question: how to stop rpc server

Hi,

This might be more of a rust question, but how do I stop EzRpcServer? I have a test that starts the server in a child task, and I'd like to stop it when the test finishes. The test below passes, but then it hangs presumably because the server is still running.

#[test]
fn my_test() {
    spawn(proc() {
        let rpc_server = EzRpcServer::new("127.0.0.1:12345").unwrap();
    });
    // Do things.
}

Thanks!

[dwrensha]

Hi,

Thanks for trying out capnproto-rust! Please note that everything in capnp-rpc is still quite experimental, so I don't recommend using it yet for anything other than playing around.

Unfortunately, I don't know of an easy way to make EzRpcServers killable. The server task blocks in a call to accept(), and at the moment Rust does not provide good support for ending such a task. Neither does Rust provide good support for wrapping the call to accept() in a call to select().

[dwrensha]

Ok, I've adjusted the interface to EzRpcServer a bit. You should now be able to do something like this:

#[test]
fn my_test() {
    use std::io::Acceptor;
    spawn(proc() {
        let mut rpc_server = EzRpcServer::new("127.0.0.1:12345").unwrap();
        rpc_server.accept();
    });
    // Do things.
}

Here we accept exactly one incoming connection.

If you instead want to start a server that repeatedly accepts new connections, you should now call rpc_server.serve().

Hi @dwrensha, thank you for your quick response! I tried modifying the calculator example to use the accept method, but I'm getting a compilation error:

diff --git a/examples/calculator/server.rs b/examples/calculator/server.rs
index deb8551..3f05472 100644
--- a/examples/calculator/server.rs
+++ b/examples/calculator/server.rs
@@ -163,11 +163,11 @@ pub fn main() {
         return;
     }

-    let rpc_server = EzRpcServer::new(args[2]).unwrap();
+    let mut rpc_server = EzRpcServer::new(args[2]).unwrap();

     // There's got to be a better way to do this.
     let calculator = (~Calculator::ServerDispatch { server : ~CalculatorImpl}) as ~Server;
     rpc_server.export_cap("calculator", calculator);

-    rpc_server.serve();
+    rpc_server.accept();
 }

examples/calculator/server.rs:172:5: 172:24 error: type `capnp-rpc::ez_rpc::EzRpcServer` does not implement any method in scope named `accept`
examples/calculator/server.rs:172     rpc_server.accept();
                                      ^~~~~~~~~~~~~~~~~~~
error: aborting due to previous error

I'm using rustc 0.10-pre (96e8c00 2014-03-07 20:36:42 -0800) on ubuntu 13.10.

[dwrensha]

Because accept() is a trait method, you need to import the Acceptor trait with a line like use std::io::Acceptor;

Duh, off course! Sorry I'm still new to rust.

Now I'm able to compile the calculator example with accept instead of serve, but both the client and the server get stuck, and the server doesn't terminate until I kill the client with ctrl-c. I'm guessing some task is holding on to the socket. How do I close the socket from the client side explicitly?

[dwrensha]

I am aware of this problem, and I currently do not have a good solution.

The client has a task that is blocking on reading from the socket, and Rust currently does not have a nice way to terminate such a task.

In case you're curious, here's some discussion relating to this issue:
rust-lang/rust#11165

Ok sounds good. Thank you for all your help!