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docs: add description for fuse() in handling_disconnection

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Ref #88
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surechen 2021-08-24 19:38:21 +08:00 committed by GitHub
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1 changed files with 4 additions and 3 deletions
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docs/src/tutorial/handling_disconnection.md
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@ -90,12 +90,12 @@ async fn connection_writer_loop(
let mut shutdown = shutdown.fuse(); let mut shutdown = shutdown.fuse();
loop { // 2 loop { // 2
select! { select! {
msg = messages.next().fuse() => match msg { msg = messages.next().fuse() => match msg { // 3
Some(msg) => stream.write_all(msg.as_bytes()).await?, Some(msg) => stream.write_all(msg.as_bytes()).await?,
None => break, None => break,
}, },
void = shutdown.next().fuse() => match void { void = shutdown.next().fuse() => match void {
Some(void) => match void {}, // 3 Some(void) => match void {}, // 4
None => break, None => break,
} }
} }
@ -106,7 +106,8 @@ async fn connection_writer_loop(
1. We add shutdown channel as an argument. 1. We add shutdown channel as an argument.
2. Because of `select`, we can't use a `while let` loop, so we desugar it further into a `loop`. 2. Because of `select`, we can't use a `while let` loop, so we desugar it further into a `loop`.
3. In the shutdown case we use `match void {}` as a statically-checked `unreachable!()`. 3. Function fuse() is used to turn any `Stream` into a `FusedStream`. This is used for fusing a stream such that poll_next will never again be called once it has finished.
4. In the shutdown case we use `match void {}` as a statically-checked `unreachable!()`.
Another problem is that between the moment we detect disconnection in `connection_writer_loop` and the moment when we actually remove the peer from the `peers` map, new messages might be pushed into the peer's channel. Another problem is that between the moment we detect disconnection in `connection_writer_loop` and the moment when we actually remove the peer from the `peers` map, new messages might be pushed into the peer's channel.
To not lose these messages completely, we'll return the messages channel back to the broker. To not lose these messages completely, we'll return the messages channel back to the broker.