MooX::Role::Pluggable - Add a plugin pipeline to your cows
## A simple pluggable dispatcher. package MyDispatcher; use Moo; use MooX::Role::Pluggable::Constants; with 'MooX::Role::Pluggable'; sub BUILD { my ($self) = @_; ## (optionally) Configure our plugin pipeline $self->_pluggable_init( reg_prefix => 'Plug_', ev_prefix => 'Event_', types => { NOTIFY => 'N', PROCESS => 'P', }, ); } around '_pluggable_event' => sub { ## Override redirecting internal events to process() my ($orig, $self) = splice @_, 0, 2; $self->process( @_ ) }; sub process { my ($self, $event, @args) = @_; ## Dispatch to 'P_' prefixed "PROCESS" type handlers: my $retval = $self->_pluggable_process( 'PROCESS', $event, \@args ); unless ($retval == EAT_ALL) { ## The pipeline allowed the event to continue. ## A dispatcher might re-dispatch elsewhere, etc. } } sub shutdown { my ($self) = @_; ## Unregister all of our plugins. $self->_pluggable_destroy; } ## A Plugin object. package MyPlugin; use MooX::Role::Pluggable::Constants; sub new { bless {}, shift } sub Plug_register { my ($self, $core) = @_; ## Subscribe to events: $core->subscribe( $self, 'PROCESS', qw/ my_event /, ); ## Log that we're here, do some initialization, etc. return EAT_NONE } sub Plug_unregister { my ($self, $core) = @_; ## Called at unregister-time. return EAT_NONE } sub P_my_event { ## Handle a dispatched "PROCESS"-type event my ($self, $core) = splice @_, 0, 2; ## Arguments are references and can be modified: my $arg = ${ $_[0] }; . . . ## Return an EAT constant to control event lifetime ## EAT_NONE allows this event to continue through the pipeline return EAT_NONE } ## An external package that interacts with our dispatcher. package MyController; use Moo; has 'dispatcher' => ( is => 'rw', default => sub { MyDispatcher->new() }, ); sub BUILD { my ($self) = @_; $self->dispatcher->plugin_add( 'MyPlugin', MyPlugin->new() ); } sub do_stuff { my $self = shift; $self->dispatcher->process( 'my_event', @_ ) }
A Moo::Role for turning instances of your class into pluggable objects. Consumers of this role gain a plugin pipeline and methods to manipulate it, as well as a flexible dispatch system (see "_pluggable_process").
The logic and behavior is based almost entirely on Object::Pluggable (see "AUTHOR"). Some methods are the same; implementation & interface differ and you will still want to read thoroughly if coming from Object::Pluggable. Dispatch is significantly faster -- see "Performance".
It may be worth noting that this is nothing at all like the Moose counterpart MooseX::Role::Pluggable. If the names confuse ... well, I lacked for better ideas. ;-)
If you're using POE, also see MooX::Role::POE::Emitter, which consumes this role.
$self->_pluggable_init( ## Prefix for registration events. ## Defaults to 'plugin_' ('plugin_register' / 'plugin_unregister') reg_prefix => 'plugin_', ## Prefix for dispatched internal events ## (add, del, error, register, unregister ...) ## Defaults to 'plugin_ev_' event_prefix => 'plugin_ev_', ## Map type names to prefixes. ## Event types are arbitrary. ## Prefix is prepended when dispathing events of a particular type. ## Defaults to: { NOTIFY => 'N', PROCESS => 'P' } types => { NOTIFY => 'N', PROCESS => 'P', }, );
A consumer can call _pluggable_init to set up pipeline-related options appropriately; this should be done prior to loading plugins or dispatching to "_pluggable_process". If it is never called, the defaults (as shown above) are used.
types => can be either an ARRAY of event types (which will be used as prefixes):
types => [ qw/ IncomingEvent OutgoingEvent / ],
... or a HASH mapping an event type to a prefix:
types => { Incoming => 'I', Outgoing => 'O', },
A '_' is automatically appended to event type prefixes when events are dispatched via "_pluggable_process", but not to reg_prefix/event_prefix. An empty string reg_prefix/event_prefix is valid.
reg_prefix
event_prefix
$self->_pluggable_destroy;
Shuts down the plugin pipeline, unregistering/unloading all known plugins.
## In our consumer sub _pluggable_event { my ($self, $event, @args) = @_; ## Dispatch out, perhaps. }
_pluggable_event is called for internal notifications, such as plugin load/unload and error reporting (see "Internal events").
_pluggable_event
It should be overriden in your consuming class to do something useful with the dispatched event (and any other arguments passed in).
The $event passed will be prefixed with the configured event_prefix.
$event
Also see "Internal events"
A plugin is any blessed object that is registered with your Pluggable object via "plugin_add" and usually subscribed to some events via "subscribe".
See "plugin_add" regarding loading plugins.
Subscribe a plugin to some pluggable events.
$self->subscribe( $plugin_obj, $type, @events );
Registers a plugin object to receive @events of type $type.
@events
$type
This is frequently called from within the plugin's registration handler (see "plugin_register"):
## In a plugin: sub plugin_register { my ($self, $core) = @_; $core->subscribe( $self, 'PROCESS', qw/ my_event another_event / ); $core->subscribe( $self, 'NOTIFY', 'all' ); EAT_NONE }
Subscribe to all to receive all events. It may be worth noting that subscribing a lot of plugins to 'all' events will cause a performance hit in "_pluggable_process" dispatch versus subscribing to specific events.
Unsubscribe a plugin from subscribed events.
The unregister counterpart to "subscribe"; stops delivering specified events to a plugin.
Carries the same arguments as "subscribe".
Defined in your plugin(s) and called at load time.
(Note that 'plugin_' is just a default register method prefix; it can be changed prior to loading plugins. See "_pluggable_init" for details.)
The plugin_register method is called on a loaded plugin when it is added to the pipeline; it is passed the plugin object ($self), the Pluggable object, and any arguments given to "plugin_add" (or similar registration methods).
plugin_register
$self
Normally one might call a "subscribe" from here to start receiving events after load-time:
sub plugin_register { my ($self, $core, @args) = @_; $core->subscribe( $self, 'NOTIFY', @events ); EAT_NONE }
The unregister counterpart to "plugin_register", called when the object is removed from the pipeline (via "plugin_del" or "_pluggable_destroy").
sub plugin_unregister { my ($self, $core) = @_; EAT_NONE }
Carries the same arguments.
my $eat = $self->_pluggable_process( $type, $event, \@args ); return 1 if $eat == EAT_ALL;
The _pluggable_process method handles dispatching.
_pluggable_process
If $event is prefixed with our event prefix (see "_pluggable_init"), the prefix is stripped prior to dispatch (to be replaced with a type prefix matching the specified $type).
Arguments should be passed in as an ARRAY. During dispatch, references to the arguments are passed to subs following automatically-prepended objects belonging to the plugin and the pluggable caller, respectively:
my @args = qw/baz bar/; $self->_pluggable_process( 'NOTIFY', 'foo', \@args ); ## In a plugin: sub N_foo { my ($self, $core) = splice @_, 0, 2; ## Dereferenced expected scalars: my $baz = ${ $_[0] }; my $bar = ${ $_[1] }; }
This allows for argument modification as an event is passed along the pipeline.
Dispatch process for $event 'foo' of $type 'NOTIFY':
- Prepend the known prefix for the specified type, and '_' 'foo' -> 'N_foo' - Attempt to dispatch to $self->N_foo() - If no such method, attempt to dispatch to $self->_default() - If the event was not eaten (see below), dispatch to plugins
"Eaten" means a handler returned a EAT_* constant from MooX::Role::Pluggable::Constants indicating that the event's lifetime should terminate.
Specifically:
If our consuming class provides a method or '_default' that returns:
EAT_ALL: skip plugin pipeline, return EAT_ALL EAT_CLIENT: continue to plugin pipeline return EAT_ALL if plugin returns EAT_PLUGIN later EAT_PLUGIN: skip plugin pipeline entirely return EAT_NONE unless EAT_CLIENT was seen previously EAT_NONE: continue to plugin pipeline
If one of our plugins in the pipeline returns:
EAT_ALL: skip further plugins, return EAT_ALL EAT_CLIENT: continue to next plugin, set pending EAT_ALL (EAT_ALL will be returned when plugin processing finishes) EAT_PLUGIN: return EAT_ALL if previous sub returned EAT_CLIENT else return EAT_NONE EAT_NONE: continue to next plugin
This functionality (derived from Object::Pluggable) provides fine-grained control over event lifetime.
Higher layers can check for an EAT_ALL return value from _pluggable_process to determine whether to continue operating on a particular event (re-dispatch elsewhere, for example). Plugins can use 'EAT_CLIENT' to indicate that an event should be eaten after plugin processing is complete, 'EAT_PLUGIN' to stop plugin processing, and 'EAT_ALL' to indicate that the event should not be dispatched further.
EAT_ALL
Plugin pipeline manipulation methods will set $@, carp(), and return empty list on error (unless otherwise noted). See "plugin_error" regarding errors raised during plugin registration and dispatch.
$@
carp()
$self->plugin_add( $alias, $plugin_obj, @args );
Add a plugin object to the pipeline. Returns the same values as "plugin_pipe_push".
$self->plugin_del( $alias_or_plugin_obj, @args );
Remove a plugin from the pipeline.
Takes either a plugin alias or object. Returns the removed plugin object.
my $plug_obj = $self->plugin_get( $alias ); my ($plug_obj, $plug_alias) = $self->plugin_get( $alias_or_plugin_obj );
In scalar context, returns the plugin object belonging to the specified alias.
In list context, returns the object and alias, respectively.
my @loaded = $self->plugin_alias_list;
Returns a list of loaded plugin aliases.
$self->plugin_replace( old => $alias_or_plugin_obj, alias => $new_alias, plugin => $new_plugin_obj, ## Optional: register_args => [ ], unregister_args => [ ], );
Replace an existing plugin object with a new one.
Returns the old (removed) plugin object.
$self->plugin_pipe_push( $alias, $plugin_obj, @args );
Add a plugin to the end of the pipeline. (Typically one would use "plugin_add" rather than calling this method directly.)
my $plug = $self->plugin_pipe_pop( @unregister_args );
Pop the last plugin off the pipeline, passing any specified arguments to "plugin_unregister".
In scalar context, returns the plugin object that was removed.
In list context, returns the plugin object and alias, respectively.
$self->plugin_pipe_unshift( $alias, $plugin_obj, @args );
Add a plugin to the beginning of the pipeline.
Returns the total number of loaded plugins (or an empty list on failure).
$self->plugin_pipe_shift( @unregister_args );
Shift the first plugin off the pipeline, passing any specified args to "plugin_unregister".
my $idx = $self->plugin_pipe_get_index( $alias_or_plugin_obj ); if ($idx < 0) { ## Plugin doesn't exist }
Returns the position of the specified plugin in the pipeline.
Returns -1 if the plugin does not exist.
$self->plugin_pipe_insert_after( after => $alias_or_plugin_obj, alias => $new_alias, plugin => $new_plugin_obj, ## Optional: register_args => [ ], );
Add a plugin to the pipeline after the specified previously-existing alias or plugin object. Returns boolean true on success.
$self->plugin_pipe_insert_before( before => $alias_or_plugin_obj, alias => $new_alias, plugin => $new_plugin_obj, ## Optional: register_args => [ ], );
Similar to "plugin_pipe_insert_after", but insert before the specified previously-existing plugin, not after.
$self->plugin_pipe_bump_up( $alias_or_plugin_obj, $count );
Move the specified plugin 'up' $count positions in the pipeline.
$count
Returns -1 if the plugin cannot be bumped up any farther.
$self->plugin_pipe_bump_down( $alias_or_plugin_obj, $count );
Move the specified plugin 'down' $count positions in the pipeline.
Returns -1 if the plugin cannot be bumped down any farther.
These events are dispatched to "_pluggable_event" prefixed with our pluggable event prefix; see "_pluggable_init".
Issued via "_pluggable_event" when an error occurs.
The arguments are, respectively: the error string, the offending object, and a string describing the offending object ('self' or 'plugin' with name appended).
Issued via "_pluggable_event" when a new plugin is registered.
Arguments are the new plugin alias and object, respectively.
Issued via "_pluggable_event" when a plugin is unregistered.
Arguments are the old plugin alias and object, respectively.
Dispatcher performance has been profiled and optimized, but I'm most certainly open to ideas ;-)
Some Benchmark runs. 30000 "_pluggable_process" calls with 20 loaded plugins dispatching one argument to one handler that does nothing except return EAT_NONE:
Rate object-pluggable moox-role-pluggable object-pluggable 6173/s -- -38% moox-role-pluggable 9967/s 61% Rate object-pluggable moox-role-pluggable object-pluggable 6224/s -- -38% moox-role-pluggable 10000/s 61% -- Rate object-pluggable moox-role-pluggable object-pluggable 6383/s -- -35% moox-role-pluggable 9868/s 55%
(Benchmark script is available in the bench/ directory of the upstream repository; see https://github.com/avenj/moox-role-pluggable)
bench/
Jon Portnoy <avenj@cobaltirc.org>
Written from the ground up, but conceptually based entirely on Object::Pluggable by BINGOS, HINRIK, APOCAL, japhy et al.
To install MooX::Role::Pluggable, copy and paste the appropriate command in to your terminal.
cpanm
cpanm MooX::Role::Pluggable
CPAN shell
perl -MCPAN -e shell install MooX::Role::Pluggable
For more information on module installation, please visit the detailed CPAN module installation guide.