Changes between Version 3 and Version 4 of Internal/OpenFlow/FloodlightFVModule

Timestamp:

Jun 13, 2012, 4:32:56 AM (12 years ago)

Author:

akoshibe

Comment:

—

Internal/OpenFlow/FloodlightFVModule

@@ -92 +92 @@
  * mapping out the module registration mechanisms in Floodlight
  * finding a "nice" way to make the modules register with FVController. 
+
+(6/13):
+[[BR]]
+[[BR]]
+A (not-so) quick revisit of the module loading system in Floodlight was done to figure out how exactly a module learns to subscribe to the main controller module. 
+
+Starting at the top, in the ''init()'' function of each module is almost always this line:
+{{{
+floodlightProvider = context.getServiceImpl(IFloodlightProviderService.class);
+}}}    
+Where ''context'' is an instance of `FloodlightModuleContext`, which contains a mapping between the interfaces and the services providing them. ''getServiceImpl()'', in the case above, returns the service providing the IFloodlightProviderService interface, which is the core controller. 
+
+`FloodlightModuleLoader` is the actual class responsible for populating `FloodlightModuleContext`'s mapping; Recalling, from Main.java:
+{{{
+FloodlightModuleLoader fml = new FloodlightModuleLoader();
+IFloodlightModuleContext moduleContext = fml.loadModulesFromConfig(settings.getModuleFile());
+}}}
+Internally, for each module exporting a service, in ''initModules()'' `FloodlightModuleLoader` calls ''getServiceImpls()'', an `IFloodlightModule` function that lets modules define the services that they export. It then uses `FloodlightModuleContext`'s ''addService()'' in order to fill its mapping.
+
+Returning to the controller mapped to ''IFloodlightProviderService.class'', we see that it is a service exported by the module `FloodlightProvider`. It is the first module to be loaded by the module loading system, and therefore the mapping to the controller is there for the rest of the modules to register with.
+
+This leads us to a potential way to place a module between the controller and the rest of the modules:
+ * Re-name the real IFloodlightProviderService to something else
+ * Implement a module that subscribes to the re-named controller service
+ * Implement a FVController from IFloodlightProviderService
+ * export this as a service with key IFloodlightProviderService.class
+
+This shouldn't require any change on the other modules (except the FloodlightProvider).