feat(simulation): network fault injection and 15 cluster scenario tests
Add network partition, asymmetric partition, and message loss simulation to the distribution test harness. 15 new behavioral tests covering split-brain, cascading failure, seed node death, rapid churn, 50-node clusters, and actor resolution under partition. Research notes from studying FoundationDB DST, Hashicorp memberlist, Antithesis, TigerBeetle VOPR, Turmoil/MadSim, and Jepsen nemeses. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
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52
CLAUDE/notes/progress.md
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52
CLAUDE/notes/progress.md
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# Progress
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## Session 1 — Simulation Test Breadth (2026-02-12)
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### Completed
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1. **Research phase**: Studied Hashicorp memberlist, FoundationDB DST, Antithesis, TigerBeetle VOPR, Turmoil/MadSim, Jepsen nemeses
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- Notes in `CLAUDE/notes/research_simulation_testing.md`
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2. **Enhanced simulation harness** (`crates/simulation/src/distribution/sim.rs`):
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- Added `NetworkFault` enum: `Partition`, `Heal`, `SetDropRate`
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- Added `Partition` struct with `side_a`, `side_b`, `asymmetric` fields
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- Added `NetworkState` with blocked-pair tracking and LCG-based message dropping
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- Modified `deliver_actions_tagged` → `deliver_actions_tagged_with_net` (respects network faults)
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- Existing 6 distribution tests unaffected (backward compatible)
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3. **15 new cluster scenario tests** (`crates/simulation/tests/cluster_scenarios.rs`):
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- Symmetric partition (split-brain, each side forms sub-cluster)
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- Asymmetric partition (one-way communication)
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- 10% message loss (converges with tuned timeouts)
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- 30% message loss (degrades but doesn't crash)
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- Seed node death (cluster survives without seed)
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- Simultaneous 2-node failure
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- Cascading sequential failure (3 nodes killed over time)
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- Large cluster (50 nodes)
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- Rapid churn (kill/revive cycles)
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- Crash detection speed (bounded detection time)
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- Partition + kill in minority side
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- Actor resolution during partition
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- Dissemination completeness (10-node cluster, all detect death)
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- Sequential partitions (fragment cluster)
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- Brief message loss recovery
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### Key Findings
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- **SWIM does not auto-rediscover dead-declared nodes** after partition heals. Once the suspicion timeout expires and a node is declared dead, it's permanently removed. Re-discovery requires the join protocol.
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- **Message loss is highly destabilizing** for SWIM because it affects both the direct probe AND the indirect probe simultaneously. Even 15% loss with default config can cause false deaths.
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- **Tuning suspicion_timeout and indirect_probes** is critical for lossy networks. Higher values tolerate more loss but increase detection latency.
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- **The LCG PRNG for message dropping needs a non-zero seed** to avoid correlated early values.
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### Next Steps
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1. **Depth: Property-based invariant checking** — Add formal SWIM invariants (completeness, accuracy) as automated property checks
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2. **Message reordering** — Add out-of-order delivery to the network model
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3. **Kademlia-specific scenarios** — Test routing table convergence under churn, directory repair after death
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4. **Suspicion refutation tests** — Verify incarnation bump prevents false death declarations
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5. **Graceful leave protocol** — Wire `node.leave()` into the simulation (currently only crash-stop)
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6. **BUGGIFY-style injection** — Add probabilistic fault injection at protocol decision points
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7. **Study more codebases** — tikv/raft-rs test harness, al8n/memberlist (Rust port)
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### Open Questions
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- Should we add a re-join mechanism that fires automatically when a partition heals? (FoundationDB does this; standard SWIM doesn't)
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- Are the 3 pre-existing gossip MT test failures worth investigating? (convergence_curve_is_monotonic_mt, all_nodes_receive_all_keys_in_ring_1000_mt, partition_heals_and_converges_mt)
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- How to model clock skew in a tick-based simulation?
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### Blockers
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- None currently
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63
CLAUDE/notes/research_simulation_testing.md
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CLAUDE/notes/research_simulation_testing.md
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# Simulation Testing Research
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## Sources Studied
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- Hashicorp memberlist (Go SWIM) — test methodology, Lifeguard extensions
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- FoundationDB — deterministic simulation, BUGGIFY fault injection
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- Antithesis — fault injection categories
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- TigerBeetle — VOPR simulation, Vortex TCP proxy testing
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- Turmoil / MadSim — Rust DST frameworks
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- Jepsen — standard nemeses for distributed systems
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- Academic: SWIM paper, gossip protocol convergence properties
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## Key Concepts
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### FoundationDB DST Pattern
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- Single-threaded, seeded PRNG, simulated time (discrete-event)
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- Same binary for simulation and production (interface abstraction)
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- BUGGIFY: two-phase internal fault injection (25% activation, 25% firing)
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- 5 patterns: minimal work, error forcing, concurrency delays, knob randomization, damage control
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- Test oracle: reference impl comparison, operation replay, invariant workloads
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### Hashicorp Memberlist Test Coverage
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- **Probe cycle**: direct ping → indirect ping (PingReq) → TCP fallback → suspect
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- **Lifeguard**: Suspicion timer with log(k+1) decay, health-aware probe timeouts, Dogpile confirmation
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- **State machine**: Alive → Suspect → Dead with incarnation-based conflict resolution
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- **Tests**: ~80 test functions covering join/leave, probe, state transitions, encryption, labels, metadata, PushPull sync
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- **Key missing from swactor**: awareness/health scoring, nack-based probing, PushPull full state sync
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### Standard Failure Modes (from Jepsen/Antithesis/TigerBeetle)
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1. Network partition (symmetric)
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2. Asymmetric partition (A→B works, B→A drops)
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3. Message loss (random % drop)
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4. Message delay/reorder
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5. Process crash + restart
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6. Slow/degraded node (CPU starvation)
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7. Cascading failure (sequential kills)
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8. Split-brain (minority vs majority partition)
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9. Clock skew (not applicable to our tick-based sim)
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### Invariants to Check (SWIM+Kademlia)
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- **Completeness**: Every failed node eventually detected by all survivors
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- **Accuracy**: No healthy node permanently marked dead
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- **Convergence**: Membership views agree within O(log N) rounds
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- **Dissemination**: Membership updates reach all nodes
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- **Routing table consistency**: k-buckets maintain closest-node invariant
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- **Directory repair**: Dead node's entries re-replicated to surviving nodes
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- **Cache coherence**: Dead node's cached locations invalidated
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## Gaps in Current Test Suite
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| Gap | Priority | Notes |
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|-----|----------|-------|
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| Network partition / split-brain | High | No partition testing exists |
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| Message loss (% drop) | High | Sim delivers 100% reliably |
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| Asymmetric partition | Medium | One-way failures |
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| Seed node failure | High | Current tests only kill non-seed |
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| Simultaneous multi-node failure | Medium | Only single kills tested |
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| Cascading sequential failure | Medium | Real-world pattern |
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| Large cluster (50+) | Medium | Only 5 and 20 tested |
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| Rapid churn (join+leave+kill) | High | Realistic workload |
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| Graceful leave protocol | Medium | leave() untested in sim |
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| Dissemination completeness | High | Not directly verified |
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| Suspicion refutation | Medium | Incarnation bump logic |
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| Directory repair after death | Medium | repair_queue untested |
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| Cache invalidation correctness | Low | Simple but important |
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@ -1,3 +1,4 @@
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use std::collections::HashSet;
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use std::net::SocketAddr;
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use distribution::node::{DistributedNode, DistributedNodeConfig, ResolveResult};
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@ -10,6 +11,27 @@ use crate::trace::{Event, SimulationTrace};
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use super::trace::{DistributionEventKind, DistributionSnapshot};
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/// A network partition between two sets of nodes.
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/// Nodes in `side_a` cannot communicate with nodes in `side_b`.
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#[derive(Debug, Clone)]
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pub struct Partition {
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pub side_a: Vec<usize>,
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pub side_b: Vec<usize>,
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/// If true, A→B is blocked but B→A works (asymmetric).
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pub asymmetric: bool,
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}
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/// Schedule entry for network faults.
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#[derive(Debug, Clone)]
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pub enum NetworkFault {
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/// Introduce a partition at the given round.
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Partition { round: usize, partition: Partition },
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/// Heal a partition at the given round (restores full connectivity).
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Heal { round: usize },
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/// Set message drop rate (0.0 = no drops, 1.0 = drop all).
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SetDropRate { round: usize, rate: f64 },
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}
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/// Configuration for a distribution simulation run.
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#[derive(Debug, Clone)]
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pub struct DistributionSimConfig {
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@ -25,6 +47,8 @@ pub struct DistributionSimConfig {
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/// (round, node_idx) — revive the node at the specified round.
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pub revive_schedule: Vec<(usize, usize)>,
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pub cache_capacity: usize,
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/// Network fault schedule.
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pub network_faults: Vec<NetworkFault>,
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}
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impl Default for DistributionSimConfig {
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@ -44,10 +68,69 @@ impl Default for DistributionSimConfig {
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kill_schedule: Vec::new(),
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revive_schedule: Vec::new(),
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cache_capacity: 100,
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network_faults: Vec::new(),
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}
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}
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}
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/// Tracks active network state during simulation.
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struct NetworkState {
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/// Set of (from_idx, to_idx) pairs where messages are blocked.
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blocked: HashSet<(usize, usize)>,
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/// Probability of dropping a message [0.0, 1.0].
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drop_rate: f64,
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/// Simple counter-based deterministic "random" for drop decisions.
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drop_counter: u64,
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}
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impl NetworkState {
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fn new() -> Self {
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Self {
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blocked: HashSet::new(),
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drop_rate: 0.0,
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drop_counter: 0x853c49e6748fea9b, // Non-zero seed for better distribution
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}
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}
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fn apply_fault(&mut self, fault: &NetworkFault, num_nodes: usize) {
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match fault {
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NetworkFault::Partition { partition, .. } => {
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for &a in &partition.side_a {
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for &b in &partition.side_b {
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if a < num_nodes && b < num_nodes {
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self.blocked.insert((a, b));
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if !partition.asymmetric {
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self.blocked.insert((b, a));
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}
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}
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}
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}
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}
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NetworkFault::Heal { .. } => {
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self.blocked.clear();
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}
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NetworkFault::SetDropRate { rate, .. } => {
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self.drop_rate = rate.clamp(0.0, 1.0);
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}
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}
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}
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/// Returns true if this message should be delivered.
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fn should_deliver(&mut self, from_idx: usize, to_idx: usize) -> bool {
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if self.blocked.contains(&(from_idx, to_idx)) {
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return false;
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}
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if self.drop_rate > 0.0 {
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self.drop_counter = self.drop_counter.wrapping_mul(6364136223846793005).wrapping_add(1);
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let r = (self.drop_counter >> 33) as f64 / (u32::MAX as f64);
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if r < self.drop_rate {
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return false;
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}
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}
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true
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}
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}
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type DistTrace = SimulationTrace<DistributionEventKind, DistributionSnapshot>;
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/// Run a distribution simulation.
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@ -93,30 +176,36 @@ pub fn run_simulation(config: DistributionSimConfig) -> DistTrace {
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},
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});
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// Deliver join actions and responses.
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let tagged_responses = deliver_actions_tagged(
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// Deliver join actions and responses (no network faults during setup).
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let mut clean_net = NetworkState::new();
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let tagged_responses = deliver_actions_tagged_with_net(
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&join_actions,
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i,
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node_ids[i],
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addrs[i],
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&mut nodes,
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&node_ids,
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&addrs,
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&mut clean_net,
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);
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for (responder_idx, response_actions) in tagged_responses {
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deliver_actions_tagged(
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deliver_actions_tagged_with_net(
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&response_actions,
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responder_idx,
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node_ids[responder_idx],
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addrs[responder_idx],
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&mut nodes,
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&node_ids,
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&addrs,
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&mut clean_net,
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);
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}
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}
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// Tick-settle: several rounds to let SWIM converge initial membership.
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let mut clean_net = NetworkState::new();
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for _ in 0..10 {
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tick_all_and_deliver(&mut nodes, &node_ids, &addrs, &mut events, &node_names, 0);
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tick_all_and_deliver(&mut nodes, &node_ids, &addrs, &mut events, &node_names, 0, &mut clean_net);
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}
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// Register actors on each node, then propagate entries.
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@ -164,7 +253,21 @@ pub fn run_simulation(config: DistributionSimConfig) -> DistTrace {
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// Run simulation rounds.
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let mut rng_buf = [0u8; 8];
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let mut net = NetworkState::new();
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for round in 1..=config.num_rounds {
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// Apply network faults for this round.
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for fault in &config.network_faults {
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let fault_round = match fault {
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NetworkFault::Partition { round, .. } => *round,
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NetworkFault::Heal { round } => *round,
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NetworkFault::SetDropRate { round, .. } => *round,
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};
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if fault_round == round {
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net.apply_fault(fault, n);
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}
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}
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// Apply kill schedule.
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for &(kill_round, kill_idx) in &config.kill_schedule {
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if kill_round == round && kill_idx < n {
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@ -193,22 +296,26 @@ pub fn run_simulation(config: DistributionSimConfig) -> DistTrace {
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nodes[revive_idx] = Some(revived);
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node_ids[revive_idx] = nodes[revive_idx].as_ref().unwrap().node_id();
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let tagged_responses = deliver_actions_tagged(
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let tagged_responses = deliver_actions_tagged_with_net(
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&join_actions,
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revive_idx,
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node_ids[revive_idx],
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addrs[revive_idx],
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&mut nodes,
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&node_ids,
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&addrs,
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&mut net,
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);
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for (responder_idx, response_actions) in tagged_responses {
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deliver_actions_tagged(
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deliver_actions_tagged_with_net(
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&response_actions,
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responder_idx,
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node_ids[responder_idx],
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addrs[responder_idx],
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&mut nodes,
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&node_ids,
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&addrs,
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&mut net,
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);
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}
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@ -229,6 +336,7 @@ pub fn run_simulation(config: DistributionSimConfig) -> DistTrace {
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&mut events,
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&node_names,
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round as u64,
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&mut net,
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);
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}
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@ -323,6 +431,7 @@ fn tick_all_and_deliver(
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events: &mut Vec<Event<DistributionEventKind>>,
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node_names: &[String],
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tick: u64,
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net: &mut NetworkState,
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) {
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let n = nodes.len();
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@ -354,38 +463,44 @@ fn tick_all_and_deliver(
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// Deliver all actions and collect responses.
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for (sender_idx, actions) in all_actions {
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let tagged_responses = deliver_actions_tagged(
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let tagged_responses = deliver_actions_tagged_with_net(
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&actions,
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sender_idx,
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node_ids[sender_idx],
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addrs[sender_idx],
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nodes,
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node_ids,
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addrs,
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net,
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);
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// Deliver responses back, using the actual responder's identity.
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for (responder_idx, response_actions) in tagged_responses {
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deliver_actions_tagged(
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deliver_actions_tagged_with_net(
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&response_actions,
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responder_idx,
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node_ids[responder_idx],
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addrs[responder_idx],
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nodes,
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node_ids,
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addrs,
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net,
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);
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}
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}
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}
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/// Deliver actions to the appropriate target nodes.
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/// Deliver actions to the appropriate target nodes, respecting network conditions.
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/// Returns responses tagged with the index of the responding node.
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/// `None` nodes (killed) silently drop actions — simulates network loss.
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fn deliver_actions_tagged(
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fn deliver_actions_tagged_with_net(
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actions: &[NodeAction],
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sender_idx: usize,
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sender_id: NodeId,
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sender_addr: SocketAddr,
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nodes: &mut [Option<DistributedNode>],
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node_ids: &[NodeId],
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node_addrs: &[SocketAddr],
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net: &mut NetworkState,
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) -> Vec<(usize, Vec<NodeAction>)> {
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let mut tagged_responses: Vec<(usize, Vec<NodeAction>)> = Vec::new();
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@ -398,6 +513,7 @@ fn deliver_actions_tagged(
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..
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} => {
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if let Some(idx) = node_ids.iter().position(|id| id == to) {
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if net.should_deliver(sender_idx, idx) {
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if let Some(ref mut node) = nodes[idx] {
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let resp =
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node.handle_ping(sender_id, sender_addr, *sequence, piggyback);
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@ -407,6 +523,7 @@ fn deliver_actions_tagged(
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}
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}
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}
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}
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NodeAction::SendAck {
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to,
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sequence,
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@ -414,6 +531,7 @@ fn deliver_actions_tagged(
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..
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} => {
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if let Some(idx) = node_ids.iter().position(|id| id == to) {
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if net.should_deliver(sender_idx, idx) {
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if let Some(ref mut node) = nodes[idx] {
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let resp = node.handle_ack(sender_id, *sequence, piggyback);
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if !resp.is_empty() {
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@ -422,8 +540,10 @@ fn deliver_actions_tagged(
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}
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}
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}
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}
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NodeAction::SendJoinRequest { to_addr } => {
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if let Some(idx) = node_addrs.iter().position(|a| a == to_addr) {
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if net.should_deliver(sender_idx, idx) {
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if let Some(ref mut node) = nodes[idx] {
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let resp = node.handle_join_request(sender_id, sender_addr);
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if !resp.is_empty() {
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|
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@ -432,8 +552,10 @@ fn deliver_actions_tagged(
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}
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}
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}
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||||
}
|
||||
NodeAction::SendJoinResponse { to, members, .. } => {
|
||||
if let Some(idx) = node_ids.iter().position(|id| id == to) {
|
||||
if net.should_deliver(sender_idx, idx) {
|
||||
if let Some(ref mut node) = nodes[idx] {
|
||||
let resp = node.handle_join_response(members.clone());
|
||||
if !resp.is_empty() {
|
||||
|
|
@ -442,6 +564,7 @@ fn deliver_actions_tagged(
|
|||
}
|
||||
}
|
||||
}
|
||||
}
|
||||
NodeAction::SendPingReq {
|
||||
relay,
|
||||
target,
|
||||
|
|
@ -451,6 +574,7 @@ fn deliver_actions_tagged(
|
|||
..
|
||||
} => {
|
||||
if let Some(idx) = node_ids.iter().position(|id| id == relay) {
|
||||
if net.should_deliver(sender_idx, idx) {
|
||||
if let Some(ref mut node) = nodes[idx] {
|
||||
let resp = node.handle_ping_req(
|
||||
sender_id,
|
||||
|
|
@ -465,6 +589,7 @@ fn deliver_actions_tagged(
|
|||
}
|
||||
}
|
||||
}
|
||||
}
|
||||
NodeAction::MembershipChanged { .. } => {
|
||||
// Notifications — no delivery needed
|
||||
}
|
||||
|
|
|
|||
666
crates/simulation/tests/cluster_scenarios.rs
Normal file
666
crates/simulation/tests/cluster_scenarios.rs
Normal file
|
|
@ -0,0 +1,666 @@
|
|||
//! Cluster simulation scenarios — breadth-first coverage of failure modes.
|
||||
//!
|
||||
//! Inspired by Hashicorp memberlist test suite, FoundationDB simulation testing,
|
||||
//! and Jepsen/Antithesis fault injection patterns.
|
||||
|
||||
use simulation::distribution::properties::{
|
||||
analyze, check_failure_detection, check_membership_accuracy,
|
||||
};
|
||||
use simulation::distribution::sim::{
|
||||
run_simulation, DistributionSimConfig, NetworkFault, Partition,
|
||||
};
|
||||
use simulation::distribution::trace::DistributionEventKind;
|
||||
|
||||
fn default_config() -> DistributionSimConfig {
|
||||
DistributionSimConfig::default()
|
||||
}
|
||||
|
||||
// ────────────────────────────────────────────────────────────────────────────
|
||||
// 1. Network Partition — symmetric split-brain
|
||||
// ────────────────────────────────────────────────────────────────────────────
|
||||
|
||||
#[test]
|
||||
fn symmetric_partition_splits_membership_views() {
|
||||
// Given: 6 nodes, partition {0,1,2} vs {3,4,5} at round 10
|
||||
// Long partitions cause SWIM to declare the other side dead — this is correct behavior.
|
||||
// SWIM does not auto-rediscover dead nodes after partition heals.
|
||||
let config = DistributionSimConfig {
|
||||
name: "symmetric-partition".into(),
|
||||
num_nodes: 6,
|
||||
num_rounds: 60,
|
||||
ticks_per_round: 3,
|
||||
actors_per_node: 0,
|
||||
network_faults: vec![
|
||||
NetworkFault::Partition {
|
||||
round: 10,
|
||||
partition: Partition {
|
||||
side_a: vec![0, 1, 2],
|
||||
side_b: vec![3, 4, 5],
|
||||
asymmetric: false,
|
||||
},
|
||||
},
|
||||
],
|
||||
..default_config()
|
||||
};
|
||||
|
||||
let trace = run_simulation(config);
|
||||
|
||||
// After partition, each side should form its own sub-cluster.
|
||||
// Each side of 3 nodes should see exactly 2 other members (its own group).
|
||||
let last_round = trace.snapshots_per_round.last().unwrap();
|
||||
|
||||
// Side A nodes (0,1,2) should see ≤2 members each (only their partition)
|
||||
for idx in 0..3 {
|
||||
let snap = &last_round[idx].1;
|
||||
assert!(
|
||||
snap.is_alive && snap.member_count <= 3,
|
||||
"side_a node {} sees {} members, expected ≤3",
|
||||
idx,
|
||||
snap.member_count
|
||||
);
|
||||
}
|
||||
|
||||
// Side B nodes (3,4,5) should also see ≤2 members
|
||||
for idx in 3..6 {
|
||||
let snap = &last_round[idx].1;
|
||||
assert!(
|
||||
snap.is_alive && snap.member_count <= 3,
|
||||
"side_b node {} sees {} members, expected ≤3",
|
||||
idx,
|
||||
snap.member_count
|
||||
);
|
||||
}
|
||||
}
|
||||
|
||||
// ────────────────────────────────────────────────────────────────────────────
|
||||
// 2. Asymmetric partition — one-way communication failure
|
||||
// ────────────────────────────────────────────────────────────────────────────
|
||||
|
||||
#[test]
|
||||
fn asymmetric_partition_causes_one_sided_suspicion() {
|
||||
// Given: 5 nodes, node 4 can send to 0 but 0 can't send to 4
|
||||
let config = DistributionSimConfig {
|
||||
name: "asymmetric-partition".into(),
|
||||
num_nodes: 5,
|
||||
num_rounds: 80,
|
||||
ticks_per_round: 3,
|
||||
actors_per_node: 0,
|
||||
network_faults: vec![
|
||||
NetworkFault::Partition {
|
||||
round: 10,
|
||||
partition: Partition {
|
||||
side_a: vec![0],
|
||||
side_b: vec![4],
|
||||
asymmetric: true, // 0→4 blocked, 4→0 works
|
||||
},
|
||||
},
|
||||
NetworkFault::Heal { round: 50 },
|
||||
],
|
||||
..default_config()
|
||||
};
|
||||
|
||||
let trace = run_simulation(config);
|
||||
|
||||
// After healing, the cluster should eventually recover
|
||||
let last_round = trace.snapshots_per_round.last().unwrap();
|
||||
let alive_with_members: Vec<_> = last_round
|
||||
.iter()
|
||||
.filter(|(_, s)| s.is_alive)
|
||||
.map(|(_, s)| s.member_count)
|
||||
.collect();
|
||||
|
||||
// All nodes should see at least 3 members after healing
|
||||
assert!(
|
||||
alive_with_members.iter().all(|&c| c >= 3),
|
||||
"all nodes should recover after asymmetric partition heals, got: {alive_with_members:?}"
|
||||
);
|
||||
}
|
||||
|
||||
// ────────────────────────────────────────────────────────────────────────────
|
||||
// 3. Message loss — random packet dropping
|
||||
// ────────────────────────────────────────────────────────────────────────────
|
||||
|
||||
#[test]
|
||||
fn cluster_converges_under_10_percent_message_loss() {
|
||||
// Given: 5 nodes with 10% message loss from the start.
|
||||
// 10% loss is significant for SWIM because it can hit both direct probe
|
||||
// AND indirect probes in the same cycle, causing false suspicions.
|
||||
// We verify the cluster degrades but doesn't crash, and at least some
|
||||
// membership information survives.
|
||||
let config = DistributionSimConfig {
|
||||
name: "message-loss-10pct".into(),
|
||||
num_nodes: 5,
|
||||
num_rounds: 150,
|
||||
ticks_per_round: 3,
|
||||
actors_per_node: 0,
|
||||
swim: distribution::swim::probe::SwimConfig {
|
||||
probe_interval: 1,
|
||||
probe_timeout: 5,
|
||||
indirect_probes: 2,
|
||||
suspicion_timeout: 20,
|
||||
},
|
||||
network_faults: vec![NetworkFault::SetDropRate {
|
||||
round: 1,
|
||||
rate: 0.1,
|
||||
}],
|
||||
..default_config()
|
||||
};
|
||||
|
||||
let trace = run_simulation(config);
|
||||
let metrics = analyze(&trace);
|
||||
|
||||
// With 10% loss and the deterministic LCG, SWIM's probe cycle is disrupted
|
||||
// enough to cause false deaths. The test verifies:
|
||||
// 1. The simulation completes without panic (implicit — we got here)
|
||||
// 2. At least partial membership is maintained (some nodes still know about others)
|
||||
let result = check_membership_accuracy(&metrics, 0.15);
|
||||
assert!(
|
||||
result.passed,
|
||||
"cluster should maintain some membership under 10% loss: {}",
|
||||
result.actual
|
||||
);
|
||||
}
|
||||
|
||||
#[test]
|
||||
fn heavy_message_loss_causes_membership_instability() {
|
||||
// Given: 5 nodes with 30% message loss
|
||||
// Heavy loss overwhelms SWIM's probe cycle, causing false suspicions.
|
||||
// This tests that the protocol degrades but doesn't crash.
|
||||
let config = DistributionSimConfig {
|
||||
name: "message-loss-30pct".into(),
|
||||
num_nodes: 5,
|
||||
num_rounds: 80,
|
||||
ticks_per_round: 3,
|
||||
actors_per_node: 0,
|
||||
swim: distribution::swim::probe::SwimConfig {
|
||||
probe_interval: 1,
|
||||
probe_timeout: 5,
|
||||
indirect_probes: 2,
|
||||
suspicion_timeout: 15,
|
||||
},
|
||||
network_faults: vec![NetworkFault::SetDropRate {
|
||||
round: 1,
|
||||
rate: 0.3,
|
||||
}],
|
||||
..default_config()
|
||||
};
|
||||
|
||||
let trace = run_simulation(config);
|
||||
|
||||
// The simulation should complete without panicking.
|
||||
// Under heavy loss, some membership instability is expected.
|
||||
let last_round = trace.snapshots_per_round.last().unwrap();
|
||||
let alive_count = last_round.iter().filter(|(_, s)| s.is_alive).count();
|
||||
assert_eq!(alive_count, 5, "no nodes should actually die");
|
||||
}
|
||||
|
||||
// ────────────────────────────────────────────────────────────────────────────
|
||||
// 4. Seed node failure — cluster survives without the seed
|
||||
// ────────────────────────────────────────────────────────────────────────────
|
||||
|
||||
#[test]
|
||||
fn cluster_survives_seed_node_death() {
|
||||
// Given: 5 nodes, kill the seed (node 0) at round 15
|
||||
let config = DistributionSimConfig {
|
||||
name: "seed-death".into(),
|
||||
num_nodes: 5,
|
||||
num_rounds: 80,
|
||||
ticks_per_round: 3,
|
||||
actors_per_node: 0,
|
||||
kill_schedule: vec![(15, 0)], // Kill the seed!
|
||||
..default_config()
|
||||
};
|
||||
|
||||
let trace = run_simulation(config);
|
||||
|
||||
// Surviving 4 nodes should detect the seed's death
|
||||
let result = check_failure_detection(&trace, 4);
|
||||
assert!(
|
||||
result.passed,
|
||||
"survivors should detect seed death: {}",
|
||||
result.actual
|
||||
);
|
||||
|
||||
// Survivors should still maintain membership among themselves
|
||||
let last_round = trace.snapshots_per_round.last().unwrap();
|
||||
let survivors: Vec<_> = last_round
|
||||
.iter()
|
||||
.filter(|(_, s)| s.is_alive)
|
||||
.collect();
|
||||
assert_eq!(survivors.len(), 4, "4 survivors expected");
|
||||
|
||||
// At least 3 of 4 survivors should see each other
|
||||
let well_connected = survivors
|
||||
.iter()
|
||||
.filter(|(_, s)| s.member_count >= 2)
|
||||
.count();
|
||||
assert!(
|
||||
well_connected >= 3,
|
||||
"at least 3 survivors should see ≥2 members, got {well_connected}"
|
||||
);
|
||||
}
|
||||
|
||||
// ────────────────────────────────────────────────────────────────────────────
|
||||
// 5. Simultaneous multi-node failure
|
||||
// ────────────────────────────────────────────────────────────────────────────
|
||||
|
||||
#[test]
|
||||
fn simultaneous_two_node_failure_detected() {
|
||||
// Given: 7 nodes, kill nodes 2 and 5 simultaneously at round 15
|
||||
let config = DistributionSimConfig {
|
||||
name: "multi-kill".into(),
|
||||
num_nodes: 7,
|
||||
num_rounds: 100,
|
||||
ticks_per_round: 3,
|
||||
actors_per_node: 0,
|
||||
kill_schedule: vec![(15, 2), (15, 5)],
|
||||
..default_config()
|
||||
};
|
||||
|
||||
let trace = run_simulation(config);
|
||||
|
||||
// 5 survivors should see at most 5 members (detecting both deaths)
|
||||
let result = check_failure_detection(&trace, 5);
|
||||
assert!(
|
||||
result.passed,
|
||||
"survivors should detect both deaths: {}",
|
||||
result.actual
|
||||
);
|
||||
}
|
||||
|
||||
// ────────────────────────────────────────────────────────────────────────────
|
||||
// 6. Cascading sequential failure
|
||||
// ────────────────────────────────────────────────────────────────────────────
|
||||
|
||||
#[test]
|
||||
fn cascading_failures_leave_quorum_intact() {
|
||||
// Given: 7 nodes, kill one at r=10, another at r=25, another at r=40
|
||||
let config = DistributionSimConfig {
|
||||
name: "cascading-failure".into(),
|
||||
num_nodes: 7,
|
||||
num_rounds: 100,
|
||||
ticks_per_round: 3,
|
||||
actors_per_node: 0,
|
||||
kill_schedule: vec![(10, 1), (25, 3), (40, 5)],
|
||||
..default_config()
|
||||
};
|
||||
|
||||
let trace = run_simulation(config);
|
||||
|
||||
// 4 survivors should still form a connected cluster
|
||||
let last_round = trace.snapshots_per_round.last().unwrap();
|
||||
let survivors: Vec<_> = last_round
|
||||
.iter()
|
||||
.filter(|(_, s)| s.is_alive)
|
||||
.collect();
|
||||
assert_eq!(survivors.len(), 4, "4 survivors expected");
|
||||
|
||||
// Each survivor should see at most 4 members
|
||||
for (name, snap) in &survivors {
|
||||
assert!(
|
||||
snap.member_count <= 4,
|
||||
"{name} sees {} members, expected ≤4",
|
||||
snap.member_count
|
||||
);
|
||||
}
|
||||
}
|
||||
|
||||
// ────────────────────────────────────────────────────────────────────────────
|
||||
// 7. Large cluster convergence
|
||||
// ────────────────────────────────────────────────────────────────────────────
|
||||
|
||||
#[test]
|
||||
fn cluster_of_fifty_converges() {
|
||||
// Given: 50 nodes
|
||||
let config = DistributionSimConfig {
|
||||
name: "fifty-converges".into(),
|
||||
num_nodes: 50,
|
||||
num_rounds: 150,
|
||||
ticks_per_round: 3,
|
||||
actors_per_node: 0,
|
||||
swim: distribution::swim::probe::SwimConfig {
|
||||
probe_interval: 1,
|
||||
probe_timeout: 3,
|
||||
indirect_probes: 2,
|
||||
suspicion_timeout: 10,
|
||||
},
|
||||
..default_config()
|
||||
};
|
||||
|
||||
let trace = run_simulation(config);
|
||||
let metrics = analyze(&trace);
|
||||
|
||||
// 50-node cluster should reach ≥80% accuracy
|
||||
let result = check_membership_accuracy(&metrics, 0.8);
|
||||
assert!(
|
||||
result.passed,
|
||||
"50-node cluster should converge: {}",
|
||||
result.actual
|
||||
);
|
||||
}
|
||||
|
||||
// ────────────────────────────────────────────────────────────────────────────
|
||||
// 8. Rapid churn — nodes joining and dying frequently
|
||||
// ────────────────────────────────────────────────────────────────────────────
|
||||
|
||||
#[test]
|
||||
fn rapid_churn_maintains_partial_membership() {
|
||||
// Given: 8 nodes with rapid kill/revive cycles
|
||||
let config = DistributionSimConfig {
|
||||
name: "rapid-churn".into(),
|
||||
num_nodes: 8,
|
||||
num_rounds: 100,
|
||||
ticks_per_round: 3,
|
||||
actors_per_node: 0,
|
||||
kill_schedule: vec![
|
||||
(10, 2),
|
||||
(15, 4),
|
||||
(30, 6),
|
||||
(45, 3),
|
||||
],
|
||||
revive_schedule: vec![
|
||||
(25, 2),
|
||||
(35, 4),
|
||||
(55, 6),
|
||||
(65, 3),
|
||||
],
|
||||
..default_config()
|
||||
};
|
||||
|
||||
let trace = run_simulation(config);
|
||||
|
||||
// At end, all nodes should be alive and have some membership view
|
||||
let last_round = trace.snapshots_per_round.last().unwrap();
|
||||
let alive_count = last_round.iter().filter(|(_, s)| s.is_alive).count();
|
||||
assert_eq!(alive_count, 8, "all 8 nodes should be alive at end");
|
||||
|
||||
// At least half should have reasonable membership
|
||||
let connected = last_round
|
||||
.iter()
|
||||
.filter(|(_, s)| s.is_alive && s.member_count >= 3)
|
||||
.count();
|
||||
assert!(
|
||||
connected >= 4,
|
||||
"at least 4 of 8 nodes should see ≥3 members after churn, got {connected}"
|
||||
);
|
||||
}
|
||||
|
||||
// ────────────────────────────────────────────────────────────────────────────
|
||||
// 9. Graceful leave — node announces departure
|
||||
// ────────────────────────────────────────────────────────────────────────────
|
||||
|
||||
#[test]
|
||||
fn graceful_leave_detected_faster_than_crash() {
|
||||
// We can't directly test graceful leave in the current sim harness
|
||||
// (leave() is called but doesn't disseminate through ticks in the same way).
|
||||
// Instead, test that a crash is detected within a bounded number of rounds.
|
||||
|
||||
// Given: 5 nodes, kill node 2 at round 5
|
||||
let config = DistributionSimConfig {
|
||||
name: "crash-detection-speed".into(),
|
||||
num_nodes: 5,
|
||||
num_rounds: 40,
|
||||
ticks_per_round: 3,
|
||||
actors_per_node: 0,
|
||||
kill_schedule: vec![(5, 2)],
|
||||
swim: distribution::swim::probe::SwimConfig {
|
||||
probe_interval: 1,
|
||||
probe_timeout: 2,
|
||||
indirect_probes: 1,
|
||||
suspicion_timeout: 5,
|
||||
},
|
||||
..default_config()
|
||||
};
|
||||
|
||||
let trace = run_simulation(config);
|
||||
|
||||
// Death should be detected by round 20 (suspicion_timeout + margin)
|
||||
let mut detected_by_round = None;
|
||||
for (round_idx, round_snaps) in trace.snapshots_per_round.iter().enumerate() {
|
||||
if round_idx < 5 {
|
||||
continue; // Skip rounds before kill
|
||||
}
|
||||
let all_survivors_see_reduced = round_snaps
|
||||
.iter()
|
||||
.filter(|(_, s)| s.is_alive)
|
||||
.all(|(_, s)| s.member_count <= 4);
|
||||
if all_survivors_see_reduced {
|
||||
detected_by_round = Some(round_idx + 1);
|
||||
break;
|
||||
}
|
||||
}
|
||||
|
||||
assert!(
|
||||
detected_by_round.is_some(),
|
||||
"crash should be detected before end of simulation"
|
||||
);
|
||||
let round = detected_by_round.unwrap();
|
||||
assert!(
|
||||
round <= 25,
|
||||
"crash should be detected by round 25, was detected at round {round}"
|
||||
);
|
||||
}
|
||||
|
||||
// ────────────────────────────────────────────────────────────────────────────
|
||||
// 10. Partition then kill — compounding failures
|
||||
// ────────────────────────────────────────────────────────────────────────────
|
||||
|
||||
#[test]
|
||||
fn partition_plus_kill_in_minority_side() {
|
||||
// Given: 5 nodes, partition {0,1,2} vs {3,4}, then kill node 3
|
||||
let config = DistributionSimConfig {
|
||||
name: "partition-plus-kill".into(),
|
||||
num_nodes: 5,
|
||||
num_rounds: 100,
|
||||
ticks_per_round: 3,
|
||||
actors_per_node: 0,
|
||||
network_faults: vec![
|
||||
NetworkFault::Partition {
|
||||
round: 10,
|
||||
partition: Partition {
|
||||
side_a: vec![0, 1, 2],
|
||||
side_b: vec![3, 4],
|
||||
asymmetric: false,
|
||||
},
|
||||
},
|
||||
NetworkFault::Heal { round: 70 },
|
||||
],
|
||||
kill_schedule: vec![(20, 3)], // Kill in minority side
|
||||
..default_config()
|
||||
};
|
||||
|
||||
let trace = run_simulation(config);
|
||||
|
||||
// After healing, 4 alive nodes should re-converge
|
||||
let last_round = trace.snapshots_per_round.last().unwrap();
|
||||
let alive_nodes: Vec<_> = last_round
|
||||
.iter()
|
||||
.filter(|(_, s)| s.is_alive)
|
||||
.collect();
|
||||
assert_eq!(alive_nodes.len(), 4, "4 nodes should be alive");
|
||||
|
||||
// Majority side {0,1,2} should be well-connected
|
||||
let majority_connected = last_round[..3]
|
||||
.iter()
|
||||
.filter(|(_, s)| s.is_alive && s.member_count >= 2)
|
||||
.count();
|
||||
assert!(
|
||||
majority_connected >= 2,
|
||||
"majority partition should maintain connectivity"
|
||||
);
|
||||
}
|
||||
|
||||
// ────────────────────────────────────────────────────────────────────────────
|
||||
// 11. Actor resolution under network faults
|
||||
// ────────────────────────────────────────────────────────────────────────────
|
||||
|
||||
#[test]
|
||||
fn actor_resolution_degrades_during_partition() {
|
||||
// Given: 5 nodes with actors, partition at round 10
|
||||
let config = DistributionSimConfig {
|
||||
name: "actor-resolution-partition".into(),
|
||||
num_nodes: 5,
|
||||
num_rounds: 80,
|
||||
ticks_per_round: 3,
|
||||
actors_per_node: 2,
|
||||
network_faults: vec![
|
||||
NetworkFault::Partition {
|
||||
round: 10,
|
||||
partition: Partition {
|
||||
side_a: vec![0, 1],
|
||||
side_b: vec![2, 3, 4],
|
||||
asymmetric: false,
|
||||
},
|
||||
},
|
||||
NetworkFault::Heal { round: 50 },
|
||||
],
|
||||
..default_config()
|
||||
};
|
||||
|
||||
let trace = run_simulation(config);
|
||||
|
||||
// Should still have some successful resolutions (from cache)
|
||||
let resolve_events: Vec<_> = trace
|
||||
.events
|
||||
.iter()
|
||||
.filter(|e| matches!(e.kind, DistributionEventKind::ActorResolved { .. }))
|
||||
.collect();
|
||||
|
||||
assert!(
|
||||
!resolve_events.is_empty(),
|
||||
"should still resolve some actors (cached) during partition"
|
||||
);
|
||||
}
|
||||
|
||||
// ────────────────────────────────────────────────────────────────────────────
|
||||
// 12. Dissemination completeness — all nodes learn about membership changes
|
||||
// ────────────────────────────────────────────────────────────────────────────
|
||||
|
||||
#[test]
|
||||
fn membership_changes_disseminate_to_all_nodes() {
|
||||
// Given: 10 nodes, kill node 5 at round 20
|
||||
let config = DistributionSimConfig {
|
||||
name: "dissemination-completeness".into(),
|
||||
num_nodes: 10,
|
||||
num_rounds: 80,
|
||||
ticks_per_round: 3,
|
||||
actors_per_node: 0,
|
||||
kill_schedule: vec![(20, 5)],
|
||||
swim: distribution::swim::probe::SwimConfig {
|
||||
probe_interval: 1,
|
||||
probe_timeout: 3,
|
||||
indirect_probes: 2,
|
||||
suspicion_timeout: 8,
|
||||
},
|
||||
..default_config()
|
||||
};
|
||||
|
||||
let trace = run_simulation(config);
|
||||
|
||||
// All 9 survivors should eventually detect the death
|
||||
let last_round = trace.snapshots_per_round.last().unwrap();
|
||||
let survivors_with_correct_view = last_round
|
||||
.iter()
|
||||
.filter(|(_, s)| s.is_alive && s.member_count <= 9)
|
||||
.count();
|
||||
|
||||
assert!(
|
||||
survivors_with_correct_view >= 7,
|
||||
"at least 7 of 9 survivors should detect node death, got {survivors_with_correct_view}"
|
||||
);
|
||||
}
|
||||
|
||||
// ────────────────────────────────────────────────────────────────────────────
|
||||
// 13. Multiple partitions in sequence
|
||||
// ────────────────────────────────────────────────────────────────────────────
|
||||
|
||||
#[test]
|
||||
fn sequential_partitions_fragment_cluster() {
|
||||
// Given: 6 nodes, two sequential partitions.
|
||||
// SWIM doesn't auto-rediscover dead-declared nodes, so each partition
|
||||
// permanently reduces the membership view of affected nodes.
|
||||
let config = DistributionSimConfig {
|
||||
name: "sequential-partitions".into(),
|
||||
num_nodes: 6,
|
||||
num_rounds: 100,
|
||||
ticks_per_round: 3,
|
||||
actors_per_node: 0,
|
||||
network_faults: vec![
|
||||
// Partition: {0,1,2} vs {3,4,5}
|
||||
NetworkFault::Partition {
|
||||
round: 10,
|
||||
partition: Partition {
|
||||
side_a: vec![0, 1, 2],
|
||||
side_b: vec![3, 4, 5],
|
||||
asymmetric: false,
|
||||
},
|
||||
},
|
||||
],
|
||||
..default_config()
|
||||
};
|
||||
|
||||
let trace = run_simulation(config);
|
||||
|
||||
// Each side should still see its own members
|
||||
let last_round = trace.snapshots_per_round.last().unwrap();
|
||||
let alive_count = last_round.iter().filter(|(_, s)| s.is_alive).count();
|
||||
assert_eq!(alive_count, 6, "all nodes still alive");
|
||||
|
||||
// Side A should maintain internal connectivity
|
||||
let side_a_connected = (0..3)
|
||||
.filter(|&i| last_round[i].1.member_count >= 1)
|
||||
.count();
|
||||
assert!(
|
||||
side_a_connected >= 2,
|
||||
"at least 2 of side_a nodes should see peers, got {side_a_connected}"
|
||||
);
|
||||
}
|
||||
|
||||
// ────────────────────────────────────────────────────────────────────────────
|
||||
// 14. Message loss then recovery
|
||||
// ────────────────────────────────────────────────────────────────────────────
|
||||
|
||||
#[test]
|
||||
fn cluster_survives_brief_message_loss() {
|
||||
// Given: 5 nodes with 15% loss for a brief window, then clean network.
|
||||
// High suspicion timeout prevents false positives during the loss period.
|
||||
let config = DistributionSimConfig {
|
||||
name: "brief-loss-recovery".into(),
|
||||
num_nodes: 5,
|
||||
num_rounds: 80,
|
||||
ticks_per_round: 3,
|
||||
actors_per_node: 0,
|
||||
swim: distribution::swim::probe::SwimConfig {
|
||||
probe_interval: 1,
|
||||
probe_timeout: 5,
|
||||
indirect_probes: 2,
|
||||
suspicion_timeout: 20,
|
||||
},
|
||||
network_faults: vec![
|
||||
NetworkFault::SetDropRate {
|
||||
round: 5,
|
||||
rate: 0.15,
|
||||
},
|
||||
NetworkFault::SetDropRate {
|
||||
round: 30,
|
||||
rate: 0.0,
|
||||
},
|
||||
],
|
||||
..default_config()
|
||||
};
|
||||
|
||||
let trace = run_simulation(config);
|
||||
|
||||
// After loss stops, most nodes should still be in each other's member lists.
|
||||
// Some nodes may have been falsely declared dead during the loss window,
|
||||
// but the majority should maintain connectivity.
|
||||
let last_round = trace.snapshots_per_round.last().unwrap();
|
||||
let well_connected = last_round
|
||||
.iter()
|
||||
.filter(|(_, s)| s.is_alive && s.member_count >= 2)
|
||||
.count();
|
||||
assert!(
|
||||
well_connected >= 2,
|
||||
"at least 2 nodes should see ≥2 members after brief loss, got {well_connected}"
|
||||
);
|
||||
}
|
||||
Loading…
Reference in a new issue