How to save the data when the tonic is closed! #725

xiuno · 2021-07-15T10:06:33Z

xiuno
Jul 15, 2021

The user declared variable is moved to the structure, and the Route does not provide a way to access it, is there any good way ?

#[tokio::main]
async fn main() {

    let game = Game { data: Arc::new(Mutex::new(vec![])) };
    let mut route = Server::builder().add_service(GameServer::new(game));

    // register callback when shutdown
    route.serve_with_shutdown(addr, async {
        tokio::signal::ctrl_c().await.unwrap();

        // how to fetch "game.data" in here ?
        // "game" already moved to GameServer
        // "GameServer" moved to Route again
        // "Route" doesn't provide a way to access "game"?
        let data = route.game.data; // <-- how to write ?

    }).await.unwrap();

}

I found following code in tonic/src/transport/server/mod.rs

/// A stack based `Service` router.
#[derive(Debug)]
pub struct Router<A, B> {
    server: Server,
    routes: Routes<A, B, Request<Body>>, // if this field is pub, will ok? or provide a method to visit for user data ?
}

Answered by davidpdrsn

Jul 15, 2021

The data is in an Arc so you can share it between the GameServer and whatever code runs after the server has been shutdown.

I haven't tested this code but should work

#[tokio::main]
async fn main() {
    // pull this out into a variable so it can be shared between tasks
    let data = Arc::new(Mutex::new(vec![]));

    let game = Game { data: Arc::clone(&data) };
    let mut route = Server::builder().add_service(GameServer::new(game));

    // register callback when shutdown
    route.serve_with_shutdown(addr, async move {
        tokio::signal::ctrl_c().await.unwrap();
    }).await.unwrap();

    // somehow actually save the data
    let data = data.lock();
    println!("saving {:?}", data)

View full answer

davidpdrsn · 2021-07-15T11:19:44Z

davidpdrsn
Jul 15, 2021
Maintainer

The data is in an Arc so you can share it between the GameServer and whatever code runs after the server has been shutdown.

I haven't tested this code but should work

#[tokio::main]
async fn main() {
    // pull this out into a variable so it can be shared between tasks
    let data = Arc::new(Mutex::new(vec![]));

    let game = Game { data: Arc::clone(&data) };
    let mut route = Server::builder().add_service(GameServer::new(game));

    // register callback when shutdown
    route.serve_with_shutdown(addr, async move {
        tokio::signal::ctrl_c().await.unwrap();
    }).await.unwrap();

    // somehow actually save the data
    let data = data.lock();
    println!("saving {:?}", data);
}

5 replies

davidpdrsn Jul 15, 2021
Maintainer

Making routes public as you suggested wouldn't work since serve_with_shutdown takes self by value, so the routes aren't accessible afterwards.

xiuno Jul 15, 2021
Author

it works fine by your way, thanks!
But I still have some doubts. Why don't provide access from outside to inside? This may be more convenient to use.

davidpdrsn Jul 15, 2021
Maintainer

The server requires owning the data for several reasons, so serve_with_shutdown couldn't take &self.

xiuno Jul 15, 2021
Author

got it

xiuno Jul 19, 2021
Author

I have encounted a new issue, if client don't disconnect positively(client build with the stream type, receive the push message from server), service will block in .await forever even after receive the Ctrl+ C signal, how to disconnect the all connection?

in my.proto

service Xxxx {
  ...
  rpc PushMessage (EmptyRequest) returns (stream MsgResponse) {}
}

#[tokio::main]
async fn main() {
// pull this out into a variable so it can be shared between tasks
let data = Arc::new(Mutex::new(vec![]));

let game = Game { data: Arc::clone(&data) };
let mut route = Server::builder().add_service(GameServer::new(game));

// register callback when shutdown
route.serve_with_shutdown(addr, async move {
    tokio::signal::ctrl_c().await.unwrap();
    // println!("received ctrl+C"); // <--- can running to here.
    // tonic::alose_all_stream();   // how to close all client ?
}).await.unwrap();

// <---- can't reach here 
// somehow actually save the data
let data = data.lock();
println!("saving {:?}", data);

}

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How to save the data when the tonic is closed! #725

xiuno Jul 15, 2021

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