Create example for parallel server

[janhohenheim]

This server sends and receives messages independently

[daboross]

Could you add futures-cpupool as a dev-dependency in Cargo.toml? I don't think it'll compile/test the example without it.

[janhohenheim]

Thanks for the reminder.
I'm brewing up a better example anyways so people can use it as a scalable start point. Gonna fix the travis build when that is ready.

[illegalprime]

Hey this is awesome! Thanks a bunch, travis was being weird but now it's fixed. Feel free to rebase on top of the latest changes.

[janhohenheim]

Hmm, any idea why my cargo fmt with your .rustfmt.toml is generating a different output than Travis?

Edit: I see, you're running an old version of rustfmt. I'm gonna downgrade my local installation then. Maybe in the future you should look into https://github.com/nabijaczleweli/cargo-update. With it you can cache your rustfmt on Travis and let it auto update as needed :)

[janhohenheim]

Feel free to merge it now. I wrote this example with a game server in mind.

As I am not that experienced in working with futures, I most probably made some things way more complicated that they could be. But hey, it's parallel and scalable to as many users as you like :)

[janhohenheim]

I think Travis bugged out there.
For me it says right here that the build is still running

While on the actual build page it says it finished 24 ago

[illegalprime]

Thank you again!

[chmnchiang]

Regarding the code in this example:

send_channel_in.for_each(move |(id, msg): (Id, String)| {
	let connections = connections.clone();
	let sink = connections.write()
	                      .unwrap()
	                      .remove(&id)
	                      .expect("Tried to send to invalid client id",);

	println!("Sending message '{}' to id {}", msg, id);
	let f = sink.send(OwnedMessage::Text(msg))
	            .and_then(move |sink| {
		                      connections.write().unwrap().insert(id, sink);
		                      Ok(())
		                     });
	remote.spawn(move |_| f.map_err(|_| ()));
	Ok(())
})
.map_err(|_| ())

Isn't it possible that the last message haven't been sent completely but the send_channel_in receive another message to the same client? The sink of the client would be removed from the hashmap temporary then.

[janhohenheim]

Good catch, I think you're right. Unfortunately I don't have time right now to fix it. Do you wanna give it a try?

[chmnchiang]

I've create the pull request #148, but since I'm a newbee to tokio and future, maybe you could check whether my fix is correct.