sq/todos/SQ-019-virtual-network.md

SQ-019: Virtual Network for Simulation

Status: [ ] TODO Blocked by: SQ-003 Priority: Medium

Description

Virtual network layer for multi-node simulation testing. Enables partition, latency, and packet drop injection.

Files to Create/Modify

• crates/sq-sim/src/network.rs - VirtualNetwork with message queues and fault injection

VirtualNetwork API

pub struct VirtualNetwork {
    queues: HashMap<(NodeId, NodeId), VecDeque<Vec<u8>>>,
    partitions: HashSet<(NodeId, NodeId)>,
    latency: Option<(Duration, Duration)>,  // min, max
    drop_probability: f64,
}

impl VirtualNetwork {
    pub fn new() -> Self;
    pub fn partition(&mut self, a: NodeId, b: NodeId);
    pub fn heal(&mut self, a: NodeId, b: NodeId);
    pub fn heal_all(&mut self);
    pub fn set_latency(&mut self, min: Duration, max: Duration);
    pub fn set_drop_probability(&mut self, prob: f64);
    pub async fn send(&self, from: NodeId, to: NodeId, msg: Vec<u8>) -> Result<()>;
    pub async fn recv(&self, node: NodeId) -> Result<(NodeId, Vec<u8>)>;
    pub fn deliver_pending(&mut self);  // Process queued messages
}

Acceptance Criteria

• Two virtual nodes exchange messages successfully
• Partition: messages from A to B are dropped
• Heal: messages resume flowing after heal
• Latency injection: messages are delayed
• Drop probability: some messages are randomly dropped
• Bidirectional partition: neither direction works