feat: Introduce Hybrid Logical Clocks in protobuf, update architecture documentation, and add HLC test cases.

lattice-store/Cargo.toml

@@ -0,0 +1,15 @@
+[package]
+name = "lattice-store"
+description = "Log-based KV store with snapshots and watermarks"
+version.workspace = true
+edition.workspace = true
+license.workspace = true
+
+[dependencies]
+lattice-core = { workspace = true }
+tokio = { workspace = true }
+thiserror = { workspace = true }
+tracing = { workspace = true }
+
+[dev-dependencies]
+tokio-test = { workspace = true }

lattice-store/src/lib.rs

@@ -0,0 +1,12 @@
+//! Lattice Store
+//!
+//! Log-based Key-Value store:
+//! - State is a "view" generated by replaying entries
+//! - Watermarks for agreeing on safe compaction points
+//! - Snapshots for replacing old logs
+
+pub mod store;
+pub mod snapshot;
+pub mod watermark;
+
+pub use store::Store;

lattice-store/src/snapshot.rs

@@ -0,0 +1,6 @@
+//! Snapshots for log compaction
+
+/// A verified snapshot that can replace old log entries.
+pub struct Snapshot {
+    // TODO: snapshot data, watermark, verification
+}

lattice-store/src/store.rs

@@ -0,0 +1,35 @@
+//! The main KV store
+
+use std::collections::HashMap;
+
+/// A log-based Key-Value store.
+///
+/// The store is a dynamic "view" generated by replaying entries.
+pub struct Store {
+    data: HashMap<Vec<u8>, Vec<u8>>,
+}
+
+impl Store {
+    /// Create a new empty store.
+    pub fn new() -> Self {
+        Self {
+            data: HashMap::new(),
+        }
+    }
+
+    /// Get a value by key.
+    pub fn get(&self, key: &[u8]) -> Option<&[u8]> {
+        self.data.get(key).map(|v| v.as_slice())
+    }
+
+    /// Set a value (this would normally go through the log).
+    pub fn set(&mut self, key: Vec<u8>, value: Vec<u8>) {
+        self.data.insert(key, value);
+    }
+}
+
+impl Default for Store {
+    fn default() -> Self {
+        Self::new()
+    }
+}

lattice-store/src/watermark.rs

@@ -0,0 +1,9 @@
+//! Watermarks for agreeing on safe compaction points
+
+/// A watermark representing a safe cut-off point for log compaction.
+///
+/// Nodes use watermarks to agree on which entries can be safely
+/// deleted and replaced with snapshots.
+pub struct Watermark {
+    // TODO: watermark data
+}