如何在 Actix-web 的 WebSocket 处理程序中正确调用异步函数

Question

我在这方面取得了一些进展，使用into_actor().spawn()，但我很难访问异步块内的ctx 变量。

我将首先展示 Web 套接字处理程序的编译 sn-p，然后是处理程序的失败 sn-p，然后参考完整的代码示例。

工作sn-p：

关注火柴盒Ok(ws::Message::Text(text))

/// Handler for `ws::Message`
impl StreamHandler<Result<ws::Message, ws::ProtocolError>> for MyWebSocket {
    fn handle(&mut self, msg: Result<ws::Message, ws::ProtocolError>, ctx: &mut Self::Context) {
        // process websocket messages
        println!("WS: {:?}", msg);
        match msg {
            Ok(ws::Message::Ping(msg)) => {
                self.hb = Instant::now();
                ctx.pong(&msg);
            }
            Ok(ws::Message::Pong(_)) => {
                self.hb = Instant::now();
            }
            Ok(ws::Message::Text(text)) => {
                let future = async move {
                    let reader = processrunner::run_process(text).await;
                    let mut reader = reader.ok().unwrap();
                    while let Some(line) = reader.next_line().await.unwrap() {
                        // ctx.text(line);
                        println!("line = {}", line);
                    }
                };

                future.into_actor(self).spawn(ctx);
            }
            Ok(ws::Message::Binary(bin)) => ctx.binary(bin),
            Ok(ws::Message::Close(reason)) => {
                ctx.close(reason);
                ctx.stop();
            }
            _ => ctx.stop(),
        }
    }
}

在未注释 ctx 行的情况下无法使用 sn-p。

/// Handler for `ws::Message`
impl StreamHandler<Result<ws::Message, ws::ProtocolError>> for MyWebSocket {
    fn handle(&mut self, msg: Result<ws::Message, ws::ProtocolError>, ctx: &mut Self::Context) {
        // process websocket messages
        println!("WS: {:?}", msg);
        match msg {
            Ok(ws::Message::Ping(msg)) => {
                self.hb = Instant::now();
                ctx.pong(&msg);
            }
            Ok(ws::Message::Pong(_)) => {
                self.hb = Instant::now();
            }
            Ok(ws::Message::Text(text)) => {
                let future = async move {
                    let reader = processrunner::run_process(text).await;
                    let mut reader = reader.ok().unwrap();
                    while let Some(line) = reader.next_line().await.unwrap() {
                         ctx.text(line);
                        println!("line = {}", line);
                    }
                };

                future.into_actor(self).spawn(ctx);
            }
            Ok(ws::Message::Binary(bin)) => ctx.binary(bin),
            Ok(ws::Message::Close(reason)) => {
                ctx.close(reason);
                ctx.stop();
            }
            _ => ctx.stop(),
        }
    }
}

完整的代码 sn-p 拆分为两个文件。

main.rs

//! Simple echo websocket server.
//! Open `http://localhost:8080/ws/index.html` in browser
//! or [python console client](https://github.com/actix/examples/blob/master/websocket/websocket-client.py)
//! could be used for testing.
mod processrunner;
use std::time::{Duration, Instant};

use actix::prelude::*;
use actix_files as fs;
use actix_web::{middleware, web, App, Error, HttpRequest, HttpResponse, HttpServer};
use actix_web_actors::ws;

/// How often heartbeat pings are sent
const HEARTBEAT_INTERVAL: Duration = Duration::from_secs(5);
/// How long before lack of client response causes a timeout
const CLIENT_TIMEOUT: Duration = Duration::from_secs(10);

/// do websocket handshake and start `MyWebSocket` actor
async fn ws_index(r: HttpRequest, stream: web::Payload) -> Result<HttpResponse, Error> {
    println!("{:?}", r);
    let res = ws::start(MyWebSocket::new(), &r, stream);
    println!("{:?}", res);
    res
}

/// websocket connection is long running connection, it easier
/// to handle with an actor
struct MyWebSocket {
    /// Client must send ping at least once per 10 seconds (CLIENT_TIMEOUT),
    /// otherwise we drop connection.
    hb: Instant,
}

impl Actor for MyWebSocket {
    type Context = ws::WebsocketContext<Self>;

    /// Method is called on actor start. We start the heartbeat process here.
    fn started(&mut self, ctx: &mut Self::Context) {
        self.hb(ctx);
    }
}

/// Handler for `ws::Message`
impl StreamHandler<Result<ws::Message, ws::ProtocolError>> for MyWebSocket {
    fn handle(&mut self, msg: Result<ws::Message, ws::ProtocolError>, ctx: &mut Self::Context) {
        // process websocket messages
        println!("WS: {:?}", msg);
        match msg {
            Ok(ws::Message::Ping(msg)) => {
                self.hb = Instant::now();
                ctx.pong(&msg);
            }
            Ok(ws::Message::Pong(_)) => {
                self.hb = Instant::now();
            }
            Ok(ws::Message::Text(text)) => {
                let future = async move {
                    let reader = processrunner::run_process(text).await;
                    let mut reader = reader.ok().unwrap();
                    while let Some(line) = reader.next_line().await.unwrap() {
                        // ctx.text(line);
                        println!("line = {}", line);
                    }
                };

                future.into_actor(self).spawn(ctx);
            }
            Ok(ws::Message::Binary(bin)) => ctx.binary(bin),
            Ok(ws::Message::Close(reason)) => {
                ctx.close(reason);
                ctx.stop();
            }
            _ => ctx.stop(),
        }
    }
}

impl MyWebSocket {
    fn new() -> Self {
        Self { hb: Instant::now() }
    }

    /// helper method that sends ping to client every second.
    ///
    /// also this method checks heartbeats from client
    fn hb(&self, ctx: &mut <Self as Actor>::Context) {
        ctx.run_interval(HEARTBEAT_INTERVAL, |act, ctx| {
            // check client heartbeats
            if Instant::now().duration_since(act.hb) > CLIENT_TIMEOUT {
                // heartbeat timed out
                println!("Websocket Client heartbeat failed, disconnecting!");

                // stop actor
                ctx.stop();

                // don't try to send a ping
                return;
            }

            ctx.ping(b"");
        });
    }
}

#[actix_web::main]
async fn main() -> std::io::Result<()> {
    std::env::set_var("RUST_LOG", "actix_server=info,actix_web=info");
    env_logger::init();

    HttpServer::new(|| {
        App::new()
            // enable logger
            .wrap(middleware::Logger::default())
            // websocket route
            .service(web::resource("/ws/").route(web::get().to(ws_index)))
            // static files
            .service(fs::Files::new("/", "static/").index_file("index.html"))
    })
    // start http server on 127.0.0.1:8080
    .bind("127.0.0.1:8080")?
    .run()
    .await
}

processrunner.rs

extern crate tokio;
use tokio::io::*;
use tokio::process::Command;

use std::process::Stdio;

//#[tokio::main]
pub async fn run_process(
    text: String,
) -> std::result::Result<
    tokio::io::Lines<BufReader<tokio::process::ChildStdout>>,
    Box<dyn std::error::Error>,
> {
    let mut cmd = Command::new(text);
    cmd.stdout(Stdio::piped());

    let mut child = cmd.spawn().expect("failed to spawn command");

    let stdout = child
        .stdout
        .take()
        .expect("child did not have a handle to stdout");

    let lines = BufReader::new(stdout).lines();

    // Ensure the child process is spawned in the runtime so it can
    // make progress on its own while we await for any output.
    tokio::spawn(async {
        let status = child.await.expect("child process encountered an error");

        println!("child status was: {}", status);
    });
    Ok(lines)
}

错误：

error[E0495]: cannot infer an appropriate lifetime due to conflicting requirements
  --> src/main.rs:57:41
   |
57 |                   let future = async move {
   |  _________________________________________^
58 | |                     let reader = processrunner::run_process(text).await;
59 | |                     let mut reader = reader.ok().unwrap();
60 | |                     while let Some(line) = reader.next_line().await.unwrap() {
...  |
63 | |                     }
64 | |                 };
   | |_________________^
   |
note: first, the lifetime cannot outlive the anonymous lifetime #2 defined on the method body at 45:5...
  --> src/main.rs:45:5
   |
45 | /     fn handle(&mut self, msg: Result<ws::Message, ws::ProtocolError>, ctx: &mut Self::Context) {
46 | |         // process websocket messages
47 | |         println!("WS: {:?}", msg);
48 | |         match msg {
...  |
74 | |         }
75 | |     }
   | |_____^
note: ...so that the types are compatible
  --> src/main.rs:57:41
   |
57 |                   let future = async move {
   |  _________________________________________^
58 | |                     let reader = processrunner::run_process(text).await;
59 | |                     let mut reader = reader.ok().unwrap();
60 | |                     while let Some(line) = reader.next_line().await.unwrap() {
...  |
63 | |                     }
64 | |                 };
   | |_________________^
   = note: expected  `&mut actix_web_actors::ws::WebsocketContext<MyWebSocket>`
              found  `&mut actix_web_actors::ws::WebsocketContext<MyWebSocket>`
   = note: but, the lifetime must be valid for the static lifetime...
note: ...so that the type `actix::fut::FutureWrap<impl std::future::Future, MyWebSocket>` will meet its required lifetime bounds
  --> src/main.rs:66:41
   |
66 |                 future.into_actor(self).spawn(ctx);
   |                                         ^^^^^

error: aborting due to previous error

For more information about this error, try `rustc --explain E0495`.

货物

[package]
name = "removed"
version = "0.1.0"
authors = ["removed"]
edition = "2018"

# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html

[dependencies]
tokio = { version = "0.2", features = ["full"] }
actix = "0.10"
actix-codec = "0.3"
actix-web = "3"
actix-web-actors = "3"
actix-files = "0.3"
awc = "2"
env_logger = "0.7"
futures = "0.3.1"
bytes = "0.5.3"

Answer 1

这里是基础知识。您可能需要在这里和那里做一些工作，但这很有效。

use actix::prelude::*;
use tokio::process::Command;
use actix_web::{ web, App, Error, HttpRequest, HttpResponse, HttpServer};
use actix_web_actors::ws;
use tokio::io::{ AsyncBufReadExt};
use actix::AsyncContext;
use tokio::stream::{ StreamExt};

use tokio::io::{BufReader};

use std::process::Stdio;

#[derive(Message)]
#[rtype(result = "Result<(), ()>")]
struct CommandRunner(String);


/// Define HTTP actor
struct MyWs;

impl Actor for MyWs {
    type Context = ws::WebsocketContext<Self>;
}

#[derive(Debug)]
struct Line(String);

impl StreamHandler<Result<Line, ws::ProtocolError>> for MyWs {
    fn handle(
        &mut self,
        msg: Result<Line, ws::ProtocolError>,
        ctx: &mut Self::Context,
    ) {
        match msg {
            Ok(line) => ctx.text(line.0),
            _ => () //Handle errors
        }
    }
}

/// Handler for ws::Message message
impl StreamHandler<Result<ws::Message, ws::ProtocolError>> for MyWs {
    fn handle(
        &mut self,
        msg: Result<ws::Message, ws::ProtocolError>,
        ctx: &mut Self::Context,
    ) {
        match msg {
            Ok(ws::Message::Ping(msg)) => ctx.pong(&msg),
            Ok(ws::Message::Text(text)) => {
                ctx.notify(CommandRunner(text.to_string()));
            },
            Ok(ws::Message::Binary(bin)) => ctx.binary(bin),
            _ => (),
        }
    }
}

impl Handler<CommandRunner> for MyWs {
    type Result = Result<(), ()>;
    fn handle(&mut self, msg: CommandRunner, ctx: &mut Self::Context) -> Self::Result  {
        let mut cmd = Command::new(msg.0);

        // Specify that we want the command's standard output piped back to us.
        // By default, standard input/output/error will be inherited from the
        // current process (for example, this means that standard input will
        // come from the keyboard and standard output/error will go directly to
        // the terminal if this process is invoked from the command line).
        cmd.stdout(Stdio::piped());

        let mut child = cmd.spawn()
            .expect("failed to spawn command");

        let stdout = child.stdout.take()
            .expect("child did not have a handle to stdout");

        let reader = BufReader::new(stdout).lines();
        
        // Ensure the child process is spawned in the runtime so it can
        // make progress on its own while we await for any output.
        let fut = async move {
            let status = child.await
                .expect("child process encountered an error");
    
            println!("child status was: {}", status);
        };
        let fut = actix::fut::wrap_future::<_, Self>(fut);
        ctx.spawn(fut);
        ctx.add_stream(reader.map(|l| Ok(Line(l.expect("Not a line")))));
        Ok(())
    }
}

async fn index(req: HttpRequest, stream: web::Payload) -> Result<HttpResponse, Error> {
    let resp = ws::start(MyWs {}, &req, stream);
    println!("{:?}", resp);
    resp
}

#[actix_web::main]
async fn main() -> std::io::Result<()> {
    HttpServer::new(|| App::new().route("/ws/", web::get().to(index)))
        .bind("127.0.0.1:8080")?
        .run()
        .await
}

运行ls 看起来像这样。

Answer 2

所以我只是在发现可接受的答案的同时明白出了什么问题。

接受的答案提出了一个干净的解决方案，但我想我会提出一个替代观点，我在下面提出的代码 sn-p 对我最初的尝试（如问题所示）所做的更改较少，希望它能证明我的基本错误理解。

我的代码的根本问题是我忽略了“每个参与者都有自己的上下文”的规则。正如您从问题中的编译错误中看到的那样，幸运的是 Actix 使用 rust 编译器来强制执行此规则。

现在我明白了，看起来我试图做的错误的事情是生成另一个演员并让该演员以某种方式在原始演员的上下文中移动/复制，以便它可以响应流程输出行。当然没有必要这样做，因为 Actor 模型就是让 Actor 通过消息进行通信。

相反，当生成一个新的 Actor 时，我应该将原始 Actor 的地址传递给它，从而允许新生成的 Actor 发送回更新。原始参与者使用处理程序处理这些消息（下面的struct Line）。

正如我所说，接受的答案也是这样做的，但使用一个看起来比我的循环更优雅的解决方案的映射器。

mod processrunner;
use std::time::{Duration, Instant};

use actix::prelude::*;
use actix_files as fs;
use actix_web::{middleware, web, App, Error, HttpRequest, HttpResponse, HttpServer};
use actix_web_actors::ws;

/// How often heartbeat pings are sent
const HEARTBEAT_INTERVAL: Duration = Duration::from_secs(5);
/// How long before lack of client response causes a timeout
const CLIENT_TIMEOUT: Duration = Duration::from_secs(10);

/// do websocket handshake and start `MyWebSocket` actor
async fn ws_index(r: HttpRequest, stream: web::Payload) -> Result<HttpResponse, Error> {
    println!("{:?}", r);
    let res = ws::start(MyWebSocket::new(), &r, stream);
    println!("{:?}", res);
    res
}

/// websocket connection is long running connection, it easier
/// to handle with an actor
struct MyWebSocket {
    /// Client must send ping at least once per 10 seconds (CLIENT_TIMEOUT),
    /// otherwise we drop connection.
    hb: Instant,
}

impl Actor for MyWebSocket {
    type Context = ws::WebsocketContext<Self>;

    /// Method is called on actor start. We start the heartbeat process here.
    fn started(&mut self, ctx: &mut Self::Context) {
        self.hb(ctx);
    }
}

#[derive(Message)]
#[rtype(result = "()")]
pub struct Line {
    line: String,
}
impl Handler<Line> for MyWebSocket {
    type Result = ();

    fn handle(&mut self, msg: Line, ctx: &mut Self::Context) {
        ctx.text(msg.line);
    }
}

/// Handler for `ws::Message`
impl StreamHandler<Result<ws::Message, ws::ProtocolError>> for MyWebSocket {
    fn handle(&mut self, msg: Result<ws::Message, ws::ProtocolError>, ctx: &mut Self::Context) {
        // process websocket messages
        println!("WS: {:?}", msg);
        match msg {
            Ok(ws::Message::Ping(msg)) => {
                self.hb = Instant::now();
                ctx.pong(&msg);
            }
            Ok(ws::Message::Pong(_)) => {
                self.hb = Instant::now();
            }
            Ok(ws::Message::Text(text)) => {
                let recipient = ctx.address().recipient();
                let future = async move {
                    let reader = processrunner::run_process(text).await;
                    let mut reader = reader.ok().unwrap();
                    while let Some(line) = reader.next_line().await.unwrap() {
                        println!("line = {}", line);
                        recipient.do_send(Line { line });
                    }
                };

                future.into_actor(self).spawn(ctx);
            }
            Ok(ws::Message::Binary(bin)) => ctx.binary(bin),
            Ok(ws::Message::Close(reason)) => {
                ctx.close(reason);
                ctx.stop();
            }
            _ => ctx.stop(),
        }
    }
}

impl MyWebSocket {
    fn new() -> Self {
        Self { hb: Instant::now() }
    }

    /// helper method that sends ping to client every second.
    ///
    /// also this method checks heartbeats from client
    fn hb(&self, ctx: &mut <Self as Actor>::Context) {
        ctx.run_interval(HEARTBEAT_INTERVAL, |act, ctx| {
            // check client heartbeats
            if Instant::now().duration_since(act.hb) > CLIENT_TIMEOUT {
                // heartbeat timed out
                println!("Websocket Client heartbeat failed, disconnecting!");

                // stop actor
                ctx.stop();

                // don't try to send a ping
                return;
            }

            ctx.ping(b"");
        });
    }
}

#[actix_web::main]
async fn main() -> std::io::Result<()> {
    std::env::set_var("RUST_LOG", "actix_server=info,actix_web=info");
    env_logger::init();

    HttpServer::new(|| {
        App::new()
            // enable logger
            .wrap(middleware::Logger::default())
            // websocket route
            .service(web::resource("/ws/").route(web::get().to(ws_index)))
            // static files
            .service(fs::Files::new("/", "static/").index_file("index.html"))
    })
    // start http server on 127.0.0.1:8080
    .bind("127.0.0.1:8080")?
    .run()
    .await
}