如何从带有客户端的 actix-web 处理程序向调用者返回错误？

Question

我使用 actix_web 创建了一个服务器，它将通过 GET 连接到另一个使用 actix 客户端的服务，并在成功时返回正文或在错误时返回错误。我已经能够返回正文，但不知道如何返回错误。

这是我的处理程序：

fn echo_client(client: web::Data<Client>) -> impl Future<Item = HttpResponse, Error = Error> {
    client
        .get("127.0.0.1:9596/echo/javier") // <- Create request builder
        .header("User-Agent", "Actix-web")
        //.finish().unwrap()
        .send() // <- Send http request
        .map_err(|_| ())
        //.map_err(Error::from)
        .and_then(|response| {
            response
                .body()
                .and_then(|body| {
                    println!("{:?}", body);
                    Ok(HttpResponse::Ok().body(body))
                })
                .map_err(|error| Err(error.error_response()))
        })
}

Answer 1

可能会失败的三件事：

1. 连接失败。
2. 非 200 状态代码。
3. 体流突然停止。

要处理 1，不 map_err 到 ()：

.map_err(|err| match err {
    SendRequestError::Connect(error) => {
        ErrorBadGateway(format!("Unable to connect to httpbin: {}", error))
    }
    error => ErrorInternalServerError(error),
})

SendRequestError 列出了在执行客户端请求时可能发生的错误。

要处理 2，请确保使用客户端响应中的状态代码：

.and_then(|response| Ok(HttpResponse::build(response.status()).streaming(response))))

actix-web 处理 3 我相信。

完整示例，也处理标题：

use actix_web::client::{Client, SendRequestError};
use actix_web::error::{ErrorBadGateway, ErrorInternalServerError};
use actix_web::{web, App, Error, HttpResponse, HttpServer};
use futures::future::Future;

fn main() {
    HttpServer::new(|| App::new().data(Client::new()).route("/", web::to(handler)))
        .bind("127.0.0.1:8000")
        .expect("Cannot bind to port 8000")
        .run()
        .expect("Unable to run server");
}

fn handler(client: web::Data<Client>) -> Box<Future<Item = HttpResponse, Error = Error>> {
    Box::new(
        client
            .get("https://httpbin.org/get")
            .no_decompress()
            .send()
            .map_err(|err| match err {
                SendRequestError::Connect(error) => {
                    ErrorBadGateway(format!("Unable to connect to httpbin: {}", error))
                }
                error => ErrorInternalServerError(error),
            })
            .and_then(|response| {
                let mut result = HttpResponse::build(response.status());
                let headers = response
                    .headers()
                    .iter()
                    .filter(|(h, _)| *h != "connection" && *h != "content-length");
                for (header_name, header_value) in headers {
                    result.header(header_name.clone(), header_value.clone());
                }
                Ok(result.streaming(response))
            }),
    )
}

实际上失败了：

$ curl -v localhost:8000
* Rebuilt URL to: localhost:8000/
*   Trying 127.0.0.1...
* TCP_NODELAY set
* Connected to localhost (127.0.0.1) port 8000 (#0)
> GET / HTTP/1.1
> Host: localhost:8000
> User-Agent: curl/7.54.0
> Accept: */*
> 
< HTTP/1.1 502 Bad Gateway
< content-length: 50
< content-type: text/plain
< date: Sun, 07 Jul 2019 21:01:39 GMT
< 
* Connection #0 to host localhost left intact
Unable to connect to httpbin: SSL is not supported

在 Cargo.toml 中添加 ssl 作为功能来修复连接错误：

actix-web = { version = "1.0", features=["ssl"] }

然后再次尝试请求：

$ curl -v localhost:8000
* Rebuilt URL to: localhost:8000/
*   Trying 127.0.0.1...
* TCP_NODELAY set
* Connected to localhost (127.0.0.1) port 8000 (#0)
> GET / HTTP/1.1
> Host: localhost:8000
> User-Agent: curl/7.54.0
> Accept: */*
> 
< HTTP/1.1 200 OK
< transfer-encoding: chunked
< x-frame-options: DENY
< date: Sun, 07 Jul 2019 21:07:18 GMT
< content-type: application/json
< access-control-allow-origin: *
< access-control-allow-credentials: true
< server: nginx
< x-content-type-options: nosniff
< x-xss-protection: 1; mode=block
< referrer-policy: no-referrer-when-downgrade
< 
{
  "args": {}, 
  "headers": {
    "Date": "Sun, 07 Jul 2019 21:07:18 GMT", 
    "Host": "httpbin.org"
  }, 
  "origin": "212.251.175.90, 212.251.175.90", 
  "url": "https://httpbin.org/get"
}