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Refactor send queue #105

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ac40c09
Simplify ThresholdWatcher
boivie Mar 20, 2026
6ed88c7
Refactor SendQueue
boivie Mar 20, 2026
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162 changes: 72 additions & 90 deletions src/tx/send_queue.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -33,8 +33,6 @@ use crate::types::StreamKey;
use std::cell::RefCell;
use std::collections::HashMap;
use std::collections::VecDeque;
use std::ops::AddAssign;
use std::ops::SubAssign;
use std::rc::Rc;
use std::time::Duration;

Expand Down Expand Up @@ -115,10 +113,9 @@ impl Item {
}
}

struct ThresholdWatcher<'a> {
struct ThresholdWatcher {
value: usize,
low_threshold: usize,
low_cb: Box<dyn Fn() + 'a>,
}

fn add_lifecycle_events(events: &Rc<RefCell<dyn EventSink>>, lifecycle_id: &Option<LifecycleId>) {
Expand All @@ -128,57 +125,54 @@ fn add_lifecycle_events(events: &Rc<RefCell<dyn EventSink>>, lifecycle_id: &Opti
}
}

impl<'a> ThresholdWatcher<'a> {
pub fn new(low_threshold: usize, low_cb: impl Fn() + 'a) -> Self {
Self { value: 0, low_threshold, low_cb: Box::new(low_cb) }
impl ThresholdWatcher {
pub fn new(low_threshold: usize) -> Self {
Self { value: 0, low_threshold }
}

pub fn set_low_threshold(&mut self, low_threshold: usize) {
if self.low_threshold < self.value && low_threshold >= self.value {
(self.low_cb)();
}
self.low_threshold = low_threshold;
pub fn add(&mut self, amount: usize) {
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@lndmrk lndmrk Mar 20, 2026

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Maybe add a comment here for consistency

self.value += amount;
}
}

impl AddAssign<usize> for ThresholdWatcher<'_> {
fn add_assign(&mut self, rhs: usize) {
self.value += rhs;
// Returns `true` if the threshold was crossed downwards.
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@lndmrk lndmrk Mar 20, 2026

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/// To make it a doc comment (since it's pub)

#[must_use]
pub fn sub(&mut self, amount: usize) -> bool {
debug_assert!(self.value >= amount);
let old_value = self.value;
self.value -= amount;
old_value > self.low_threshold && self.value <= self.low_threshold
}
}

impl SubAssign<usize> for ThresholdWatcher<'_> {
fn sub_assign(&mut self, rhs: usize) {
debug_assert!(self.value >= rhs);

let old_value = self.value;
self.value -= rhs;
if old_value > self.low_threshold && self.value <= self.low_threshold {
(self.low_cb)();
}
// Returns `true` if the new threshold is lower than the current value, which means that the
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@lndmrk lndmrk Mar 20, 2026

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Ditto

// new low threshold was crossed.
#[must_use]
pub fn set_low_threshold(&mut self, low_threshold: usize) -> bool {
let triggered = self.low_threshold < self.value && low_threshold >= self.value;
self.low_threshold = low_threshold;
triggered
}
}

/// Per-stream information.
struct OutgoingStream<'a> {
struct OutgoingStream {
priority: u16,
pause_state: PauseState,
next_unordered_mid: Mid,
next_ordered_mid: Mid,
next_ssn: Ssn,
buffered_amount: ThresholdWatcher<'a>,
buffered_amount: ThresholdWatcher,
items: VecDeque<Item>,
}

impl<'a> OutgoingStream<'a> {
fn new(priority: u16, low_threshold: usize, low_cb: impl Fn() + 'a) -> Self {
impl OutgoingStream {
fn new(priority: u16, low_threshold: usize) -> Self {
Self {
priority,
pause_state: PauseState::NotPaused,
next_unordered_mid: Mid(0),
next_ordered_mid: Mid(0),
next_ssn: Ssn(0),
buffered_amount: ThresholdWatcher::new(low_threshold, low_cb),
buffered_amount: ThresholdWatcher::new(low_threshold),
items: VecDeque::new(),
}
}
Expand All @@ -188,10 +182,10 @@ pub struct SendQueue {
enable_message_interleaving: bool,
default_priority: u16,
default_low_buffered_amount_low_threshold: usize,
buffered_amount: ThresholdWatcher<'static>,
buffered_amount: ThresholdWatcher,
current_message_id: OutgoingMessageId,
scheduler: StreamScheduler,
streams: HashMap<StreamId, OutgoingStream<'static>>,
streams: HashMap<StreamId, OutgoingStream>,
events: Rc<RefCell<dyn EventSink>>,
}

Expand All @@ -201,24 +195,16 @@ impl SendQueue {
options: &Options,
events: Rc<RefCell<dyn EventSink>>,
) -> Self {
let buffered_amount_low_events = Rc::clone(&events);
Self {
enable_message_interleaving: false,
default_priority: options.default_stream_priority,
default_low_buffered_amount_low_threshold: options
.default_stream_buffered_amount_low_threshold,
buffered_amount: ThresholdWatcher::new(
options.total_buffered_amount_low_threshold,
move || {
buffered_amount_low_events
.borrow_mut()
.add(SocketEvent::OnTotalBufferedAmountLow());
},
),
buffered_amount: ThresholdWatcher::new(options.total_buffered_amount_low_threshold),
current_message_id: OutgoingMessageId(0),
streams: HashMap::new(),
scheduler: StreamScheduler::new(max_payload_bytes),
events: Rc::clone(&events),
events,
}
}

Expand Down Expand Up @@ -247,8 +233,12 @@ impl SendQueue {
let item = stream.items.front().unwrap();
if item.attributes.expires_at <= now {
// Oops, this entire message has already expired. Try the next one.
self.buffered_amount -= item.remaining_size;
stream.buffered_amount -= item.remaining_size;
if self.buffered_amount.sub(item.remaining_size) {
self.events.borrow_mut().add(SocketEvent::OnTotalBufferedAmountLow());
}
if stream.buffered_amount.sub(item.remaining_size) {
self.events.borrow_mut().add(SocketEvent::OnBufferedAmountLow(stream_id));
}
add_lifecycle_events(&self.events, &item.attributes.lifecycle_id);
stream.items.pop_front();
let priority = self.enable_message_interleaving.then_some(stream.priority);
Expand All @@ -268,15 +258,8 @@ impl SendQueue {
self.scheduler.peek(usize::MAX).is_some()
}

fn make_stream(
stream_id: StreamId,
priority: u16,
low_threshold: usize,
events: Rc<RefCell<dyn EventSink>>,
) -> OutgoingStream<'static> {
OutgoingStream::new(priority, low_threshold, move || {
events.borrow_mut().add(SocketEvent::OnBufferedAmountLow(stream_id));
})
fn make_stream(priority: u16, low_threshold: usize) -> OutgoingStream {
OutgoingStream::new(priority, low_threshold)
}

pub fn add(&mut self, now: SocketTime, message: Message, send_options: &SendOptions) {
Expand All @@ -291,16 +274,14 @@ impl SendQueue {
let stream_id = message.stream_id;
let stream = self.streams.entry(stream_id).or_insert_with(|| {
SendQueue::make_stream(
stream_id,
self.default_priority,
self.default_low_buffered_amount_low_threshold,
Rc::clone(&self.events),
)
});
let message_id = self.current_message_id;
self.current_message_id += 1;
stream.buffered_amount += message.payload.len();
self.buffered_amount += message.payload.len();
stream.buffered_amount.add(message.payload.len());
self.buffered_amount.add(message.payload.len());
stream.items.push_back(Item::new(message_id, message, attributes));
if (stream.pause_state == PauseState::NotPaused
|| stream.pause_state == PauseState::Pending)
Expand Down Expand Up @@ -338,8 +319,12 @@ impl SendQueue {
.get(item.remaining_offset..size + item.remaining_offset)
.unwrap()
.to_vec();
self.buffered_amount -= payload.len();
stream.buffered_amount -= payload.len();
if self.buffered_amount.sub(payload.len()) {
self.events.borrow_mut().add(SocketEvent::OnTotalBufferedAmountLow());
}
if stream.buffered_amount.sub(payload.len()) {
self.events.borrow_mut().add(SocketEvent::OnBufferedAmountLow(stream_id));
}

let data = Data {
stream_key: StreamKey::new(item.attributes.unordered, stream_id),
Expand Down Expand Up @@ -392,8 +377,12 @@ impl SendQueue {
if item.message_id != message_id {
return;
}
self.buffered_amount -= item.remaining_size;
stream.buffered_amount -= item.remaining_size;
if self.buffered_amount.sub(item.remaining_size) {
self.events.borrow_mut().add(SocketEvent::OnTotalBufferedAmountLow());
}
if stream.buffered_amount.sub(item.remaining_size) {
self.events.borrow_mut().add(SocketEvent::OnBufferedAmountLow(stream_id));
}
add_lifecycle_events(&self.events, &item.attributes.lifecycle_id);
stream.items.pop_front();

Expand All @@ -413,10 +402,8 @@ impl SendQueue {
pub fn prepare_reset_stream(&mut self, stream_id: StreamId) {
let stream = self.streams.entry(stream_id).or_insert_with(|| {
SendQueue::make_stream(
stream_id,
self.default_priority,
self.default_low_buffered_amount_low_threshold,
Rc::clone(&self.events),
)
});
if stream.pause_state != PauseState::NotPaused {
Expand All @@ -442,8 +429,12 @@ impl SendQueue {
// will always deliver all the fragments before actually resetting the stream.
stream.items.retain_mut(|i| {
if i.remaining_offset == 0 {
stream.buffered_amount -= i.remaining_size;
self.buffered_amount -= i.remaining_size;
if stream.buffered_amount.sub(i.remaining_size) {
self.events.borrow_mut().add(SocketEvent::OnBufferedAmountLow(stream_id));
}
if self.buffered_amount.sub(i.remaining_size) {
self.events.borrow_mut().add(SocketEvent::OnTotalBufferedAmountLow());
}
add_lifecycle_events(&self.events, &i.attributes.lifecycle_id);
return false;
}
Expand All @@ -465,14 +456,14 @@ impl SendQueue {
}

pub fn get_streams_ready_to_reset(&mut self) -> Vec<StreamId> {
let mut ready: Vec<StreamId> = Vec::new();
self.streams.iter_mut().for_each(|(stream_id, stream)| {
if stream.pause_state == PauseState::Paused {
self.streams
.iter_mut()
.filter(|(_, stream)| stream.pause_state == PauseState::Paused)
.map(|(stream_id, stream)| {
stream.pause_state = PauseState::Resetting;
ready.push(*stream_id);
}
});
ready
*stream_id
})
.collect()
}

pub fn commit_reset_streams(&mut self) {
Expand Down Expand Up @@ -510,8 +501,8 @@ impl SendQueue {
stream.next_ssn = Ssn(0);
if let Some(item) = stream.items.front_mut() {
let item_size = item.message.payload.len();
self.buffered_amount += item_size - item.remaining_size;
stream.buffered_amount += item_size - item.remaining_size;
self.buffered_amount.add(item_size - item.remaining_size);
stream.buffered_amount.add(item_size - item.remaining_size);
item.remaining_offset = 0;
item.remaining_size = item_size;
let priority = self.enable_message_interleaving.then_some(stream.priority);
Expand All @@ -521,10 +512,7 @@ impl SendQueue {
}

pub fn buffered_amount(&self, stream_id: StreamId) -> usize {
match self.streams.get(&stream_id) {
Some(stream) => stream.buffered_amount.value,
None => 0,
}
self.streams.get(&stream_id).map_or(0, |s| s.buffered_amount.value)
}

pub fn total_buffered_amount(&self) -> usize {
Expand All @@ -541,22 +529,20 @@ impl SendQueue {
pub fn set_buffered_amount_low_threshold(&mut self, stream_id: StreamId, threshold: usize) {
let stream = self.streams.entry(stream_id).or_insert_with(|| {
SendQueue::make_stream(
stream_id,
self.default_priority,
self.default_low_buffered_amount_low_threshold,
Rc::clone(&self.events),
)
});
stream.buffered_amount.set_low_threshold(threshold);
if stream.buffered_amount.set_low_threshold(threshold) {
self.events.borrow_mut().add(SocketEvent::OnBufferedAmountLow(stream_id));
}
}

pub fn set_priority(&mut self, stream_id: StreamId, priority: u16) {
let stream = self.streams.entry(stream_id).or_insert_with(|| {
SendQueue::make_stream(
stream_id,
self.default_priority,
self.default_low_buffered_amount_low_threshold,
Rc::clone(&self.events),
)
});
stream.priority = priority;
Expand Down Expand Up @@ -594,12 +580,8 @@ impl SendQueue {
pub(crate) fn restore_from_state(&mut self, state: &SocketHandoverState) {
state.tx.streams.iter().for_each(|s| {
let stream_id = StreamId(s.id);
let mut stream = SendQueue::make_stream(
stream_id,
s.priority,
self.default_low_buffered_amount_low_threshold,
Rc::clone(&self.events),
);
let mut stream =
SendQueue::make_stream(s.priority, self.default_low_buffered_amount_low_threshold);
stream.next_ssn = Ssn(s.next_ssn);
stream.next_unordered_mid = Mid(s.next_unordered_mid);
stream.next_ordered_mid = Mid(s.next_ordered_mid);
Expand Down
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