Module priority_queue 

Multi-level priority queue for outbound peer messages.

Provides PeerPriorityQueue with three priority tiers (Urgent, Normal, Background), per-peer fairness enforcement, and a global byte-budget cap.

Design

Messages are placed into one of three FIFO sub-queues based on their MessagePriority. On dequeue, the implementation drains the highest non-empty tier first (Urgent → Normal → Background), guaranteeing strict priority ordering while still allowing lower-priority traffic to be sent whenever the higher tiers are empty.

Backpressure is enforced in two independent dimensions:

• Global byte budget — the sum of all payload_bytes across all enqueued messages must not exceed QueueConfig::max_total_bytes.
• Per-peer message cap — a single peer may not have more than QueueConfig::max_per_peer_messages messages pending (across all priority levels).

When either limit would be exceeded the incoming message is dropped and QueueStats::total_dropped is incremented.

Structs

PeerPriorityQueue

Multi-level priority queue for outbound peer messages.

QueueConfig

Configuration for PeerPriorityQueue.

QueueStats

Running statistics for a PeerPriorityQueue.

QueuedMessage

A message waiting to be sent to a remote peer.

Enums

MessagePriority

Priority tier for a queued peer message.