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|
use smol::{
lock::{Mutex, RwLock},
prelude::*,
Task, Timer,
};
use std::{
collections::{HashMap, HashSet},
sync::Arc,
time::Duration,
};
use crate::msg::*;
use common::{
msg::{MessageHeader, Output},
msg_id::{gen_msg_id, MessageID},
Handler,
};
const RETRY_TIMEOUT: u64 = 2;
pub struct BroadcastHandler {
node_id: String,
seen: RwLock<HashSet<BroadcastTarget>>,
broadcast_targets: RwLock<Vec<String>>,
output: Output<BroadcastBody>,
attempted_broadcasts: Mutex<HashMap<MessageID, Task<()>>>,
}
impl Handler for BroadcastHandler {
type Body = BroadcastBody;
fn init(node_id: String, mut node_ids: Vec<String>, output: Output<Self::Body>) -> Self {
node_ids.retain(|x| *x != node_id);
BroadcastHandler {
node_id,
broadcast_targets: RwLock::new(node_ids),
seen: RwLock::new(HashSet::new()),
output,
attempted_broadcasts: Mutex::default(),
}
}
fn handle<'a>(
self: &'a Arc<Self>,
header: MessageHeader,
body: BroadcastBody,
) -> impl Future<Output = ()> + Send + 'a {
async move {
match body {
BroadcastBody::Broadcast {
msg_id: Some(msg_id),
message,
} => {
self.receive_broadcast(&header.src, message).await;
self.send_broadcast_ok(&header.src, msg_id).await;
}
BroadcastBody::Broadcast {
msg_id: None,
message,
} => {
self.receive_broadcast(&header.src, message).await;
}
BroadcastBody::Topology {
msg_id,
mut topology,
} => {
// Start using the new topology
if let Some(broadcast_targets) = topology.remove(&self.node_id) {
*self.broadcast_targets.write().await = broadcast_targets;
}
// Send reply if needed
if let Some(msg_id) = msg_id {
self.output
.send(
&header.src,
&BroadcastBody::TopologyOk {
in_reply_to: msg_id,
},
)
.await;
}
}
BroadcastBody::Read { msg_id } => {
// Send all received messages back
self.output
.send(
&header.src,
&BroadcastBody::ReadOk {
in_reply_to: msg_id,
messages: self.seen.read().await.clone(),
},
)
.await
}
// Ignore OK messages - we never actually request them
BroadcastBody::BroadcastOk { in_reply_to } => {
if let Some(task) = self.attempted_broadcasts.lock().await.remove(&in_reply_to)
{
task.cancel().await;
}
}
BroadcastBody::TopologyOk { .. } => {}
BroadcastBody::ReadOk { .. } => {}
}
}
}
}
impl BroadcastHandler {
/// Reply with a broadcast OK message
async fn send_broadcast_ok(&self, src: &str, msg_id: MessageID) {
self.output
.send(
&src,
&BroadcastBody::BroadcastOk {
in_reply_to: msg_id,
},
)
.await;
}
/// Receive a given message, and broadcast it onwards if it is new
async fn receive_broadcast(self: &Arc<Self>, src: &str, message: BroadcastTarget) {
let new = self.seen.write().await.insert(message);
if !new {
return;
}
// Ensure we don't keep holding the read lock
let targets = self.broadcast_targets.read().await.clone();
// Race all send futures
let mut tasks = self.attempted_broadcasts.lock().await;
for target in targets.into_iter() {
if &target == &src {
return;
}
let msg_id = gen_msg_id();
let this = self.clone();
tasks.insert(
msg_id,
smol::spawn(async move {
loop {
this.output
.send(
&target,
&BroadcastBody::Broadcast {
msg_id: None,
message,
},
)
.await;
Timer::after(Duration::from_secs(RETRY_TIMEOUT)).await;
}
}),
);
}
}
}
|
