refactor(iroh): Remove flume from iroh gossip (#2542)

## Description

refactor(iroh): Remove flume from iroh gossip

Yes, I know there is a PR that touches gossip. But just let me do my
purge.

## Breaking Changes

None

## Notes & open questions

None

## Change checklist

- [x] Self-review.
- [x] Documentation updates following the [style
guide](https://rust-lang.github.io/rfcs/1574-more-api-documentation-conventions.html#appendix-a-full-conventions-text),
if relevant.
- [x] Tests if relevant.
- [x] All breaking changes documented.

iroh-gossip/Cargo.toml

@@ -38,8 +38,8 @@ tokio-util = { version = "0.7.8", optional = true, features = ["codec"] }
 genawaiter = { version = "0.99.1", default-features = false, features = ["futures03"] }
 
 # dispatcher dependencies (optional)
+async-channel = { version = "2.3.1", optional = true }
 futures-util = { version = "0.3.30", optional = true }
-flume = { version = "0.11", optional = true }
 
 [dev-dependencies]
 clap = { version = "4", features = ["derive"] }
@@ -51,7 +51,7 @@ url = "2.4.0"
 [features]
 default = ["net", "dispatcher"]
 net = ["dep:futures-lite", "dep:iroh-net", "dep:tokio", "dep:tokio-util"]
-dispatcher = ["dep:flume", "dep:futures-util"]
+dispatcher = ["dep:async-channel", "dep:futures-util"]
 
 [[example]]
 name = "chat"

iroh-gossip/src/dispatcher.rs

@@ -10,6 +10,7 @@ use crate::{
     proto::{DeliveryScope, TopicId},
 };
 use bytes::Bytes;
+use futures_lite::StreamExt;
 use futures_util::Stream;
 use iroh_base::rpc::{RpcError, RpcResult};
 use iroh_net::{key::PublicKey, util::AbortingJoinHandle, NodeId};
@@ -106,7 +107,7 @@ struct State {
 /// Type alias for a stream of gossip updates, so we don't have to repeat all the bounds.
 type CommandStream = Box<dyn Stream<Item = Command> + Send + Sync + Unpin + 'static>;
 /// Type alias for a sink of gossip events.
-type EventSink = flume::Sender<RpcResult<Event>>;
+type EventSink = async_channel::Sender<RpcResult<Event>>;
 
 #[derive(derive_more::Debug)]
 enum TopicState {
@@ -214,7 +215,7 @@ impl GossipDispatcher {
     /// This will not wait until the sink is full, but send a `Lagged` response if the sink is almost full.
     fn try_send(send: &EventSink, event: &IrohGossipEvent) -> bool {
         // If the stream is disconnected, we don't need to send to it.
-        if send.is_disconnected() {
+        if send.is_closed() {
             return false;
         }
         // Check if the send buffer is almost full, and send a lagged response if it is.
@@ -234,7 +235,6 @@ impl GossipDispatcher {
     ///
     /// This should not fail unless the gossip instance is faulty.
     async fn dispatch_loop(mut self) -> anyhow::Result<()> {
-        use futures_lite::stream::StreamExt;
         let stream = self.gossip.clone().subscribe_all();
         tokio::pin!(stream);
         while let Some(item) = stream.next().await {
@@ -306,7 +306,6 @@ impl GossipDispatcher {
         topic: TopicId,
         mut updates: CommandStream,
     ) -> anyhow::Result<()> {
-        use futures_lite::stream::StreamExt;
         while let Some(update) = Pin::new(&mut updates).next().await {
             match update {
                 Command::Broadcast(msg) => {
@@ -404,7 +403,7 @@ impl GossipDispatcher {
                         let mut update_tasks = vec![];
                         for (updates, event_sink) in waiting {
                             // if the stream is disconnected, we don't need to keep it and start the update task
-                            if event_sink.is_disconnected() {
+                            if event_sink.is_closed() {
                                 continue;
                             }
                             event_sinks.push(event_sink);
@@ -438,9 +437,9 @@ impl GossipDispatcher {
         topic: TopicId,
         options: SubscribeOptions,
         updates: CommandStream,
-    ) -> impl Stream<Item = RpcResult<Event>> {
+    ) -> impl Stream<Item = RpcResult<Event>> + Unpin {
         let mut inner = self.inner.lock().unwrap();
-        let (send, recv) = flume::bounded(options.subscription_capacity);
+        let (send, recv) = async_channel::bounded(options.subscription_capacity);
         match inner.current_subscriptions.entry(topic) {
             Entry::Vacant(entry) => {
                 // There is no existing subscription, so we need to start a new one.
@@ -490,7 +489,7 @@ impl GossipDispatcher {
                 }
             }
         }
-        recv.into_stream()
+        recv.boxed()
     }
 }