How to return an error to caller from an actix-web handler with client? - rust

Question

I created a server with actix_web that will connect through GET to another service using actix client and return body on success or error on error. I have been able to return the body but have no clue about how to return the error.
This is my handler:
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

There are three things that may fail:
Failing connection.
Non 200-status code.
Abrupt stop in body stream.
To handle 1, do not map_err to ():
.map_err(|err| match err {
SendRequestError::Connect(error) => {
ErrorBadGateway(format!("Unable to connect to httpbin: {}", error))
}
error => ErrorInternalServerError(error),
})
SendRequestError lists the errors that can occur when doing client requests.
To handle 2, make sure you use the status code from the client response:
.and_then(|response| Ok(HttpResponse::build(response.status()).streaming(response))))
actix-web handles 3 I believe.
Complete example, handling headers too:
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))
}),
)
}
Which actually failed:
$ 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
Add ssl as a feature in Cargo.toml to fix the connection error:
actix-web = { version = "1.0", features=["ssl"] }
Then try the request again:
$ 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"
}