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|
use smol::{
future,
lock::{Mutex, RwLock},
prelude::*,
Task, Timer,
};
use std::{
collections::{HashMap, HashSet},
sync::Arc,
time::Duration,
};
use crate::{msg::*, topology::Topology};
use common::{
msg::{MessageHeader, Output},
msg_id::{gen_msg_id, MessageID},
Handler,
};
const RETRY_TIMEOUT_SECS: u64 = 1;
pub struct BroadcastHandler {
node_id: String,
seen: RwLock<HashSet<BroadcastTarget>>,
topology: Topology,
output: Output<BroadcastBody>,
attempted_broadcasts: Mutex<HashMap<MessageID, Task<()>>>,
}
impl Handler for BroadcastHandler {
type Body = BroadcastBody;
fn init(node_id: String, node_ids: Vec<String>, output: Output<Self::Body>) -> Self {
BroadcastHandler {
node_id,
topology: Topology::dense(node_ids.clone()),
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,
path,
} => {
future::zip(
self.receive_broadcast(&header.src, path, message),
self.send_broadcast_ok(&header.src, msg_id),
)
.await;
}
BroadcastBody::Broadcast {
msg_id: None,
message,
path,
} => {
self.receive_broadcast(&header.src, path, message).await;
}
BroadcastBody::Topology { msg_id, topology } => {
// Start using the new topology
self.topology.replace(topology).await;
// 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
}
BroadcastBody::BroadcastOk { in_reply_to } => {
// Stop retrying, if we still are
if let Some(task) = self.attempted_broadcasts.lock().await.remove(&in_reply_to)
{
task.cancel().await;
}
}
// Ignore other OK messages - we never actually request them
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,
previous_path: Option<Vec<String>>,
message: BroadcastTarget,
) {
let new = self.seen.write().await.insert(message);
if !new {
return;
}
// Race all send futures
let mut previous_path = previous_path.unwrap_or_else(|| vec![]);
previous_path.push(src.to_string());
let mut tasks = self.attempted_broadcasts.lock().await;
for target in self
.topology
.targets(&self.node_id, previous_path.iter().map(String::as_str))
.await
{
let msg_id = gen_msg_id();
let this = self.clone();
let path = previous_path.clone();
tasks.insert(
msg_id,
smol::spawn(async move {
loop {
this.output
.send(
&target,
&BroadcastBody::Broadcast {
msg_id: Some(msg_id),
message,
path: Some(path.clone()),
},
)
.await;
Timer::after(Duration::from_secs(RETRY_TIMEOUT_SECS)).await;
}
}),
);
}
}
}
|
