State machine

.github/workflows/test.yaml

@@ -0,0 +1,21 @@
+name: Go
+on: [push]
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v4
+      - name: Setup Go
+        uses: actions/setup-go@v4
+        with:
+          go-version: "1.22.x"
+      - name: Install dependencies
+        run: go get .
+      - name: Vet
+        run: go vet -v ./...
+      - name: Build
+        run: go build -v ./...
+      - name: Test with the Go CLI
+        run: go test -v ./...

.gitignore

@@ -1 +0,0 @@
-go.sum

go.sum

@@ -0,0 +1,34 @@
+github.com/coreos/go-systemd/v22 v22.5.0/go.mod h1:Y58oyj3AT4RCenI/lSvhwexgC+NSVTIJ3seZv2GcEnc=
+github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
+github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/godbus/dbus/v5 v5.0.4/go.mod h1:xhWf0FNVPg57R7Z0UbKHbJfkEywrmjJnf7w5xrFpKfA=
+github.com/mattn/go-colorable v0.1.13 h1:fFA4WZxdEF4tXPZVKMLwD8oUnCTTo08duU7wxecdEvA=
+github.com/mattn/go-colorable v0.1.13/go.mod h1:7S9/ev0klgBDR4GtXTXX8a3vIGJpMovkB8vQcUbaXHg=
+github.com/mattn/go-isatty v0.0.16/go.mod h1:kYGgaQfpe5nmfYZH+SKPsOc2e4SrIfOl2e/yFXSvRLM=
+github.com/mattn/go-isatty v0.0.19 h1:JITubQf0MOLdlGRuRq+jtsDlekdYPia9ZFsB8h/APPA=
+github.com/mattn/go-isatty v0.0.19/go.mod h1:W+V8PltTTMOvKvAeJH7IuucS94S2C6jfK/D7dTCTo3Y=
+github.com/pkg/errors v0.9.1/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=
+github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
+github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/posener/h2conn v0.0.0-20231204025407-3997deeca0f0 h1:zZg03nifrj6ayWNaDO8tNj57tqrOIKDwiBaLkhtK7Kk=
+github.com/posener/h2conn v0.0.0-20231204025407-3997deeca0f0/go.mod h1:bblJa8QcHntareAJYfLJUzLj42sUFBKCBeTDK5LyUrw=
+github.com/rs/xid v1.5.0/go.mod h1:trrq9SKmegXys3aeAKXMUTdJsYXVwGY3RLcfgqegfbg=
+github.com/rs/zerolog v1.32.0 h1:keLypqrlIjaFsbmJOBdB/qvyF8KEtCWHwobLp5l/mQ0=
+github.com/rs/zerolog v1.32.0/go.mod h1:/7mN4D5sKwJLZQ2b/znpjC3/GQWY/xaDXUM0kKWRHss=
+github.com/stretchr/testify v1.9.0 h1:HtqpIVDClZ4nwg75+f6Lvsy/wHu+3BoSGCbBAcpTsTg=
+github.com/stretchr/testify v1.9.0/go.mod h1:r2ic/lqez/lEtzL7wO/rwa5dbSLXVDPFyf8C91i36aY=
+golang.org/x/net v0.21.0 h1:AQyQV4dYCvJ7vGmJyKki9+PBdyvhkSd8EIx/qb0AYv4=
+golang.org/x/net v0.21.0/go.mod h1:bIjVDfnllIU7BJ2DNgfnXvpSvtn8VRwhlsaeUTyUS44=
+golang.org/x/sys v0.0.0-20220811171246-fbc7d0a398ab/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
+golang.org/x/sys v0.6.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
+golang.org/x/sys v0.12.0 h1:CM0HF96J0hcLAwsHPJZjfdNzs0gftsLfgKt57wWHJ0o=
+golang.org/x/sys v0.12.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
+golang.org/x/sys v0.17.0 h1:25cE3gD+tdBA7lp7QfhuV+rJiE9YXTcS3VG1SqssI/Y=
+golang.org/x/sys v0.17.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
+golang.org/x/text v0.14.0 h1:ScX5w1eTa3QqT8oi6+ziP7dTV1S2+ALU0bI+0zXKWiQ=
+golang.org/x/text v0.14.0/go.mod h1:18ZOQIKpY8NJVqYksKHtTdi31H5itFRjB5/qKTNYzSU=
+google.golang.org/protobuf v1.32.0 h1:pPC6BG5ex8PDFnkbrGU3EixyhKcQ2aDuBS36lqK/C7I=
+google.golang.org/protobuf v1.32.0/go.mod h1:c6P6GXX6sHbq/GpV6MGZEdwhWPcYBgnhAHhKbcUYpos=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
+gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=

handler.go

@@ -9,8 +9,9 @@ import (
 	"google.golang.org/protobuf/types/known/structpb"
 )
 
-// Empty struct used as a quick shortcut when you don't care about
-// the input or output type
+// Void is a placeholder used usually for functions that their signature require that
+// you accept an input or return an output but the function implementation does not
+// require them
 type Void struct{}
 
 func (v Void) MarshalJSON() ([]byte, error) {

internal/state/call.go

@@ -1,6 +1,7 @@
 package state
 
 import (
+	"bytes"
 	"encoding/json"
 	"fmt"
 	"time"
@@ -69,18 +70,39 @@ func (c *Machine) makeRequest(key string, body any) ([]byte, error) {
 }
 
 func (c *Machine) doCall(service, method, key string, body any) ([]byte, error) {
-	c.mutex.Lock()
-	defer c.mutex.Unlock()
-
-	input, err := c.makeRequest(key, body)
+	params, err := c.makeRequest(key, body)
 	if err != nil {
 		return nil, err
 	}
 
-	err = c.protocol.Write(&protocol.InvokeEntryMessage{
+	return replayOrNew(
+		c,
+		wire.InvokeEntryMessageType,
+		func(entry *wire.InvokeEntryMessage) ([]byte, error) {
+			if entry.Payload.ServiceName != service ||
+				entry.Payload.MethodName != method ||
+				!bytes.Equal(entry.Payload.Parameter, params) {
+				return nil, errEntryMismatch
+			}
+
+			switch result := entry.Payload.Result.(type) {
+			case *protocol.InvokeEntryMessage_Failure:
+				return nil, fmt.Errorf("[%d] %s", result.Failure.Code, result.Failure.Message)
+			case *protocol.InvokeEntryMessage_Value:
+				return result.Value, nil
+			}
+
+			return nil, errUnreachable
+		}, func() ([]byte, error) {
+			return c._doCall(service, method, params)
+		})
+}
+
+func (c *Machine) _doCall(service, method string, params []byte) ([]byte, error) {
+	err := c.protocol.Write(&protocol.InvokeEntryMessage{
 		ServiceName: service,
 		MethodName:  method,
-		Parameter:   input,
+		Parameter:   params,
 	})
 
 	if err != nil {
@@ -121,23 +143,41 @@ func (c *Machine) doCall(service, method, key string, body any) ([]byte, error)
 }
 
 func (c *Machine) sendCall(service, method, key string, body any, delay time.Duration) error {
-	c.mutex.Lock()
-	defer c.mutex.Unlock()
-
-	input, err := c.makeRequest(key, body)
+	params, err := c.makeRequest(key, body)
 	if err != nil {
 		return err
 	}
 
+	_, err = replayOrNew(
+		c,
+		wire.BackgroundInvokeEntryMessageType,
+		func(entry *wire.BackgroundInvokeEntryMessage) (restate.Void, error) {
+			if entry.Payload.ServiceName != service ||
+				entry.Payload.MethodName != method ||
+				!bytes.Equal(entry.Payload.Parameter, params) {
+				return restate.Void{}, errEntryMismatch
+			}
+
+			return restate.Void{}, nil
+		},
+		func() (restate.Void, error) {
+			return restate.Void{}, c._sendCall(service, method, params, delay)
+		},
+	)
+
+	return err
+}
+
+func (c *Machine) _sendCall(service, method string, params []byte, delay time.Duration) error {
 	var invokeTime uint64
 	if delay != 0 {
 		invokeTime = uint64(time.Now().Add(delay).UnixMilli())
 	}
 
-	err = c.protocol.Write(&protocol.BackgroundInvokeEntryMessage{
+	err := c.protocol.Write(&protocol.BackgroundInvokeEntryMessage{
 		ServiceName: service,
 		MethodName:  method,
-		Parameter:   input,
+		Parameter:   params,
 		InvokeTime:  invokeTime,
 	})
 

internal/state/state.go

@@ -25,8 +25,6 @@ const (
 var (
 	ErrUnexpectedMessage = fmt.Errorf("unexpected message")
 	ErrInvalidVersion    = fmt.Errorf("invalid version number")
-
-	errUnreachable = fmt.Errorf("unreachable")
 )
 
 var (
@@ -61,6 +59,10 @@ func (c *Context) Get(key string) ([]byte, error) {
 	return c.machine.get(key)
 }
 
+func (c *Context) Keys() ([]string, error) {
+	return c.machine.keys()
+}
+
 func (c *Context) Sleep(until time.Time) error {
 	return c.machine.sleep(until)
 }
@@ -98,7 +100,8 @@ type Machine struct {
 	partial bool
 	current map[string][]byte
 
-	entries []wire.Message
+	entries    []wire.Message
+	entryIndex int
 }
 
 func NewMachine(handler restate.Handler, conn io.ReadWriter) *Machine {
@@ -109,11 +112,33 @@ func NewMachine(handler restate.Handler, conn io.ReadWriter) *Machine {
 	}
 }
 
-func (m *Machine) output(r *dynrpc.RpcResponse, err error) proto.Message {
-	// TODO: if err is terminal return outputStreamEntryMessage but if error is
-	// not terminal, return ErrorMessage instead.
-	//var output protocol.OutputStreamEntryMessage
+// Start starts the state machine
+func (m *Machine) Start(inner context.Context) error {
+	// reader starts a rea
+	msg, err := m.protocol.Read()
+	if err != nil {
+		return err
+	}
+
+	if msg.Type() != wire.StartMessageType {
+		// invalid negotiation
+		return ErrUnexpectedMessage
+	}
+
+	start := msg.(*wire.StartMessage)
 
+	if start.Version != Version {
+		return ErrInvalidVersion
+	}
+
+	ctx := newContext(inner, m)
+
+	log.Trace().Str("id", base64.URLEncoding.EncodeToString(m.id)).Msg("start invocation")
+	return m.process(ctx, start)
+}
+
+// handle handler response and build proper response message
+func (m *Machine) output(r *dynrpc.RpcResponse, err error) proto.Message {
 	if err != nil && restate.IsTerminalError(err) {
 		// terminal errors.
 		return &protocol.OutputStreamEntryMessage{
@@ -195,14 +220,18 @@ func (m *Machine) process(ctx *Context, start *wire.StartMessage) error {
 		return ErrUnexpectedMessage
 	}
 
-	log.Debug().Uint32("known entries", start.Payload.KnownEntries).Msg("known entires")
+	log.Trace().Uint32("known entries", start.Payload.KnownEntries).Msg("known entires")
+	m.entries = make([]wire.Message, 0, start.Payload.KnownEntries-1)
+
+	// we don't track the poll input entry
 	for i := uint32(1); i < start.Payload.KnownEntries; i++ {
 		msg, err := m.protocol.Read()
 		if err != nil {
 			return fmt.Errorf("failed to read entry: %w", err)
 		}
 
-		log.Debug().Uint16("type", uint16(msg.Type())).Msg("received entry")
+		log.Trace().Uint16("type", uint16(msg.Type())).Msg("replay log entry")
+		m.entries = append(m.entries, msg)
 	}
 
 	inputMsg := msg.(*wire.PollInputEntry)
@@ -216,26 +245,57 @@ func (m *Machine) process(ctx *Context, start *wire.StartMessage) error {
 
 }
 
-func (m *Machine) Start(inner context.Context) error {
-	// reader starts a rea
-	msg, err := m.protocol.Read()
-	if err != nil {
-		return err
+func (c *Machine) currentEntry() (wire.Message, bool) {
+	if c.entryIndex < len(c.entries) {
+		return c.entries[c.entryIndex], true
 	}
 
-	if msg.Type() != wire.StartMessageType {
-		// invalid negotiation
-		return ErrUnexpectedMessage
-	}
+	return nil, false
+}
 
-	start := msg.(*wire.StartMessage)
+// replayOrNew is a utility function to easily either
+// replay a log entry, or create a new one if one
+// does not exist
+//
+// this should be an instance method on Machine but unfortunately
+// go does not support generics on instance methods
+//
+// the idea is when called, it will check if there is a log
+// entry at current index, then compare the entry message type
+// if not matching, that's obviously an error with the code version
+// (code has changed and now doesn't match the play log)
+//
+// if type is okay, the function will then call a `replay“ callback.
+// the replay callback just need to extract the result from the entry
+//
+// otherwise this function will call a `new` callback to create a new entry in the log
+// by sending the proper runtime messages
+func replayOrNew[M wire.Message, O any](
+	m *Machine,
+	typ wire.Type,
+	replay func(msg M) (O, error),
+	new func() (O, error),
+) (output O, err error) {
+
+	m.mutex.Lock()
+	defer m.mutex.Unlock()
 
-	if start.Version != Version {
-		return ErrInvalidVersion
-	}
+	defer func() {
+		m.entryIndex += 1
+	}()
 
-	ctx := newContext(inner, m)
+	// check if there is an entry as this index
+	entry, ok := m.currentEntry()
 
-	log.Trace().Str("id", base64.URLEncoding.EncodeToString(m.id)).Msg("start invocation")
-	return m.process(ctx, start)
+	// if entry exists, we need to replay it
+	// by calling the replay function
+	if ok {
+		if entry.Type() != typ {
+			return output, errEntryMismatch
+		}
+		return replay(entry.(M))
+	}
+
+	// other wise call the new function
+	return new()
 }