Add MVCC support and integrate HLC timestamps

AGENTS.md

@@ -0,0 +1,35 @@
+# Repository Guidelines
+
+## Project Structure & Modules
+- `cmd/server`, `cmd/client`: entrypoints for running the KV server and client.
+- `store/`: MVCC storage engine, OCC/TTL, and related tests.
+- `kv/`: hybrid logical clock (HLC) utilities and KV interfaces.
+- `adapter/`: protocol adapters (e.g., Redis), plus integration tests.
+- `jepsen/`, `jepsen/redis/`: Jepsen test harnesses and workloads.
+- `proto/`, `distribution/`, `internal/`: supporting protobufs, build assets, and shared helpers.
+
+## Build, Test, and Development Commands
+- `go test ./...` — run unit/integration tests. If macOS sandbox blocks `$GOCACHE`, prefer `GOCACHE=$(pwd)/.cache GOTMPDIR=$(pwd)/.cache/tmp go test ./...`.
+- `GOCACHE=$(pwd)/.cache GOLANGCI_LINT_CACHE=$(pwd)/.golangci-cache golangci-lint run ./... --timeout=5m` — full lint suite.
+- `HOME=$(pwd)/jepsen/tmp-home LEIN_HOME=$(pwd)/jepsen/.lein LEIN_JVM_OPTS="-Duser.home=$(pwd)/jepsen/tmp-home" /tmp/lein test` (from `jepsen/` or `jepsen/redis/`) — Jepsen tests.
+- `go run ./cmd/server` / `go run ./cmd/client` — start server or CLI locally.
+
+## Coding Style & Naming
+- Go code: `gofmt` + project lint rules (`golangci-lint`). Avoid adding `//nolint` unless absolutely required; prefer refactoring.
+- Naming: Go conventions (MixedCaps for exported identifiers, short receiver names). Filenames remain lowercase with underscores only where existing.
+- Logging: use `slog` where present; maintain structured keys (`key`, `commit_ts`, etc.).
+
+## Testing Guidelines
+- Unit tests co-located with packages (`*_test.go`); prefer table-driven cases.
+- TTL/HLC behaviors live in `store/` and `kv/`; add coverage when touching clocks, OCC, or replication logic.
+- Integration: run Jepsen suites after changes affecting replication, MVCC, or Redis adapter.
+  - `cd jepsen && HOME=$(pwd)/tmp-home LEIN_HOME=$(pwd)/.lein LEIN_JVM_OPTS="-Duser.home=$(pwd)/tmp-home" /tmp/lein test`
+  - `cd jepsen/redis && HOME=$(pwd)/../tmp-home LEIN_HOME=$(pwd)/../.lein LEIN_JVM_OPTS="-Duser.home=$(pwd)/../tmp-home" /tmp/lein test`
+
+## Commit & Pull Request Guidelines
+- Messages: short imperative summary (e.g., “Add HLC TTL handling”). Include scope when helpful (`store:`, `adapter:`).
+- Pull requests: describe behavior change, risk, and test evidence (`go test`, lint, Jepsen). Add repro steps for bug fixes.
+
+## Security & Configuration Tips
+- Hybrid clock derives from wall-clock millis; keep system clock reasonably synchronized across nodes.
+- Avoid leader-local timestamps in persistence; timestamp issuance should originate from the Raft leader to prevent skewed OCC decisions.

adapter/internal.go

@@ -9,16 +9,18 @@ import (
 	"github.com/hashicorp/raft"
 )
 
-func NewInternal(txm kv.Transactional, r *raft.Raft) *Internal {
+func NewInternal(txm kv.Transactional, r *raft.Raft, clock *kv.HLC) *Internal {
 	return &Internal{
 		raft:               r,
 		transactionManager: txm,
+		clock:              clock,
 	}
 }
 
 type Internal struct {
 	raft               *raft.Raft
 	transactionManager kv.Transactional
+	clock              *kv.HLC
 
 	pb.UnimplementedInternalServer
 }
@@ -33,6 +35,15 @@ func (i *Internal) Forward(_ context.Context, req *pb.ForwardRequest) (*pb.Forwa
 		return nil, errors.WithStack(ErrNotLeader)
 	}
 
+	// Ensure leader issues start_ts when followers forward txn groups without it.
+	if req.IsTxn {
+		for _, r := range req.Requests {
+			if r.Ts == 0 {
+				r.Ts = i.clock.Next()
+			}
+		}
+	}
+
 	r, err := i.transactionManager.Commit(req.Requests)
 	if err != nil {
 		return &pb.ForwardResponse{

adapter/test_util.go

@@ -322,9 +322,8 @@ func setupNodes(t *testing.T, ctx context.Context, n int, ports []portsAdress) (
 	cfg := buildRaftConfig(n, ports)
 
 	for i := 0; i < n; i++ {
-		st := store.NewRbMemoryStore()
-		trxSt := store.NewMemoryStoreDefaultTTL()
-		fsm := kv.NewKvFSM(st, trxSt)
+		st := store.NewMVCCStore()
+		fsm := kv.NewKvFSM(st)
 
 		port := ports[i]
 		grpcSock := lis[i].grpc
@@ -351,7 +350,7 @@ func setupNodes(t *testing.T, ctx context.Context, n int, ports []portsAdress) (
 		tm.Register(s)
 		pb.RegisterRawKVServer(s, gs)
 		pb.RegisterTransactionalKVServer(s, gs)
-		pb.RegisterInternalServer(s, NewInternal(trx, r))
+		pb.RegisterInternalServer(s, NewInternal(trx, r, coordinator.Clock()))
 
 		leaderhealth.Setup(r, s, []string{"Example"})
 		raftadmin.Register(s, r)

cmd/server/demo.go

@@ -81,9 +81,8 @@ func run(eg *errgroup.Group) error {
 	}
 
 	for i := 0; i < 3; i++ {
-		st := store.NewRbMemoryStore()
-		trxSt := store.NewMemoryStoreDefaultTTL()
-		fsm := kv.NewKvFSM(st, trxSt)
+		st := store.NewMVCCStore()
+		fsm := kv.NewKvFSM(st)
 
 		r, tm, err := newRaft(strconv.Itoa(i), grpcAdders[i], fsm, i == 0, cfg)
 		if err != nil {
@@ -97,7 +96,7 @@ func run(eg *errgroup.Group) error {
 		tm.Register(s)
 		pb.RegisterRawKVServer(s, gs)
 		pb.RegisterTransactionalKVServer(s, gs)
-		pb.RegisterInternalServer(s, adapter.NewInternal(trx, r))
+		pb.RegisterInternalServer(s, adapter.NewInternal(trx, r, coordinator.Clock()))
 		leaderhealth.Setup(r, s, []string{"RawKV"})
 		raftadmin.Register(s, r)
 

go.mod

@@ -25,6 +25,7 @@ require (
 	github.com/tidwall/redcon v1.6.2
 	go.etcd.io/bbolt v1.4.3
 	golang.org/x/sync v0.19.0
+	golang.org/x/sys v0.38.0
 	google.golang.org/grpc v1.78.0
 	google.golang.org/protobuf v1.36.11
 )
@@ -68,7 +69,6 @@ require (
 	github.com/tidwall/btree v1.1.0 // indirect
 	github.com/tidwall/match v1.1.1 // indirect
 	golang.org/x/net v0.47.0 // indirect
-	golang.org/x/sys v0.38.0 // indirect
 	golang.org/x/text v0.31.0 // indirect
 	google.golang.org/genproto/googleapis/rpc v0.0.0-20251029180050-ab9386a59fda // indirect
 	gopkg.in/yaml.v3 v3.0.1 // indirect

kv/coordinator.go

@@ -14,6 +14,7 @@ func NewCoordinator(txm Transactional, r *raft.Raft) *Coordinate {
 	return &Coordinate{
 		transactionManager: txm,
 		raft:               r,
+		clock:              NewHLC(),
 	}
 }
 
@@ -24,6 +25,7 @@ type CoordinateResponse struct {
 type Coordinate struct {
 	transactionManager Transactional
 	raft               *raft.Raft
+	clock              *HLC
 }
 
 var _ Coordinator = (*Coordinate)(nil)
@@ -39,8 +41,13 @@ func (c *Coordinate) Dispatch(reqs *OperationGroup[OP]) (*CoordinateResponse, er
 		return c.redirect(reqs)
 	}
 
+	if reqs.IsTxn && reqs.StartTS == 0 {
+		// Leader-only timestamp issuance to avoid divergence across shards.
+		reqs.StartTS = c.nextStartTS()
+	}
+
 	if reqs.IsTxn {
-		return c.dispatchTxn(reqs.Elems)
+		return c.dispatchTxn(reqs.Elems, reqs.StartTS)
 	}
 
 	return c.dispatchRaw(reqs.Elems)
@@ -56,10 +63,18 @@ func (c *Coordinate) RaftLeader() raft.ServerAddress {
 	return addr
 }
 
-func (c *Coordinate) dispatchTxn(reqs []*Elem[OP]) (*CoordinateResponse, error) {
+func (c *Coordinate) Clock() *HLC {
+	return c.clock
+}
+
+func (c *Coordinate) nextStartTS() uint64 {
+	return c.clock.Next()
+}
+
+func (c *Coordinate) dispatchTxn(reqs []*Elem[OP], startTS uint64) (*CoordinateResponse, error) {
 	var logs []*pb.Request
 	for _, req := range reqs {
-		m := c.toTxnRequests(req)
+		m := c.toTxnRequests(req, startTS)
 		logs = append(logs, m...)
 	}
 
@@ -96,6 +111,7 @@ func (c *Coordinate) toRawRequest(req *Elem[OP]) *pb.Request {
 		return &pb.Request{
 			IsTxn: false,
 			Phase: pb.Phase_NONE,
+			Ts:    c.clock.Next(),
 			Mutations: []*pb.Mutation{
 				{
 					Op:    pb.Op_PUT,
@@ -109,6 +125,7 @@ func (c *Coordinate) toRawRequest(req *Elem[OP]) *pb.Request {
 		return &pb.Request{
 			IsTxn: false,
 			Phase: pb.Phase_NONE,
+			Ts:    c.clock.Next(),
 			Mutations: []*pb.Mutation{
 				{
 					Op:  pb.Op_DEL,
@@ -121,16 +138,14 @@ func (c *Coordinate) toRawRequest(req *Elem[OP]) *pb.Request {
 	panic("unreachable")
 }
 
-const defaultTxnLockTTLSeconds = uint64(30)
-
-func (c *Coordinate) toTxnRequests(req *Elem[OP]) []*pb.Request {
+func (c *Coordinate) toTxnRequests(req *Elem[OP], startTS uint64) []*pb.Request {
 	switch req.Op {
 	case Put:
 		return []*pb.Request{
 			{
 				IsTxn: true,
 				Phase: pb.Phase_PREPARE,
-				Ts:    defaultTxnLockTTLSeconds,
+				Ts:    startTS,
 				Mutations: []*pb.Mutation{
 					{
 						Key:   req.Key,
@@ -141,7 +156,7 @@ func (c *Coordinate) toTxnRequests(req *Elem[OP]) []*pb.Request {
 			{
 				IsTxn: true,
 				Phase: pb.Phase_COMMIT,
-				Ts:    defaultTxnLockTTLSeconds,
+				Ts:    startTS,
 				Mutations: []*pb.Mutation{
 					{
 						Key:   req.Key,
@@ -156,7 +171,7 @@ func (c *Coordinate) toTxnRequests(req *Elem[OP]) []*pb.Request {
 			{
 				IsTxn: true,
 				Phase: pb.Phase_PREPARE,
-				Ts:    defaultTxnLockTTLSeconds,
+				Ts:    startTS,
 				Mutations: []*pb.Mutation{
 					{
 						Key: req.Key,
@@ -166,7 +181,7 @@ func (c *Coordinate) toTxnRequests(req *Elem[OP]) []*pb.Request {
 			{
 				IsTxn: true,
 				Phase: pb.Phase_COMMIT,
-				Ts:    defaultTxnLockTTLSeconds,
+				Ts:    startTS,
 				Mutations: []*pb.Mutation{
 					{
 						Key: req.Key,
@@ -204,7 +219,7 @@ func (c *Coordinate) redirect(reqs *OperationGroup[OP]) (*CoordinateResponse, er
 	var requests []*pb.Request
 	if reqs.IsTxn {
 		for _, req := range reqs.Elems {
-			requests = append(requests, c.toTxnRequests(req)...)
+			requests = append(requests, c.toTxnRequests(req, reqs.StartTS)...)
 		}
 	} else {
 		for _, req := range reqs.Elems {