refactor wal2

Author: CMGS

Makefile

@@ -36,6 +36,7 @@ mock: deps
 	mockery --dir store --output store/mocks --name Store
 	mockery --dir engine --output engine/mocks --name API
 	mockery --dir cluster --output cluster/mocks --name Cluster
+	mockery --dir wal2 --output wal2/mocks --name WAL
 	mockery --dir lock --output lock/mocks --name DistributedLock
 	mockery --dir store/etcdv3/meta --output store/etcdv3/meta/mocks --all
 	mockery --dir vendor/go.etcd.io/etcd/client/v3 --output store/etcdv3/meta/mocks --name Txn

types/errors.go

@@ -87,6 +87,7 @@ var (
 	ErrEntityNotExists   = errors.New("entity not exists")
 
 	ErrUnregisteredWALEventType = errors.New("unregistered WAL event type")
+	ErrBadWALEvent              = errors.New("bad WAL event type")
 	ErrInvalidWALBucket         = errors.New("invalid WAL bucket")
 	ErrInvalidType              = errors.New("invalid type")
 	ErrLockSessionDone          = errors.New("lock session done")

wal2/event.go

@@ -0,0 +1,42 @@
+package wal2
+
+import (
+	"encoding/json"
+	"fmt"
+	"path/filepath"
+	"strconv"
+	"strings"
+)
+
+// HydroEvent indicates a log event.
+type HydroEvent struct {
+	// A global unique identifier.
+	ID uint64 `json:"id"`
+
+	// Registered event type name.
+	Type string `json:"type"`
+
+	// The encoded log item.
+	Item []byte `json:"item"`
+}
+
+// NewHydroEvent initializes a new HydroEvent instance.
+func NewHydroEvent(ID uint64, typ string, item []byte) *HydroEvent {
+	return &HydroEvent{ID: ID, Type: typ, Item: item}
+}
+
+// Encode this event
+func (e HydroEvent) Encode() ([]byte, error) {
+	return json.MarshalIndent(e, "", "\t")
+}
+
+// Key returns this event's key path.
+func (e HydroEvent) Key() []byte {
+	return []byte(filepath.Join(eventPrefix, fmt.Sprintf("%016x", e.ID)))
+}
+
+func parseHydroEventID(key []byte) (uint64, error) {
+	// Trims the EventPrefix, then trims the padding 0.
+	id := strings.TrimLeft(strings.TrimPrefix(string(key), eventPrefix), "0")
+	return strconv.ParseUint(id, 16, 64)
+}

wal2/hydro.go

@@ -0,0 +1,146 @@
+package wal2
+
+import (
+	"context"
+	"encoding/json"
+	"time"
+
+	"github.com/cornelk/hashmap"
+	"github.com/projecteru2/core/log"
+	coretypes "github.com/projecteru2/core/types"
+	"github.com/projecteru2/core/wal2/kv"
+)
+
+const (
+	fileMode = 0600
+)
+
+// Hydro is the simplest wal implementation.
+type Hydro struct {
+	hashmap.HashMap
+	stor kv.KV
+}
+
+// NewHydro initailizes a new Hydro instance.
+func NewHydro(path string, timeout time.Duration) (*Hydro, error) {
+	stor := kv.NewLithium()
+	if err := stor.Open(path, fileMode, timeout); err != nil {
+		return nil, err
+	}
+	return &Hydro{HashMap: hashmap.HashMap{}, stor: stor}, nil
+}
+
+// Close disconnects the kvdb.
+func (h *Hydro) Close() error {
+	return h.stor.Close()
+}
+
+// Register registers a new event handler.
+func (h *Hydro) Register(handler EventHandler) {
+	h.Set(handler.Typ(), handler)
+}
+
+// Recover starts a disaster recovery, which will replay all the events.
+func (h *Hydro) Recover(ctx context.Context) {
+	ch, _ := h.stor.Scan([]byte(eventPrefix))
+
+	events := []HydroEvent{}
+	for scanEntry := range ch {
+		event, err := h.decodeEvent(scanEntry)
+		if err != nil {
+			log.Errorf(nil, "[Recover] decode event error: %v", err) // nolint
+			continue
+		}
+		events = append(events, event)
+	}
+
+	for _, event := range events {
+		handler, ok := h.getEventHandler(event.Type)
+		if !ok {
+			log.Errorf(nil, "[Recover] no such event handler for %s", event.Type) // nolint
+			continue
+		}
+
+		if err := h.recover(ctx, handler, event); err != nil {
+			log.Errorf(nil, "[Recover] handle event %d (%s) failed: %v", event.ID, event.Type, err) // nolint
+			continue
+		}
+	}
+}
+
+// Log records a log item.
+func (h *Hydro) Log(eventyp string, item interface{}) (Commit, error) {
+	handler, ok := h.getEventHandler(eventyp)
+	if !ok {
+		return nil, coretypes.NewDetailedErr(coretypes.ErrUnregisteredWALEventType, eventyp)
+	}
+
+	bs, err := handler.Encode(item) // TODO 2 times encode is necessary?
+	if err != nil {
+		return nil, err
+	}
+
+	var id uint64
+	if id, err = h.stor.NextSequence(); err != nil {
+		return nil, err
+	}
+
+	event := NewHydroEvent(id, eventyp, bs)
+	if bs, err = event.Encode(); err != nil {
+		return nil, coretypes.ErrBadWALEvent
+	}
+
+	if err = h.stor.Put(event.Key(), bs); err != nil {
+		return nil, err
+	}
+
+	return func() error {
+		return h.stor.Delete(event.Key())
+	}, nil
+}
+
+func (h *Hydro) recover(ctx context.Context, handler EventHandler, event HydroEvent) error {
+	item, err := handler.Decode(event.Item)
+	if err != nil {
+		return err
+	}
+
+	delete := func() error {
+		return h.stor.Delete(event.Key())
+	}
+
+	switch handle, err := handler.Check(ctx, item); {
+	case err != nil:
+		return err
+	case !handle:
+		return delete()
+	default:
+		if err := handler.Handle(ctx, item); err != nil {
+			return err
+		}
+	}
+	return delete()
+}
+
+func (h *Hydro) getEventHandler(eventyp string) (EventHandler, bool) {
+	v, ok := h.GetStringKey(eventyp)
+	if !ok {
+		return nil, ok
+	}
+	handler, ok := v.(EventHandler)
+	return handler, ok
+}
+
+func (h *Hydro) decodeEvent(scanEntry kv.ScanEntry) (event HydroEvent, err error) {
+	if err = scanEntry.Error(); err != nil {
+		return
+	}
+
+	key, value := scanEntry.Pair()
+	if err = json.Unmarshal(value, &event); err != nil {
+		return
+	}
+
+	event.ID, err = parseHydroEventID(key)
+	return
+}