NAME
Catalyst::Engine::XMPP2 - Net::XMPP2::Connection Catalyst Engine
SYNOPSIS
MyApp->config->{Engine::XMPP2} =
{
username => "abc",
domain => "jabber.org",
password => "foo",
override_host => "myserver",
override_port => 5722
};
MyApp->run();
DESCRIPTION
This engine enables you to deploy a Catalyst application that can be accessed using the XMPP protocol. This is done by a mapping of each XMPP stanza to a HTTP Request, using the Catalyst::Engine::Embeddable as a base.
Semantics mapping
One important thing to realise is that the XMPP semantics are considerably different than the HTTP semantics, that way, a set of mappings must be done.
Request-Response
Usually, an HTTP application implements only Request-Response
semantics for every action. That is not always true for the XMPP
protocol. In fact, the only stanza that implements this semantics is
the <iq/> stanza.
That way, when receiving <message/> or <presence/> stanzas, the
response will be ignored on success. If the response is a failure
(400 or 500), an error response will be sent. If wanting to send an
explicit message, that should be done explicitly.
When receiving <iq/> stanzas, the response will be sent back as the
action processing returns, independent of the response status.
In any way, the attributes of the stanza root element will be
translated as HTTP Headers with the "XMPP_Stanza_" prefix.
SCRIPT_NAME
This is the most relevant aspect of this mapping. As XMPP doesn't
have a URI definition for each stanza, that means that there's no
proper way of dispatching a message to a given controller action in
Catalyst.
What this mapping does is, at the beggining, creating several
connections to the server, providing different resource identifiers
based on the Path actions registered in the application.
This have two important side-effects to realize:
A Catalyst XMPP application can only use 'Path' actions, because
that is the only DispatchType that have a static mapping of the
available actions. Other DispatchTypes, like Chained or Index,
depends on the current request to find out which action to dispatch.
This doesn't forbid the use of the other DispatchTypes for internal
forward and dispatch, but the only really public actions will be the
ones seen by the 'Path' DispatchType.
You have to keep in mind that the resources will be pre-advertised,
and that for each public path action, you will have a public jabber
id, and, at least by now, a separated connection to the server, so
it's probably a good idea to do a carefull planning of which actions
to make public.
Content-Type
XMPP has no support for MIME types. Every message is, by definition,
a XML document. So every request will have the "application/xml"
MIME type. If the response content-type is also "application/xml",
it will be written as raw into the XMPP stream. This will allow SOAP
responses, for instance, to be sent as in XEP-0072.
On the other hand, if the content type is of some other type, it
will be sent as literal string inside a <body> tag, as described by
XMPP RFC3921, this way, interaction with regular IM clients should
be natural.
Scalability
At this point, this engine is single-threaded, which means that it
will block in each operation, and, therefore it cannot handle more
than one request at a time. At the time of this writing, two options
are available to solve this problem:
The first would be to turn this engine into a pre-fork server that
would keep pipes to every child and dispatch the requests to them,
while keeping a single control thread for the XMPP connections.
The other option would be to implement a balancer server that would
accept several connections for the same JID and connect only once
for each JID, dispatching a message sent to some JID among each of
the candidate connections.
The second option is probably a better idea, as the handling of that
number of connections could be implemented in C, for instance, and
using low-level OS operations, like libevent for linux, making it
easier to scale in several machines.
Error handling
Error handling in XMPP is also different than from HTTP. While HTTP
defines numeric error codes, XMPP defines a set of named conditions.
But both provide a way to return a custom text to the requestor.
This way, the HTTP error codes will be mapped to the XMPP error
conditions, and the content of the response will be set as the error
text. The XMPP spec also define the "error-type" concept which
indicates what the requestor can do about, and the recommended
error-type for each of the known conditions. The user can override
this default by sending the XMPP_error-type header in the failure
case.
The HTTP-XMPP error code mapping will happen as described in the
following table.
bad-request 400
conflict 409
feature-not-implemented 501
forbidden 403
gone 410
internal-server-error 500
item-not-found 404
jid-malformed 520
not-acceptable 406
not-allowed 420
not-authorized 401
payment-required 402
recipient-unavailable 521
redirect 302
registration-required 421
remote-server-not-found 502
remote-server-timeout 504
resource-constraint 412
service-unavailable 503
subscription-required 422
undefined-condition 423
unexpected-request 424*
The items marked with an * are of codes that are not standard HTTP
error codes. Most error codes in this list could be mapped
literally.
USAGE
The 'Engine::XMPP2' configuration key expects a hashref that will be sent to Net::XMPP2::Connection->new dereferenced. It's important to notice, however, that setting "jid" or "resource" in this hash has no effect as this values will be set according to the Action-Resource mapping.
SENDING MESSAGES
One of the greater benefits of the XMPP protocol is the hability to chain operations in a more complex choreography. In order to do that, you just need to send new messages while processing other messages, in order to do that, you can access the engine object by using $c->engine and use one of the following methods
$c->engine->send_message($c, $to, $type, $create_cb, %attrs)
This will call send_message on the connection that generated the
current request with the parameters as described in
Net::XMPP2::Connection.
One important hint: if $create_db is a CODE ref, it will be executed
with a XML::Writer object in UNSAFE mode as its first argument,
which means you can call "raw" on it to send unencoded data.
As you'll be sending the message with the connection that generated
this request, it will have the complete JID, with the resource, as
the "from".
$c->engine->send_presence($c, $type, $create_cb, %attrs)
Same as above.
$c->engine->send_iq($c, $type, $create_cb, $result_cb, %attrs)
Same as above.
Hint: $result_cb is a coderef that will be executed once the
response for this iq arrives. This method won't block, so you might
have to implement a semaphore if the reply for this iq is relevant
to the rest of this request.
DIRECT CONNECTION MANIPULATION
This is strongly discouraged, but it might be life-saving for some corner cases.
$c->engine->connection($c)
Access the connection object that generated the current request.
$c->engine->connections()
This returns a hashref identifying all the connections by the
resource name.
INTERNAL METHODS
$engine->handle_xmpp_node($app, $resource, $node)
This method is called by the stanza callbacks in the connections.
SEE ALSO
Catalyst::Engine, Catalyst::Engine::CGI, HTTP::Request, HTTP::Reponse, Catalyst, Net::XMPP2::Connection, Catalyst::Engine::Embeddable
AUTHORS
Daniel Ruoso "daniel@ruoso.com"
BUG REPORTS
Please submit all bugs regarding "Catalyst::Engine::XMPP2" to "bug-catalyst-engine-xmpp2@rt.cpan.org"
LICENSE
This library is free software, you can redistribute it and/or modify it under the same terms as Perl itself.