src/client/dns.rs

// 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::net::ToSocketAddrs;

use rand::prelude::SliceRandom;
use reqwest::dns::{Addrs, Name, Resolve, Resolving};
use tokio::task::JoinSet;

type DynErr = Box<dyn std::error::Error + Send + Sync>;

#[derive(Debug)]
pub(crate) struct ShuffleResolver;

impl Resolve for ShuffleResolver {
    fn resolve(&self, name: Name) -> Resolving {
        Box::pin(async move {
            // use `JoinSet` to propagate cancelation to tasks that haven't started running yet.
            let mut tasks = JoinSet::new();
            tasks.spawn_blocking(move || {
                let it = (name.as_str(), 0).to_socket_addrs()?;
                let mut addrs = it.collect::<Vec<_>>();

                addrs.shuffle(&mut rand::rng());

                Ok(Box::new(addrs.into_iter()) as Addrs)
            });

            tasks
                .join_next()
                .await
                .expect("spawned on task")
                .map_err(|err| Box::new(err) as DynErr)?
        })
    }
}