ObjectServer with multiple Connection

[zeenix]

In GitLab by @DataTriny on Jul 17, 2021, 13:28

Hello,

I am trying to build a D-Bus server application that connects to a private bus (let's call it A). For performance reasons, one of the interfaces I need to implement must expose a method (let's call it GetBusAddress) that return the address of another private bus I should create myself (let's call it bus B).

A typical workflow look like this:

• my server is launched, connects to bus A and exposes a bunch of objects,
• a client that is listening on bus A detects my server and makes a call to GetBusAddress,
• my server potentially create bus B if it is not already, and returns its address to the client,
• the client can now communicate with my server through bus B.

The problem here is that my server must expose the whole object tree on both buses. The only solutions I see around this are:

• maintain two copies of the tree (one ObjectServer for each Connection: I don't think this is a good idea as the tree can get pretty big,
• handle message dispatching on my own: this would be possible but rather hard I guess.

My question then is: is handling this situation part of the plans for zbus?

Thanks in advance.

Kind regards,

[zeenix]

@DataTriny I'm currently on vacation. I'll reply when I'm back later this week.

[zeenix]

maintain two copies of the tree (one ObjectServer for each Connection: I don't think this is a good idea as the tree can get pretty big,

Are you certain that size of the tree is very relevant here? As long as you don't duplicate a lot of state (for which you can use Arc etc) between them, your code's memory usage should be pretty minimum. ObjectServer OTOH uses allocated strings for object paths though (not interfaces though) so that will have an impact but I'd check if it's large enough in your case to worry about.

handle message dispatching on my own: this would be possible but rather hard I guess.

If the ObjectServer duplication isn't an option for you, I'm afraid this is the only alternative you're left with. You'll need to use the low-level (Connection) API instead. It might feel like a lot of work but for such special use cases, I think it's not too bad but that's just my opinion. :)

My question then is: is handling this situation part of the plans for zbus?

We don't have any plans for such cases but if you've suggestion on how we can support that, please feel free to suggest.

[zeenix]

@DataTriny ping?

[zeenix]

In GitLab by @danieldg on Aug 3, 2021, 02:30

Note that if you ever want to expose any differences between the two buses, you'll need to split the ObjectServer anyway - and I suspect you will eventually want to do that. You can still use Arc as suggested to share the large (common) parts of the tree.

[zeenix]

@DataTriny ObjectServer is now Sync+Send in the main branch btw.