Implement v2 Protocol. Adding expectedVersion for optimistic concurrency and metadata.

LICENSE

@@ -0,0 +1,10 @@
+Copyright (c) 2016 GoES Contributors
+
+Contributors can be found at https://github.com/adymitruk/goes/graphs/contributors
+
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

README.md

@@ -1,8 +1,12 @@
+# Goes
+
 GoLang implementation of a simple EventStore
 
-# Getting started
+Released under the MIT license. See [LICENSE](https://github.com/adymitruk/goes/blob/master/LICENSE) file.
 
-## Pre-requisites
+## Getting started
+
+### Pre-requisites
 
 - Install [GoLang](https://golang.org/doc/install) version 1.6+
 - Install [libsodium](https://download.libsodium.org/libsodium/releases/)\* version 1.0.10+ (Linux only^)
@@ -14,9 +18,9 @@ GoLang implementation of a simple EventStore
 
 You can look at [scripts/bootstrap.sh](https://github.com/adymitruk/goes/blob/master/scripts/bootstrap.sh) to get an idea on how to install all the pre-requisites.
 
-## Build
+### Build
 
-### Fetching GO packages
+#### Fetching GO packages
 
 In your GOPATH folder, execute the following commands:
 
@@ -24,13 +28,13 @@ In your GOPATH folder, execute the following commands:
   `go get github.com/pebbe/zmq4`  
   `go get github.com/satori/go.uuid`  
   
-### Compiling the binary
+#### Compiling the binary
 
 In the project root folder, execute the following command:
 
   `go build`
   
-## Running the server
+### Running the server
 
 In the project root folder, execute the following command:
 

actions/actions.go

@@ -1,16 +1,26 @@
 package actions
 
 import (
-	"time"
-	"github.com/satori/go.uuid"
-	storage "../storage"
-	serializer "../serializer"
 	data "../data"
+	serializer "../serializer"
+	storage "../storage"
+	"errors"
+	"fmt"
+	"github.com/satori/go.uuid"
+	"time"
 )
 
+const NO_EXPECTEDVERSION = uint32(0xFFFFFFFF)
+
 var mapLock chan int = make(chan int, 1)
 var streamsLock map[string]chan int = make(map[string]chan int)
 
+type Handler interface {
+	AddEvent(data.Event, uint32) error
+	RetrieveFor(uuid.UUID) ([]*data.Event, error)
+	RetrieveAll() ([]*data.Event, error)
+}
+
 type ActionsHandler struct {
 	storage    storage.Storage
 	serializer serializer.Serializer
@@ -22,7 +32,7 @@ func NewActionsHandler(storage storage.Storage, serializer serializer.Serializer
 
 func lockStream(streamName string) {
 	mapLock <- 1
-	defer func(){
+	defer func() {
 		<-mapLock
 	}()
 
@@ -39,7 +49,7 @@ func unlockStream(streamName string) {
 	<-streamsLock[streamName]
 }
 
-func (me ActionsHandler) AddEvent(event data.Event) error {
+func (me ActionsHandler) AddEvent(event data.Event, expectedVersion uint32) error {
 	streamName := event.AggregateId.String()
 
 	lockStream(streamName)
@@ -50,11 +60,34 @@ func (me ActionsHandler) AddEvent(event data.Event) error {
 		return err
 	}
 
-	return me.storage.Write(&storage.StoredEvent{StreamId: event.AggregateId, CreationTime: time.Now(), TypeId: typeId, Data: serializedPayload})
+	serializedMetadata, _, err := me.serializer.Serialize(event.Metadata)
+	if err != nil {
+		return err
+	}
+
+	if expectedVersion != NO_EXPECTEDVERSION {
+		ver, err := me.storage.StreamVersion(event.AggregateId)
+		if err != nil && err.Error()[0:9] != "NOT_FOUND" {
+			return err
+		}
+		if ver != expectedVersion {
+			return errors.New(fmt.Sprint("WrongExpectedVersion: expected ", expectedVersion, " got ", ver))
+		}
+	}
+
+	return me.storage.Write(&storage.StoredEvent{
+		StreamId: event.AggregateId,
+		CreationTime: time.Now(),
+		TypeId: typeId,
+		Data: serializedPayload,
+		Metadata: serializedMetadata})
 }
 
 func (me ActionsHandler) RetrieveFor(aggregateId uuid.UUID) ([]*data.Event, error) {
 	results, err := me.storage.ReadStream(aggregateId)
+	if err != nil && err.Error()[0:9] == "NOT_FOUND" {
+		return make([]*data.Event, 0), nil
+	}
 	if err != nil {
 		return nil, err
 	}
@@ -65,7 +98,15 @@ func (me ActionsHandler) RetrieveFor(aggregateId uuid.UUID) ([]*data.Event, erro
 		if err != nil {
 			return nil, err
 		}
-		events = append(events, &data.Event{AggregateId: storedEvent.StreamId, Payload: event})
+		metadata, err := me.serializer.Deserialize(storedEvent.Metadata, storedEvent.MetadataTypeId)
+		if err != nil {
+			return nil, err
+		}
+		events = append(events, &data.Event{
+			AggregateId: storedEvent.StreamId,
+			CreationTime: storedEvent.CreationTime,
+			Payload: event,
+			Metadata: metadata})
 	}
 
 	return events, nil
@@ -83,9 +124,16 @@ func (me ActionsHandler) RetrieveAll() ([]*data.Event, error) {
 		if err != nil {
 			return nil, err
 		}
-		events = append(events, &data.Event{AggregateId: storedEvent.StreamId, Payload: event})
+		metadata, err := me.serializer.Deserialize(storedEvent.Metadata, storedEvent.MetadataTypeId)
+		if err != nil {
+			return nil, err
+		}
+		events = append(events, &data.Event{
+			AggregateId: storedEvent.StreamId,
+			CreationTime: storedEvent.CreationTime,
+			Payload: event,
+			Metadata: metadata})
 	}
 
 	return events, nil
 }
-

data/event.go

@@ -3,11 +3,14 @@ package data
 import (
 	"github.com/satori/go.uuid"
 	"reflect"
+	"time"
 )
 
 type Event struct {
 	AggregateId 	uuid.UUID
+	CreationTime 	time.Time
 	Payload     	interface{}
+	Metadata    	interface{}
 }
 
 func (me *Event) Equals(other *Event) bool {

goes.go

@@ -1,14 +1,12 @@
 package main
 
 import (
-	"fmt"
 	actions "./actions"
-	storage "./storage"
 	serializer "./serializer"
-	data "./data"
+	server "./server"
-	"github.com/satori/go.uuid"
+	storage "./storage"
-	"github.com/pebbe/zmq4"
 	"flag"
+	"fmt"
 	"os"
 	"path"
 )
@@ -24,7 +22,9 @@ func PathIsAbsolute(s string) bool {
 }
 
 func main() {
-	fmt.Println("Simple ZeroMQ server for goes.")
+	fmt.Println("GoES - Go Event Store")
+	fmt.Println("Released under the MIT license. See LICENSE file.")
+	fmt.Println()
 
 	flag.Parse()
 
@@ -38,86 +38,7 @@ func main() {
 	fmt.Println("Storage path:", storagePath)
 
 	var handler = actions.NewActionsHandler(storage.NewDailyDiskStorage(storagePath), serializer.NewPassthruSerializer())
-
+	server.Bind(*addr)
-	context, err := zmq4.NewContext()
+	server.Listen(handler)
-	if err != nil {
+	server.Destroy()
-		panic(err)
-	}
-	defer context.Term()
-
-	replySocket, err := context.NewSocket(zmq4.REP)
-	if err != nil {
-		panic(err)
-	}
-	defer replySocket.Close()
-
-	err = replySocket.Bind(*addr)
-	if err != nil {
-		panic(err)
-	}
-
-	for {
-		message, err := replySocket.RecvMessageBytes(0)
-		if err != nil {
-			fmt.Println("Error receiving command from client", err)
-			continue
-		}
-
-		command := string(message[0])
-		switch command {
-		case "AddEvent":
-			aggregateId, err := uuid.FromBytes(message[1])
-			if err != nil {
-				fmt.Println("Wrong format for AggregateId", err)
-				break
-			}
-			fmt.Println("->", command, aggregateId.String())
-			payload := message[2]
-			err = handler.AddEvent(data.Event{AggregateId: aggregateId, Payload: payload})
-			if err != nil {
-				replySocket.Send(fmt.Sprintf("Error: %v", err), 0)
-				fmt.Println(err)
-				break
-			}
-			replySocket.Send("Ok", 0)
-		case "ReadStream":
-			aggregateId, err := uuid.FromBytes(message[1])
-			if err != nil {
-				fmt.Println("Wrong format for AggregateId", err)
-				break
-			}
-			fmt.Println("->", command, aggregateId.String())
-			events, err := handler.RetrieveFor(aggregateId)
-			if err != nil {
-				replySocket.Send(fmt.Sprintf("Error: %v", err), 0)
-				fmt.Println(err)
-				break
-			}
-			sendEvents(replySocket, events)
-		case "ReadAll":
-			fmt.Println("->", command)
-			events, err := handler.RetrieveAll()
-			if err != nil {
-				replySocket.Send(fmt.Sprintf("Error: %v", err), 0)
-				fmt.Println(err)
-				break
-			}
-			sendEvents(replySocket, events)
-		case "Shutdown":
-			fmt.Println("->", command)
-			return
-		}
-	}
-}
-
-func sendEvents(socket *zmq4.Socket, events []*data.Event) {
-	len := len(events)
-	socket.Send(fmt.Sprintf("%v", len), zmq4.SNDMORE)
-
-	i := 0
-	for ; i < len-1; i++ {
-		socket.SendBytes(events[i].Payload.([]byte), zmq4.SNDMORE)
-	}
-	socket.SendBytes(events[i].Payload.([]byte), 0)
-	fmt.Println("<-", len, "events")
 }

goes_test.go

@@ -1,17 +1,16 @@
 package main
 
-import
+import (
-(
+	actions "./actions"
-	"testing"
+	data "./data"
+	serializer "./serializer"
+	storage "./storage"
+	"bytes"
 	"github.com/satori/go.uuid"
+	"io/ioutil"
 	"os"
 	"path"
-	"io/ioutil"
+	"testing"
-	"bytes"
-	storage "./storage"
-	serializer "./serializer"
-	data "./data"
-	actions "./actions"
 )
 
 var tempDir string
@@ -31,7 +30,7 @@ type AnotherEvent struct {
 }
 
 func setUp() {
-	tempDir := path.Join(os.TempDir(), uuid.NewV4().String())
+	tempDir = path.Join(os.TempDir(), uuid.NewV4().String())
 	_storage = storage.NewSimpleDiskStorage(tempDir)
 	_serializer = serializer.NewJsonSerializer((*AnEvent)(nil), (*AnotherEvent)(nil))
 	handler = actions.NewActionsHandler(_storage, _serializer)
@@ -45,7 +44,7 @@ func tearDown() {
 }
 
 func wrapEvent(aggregateId uuid.UUID, event interface{}) data.Event {
-	return data.Event{AggregateId: aggregateId, Payload: event}
+	return data.Event{AggregateId: aggregateId, Payload: event, Metadata: nil}
 }
 
 func TestSerializeEventToJson(t *testing.T) {
@@ -53,13 +52,13 @@ func TestSerializeEventToJson(t *testing.T) {
 	defer tearDown()
 
 	ev := wrapEvent(uuid.NewV4(), AnEvent{int64(1024), "Tests"})
-	err := handler.AddEvent(ev)
+	err := handler.AddEvent(ev, actions.NO_EXPECTEDVERSION)
 	if err != nil {
 		t.Errorf("AddEvent failed with %q", err)
 		return
 	}
 
-	filename := (_storage.(*storage.SimpleDiskStorage)).GetFilenameForEvents(ev.AggregateId.String());
+	filename := (_storage.(*storage.SimpleDiskStorage)).GetFilenameForEvents(ev.AggregateId.String())
 	if fi, _ := os.Stat(filename); fi == nil {
 		t.Errorf("AddEvent failed to create file %q", filename)
 		return
@@ -77,13 +76,13 @@ func TestSerializeEventsForSameAggregateInSameFile(t *testing.T) {
 
 	aggregateId := uuid.NewV4()
 	ev1 := wrapEvent(aggregateId, AnEvent{int64(12345), "Hello"})
-	err := handler.AddEvent(ev1)
+	err := handler.AddEvent(ev1, actions.NO_EXPECTEDVERSION)
 	if err != nil {
 		t.Errorf("AddEvent failed with %q", err)
 		return
 	}
 	ev2 := wrapEvent(aggregateId, AnotherEvent{int64(23456), "Bob", 123.45})
-	err = handler.AddEvent(ev2)
+	err = handler.AddEvent(ev2, actions.NO_EXPECTEDVERSION)
 	if err != nil {
 		t.Errorf("AddEvent failed with %q", err)
 		return
@@ -102,13 +101,13 @@ func TestTypeInformationIsProvided(t *testing.T) {
 	defer tearDown()
 
 	ev := wrapEvent(uuid.NewV4(), AnEvent{int64(1024), "Tests"})
-	err := handler.AddEvent(ev)
+	err := handler.AddEvent(ev, actions.NO_EXPECTEDVERSION)
 	if err != nil {
 		t.Errorf("AddEvent failed with %q", err)
 		return
 	}
 
-	filename := (_storage.(*storage.SimpleDiskStorage)).GetFilenameForEvents(ev.AggregateId.String());
+	filename := (_storage.(*storage.SimpleDiskStorage)).GetFilenameForEvents(ev.AggregateId.String())
 	if fi, _ := os.Stat(filename); fi == nil {
 		t.Errorf("AddEvent failed to create file %q", filename)
 		return
@@ -126,13 +125,13 @@ func TestEventsCanBeRetrieved(t *testing.T) {
 
 	aggregateId := uuid.NewV4()
 	ev1 := wrapEvent(aggregateId, AnEvent{int64(12345), "Hello"})
-	err := handler.AddEvent(ev1)
+	err := handler.AddEvent(ev1, actions.NO_EXPECTEDVERSION)
 	if err != nil {
 		t.Errorf("AddEvent failed with %q", err)
 		return
 	}
 	ev2 := wrapEvent(aggregateId, AnotherEvent{int64(23456), "Bob", 123.45})
-	err = handler.AddEvent(ev2)
+	err = handler.AddEvent(ev2, actions.NO_EXPECTEDVERSION)
 	if err != nil {
 		t.Errorf("AddEvent failed with %q", err)
 		return
@@ -141,7 +140,7 @@ func TestEventsCanBeRetrieved(t *testing.T) {
 	events, err := handler.RetrieveFor(aggregateId)
 	switch {
 	case err != nil:
-		t.Errorf("RetrieveFor(%q) failed with %q", aggregateId.String(), err)
+		t.Errorf("RetrieveFor(%q) failed with %q. %q", aggregateId.String(), err, tempDir)
 	case len(events) != 2:
 		t.Errorf("RetrieveFor(%q) returned %v events, expected %v", aggregateId.String(), len(events), 2)
 	case !ev1.Equals(events[0]):
@@ -160,14 +159,14 @@ func TestEventsCanBeReplayedInOrder(t *testing.T) {
 	testEvent1 := wrapEvent(aggregateId1, AnEvent{int64(123), "Hello 1"})
 	testEvent2 := wrapEvent(aggregateId2, AnEvent{int64(456), "Hello 2"})
 	testEvent3 := wrapEvent(aggregateId1, AnEvent{int64(789), "Hello 3"})
-	handler.AddEvent(testEvent1)
+	handler.AddEvent(testEvent1, actions.NO_EXPECTEDVERSION)
-	handler.AddEvent(testEvent2)
+	handler.AddEvent(testEvent2, actions.NO_EXPECTEDVERSION)
-	handler.AddEvent(testEvent3)
+	handler.AddEvent(testEvent3, actions.NO_EXPECTEDVERSION)
 
 	events, err := handler.RetrieveAll()
 	switch {
 	case err != nil:
-		t.Errorf("RetrieveAll failed with %q", err)
+		t.Errorf("RetrieveAll failed with %q %q", err, tempDir)
 	case len(events) != 3:
 		t.Errorf("RetrieveAll returned %v events, expected %v", len(events), 3)
 	case !testEvent1.Equals(events[0]) || !testEvent2.Equals(events[1]) || !testEvent3.Equals(events[2]):
@@ -179,4 +178,4 @@ func TestEventsCanBeReplayedInOrder(t *testing.T) {
 	Missing tests from https://gist.github.com/adymitruk/b4627b74617a37b6d949
 	- GUID reversal for distribution
 	- Created date stored with event
- */
+*/

serializer/json.go

@@ -4,6 +4,7 @@ import (
 	"reflect"
 	"encoding/json"
 	"errors"
+	"fmt"
 )
 
 type JsonSerializer struct {
@@ -27,6 +28,9 @@ func (me *JsonSerializer) RegisterType(t interface{}) {
 }
 
 func (me *JsonSerializer) Serialize(obj interface{}) ([]byte, string, error) {
+	if obj == nil {
+		return []byte(""), "", nil
+	}
 	type_ := reflect.TypeOf(obj)
 	if (type_.Kind() == reflect.Interface || type_.Kind() == reflect.Ptr) {
 		return nil, "", errors.New("Trying to serialize a Ptr type.")
@@ -40,9 +44,12 @@ func (me *JsonSerializer) Serialize(obj interface{}) ([]byte, string, error) {
 }
 
 func (me *JsonSerializer) Deserialize(serialized []byte, typeId string) (interface{}, error) {
+	if (typeId == "") {
+		return nil, nil
+	}
 	type_ := me.types[typeId]
 	if type_ == nil {
-		return nil, errors.New("type not registered in serializer")
+		return nil, errors.New(fmt.Sprintf("type %q not registered in serializer", typeId))
 	}
 	objPtr := reflect.New(type_).Interface()
 	err := json.Unmarshal(serialized, objPtr)

serializer/passthru.go

@@ -12,6 +12,10 @@ func NewPassthruSerializer() *PassthruSerializer {
 }
 
 func (me PassthruSerializer) Serialize(input interface{}) (output []byte, typeId string, err error) {
+	if input == nil {
+		return nil, "", nil
+	}
+
 	content, ok := input.([]byte)
 	if !ok {
 		err = errors.New("input should be []byte")
@@ -30,6 +34,10 @@ func (me PassthruSerializer) Serialize(input interface{}) (output []byte, typeId
 }
 
 func (me PassthruSerializer) Deserialize(input []byte, typeId string) (interface{}, error) {
+	if (typeId == "") {
+		return nil, nil
+	}
+
 	output := []byte(typeId)
 	output = append(output, ' ')
 	output = append(output, input...)

server/zeromq.go

@@ -0,0 +1,175 @@
+package server
+
+import (
+	"fmt"
+	data "../data"
+	actions "../actions"
+	"github.com/satori/go.uuid"
+	"github.com/pebbe/zmq4"
+	"encoding/binary"
+)
+
+var context *zmq4.Context
+var replySocket *zmq4.Socket
+
+func Bind(addr string) {
+	var err error;
+
+	context, err = zmq4.NewContext()
+	if err != nil {
+		panic(err)
+	}
+
+	replySocket, err = context.NewSocket(zmq4.REP)
+	if err != nil {
+		panic(err)
+	}
+
+	err = replySocket.Bind(addr)
+	if err != nil {
+		panic(err)
+	}
+}
+
+func Destroy() {
+	replySocket.Close()
+	context.Term()
+}
+
+const NO_FLAGS = zmq4.Flag(0)
+const UUID_SIZE = 16
+const COMMAND_FRAME = 0
+const ARGS_FRAME = 1
+const PAYLOAD_FRAME = 2
+const METADATA_FRAME = 3
+
+func Listen(handler actions.Handler) {
+	for {
+		message, err := replySocket.RecvMessageBytes(NO_FLAGS)
+		if err != nil {
+			fmt.Println("Error receiving command from client", err)
+			continue
+		}
+
+		command := string(message[COMMAND_FRAME])
+		switch command {
+		case "AddEvent":
+			// v1 - "AddEvent" [AggregateId] {payload}
+			aggregateId, err := uuid.FromBytes(message[ARGS_FRAME])
+			if err != nil {
+				fmt.Println("Wrong format for AggregateId", err)
+				break
+			}
+			fmt.Println("->", command, aggregateId.String())
+			payload := message[PAYLOAD_FRAME]
+			err = handler.AddEvent(data.Event{AggregateId: aggregateId, Payload: payload, Metadata: nil}, actions.NO_EXPECTEDVERSION)
+			if err != nil {
+				replySocket.Send(fmt.Sprintf("Error: %v", err), NO_FLAGS)
+				fmt.Println(err)
+				break
+			}
+			replySocket.Send("Ok", NO_FLAGS)
+		case "AddEvent_v2":
+			// v2 - "AddEvent" 16:AggregateId,4:expectedVersion {payload} {metadata}
+			aggregateId, err := uuid.FromBytes(message[ARGS_FRAME][0:UUID_SIZE])
+			if err != nil {
+				fmt.Println("Wrong format for AggregateId", err)
+				break
+			}
+			expectedVersion := binary.LittleEndian.Uint32(message[ARGS_FRAME][UUID_SIZE:])
+			fmt.Println("->", command, aggregateId.String(), expectedVersion)
+			payload := message[PAYLOAD_FRAME]
+			metadata := message[METADATA_FRAME]
+			err = handler.AddEvent(data.Event{AggregateId: aggregateId, Payload: payload, Metadata: metadata}, expectedVersion)
+			if err != nil {
+				replySocket.Send(fmt.Sprintf("Error: %v", err), NO_FLAGS)
+				fmt.Println(err)
+				break
+			}
+			replySocket.Send("Ok", NO_FLAGS)
+		case "ReadStream", "ReadStream_v2":
+			aggregateId, err := uuid.FromBytes(message[ARGS_FRAME])
+			if err != nil {
+				fmt.Println("Wrong format for AggregateId", err)
+				break
+			}
+			fmt.Println("->", command, aggregateId.String())
+			events, err := handler.RetrieveFor(aggregateId)
+			if err != nil {
+				replySocket.Send(fmt.Sprintf("Error: %v", err), NO_FLAGS)
+				fmt.Println(err)
+				break
+			}
+			if command == "ReadStream_v2" {
+				sendEvents_v2(replySocket, events)
+				break;
+			}
+			sendEvents_v1(replySocket, events)
+		case "ReadAll", "ReadAll_v2":
+			fmt.Println("->", command)
+			events, err := handler.RetrieveAll()
+			if err != nil {
+				replySocket.Send(fmt.Sprintf("Error: %v", err), NO_FLAGS)
+				fmt.Println(err)
+				break
+			}
+			if command == "ReadAll_v2" {
+				sendEvents_v2(replySocket, events)
+				break;
+			}
+			sendEvents_v1(replySocket, events)
+		case "Shutdown":
+			fmt.Println("->", command)
+			return
+		}
+	}
+}
+
+func sendEvent_v1(socket *zmq4.Socket, event *data.Event, isLast bool) {
+	lastFlag := zmq4.SNDMORE
+	if (isLast) {
+		lastFlag = NO_FLAGS
+	}
+	socket.SendBytes(event.Payload.([]byte), lastFlag)
+}
+
+func sendEvents_v1(socket *zmq4.Socket, events []*data.Event) {
+	len := len(events)
+	if (len == 0) {
+		socket.Send("0", NO_FLAGS)
+		return
+	}
+
+	socket.Send(fmt.Sprintf("%v", len), zmq4.SNDMORE)
+
+	i := 0
+	for ; i < len; i++ {
+		sendEvent_v1(socket, events[i], i == len - 1)
+	}
+	fmt.Println("<-", len, "events")
+}
+
+func sendEvent_v2(socket *zmq4.Socket, event *data.Event, isLast bool) {
+	socket.SendBytes(event.Payload.([]byte), zmq4.SNDMORE)
+	lastFlag := zmq4.SNDMORE
+	if (isLast) {
+		lastFlag = NO_FLAGS
+	}
+	socket.SendBytes(event.Metadata.([]byte), lastFlag)
+}
+
+func sendEvents_v2(socket *zmq4.Socket, events []*data.Event) {
+	len := len(events)
+	if (len == 0) {
+		socket.Send("0", NO_FLAGS)
+		return
+	}
+
+	socket.Send(fmt.Sprintf("%v", len), zmq4.SNDMORE)
+
+	i := 0
+	for ; i < len; i++ {
+		sendEvent_v2(socket, events[i], i == len - 1)
+	}
+	fmt.Println("<-", len, "events")
+}

storage/dailydisk.go

@@ -8,8 +8,12 @@ import (
 	"fmt"
 	"errors"
 	"io/ioutil"
+	"bytes"
 )
 
+const EMPTY_STREAM = uint32(0)
+var CRLF = []byte {'\r', '\n'}
+
 type DailyDiskStorage struct {
 	storagePath string
 	indexesPath string
@@ -94,7 +98,7 @@ func readIndexNextEntry(f *os.File) (*IndexEntry, error) {
 	return &index, nil;
 }
 
-func writeEvent(filename string, data []byte) error {
+func writeEvent(filename string, data []byte, metadata []byte) error {
 	eventFile, err := os.OpenFile(filename, os.O_APPEND | os.O_WRONLY | os.O_CREATE, 0644)
 	if err != nil {
 		return err
@@ -102,12 +106,26 @@ func writeEvent(filename string, data []byte) error {
 	defer eventFile.Close()
 
 	eventFile.Write(data)
+	eventFile.Write(CRLF)
+	eventFile.Write(metadata)
 
 	return nil
 }
 
-func readEvent(filename string) ([]byte, error) {
+func readEvent(filename string) (data []byte, metadata []byte, err error) {
-	return ioutil.ReadFile(filename)
+	content, err := ioutil.ReadFile(filename)
+	if err != nil {
+		return
+	}
+	sep := bytes.Index(content, CRLF)
+	if sep == -1 {
+		data = content
+		metadata = make([]byte, 0)
+		return
+	}
+	data = content[:sep]
+	metadata = content[sep+2:]
+	return
 }
 
 func (me DailyDiskStorage) Write(event *StoredEvent) error {
@@ -115,7 +133,7 @@ func (me DailyDiskStorage) Write(event *StoredEvent) error {
 	eventFilename := me.getEventFilename(event.CreationTime, event.TypeId)
 	os.MkdirAll(path.Dir(eventFilename), 0777)
 
-	err := writeEvent(eventFilename, event.Data)
+	err := writeEvent(eventFilename, event.Data, event.Metadata)
 	if err != nil {
 		return err
 	}
@@ -135,11 +153,33 @@ func (me DailyDiskStorage) Write(event *StoredEvent) error {
 	return nil
 }
 
+func (me DailyDiskStorage) StreamVersion(streamId uuid.UUID) (uint32, error) {
+	indexFile, err := os.OpenFile(me.getStreamIndexFilename(streamId), os.O_RDONLY, 0)
+	if err != nil {
+		return EMPTY_STREAM, errors.New("NOT_FOUND: " + err.Error())
+	}
+	defer indexFile.Close()
+
+	ver := EMPTY_STREAM
+	for {
+		_, err := readIndexNextEntry(indexFile)
+		if err != nil && err.Error() == "EOF" {
+			break
+		}
+		if err != nil {
+			return EMPTY_STREAM, err
+		}
+		ver++
+	}
+
+	return ver, nil
+}
+
 func (me DailyDiskStorage) ReadStream(streamId uuid.UUID) ([]*StoredEvent, error) {
 
 	indexFile, err := os.OpenFile(me.getStreamIndexFilename(streamId), os.O_RDONLY, 0)
 	if err != nil {
-		return nil, err
+		return nil, errors.New("NOT_FOUND: " + err.Error())
 	}
 	defer indexFile.Close()
 
@@ -152,11 +192,11 @@ func (me DailyDiskStorage) ReadStream(streamId uuid.UUID) ([]*StoredEvent, error
 		if err != nil {
 			return nil, err
 		}
-		data, err := readEvent(me.getEventFilename(indexEntry.creationTime, indexEntry.typeId))
+		data, metadata, err := readEvent(me.getEventFilename(indexEntry.creationTime, indexEntry.typeId))
 		if err != nil {
 			return nil, err
 		}
-		event := &StoredEvent{streamId, indexEntry.creationTime, indexEntry.typeId, data}
+		event := &StoredEvent{streamId, indexEntry.creationTime, indexEntry.typeId, data, "Metadata", metadata}
 		events = append(events, event)
 	}
 
@@ -179,11 +219,11 @@ func (me DailyDiskStorage) ReadAll() ([]*StoredEvent, error) {
 		if err != nil {
 			return nil, err
 		}
-		data, err := readEvent(me.getEventFilename(indexEntry.creationTime, indexEntry.typeId))
+		data, metadata, err := readEvent(me.getEventFilename(indexEntry.creationTime, indexEntry.typeId))
 		if err != nil {
 			return nil, err
 		}
-		event := &StoredEvent{indexEntry.streamId, indexEntry.creationTime, indexEntry.typeId, data}
+		event := &StoredEvent{indexEntry.streamId, indexEntry.creationTime, indexEntry.typeId, data, "Metadata", metadata}
 		events = append(events, event)
 	}
 

storage/dailydisk_test.go

@@ -20,9 +20,10 @@ func TestAddEvent(t *testing.T) {
 	aggregateId := uuid.NewV4()
 	aType := "myType"
 	data := []byte("{}")
+	metadata := []byte("{}")
 
 	//Act
-	err := storage.Write(&StoredEvent{aggregateId, aTime, aType, data})
+	err := storage.Write(&StoredEvent{aggregateId, aTime, aType, data, "Metadata", metadata})
 
 	//Assert
 	if err != nil {
@@ -54,9 +55,9 @@ func TestReadStream(t *testing.T) {
 	storage := NewDailyDiskStorage(storagePath)
 
 	streamId := uuid.NewV4()
-	ev1 := &StoredEvent{streamId, time.Now(), "1stType", []byte("1stEvent")}
+	ev1 := &StoredEvent{streamId, time.Now(), "1stType", []byte("1stEvent"), "Metadata", []byte("{}")}
 	storage.Write(ev1)
-	ev2 := &StoredEvent{streamId, time.Now(), "2ndType", []byte("2ndEvent")}
+	ev2 := &StoredEvent{streamId, time.Now(), "2ndType", []byte("2ndEvent"), "Metadata", []byte("{}")}
 	storage.Write(ev2)
 
 	//Act
@@ -89,11 +90,11 @@ func TestReadAll(t *testing.T) {
 
 	stream1Id := uuid.NewV4()
 	stream2Id := uuid.NewV4()
-	ev1 := &StoredEvent{stream1Id, time.Now(), "1stType", []byte("1stEvent")}
+	ev1 := &StoredEvent{stream1Id, time.Now(), "1stType", []byte("1stEvent"), "Metadata", []byte("{}")}
 	storage.Write(ev1)
-	ev2 := &StoredEvent{stream2Id, time.Now(), "2ndType", []byte("2ndEvent")}
+	ev2 := &StoredEvent{stream2Id, time.Now(), "2ndType", []byte("2ndEvent"), "Metadata", []byte("{}")}
 	storage.Write(ev2)
-	ev3 := &StoredEvent{stream1Id, time.Now(), "3rdType", []byte("3rdEvent")}
+	ev3 := &StoredEvent{stream1Id, time.Now(), "3rdType", []byte("3rdEvent"), "Metadata", []byte("{}")}
 	storage.Write(ev3)
 
 	//Act

storage/simpledisk.go

@@ -111,6 +111,11 @@ func (me SimpleDiskStorage) Write(event *StoredEvent) error {
 	return nil
 }
 
+func (me SimpleDiskStorage) StreamVersion(streamId uuid.UUID) (uint32, error) {
+	//TODO
+	return EMPTY_STREAM, nil
+}
+
 func (me SimpleDiskStorage) ReadStream(streamId uuid.UUID) ([]*StoredEvent, error) {
 	streamName := streamId.String()
 	offset := int64(0) //TODO snapshots
@@ -134,7 +139,8 @@ func (me SimpleDiskStorage) ReadStream(streamId uuid.UUID) ([]*StoredEvent, erro
 			return nil, err
 		}
 
-		event := &StoredEvent{streamId, creationTime, typeId, data}
+		//TODO metadata
+		event := &StoredEvent{streamId, creationTime, typeId, data, "", nil}
 		results = append(results, event)
 	}
 	return results, nil
@@ -197,7 +203,8 @@ func (me SimpleDiskStorage) retrieveStoredEvent(streamId uuid.UUID, offset int64
 		return nil, err
 	}
 
-	event := &StoredEvent{streamId, creationTime, typeId, data}
+	//TODO metadata
+	event := &StoredEvent{streamId, creationTime, typeId, data, "", nil}
 	return event, nil
 }
 

storage/storage.go

@@ -13,6 +13,8 @@ type StoredEvent struct {
 	CreationTime time.Time
 	TypeId string
 	Data []byte
+	MetadataTypeId string
+	Metadata []byte
 }
 
 //TODO: performance - change reads array for some kind of iterator
@@ -20,4 +22,5 @@ type Storage interface {
 	Write(event *StoredEvent) error
 	ReadStream(streamId uuid.UUID) ([]*StoredEvent, error)
 	ReadAll() ([]*StoredEvent, error)
+	StreamVersion(streamId uuid.UUID) (uint32, error)
 }