dubbo 0.4.0

dubbo
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

use std::task::Poll;

use crate::StdError;
use futures_util::future;
use http::Request;
use tower::{retry::Retry, util::Oneshot, ServiceExt};
use tower_service::Service;

pub struct Failover<N> {
    inner: N, // loadbalancer service
}

#[derive(Clone)]
pub struct FailoverPolicy;

impl<N> Failover<N> {
    pub fn new(inner: N) -> Self {
        Self { inner }
    }
}

impl<B, Res, E> tower::retry::Policy<Request<B>, Res, E> for FailoverPolicy
where
    B: http_body::Body + Clone,
{
    type Future = future::Ready<Self>;

    fn retry(&self, _req: &Request<B>, result: Result<&Res, &E>) -> Option<Self::Future> {
        //TODO some error handling or logging
        match result {
            Ok(_) => None,
            Err(_) => Some(future::ready(self.clone())),
        }
    }

    fn clone_request(&self, req: &Request<B>) -> Option<Request<B>> {
        let mut clone = http::Request::new(req.body().clone());
        *clone.method_mut() = req.method().clone();
        *clone.uri_mut() = req.uri().clone();
        *clone.headers_mut() = req.headers().clone();
        *clone.version_mut() = req.version();

        Some(clone)
    }
}

impl<N, B> Service<Request<B>> for Failover<N>
where
    // B is CloneBody<B>
    B: http_body::Body + Clone,
    // loadbalancer service
    N: Service<Request<B>> + Clone + 'static,
    N::Error: Into<StdError>,
    N::Future: Send,
{
    type Response = N::Response;

    type Error = N::Error;

    type Future = Oneshot<Retry<FailoverPolicy, N>, Request<B>>;

    fn poll_ready(&mut self, cx: &mut std::task::Context<'_>) -> Poll<Result<(), Self::Error>> {
        self.inner.poll_ready(cx)
    }

    fn call(&mut self, req: Request<B>) -> Self::Future {
        let retry = Retry::new(FailoverPolicy, self.inner.clone());
        retry.oneshot(req)
    }
}