), ) Now AtomMQ will be running via FastCGI under /atommq. PSGI AtomMQ can also be run in a PSGI environment via Plack. Here is one way to do it. You will need to have Plack, CGI::Emulate::PSGI and CGI::Compile installed for this example. Copy the following to atommq.psgi. use Plack::App::WrapCGI; my $app = Plack::App::WrapCGI->new(script => "/path/to/atommq.cgi")->to_app; The "/path/to/atommq.cgi" string should be changed to the path to a cgi script such as the one in the "SYNOPSIS". Then you can for example run: plackup -p 5000 atommq.psgi Now AtomMQ is running on port 5000 via the HTTP::Server::PSGI web server. Of course you can use any PSGI/Plack web server via the -s option to plackup. MOTIVATION I like messaging systems because they make it so easy to create scalable applications. Existing message brokers are great for creating message queues. But once a consumer reads a message off of a queue, it is gone. I needed a system to publish events such that multiple heterogeneous services could subscribe to them. So I really needed a message bus, not a message queue. I could for example have used something called topics in ActiveMQ, but I have found them to have issues with persistence. Actually, I have found ActiveMQ to be broken in general. An instance I manage has to be restarted at least twice a week. AtomMQ on the other hand will be extremely stable, because it is so simple. It is in essence just an interface to a database. As long as your database and web server are up, AtomMQ will be there for you. She will not let you down. And there are all sorts of ways to add redundancy to databases and web heads. Another advantage of using AtomMQ is that atompub is an RFC standard. Everyone already has a client for it, their browser. Aren't standards great! By the way, if you just need message queues, try POE::Component::MessageQueue. It rocks. If you need a message bus, give AtomMQ a shot. AUTHOR Naveed Massjouni COPYRIGHT AND LICENSE This software is copyright (c) 2010 by Naveed Massjouni. This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.