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db.go
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db.go
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package paxoskv
import (
"errors"
"sync"
"github.com/LiuzhouChan/go-paxos/logger"
"github.com/LiuzhouChan/go-paxos/statemachine"
)
var (
plog = logger.GetLogger("paxoskv")
)
var (
// ErrKeyNotExist means the key is not exist
ErrKeyNotExist = errors.New("key not exists")
//ErrKeyVersionConflict means the key version is conflict
ErrKeyVersionConflict = errors.New("key version conflict")
)
// BytesDeepCopy ...
func BytesDeepCopy(b []byte) []byte {
ret := make([]byte, 0)
ret = append(ret, b...)
return ret
}
type kvMap struct {
mu sync.Mutex
kv map[string][]byte
}
func (kv *kvMap) get(key string) ([]byte, uint64, error) {
if len(key) == 0 {
panic("empty key is not allowed")
}
v, ok := kv.kv[key]
if !ok {
return nil, 0, ErrKeyNotExist
}
var kvdata KVData
err := kvdata.Unmarshal(v)
if err != nil {
panic(err)
}
if kvdata.Isdeleted {
return nil, kvdata.Version, ErrKeyNotExist
}
return kvdata.Value, kvdata.Version, nil
}
func (kv *kvMap) set(key string, value []byte, version uint64) error {
kv.mu.Lock()
defer kv.mu.Unlock()
_, serverVersion, err := kv.get(key)
if err != nil && err != ErrKeyNotExist {
return err
}
if serverVersion != version {
return ErrKeyVersionConflict
}
serverVersion++
kvdata := &KVData{
Version: serverVersion,
Isdeleted: false,
Value: BytesDeepCopy(value),
}
data, err := kvdata.Marshal()
if err != nil {
panic(err)
}
kv.kv[key] = data
return nil
}
func (kv *kvMap) del(key string, version uint64) error {
kv.mu.Lock()
defer kv.mu.Unlock()
serverValue, serverVersion, err := kv.get(key)
if err != nil && err != ErrKeyNotExist {
return err
}
if serverVersion != version {
return ErrKeyVersionConflict
}
serverVersion++
kvdata := &KVData{
Version: serverVersion,
Isdeleted: true,
Value: BytesDeepCopy(serverValue),
}
data, err := kvdata.Marshal()
if err != nil {
panic(err)
}
kv.kv[key] = data
return nil
}
// DB is the IStateMachine implementation used in the
// paxoskv example.
type DB struct {
GroupID uint64
NodeID uint64
KVMap *kvMap
}
// NewDB creates a new DB instance.
func NewDB(groupID uint64, nodeID uint64) statemachine.IStateMachine {
d := &DB{
GroupID: groupID,
NodeID: nodeID,
KVMap: &kvMap{
kv: make(map[string][]byte),
},
}
return d
}
// Close closes the DB instance.
func (d *DB) Close() {}
// GetHash returns the state machine hash.
func (d *DB) GetHash() uint64 {
return 1
}
// Update updates the DB instance.
func (d *DB) Update(data []byte) uint64 {
var req KVRequest
err := req.Unmarshal(data)
if err != nil {
panic(err)
}
if req.Operator == KVRequest_READ {
plog.Panicf("invalid operator type in update %v", KVRequest_READ)
} else if req.Operator == KVRequest_WRITE {
err = d.KVMap.set(req.Key, req.Value, req.Version)
} else if req.Operator == KVRequest_DELETE {
err = d.KVMap.del(req.Key, req.Version)
}
if err == ErrKeyVersionConflict {
return uint64(KVResponse_VERSION_CONFLICT)
}
return uint64(KVResponse_OK)
}
// Lookup ...
func (d *DB) Lookup(key []byte) []byte {
var req KVRequest
err := req.Unmarshal(key)
if err != nil {
panic(err)
}
if req.Operator != KVRequest_READ {
plog.Panicf("the operator in loopup should be KVRequest_READ")
}
value, version, err := d.KVMap.get(req.Key)
res := KVResponse{
Data: KVData{
Value: BytesDeepCopy(value),
Version: version,
},
}
if err == ErrKeyNotExist {
res.Code = KVResponse_KEY_NOT_EXIST
} else {
res.Code = KVResponse_OK
}
data, err := res.Marshal()
if err != nil {
panic(err)
}
return data
}