尝试做 courses/dss/raft test_2a，将 Raft::send_request_vote 方法中的注释解开，期望能正常调用RPC。 以下是 send_request_vote 的代码：
fn send_request_vote(
&self,
server: usize,
args: &RequestVoteArgs,
) -> Receiver<Result<RequestVoteReply>> {
// Your code here if you want the rpc becomes async.
// Example:
// ```
// let peer = &self.peers[server];
// let (tx, rx) = channel();
// peer.spawn(
// peer.request_vote(&args)
// .map_err(Error::Rpc)
// .then(move |res| {
// tx.send(res);
// Ok(())
// }),
// );
// rx
// ```
let (tx, rx) = sync_channel::<Result<RequestVoteReply>>(1);
// crate::your_code_here((server, args, tx, rx))
let peer = &self.peers[server];
peer.spawn(
peer.request_vote(&args)
.map_err(Error::Rpc)
.then(move |res| {
tx.send(res);
Ok(())
}),
);
rx
}
自己理解没有错的话，peer.request_vote 语句调用的是 raft/src/proto/mod.rs:6 中的代码
pub mod raftpb {
include!(concat!(env!("OUT_DIR"), "/raftpb.rs"));
labrpc::service! {
service raft {
rpc request_vote(RequestVoteArgs) returns (RequestVoteReply);
rpc heart_beat(AppendEntriesArgs) returns (AppendEntriesReply);
// Your code here if more rpc desired.
// rpc xxx(yyy) returns (zzz)
}
}
pub use self::raft::{
add_service as add_raft_service, Client as RaftClient, Service as RaftService,
};
}
- request_vote 方法 return 的对象是
RpcFuture，也就是一个Box包装过的Future。Future本身是有这个map_err方法的。 - raft/mod.rs 也引入了
use labrpc::RpcFuture; - 整个 RPC 调用逻辑，我并没有做修改。只修改了以下文件
- dss/raft/src/raft/mod.rs
- dss/raft/src/proto/raft.proto
- dss/raft/src/proto/mod.rs
问题
执行命令 make test_2a 后，报错：
cargo fmt --all -- --check
cargo clippy --all --tests -- -D clippy::all
Checking raft v0.1.0 (/Users/asiafrank/workspace/pingcap-talent-plan-learning/dss/raft)
error: the `map_err` method cannot be invoked on a trait object
--> raft/src/raft/mod.rs:208:18
|
208 | .map_err(Error::Rpc)
| ^^^^^^^
|
::: /Users/asiafrank/.cargo/registry/src/github.com-1ecc6299db9ec823/futures-0.1.27/src/future/mod.rs:412:21
|
412 | Self: Sized,
| ----- this has a `Sized` requirement
|
= note: another candidate was found in the following trait, perhaps add a `use` for it:
`use crate::proto::raftpb::raft::__futures::Future;`
error: aborting due to 2 previous errors
error: could not compile `raft`.
To learn more, run the command again with --verbose.
make: *** [check] Error 101
求助各位大神，这个问题出现的原因是什么，怎么解决？