etcdserver: start real txn for txn request

We should open real txn for applying txn requests. Or the intermediate
state might be observed by reader.

This also fixes #3803. Same consistent(raft) index per multiple indenpendent
operations confuses consistentStore.

etcdserver/v3demo_server.go

@@ -16,11 +16,13 @@ package etcdserver
 
 import (
 	"bytes"
+	"fmt"
 
 	"github.com/coreos/etcd/Godeps/_workspace/src/github.com/gogo/protobuf/proto"
 	"github.com/coreos/etcd/Godeps/_workspace/src/golang.org/x/net/context"
 	pb "github.com/coreos/etcd/etcdserver/etcdserverpb"
 	dstorage "github.com/coreos/etcd/storage"
+	"github.com/coreos/etcd/storage/storagepb"
 )
 
 type RaftKV interface {
@@ -103,16 +105,23 @@ func (s *EtcdServer) Watchable() dstorage.Watchable {
 	return s.kv
 }
 
+const (
+	// noTxn is an invalid txn ID.
+	// To apply with independent Range, Put, Delete, you can pass noTxn
+	// to apply functions instead of a valid txn ID.
+	noTxn = -1
+)
+
 func (s *EtcdServer) applyV3Request(r *pb.InternalRaftRequest) interface{} {
 	ar := &applyResult{}
 
 	switch {
 	case r.Range != nil:
-		ar.resp, ar.err = applyRange(s.kv, r.Range)
+		ar.resp, ar.err = applyRange(noTxn, s.kv, r.Range)
 	case r.Put != nil:
-		ar.resp, ar.err = applyPut(s.kv, r.Put)
+		ar.resp, ar.err = applyPut(noTxn, s.kv, r.Put)
 	case r.DeleteRange != nil:
-		ar.resp, ar.err = applyDeleteRange(s.kv, r.DeleteRange)
+		ar.resp, ar.err = applyDeleteRange(noTxn, s.kv, r.DeleteRange)
 	case r.Txn != nil:
 		ar.resp, ar.err = applyTxn(s.kv, r.Txn)
 	case r.Compaction != nil:
@@ -124,21 +133,46 @@ func (s *EtcdServer) applyV3Request(r *pb.InternalRaftRequest) interface{} {
 	return ar
 }
 
-func applyPut(kv dstorage.KV, p *pb.PutRequest) (*pb.PutResponse, error) {
+func applyPut(txnID int64, kv dstorage.KV, p *pb.PutRequest) (*pb.PutResponse, error) {
 	resp := &pb.PutResponse{}
 	resp.Header = &pb.ResponseHeader{}
-	rev := kv.Put(p.Key, p.Value)
+	var (
+		rev int64
+		err error
+	)
+	if txnID != noTxn {
+		rev, err = kv.TxnPut(txnID, p.Key, p.Value)
+		if err != nil {
+			return nil, err
+		}
+	} else {
+		rev = kv.Put(p.Key, p.Value)
+	}
 	resp.Header.Revision = rev
 	return resp, nil
 }
 
-func applyRange(kv dstorage.KV, r *pb.RangeRequest) (*pb.RangeResponse, error) {
+func applyRange(txnID int64, kv dstorage.KV, r *pb.RangeRequest) (*pb.RangeResponse, error) {
 	resp := &pb.RangeResponse{}
 	resp.Header = &pb.ResponseHeader{}
-	kvs, rev, err := kv.Range(r.Key, r.RangeEnd, r.Limit, 0)
+
+	var (
+		kvs []storagepb.KeyValue
+		rev int64
+		err error
+	)
+
+	if txnID != noTxn {
+		kvs, rev, err = kv.TxnRange(txnID, r.Key, r.RangeEnd, r.Limit, 0)
 		if err != nil {
 			return nil, err
 		}
+	} else {
+		kvs, rev, err = kv.Range(r.Key, r.RangeEnd, r.Limit, 0)
+		if err != nil {
+			return nil, err
+		}
+	}
 
 	resp.Header.Revision = rev
 	for i := range kvs {
@@ -147,10 +181,24 @@ func applyRange(kv dstorage.KV, r *pb.RangeRequest) (*pb.RangeResponse, error) {
 	return resp, nil
 }
 
-func applyDeleteRange(kv dstorage.KV, dr *pb.DeleteRangeRequest) (*pb.DeleteRangeResponse, error) {
+func applyDeleteRange(txnID int64, kv dstorage.KV, dr *pb.DeleteRangeRequest) (*pb.DeleteRangeResponse, error) {
 	resp := &pb.DeleteRangeResponse{}
 	resp.Header = &pb.ResponseHeader{}
-	_, rev := kv.DeleteRange(dr.Key, dr.RangeEnd)
+
+	var (
+		rev int64
+		err error
+	)
+
+	if txnID != noTxn {
+		_, rev, err = kv.TxnDeleteRange(txnID, dr.Key, dr.RangeEnd)
+		if err != nil {
+			return nil, err
+		}
+	} else {
+		_, rev = kv.DeleteRange(dr.Key, dr.RangeEnd)
+	}
+
 	resp.Header.Revision = rev
 	return resp, nil
 }
@@ -158,9 +206,17 @@ func applyDeleteRange(kv dstorage.KV, dr *pb.DeleteRangeRequest) (*pb.DeleteRang
 func applyTxn(kv dstorage.KV, rt *pb.TxnRequest) (*pb.TxnResponse, error) {
 	var revision int64
 
+	txnID := kv.TxnBegin()
+	defer func() {
+		err := kv.TxnEnd(txnID)
+		if err != nil {
+			panic(fmt.Sprint("unexpected error when closing txn", txnID))
+		}
+	}()
+
 	ok := true
 	for _, c := range rt.Compare {
-		if revision, ok = applyCompare(kv, c); !ok {
+		if revision, ok = applyCompare(txnID, kv, c); !ok {
 			break
 		}
 	}
@@ -173,10 +229,12 @@ func applyTxn(kv dstorage.KV, rt *pb.TxnRequest) (*pb.TxnResponse, error) {
 	} else {
 		reqs = rt.Failure
 	}
+
 	resps := make([]*pb.ResponseUnion, len(reqs))
 	for i := range reqs {
-		resps[i] = applyUnion(kv, reqs[i])
+		resps[i] = applyUnion(txnID, kv, reqs[i])
 	}
+
 	if len(resps) != 0 {
 		revision += 1
 	}
@@ -201,22 +259,22 @@ func applyCompaction(kv dstorage.KV, compaction *pb.CompactionRequest) (*pb.Comp
 	return resp, err
 }
 
-func applyUnion(kv dstorage.KV, union *pb.RequestUnion) *pb.ResponseUnion {
+func applyUnion(txnID int64, kv dstorage.KV, union *pb.RequestUnion) *pb.ResponseUnion {
 	switch {
 	case union.RequestRange != nil:
-		resp, err := applyRange(kv, union.RequestRange)
+		resp, err := applyRange(txnID, kv, union.RequestRange)
 		if err != nil {
 			panic("unexpected error during txn")
 		}
 		return &pb.ResponseUnion{ResponseRange: resp}
 	case union.RequestPut != nil:
-		resp, err := applyPut(kv, union.RequestPut)
+		resp, err := applyPut(txnID, kv, union.RequestPut)
 		if err != nil {
 			panic("unexpected error during txn")
 		}
 		return &pb.ResponseUnion{ResponsePut: resp}
 	case union.RequestDeleteRange != nil:
-		resp, err := applyDeleteRange(kv, union.RequestDeleteRange)
+		resp, err := applyDeleteRange(txnID, kv, union.RequestDeleteRange)
 		if err != nil {
 			panic("unexpected error during txn")
 		}
@@ -227,9 +285,20 @@ func applyUnion(kv dstorage.KV, union *pb.RequestUnion) *pb.ResponseUnion {
 	}
 }
 
-func applyCompare(kv dstorage.KV, c *pb.Compare) (int64, bool) {
+// applyCompare applies the compare request.
-	ckvs, rev, err := kv.Range(c.Key, nil, 1, 0)
+// applyCompare should only be called within a txn request and an valid txn ID must
+// be presented. Or applyCompare panics.
+// It returns the revision at which the comparison happens. If the comparison
+// succeeds, the it returns true. Otherwise it returns false.
+func applyCompare(txnID int64, kv dstorage.KV, c *pb.Compare) (int64, bool) {
+	if txnID == noTxn {
+		panic("applyCompare called with noTxn")
+	}
+	ckvs, rev, err := kv.TxnRange(txnID, c.Key, nil, 1, 0)
 	if err != nil {
+		if err == dstorage.ErrTxnIDMismatch {
+			panic("unexpected txn ID mismatch error")
+		}
 		return rev, false
 	}