Struct QueueFilter 

pub struct QueueFilter { /* private fields */ }

3-priority FIFO queue with WaitingForAck backpressure.

The QueueFilter classifies frames by priority and queues them when the target connection is in WaitingForAck state. This prevents frame loss from the server overwhelming the client before it has acknowledged the previous frame.

When backpressure is released (ACK received), queued frames are drained in strict priority order: High → Normal → Low.

Implementations

impl QueueFilter

pub fn new(config: QueueFilterConfig) -> Self

Create a new QueueFilter with the given configuration.

pub fn process_send(&self, envelope: &mut FrameEnvelope) -> FilterResult

Process a frame in the send direction.

1. Classify the frame’s priority based on message code
2. If backpressure is active (WaitingForAck), queue the frame
3. Otherwise, pass through with priority set on envelope

pub fn process_recv(&self, _envelope: &FrameEnvelope) -> FilterResult

Process a frame in the recv direction.

On the receive path, we just pass through. The actual backpressure release happens via on_ack_received().

pub fn set_waiting_for_ack(&self, channel_id: u8, waiting: bool)

Set a channel’s WaitingForAck backpressure flag.

pub fn on_ack_received(&self, channel_id: u8)

Notify that an ACK was received for a channel.

This releases backpressure and allows queued frames to be drained.

pub fn on_send_error(&self, channel_id: u8)

Notify that a send error occurred for a channel.

This does not change backpressure state — the connection may retry.

pub fn has_pending(&self, channel_id: u8) -> bool

Check if there are pending frames for a channel.

pub fn total_pending(&self) -> usize

Get the total number of pending frames across all channels.

pub fn drain(&self, channel_id: u8, max_count: usize) -> Vec<FrameEnvelope>

Drain up to max_count frames from a channel in priority order.

Returns frames in descending priority order: High → Normal → Low.

pub fn pending_by_priority(&self, channel_id: u8) -> [usize; 3]

Get pending frame counts per priority for a channel.

pub fn clear_channel(&self, channel_id: u8)

Remove all queued frames for a channel (e.g., on disconnect).

pub fn stats_snapshot(&self) -> QueueFilterStatsSnapshot

Get a snapshot of the statistics.

Trait Implementations

impl Debug for QueueFilter

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.