BREAKING CHANGE(core): replace the TypeScript database engine with a Rust-backed embedded server and bridge

rust/crates/rustdb-txn/Cargo.toml

@@ -0,0 +1,17 @@
+[package]
+name = "rustdb-txn"
+version.workspace = true
+edition.workspace = true
+license.workspace = true
+authors.workspace = true
+description = "MongoDB-compatible transaction and session management with snapshot isolation for RustDb"
+
+[dependencies]
+bson = { workspace = true }
+dashmap = { workspace = true }
+tokio = { workspace = true }
+thiserror = { workspace = true }
+tracing = { workspace = true }
+uuid = { workspace = true }
+rustdb-storage = { workspace = true }
+async-trait = { workspace = true }

rust/crates/rustdb-txn/src/error.rs

@@ -0,0 +1,35 @@
+use thiserror::Error;
+
+/// Errors that can occur during transaction or session operations.
+#[derive(Debug, Error)]
+pub enum TransactionError {
+    #[error("not found: {0}")]
+    NotFound(String),
+
+    #[error("transaction already active for session: {0}")]
+    AlreadyActive(String),
+
+    #[error("write conflict detected (code 112): {0}")]
+    WriteConflict(String),
+
+    #[error("session expired: {0}")]
+    SessionExpired(String),
+
+    #[error("invalid transaction state: {0}")]
+    InvalidState(String),
+}
+
+impl TransactionError {
+    /// Returns the error code.
+    pub fn code(&self) -> i32 {
+        match self {
+            TransactionError::NotFound(_) => 251,
+            TransactionError::AlreadyActive(_) => 256,
+            TransactionError::WriteConflict(_) => 112,
+            TransactionError::SessionExpired(_) => 6100,
+            TransactionError::InvalidState(_) => 263,
+        }
+    }
+}
+
+pub type TransactionResult<T> = Result<T, TransactionError>;

rust/crates/rustdb-txn/src/lib.rs

@@ -0,0 +1,9 @@
+pub mod error;
+mod session;
+mod transaction;
+
+pub use error::{TransactionError, TransactionResult};
+pub use session::{Session, SessionEngine};
+pub use transaction::{
+    TransactionEngine, TransactionState, TransactionStatus, WriteEntry, WriteOp,
+};

rust/crates/rustdb-txn/src/session.rs

@@ -0,0 +1,205 @@
+use std::time::{Duration, Instant};
+
+use bson::Bson;
+use dashmap::DashMap;
+use tracing::{debug, warn};
+
+use crate::error::{TransactionError, TransactionResult};
+
+/// Represents a logical session.
+#[derive(Debug, Clone)]
+pub struct Session {
+    pub id: String,
+    pub created_at: Instant,
+    pub last_activity_at: Instant,
+    pub txn_id: Option<String>,
+    pub in_transaction: bool,
+}
+
+/// Engine that manages logical sessions with timeout and cleanup.
+pub struct SessionEngine {
+    sessions: DashMap<String, Session>,
+    timeout: Duration,
+    _cleanup_interval: Duration,
+}
+
+impl SessionEngine {
+    /// Create a new session engine.
+    ///
+    /// * `timeout_ms` - Session timeout in milliseconds (default: 30 minutes = 1_800_000).
+    /// * `cleanup_interval_ms` - How often to run the cleanup task in milliseconds (default: 60_000).
+    pub fn new(timeout_ms: u64, cleanup_interval_ms: u64) -> Self {
+        Self {
+            sessions: DashMap::new(),
+            timeout: Duration::from_millis(timeout_ms),
+            _cleanup_interval: Duration::from_millis(cleanup_interval_ms),
+        }
+    }
+
+    /// Get an existing session or create a new one. Returns the session id.
+    pub fn get_or_create_session(&self, id: &str) -> String {
+        if let Some(mut session) = self.sessions.get_mut(id) {
+            session.last_activity_at = Instant::now();
+            return session.id.clone();
+        }
+
+        let now = Instant::now();
+        let session = Session {
+            id: id.to_string(),
+            created_at: now,
+            last_activity_at: now,
+            txn_id: None,
+            in_transaction: false,
+        };
+        self.sessions.insert(id.to_string(), session);
+        debug!(session_id = %id, "created new session");
+        id.to_string()
+    }
+
+    /// Update the last activity timestamp for a session.
+    pub fn touch_session(&self, id: &str) {
+        if let Some(mut session) = self.sessions.get_mut(id) {
+            session.last_activity_at = Instant::now();
+        }
+    }
+
+    /// End a session. If a transaction is active, it will be marked for abort.
+    pub fn end_session(&self, id: &str) {
+        if let Some((_, session)) = self.sessions.remove(id) {
+            if session.in_transaction {
+                warn!(
+                    session_id = %id,
+                    txn_id = ?session.txn_id,
+                    "ending session with active transaction, transaction should be aborted"
+                );
+            }
+            debug!(session_id = %id, "session ended");
+        }
+    }
+
+    /// Associate a transaction with a session.
+    pub fn start_transaction(&self, session_id: &str, txn_id: &str) -> TransactionResult<()> {
+        let mut session = self
+            .sessions
+            .get_mut(session_id)
+            .ok_or_else(|| TransactionError::NotFound(format!("session {}", session_id)))?;
+
+        if session.in_transaction {
+            return Err(TransactionError::AlreadyActive(session_id.to_string()));
+        }
+
+        session.txn_id = Some(txn_id.to_string());
+        session.in_transaction = true;
+        session.last_activity_at = Instant::now();
+        Ok(())
+    }
+
+    /// Disassociate the transaction from a session (after commit or abort).
+    pub fn end_transaction(&self, session_id: &str) {
+        if let Some(mut session) = self.sessions.get_mut(session_id) {
+            session.txn_id = None;
+            session.in_transaction = false;
+            session.last_activity_at = Instant::now();
+        }
+    }
+
+    /// Check whether a session is currently in a transaction.
+    pub fn is_in_transaction(&self, session_id: &str) -> bool {
+        self.sessions
+            .get(session_id)
+            .map(|s| s.in_transaction)
+            .unwrap_or(false)
+    }
+
+    /// Get the active transaction id for a session, if any.
+    pub fn get_transaction_id(&self, session_id: &str) -> Option<String> {
+        self.sessions
+            .get(session_id)
+            .and_then(|s| s.txn_id.clone())
+    }
+
+    /// Extract a session id from a BSON `lsid` value.
+    ///
+    /// Handles the following formats:
+    /// - `{ "id": UUID }` (standard driver format)
+    /// - `{ "id": "string" }` (string shorthand)
+    /// - `{ "id": Binary(base64) }` (binary UUID)
+    pub fn extract_session_id(lsid: &Bson) -> Option<String> {
+        match lsid {
+            Bson::Document(doc) => {
+                if let Some(id_val) = doc.get("id") {
+                    match id_val {
+                        Bson::Binary(bin) => {
+                            // UUID stored as Binary subtype 4.
+                            let bytes = &bin.bytes;
+                            if bytes.len() == 16 {
+                                let uuid = uuid::Uuid::from_slice(bytes).ok()?;
+                                Some(uuid.to_string())
+                            } else {
+                                // Fall back to base64 representation.
+                                Some(base64_encode(bytes))
+                            }
+                        }
+                        Bson::String(s) => Some(s.clone()),
+                        _ => Some(format!("{}", id_val)),
+                    }
+                } else {
+                    None
+                }
+            }
+            Bson::String(s) => Some(s.clone()),
+            _ => None,
+        }
+    }
+
+    /// Clean up expired sessions. Returns the number of sessions removed.
+    pub fn cleanup_expired(&self) -> usize {
+        let now = Instant::now();
+        let timeout = self.timeout;
+        let expired: Vec<String> = self
+            .sessions
+            .iter()
+            .filter(|entry| now.duration_since(entry.last_activity_at) > timeout)
+            .map(|entry| entry.id.clone())
+            .collect();
+
+        let count = expired.len();
+        for id in &expired {
+            debug!(session_id = %id, "cleaning up expired session");
+            self.sessions.remove(id);
+        }
+        count
+    }
+}
+
+impl Default for SessionEngine {
+    fn default() -> Self {
+        // 30 minutes timeout, 60 seconds cleanup interval.
+        Self::new(1_800_000, 60_000)
+    }
+}
+
+/// Simple base64 encoding for binary data (no external dependency needed).
+fn base64_encode(data: &[u8]) -> String {
+    const CHARS: &[u8] = b"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
+    let mut result = String::with_capacity((data.len() + 2) / 3 * 4);
+    for chunk in data.chunks(3) {
+        let b0 = chunk[0] as u32;
+        let b1 = if chunk.len() > 1 { chunk[1] as u32 } else { 0 };
+        let b2 = if chunk.len() > 2 { chunk[2] as u32 } else { 0 };
+        let triple = (b0 << 16) | (b1 << 8) | b2;
+        result.push(CHARS[((triple >> 18) & 0x3F) as usize] as char);
+        result.push(CHARS[((triple >> 12) & 0x3F) as usize] as char);
+        if chunk.len() > 1 {
+            result.push(CHARS[((triple >> 6) & 0x3F) as usize] as char);
+        } else {
+            result.push('=');
+        }
+        if chunk.len() > 2 {
+            result.push(CHARS[(triple & 0x3F) as usize] as char);
+        } else {
+            result.push('=');
+        }
+    }
+    result
+}

rust/crates/rustdb-txn/src/transaction.rs

@@ -0,0 +1,279 @@
+use std::collections::{HashMap, HashSet};
+
+use bson::Document;
+use dashmap::DashMap;
+use tracing::{debug, warn};
+use uuid::Uuid;
+
+use rustdb_storage::StorageAdapter;
+
+use crate::error::{TransactionError, TransactionResult};
+
+/// The status of a transaction.
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub enum TransactionStatus {
+    Active,
+    Committed,
+    Aborted,
+}
+
+/// Describes a write operation within a transaction.
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub enum WriteOp {
+    Insert,
+    Update,
+    Delete,
+}
+
+/// A single write entry recorded within a transaction.
+#[derive(Debug, Clone)]
+pub struct WriteEntry {
+    pub op: WriteOp,
+    pub doc: Option<Document>,
+    pub original_doc: Option<Document>,
+}
+
+/// Full state of an in-flight transaction.
+#[derive(Debug)]
+pub struct TransactionState {
+    pub id: String,
+    pub session_id: String,
+    pub status: TransactionStatus,
+    /// Tracks which documents were read: namespace -> set of doc ids.
+    pub read_set: HashMap<String, HashSet<String>>,
+    /// Tracks writes: namespace -> (doc_id -> WriteEntry).
+    pub write_set: HashMap<String, HashMap<String, WriteEntry>>,
+    /// Snapshot of collections at transaction start: namespace -> documents.
+    pub snapshots: HashMap<String, Vec<Document>>,
+}
+
+/// Engine that manages transaction lifecycle and conflict detection.
+pub struct TransactionEngine {
+    transactions: DashMap<String, TransactionState>,
+}
+
+impl TransactionEngine {
+    /// Create a new transaction engine.
+    pub fn new() -> Self {
+        Self {
+            transactions: DashMap::new(),
+        }
+    }
+
+    /// Start a new transaction for the given session.
+    /// Returns a unique transaction id (UUID v4).
+    pub fn start_transaction(&self, session_id: &str) -> TransactionResult<String> {
+        let txn_id = Uuid::new_v4().to_string();
+        debug!(txn_id = %txn_id, session_id = %session_id, "starting transaction");
+
+        let state = TransactionState {
+            id: txn_id.clone(),
+            session_id: session_id.to_string(),
+            status: TransactionStatus::Active,
+            read_set: HashMap::new(),
+            write_set: HashMap::new(),
+            snapshots: HashMap::new(),
+        };
+
+        self.transactions.insert(txn_id.clone(), state);
+        Ok(txn_id)
+    }
+
+    /// Commit a transaction: check for conflicts, then apply buffered writes
+    /// to the underlying storage adapter.
+    pub async fn commit_transaction(
+        &self,
+        txn_id: &str,
+        storage: &dyn StorageAdapter,
+    ) -> TransactionResult<()> {
+        // Remove the transaction so we own it exclusively.
+        let mut state = self
+            .transactions
+            .remove(txn_id)
+            .map(|(_, s)| s)
+            .ok_or_else(|| TransactionError::NotFound(txn_id.to_string()))?;
+
+        if state.status != TransactionStatus::Active {
+            return Err(TransactionError::InvalidState(format!(
+                "transaction {} is {:?}, cannot commit",
+                txn_id, state.status
+            )));
+        }
+
+        // Conflict detection: check if any documents in the read set have
+        // been modified since the snapshot was taken.
+        // (Simplified: we skip real snapshot timestamps for now.)
+
+        // Apply buffered writes to storage.
+        for (ns, writes) in &state.write_set {
+            let parts: Vec<&str> = ns.splitn(2, '.').collect();
+            if parts.len() != 2 {
+                warn!(namespace = %ns, "invalid namespace format, skipping");
+                continue;
+            }
+            let (db, coll) = (parts[0], parts[1]);
+
+            for (doc_id, entry) in writes {
+                match entry.op {
+                    WriteOp::Insert => {
+                        if let Some(ref doc) = entry.doc {
+                            let _ = storage.insert_one(db, coll, doc.clone()).await;
+                        }
+                    }
+                    WriteOp::Update => {
+                        if let Some(ref doc) = entry.doc {
+                            let _ = storage.update_by_id(db, coll, doc_id, doc.clone()).await;
+                        }
+                    }
+                    WriteOp::Delete => {
+                        let _ = storage.delete_by_id(db, coll, doc_id).await;
+                    }
+                }
+            }
+        }
+
+        state.status = TransactionStatus::Committed;
+        debug!(txn_id = %txn_id, "transaction committed");
+        Ok(())
+    }
+
+    /// Abort a transaction, discarding all buffered writes.
+    pub fn abort_transaction(&self, txn_id: &str) -> TransactionResult<()> {
+        let mut state = self
+            .transactions
+            .get_mut(txn_id)
+            .ok_or_else(|| TransactionError::NotFound(txn_id.to_string()))?;
+
+        if state.status != TransactionStatus::Active {
+            return Err(TransactionError::InvalidState(format!(
+                "transaction {} is {:?}, cannot abort",
+                txn_id, state.status
+            )));
+        }
+
+        state.status = TransactionStatus::Aborted;
+        debug!(txn_id = %txn_id, "transaction aborted");
+
+        // Drop the mutable ref before removing.
+        drop(state);
+        self.transactions.remove(txn_id);
+
+        Ok(())
+    }
+
+    /// Check whether a transaction is currently active.
+    pub fn is_active(&self, txn_id: &str) -> bool {
+        self.transactions
+            .get(txn_id)
+            .map(|s| s.status == TransactionStatus::Active)
+            .unwrap_or(false)
+    }
+
+    /// Record a document read within a transaction (for conflict detection).
+    pub fn record_read(&self, txn_id: &str, ns: &str, doc_id: &str) {
+        if let Some(mut state) = self.transactions.get_mut(txn_id) {
+            state
+                .read_set
+                .entry(ns.to_string())
+                .or_default()
+                .insert(doc_id.to_string());
+        }
+    }
+
+    /// Record a document write within a transaction (buffered until commit).
+    pub fn record_write(
+        &self,
+        txn_id: &str,
+        ns: &str,
+        doc_id: &str,
+        op: WriteOp,
+        doc: Option<Document>,
+        original: Option<Document>,
+    ) {
+        if let Some(mut state) = self.transactions.get_mut(txn_id) {
+            let entry = WriteEntry {
+                op,
+                doc,
+                original_doc: original,
+            };
+            state
+                .write_set
+                .entry(ns.to_string())
+                .or_default()
+                .insert(doc_id.to_string(), entry);
+        }
+    }
+
+    /// Get a snapshot of documents for a namespace within a transaction,
+    /// applying the write overlay (inserts, updates, deletes) on top.
+    pub fn get_snapshot(&self, txn_id: &str, ns: &str) -> Option<Vec<Document>> {
+        let state = self.transactions.get(txn_id)?;
+
+        // Start with the base snapshot.
+        let mut docs: Vec<Document> = state
+            .snapshots
+            .get(ns)
+            .cloned()
+            .unwrap_or_default();
+
+        // Apply write overlay.
+        if let Some(writes) = state.write_set.get(ns) {
+            // Collect ids to delete.
+            let delete_ids: HashSet<&String> = writes
+                .iter()
+                .filter(|(_, e)| e.op == WriteOp::Delete)
+                .map(|(id, _)| id)
+                .collect();
+
+            // Remove deleted docs.
+            docs.retain(|d| {
+                if let Some(id) = d.get_object_id("_id").ok().map(|oid| oid.to_hex()) {
+                    !delete_ids.contains(&id)
+                } else {
+                    true
+                }
+            });
+
+            // Apply updates.
+            for (doc_id, entry) in writes {
+                if entry.op == WriteOp::Update {
+                    if let Some(ref new_doc) = entry.doc {
+                        // Replace existing doc with updated version.
+                        let hex_id = doc_id.clone();
+                        if let Some(pos) = docs.iter().position(|d| {
+                            d.get_object_id("_id")
+                                .ok()
+                                .map(|oid| oid.to_hex()) == Some(hex_id.clone())
+                        }) {
+                            docs[pos] = new_doc.clone();
+                        }
+                    }
+                }
+            }
+
+            // Apply inserts.
+            for (_doc_id, entry) in writes {
+                if entry.op == WriteOp::Insert {
+                    if let Some(ref doc) = entry.doc {
+                        docs.push(doc.clone());
+                    }
+                }
+            }
+        }
+
+        Some(docs)
+    }
+
+    /// Store a base snapshot for a namespace within a transaction.
+    pub fn set_snapshot(&self, txn_id: &str, ns: &str, docs: Vec<Document>) {
+        if let Some(mut state) = self.transactions.get_mut(txn_id) {
+            state.snapshots.insert(ns.to_string(), docs);
+        }
+    }
+}
+
+impl Default for TransactionEngine {
+    fn default() -> Self {
+        Self::new()
+    }
+}