Crate mdcs_compaction 

mdcs-compaction

Compaction and stability subsystem for the MDCS (Merkle-Delta CRDT Store).

This crate provides:

• Snapshotting: Serialize full CRDT state at stable frontiers
• DAG pruning: Remove nodes older than the last snapshot
• Stability monitoring: Track delivered and stable frontiers
• Version vectors: Compact representation of causal context

Architecture

The compaction subsystem ensures bounded metadata growth by:

1. Tracking which updates have been durably replicated (stability)
2. Creating periodic snapshots at stable points
3. Pruning DAG history before the snapshot root
4. Preventing resurrection of deleted items

Example

use mdcs_compaction::{StabilityMonitor, SnapshotManager, PruningPolicy};

// Create a stability monitor
let mut monitor = StabilityMonitor::new("replica_1");

// Track frontier updates from peers
monitor.update_peer_frontier("replica_2", frontier_2);
monitor.update_peer_frontier("replica_3", frontier_3);

// Check if a node is stable (delivered to all tracked peers)
if monitor.is_stable(&node_cid) {
    // Safe to compact
}

Modules

compactor 🔒

High-level compaction orchestrator.

pruning 🔒

DAG pruning for bounded history growth.

snapshot 🔒

Snapshot management for CRDT state persistence.

stability 🔒

Stability monitoring for safe compaction.

version_vector 🔒

Version vector for compact causal context representation.

Structs

CompactionConfig

Configuration for the compactor.

CompactionStats

Statistics about compaction operations.

Compactor

High-level compactor that orchestrates all compaction operations.

FrontierUpdate

Update about a peer’s frontier.

Pruner

Pruner for removing old DAG nodes.

PruningPolicy

Policy for DAG pruning decisions.

PruningResult

Result of a pruning operation.

PruningVerifier

Verification utilities for pruning safety.

Snapshot

A snapshot of CRDT state at a specific point in causal history.

SnapshotManager

Manages snapshot creation and retrieval.

StabilityConfig

Configuration for stability monitoring.

StabilityMonitor

Monitors stability across replicas for safe compaction decisions.

VectorEntry

A single entry in a version vector.

VersionVector

A version vector tracking the frontier of seen updates per replica.

Enums

CompactionError

Errors that can occur during compaction.

SnapshotError

Errors that can occur during snapshot operations.

StabilityState

State of stability tracking for a single item.

Traits

PrunableStore

Extension trait for stores that support node removal.