On 11/25/2013 09:11 AM, Tanu Kaskinen wrote: > On Mon, 2013-11-25 at 04:50 +0100, David Henningsson wrote: >> On 11/20/2013 10:26 AM, Tanu Kaskinen wrote: >>> Router modules will create a pa_router object, and extend its >>> functionality with callbacks. There can be only one router in the >>> system at a time. At this first stage, the only functionality the base >>> pa_router is to notify the router modules about new and removed nodes. >> >> Then there is another concept we can take away to keep it simple atm - >> there is no need to have a "base pa_router", you can just notify the >> router implementation through hooks instead. > > One point of pa_router is that it's ensured that there's only one router > loaded at a time in the system. That's useful, because a router is > responsible of managing all stream routing and profile and port > activation, so having two routers in the system would make the behaviour > unpredictable when those two routers conflict. We currently have a system where several modules to their own part of the routing. I'm not saying it's perfect, but it's quite flexible. If only one router can be active at a time, that sounds less flexible/configurable. > Another benefit of a dedicated object is that it's easier to define a > proper interface for the routers. It's usually not documented what a > hook callback is expected to do. I failed with the naming and > documentation of the pa_router_add_node() function and the associated > callback, though. That really isn't any better than a hook in terms of > interface clarity. I should have named it > pa_router_set_initial_routing() or something like that, because setting > the initial routing for a node is what the router is expected to do. > > One more benefit of not using hooks is that hooks can have just one > "call data" parameter. I extended the interface of pa_router.add_node() > yesterday: > > int (*add_node)(pa_router *router, pa_node *node, pa_node **initial_connections, unsigned n_initial_connections); Eh, I thought the router was supposed to determine and set the initial connections, but now it looks like you're sending the initial connections into the router instead...? > So it can now return an error, and it has access to the requested > initial connections. This is more cumbersome to do with hooks. I have to > either define a new struct holding the connection request data that will > be passed to the hook, or I'll have to add fields to pa_node that > contain that same information (not nice, because the information is > relevant only at the node creation phase). > > Those were the reasons why I prefer pa_router over just using hooks. > Tell me if you changed your mind and you prefer pa_router too, otherwise > I'll remove pa_router for now and make do with hooks. -- David Henningsson, Canonical Ltd. https://launchpad.net/~diwic
