smegmesh/pkg/crdt/two_phase_map_syncer.go
Tim Beatham 3ef1b68ba5 BUGFIX: Hashing datastore to work out changes
Changed hashing implementation to work out if there are changes
in the data store
2023-11-30 15:58:26 +00:00

145 lines
2.9 KiB
Go

package crdt
import (
"bytes"
"encoding/gob"
logging "github.com/tim-beatham/wgmesh/pkg/log"
)
type SyncState int
const (
PREPARE SyncState = iota
PRESENT
EXCHANGE
MERGE
FINISHED
)
// TwoPhaseSyncer is a type to sync a TwoPhase data store
type TwoPhaseSyncer struct {
manager *TwoPhaseStoreMeshManager
generateMessageFSM SyncFSM
state SyncState
mapState *TwoPhaseMapState[string]
peerMsg []byte
}
type SyncFSM map[SyncState]func(*TwoPhaseSyncer) ([]byte, bool)
func prepare(syncer *TwoPhaseSyncer) ([]byte, bool) {
var buffer bytes.Buffer
enc := gob.NewEncoder(&buffer)
err := enc.Encode(*syncer.mapState)
if err != nil {
logging.Log.WriteInfof(err.Error())
}
syncer.IncrementState()
return buffer.Bytes(), true
}
func present(syncer *TwoPhaseSyncer) ([]byte, bool) {
if syncer.peerMsg == nil {
panic("peer msg is nil")
}
var recvBuffer = bytes.NewBuffer(syncer.peerMsg)
dec := gob.NewDecoder(recvBuffer)
var mapState TwoPhaseMapState[string]
err := dec.Decode(&mapState)
if err != nil {
logging.Log.WriteInfof(err.Error())
}
difference := syncer.mapState.Difference(&mapState)
var sendBuffer bytes.Buffer
enc := gob.NewEncoder(&sendBuffer)
enc.Encode(*difference)
syncer.IncrementState()
return sendBuffer.Bytes(), true
}
func exchange(syncer *TwoPhaseSyncer) ([]byte, bool) {
if syncer.peerMsg == nil {
panic("peer msg is nil")
}
var recvBuffer = bytes.NewBuffer(syncer.peerMsg)
dec := gob.NewDecoder(recvBuffer)
var mapState TwoPhaseMapState[string]
dec.Decode(&mapState)
snapshot := syncer.manager.store.SnapShotFromState(&mapState)
var sendBuffer bytes.Buffer
enc := gob.NewEncoder(&sendBuffer)
enc.Encode(*snapshot)
syncer.IncrementState()
return sendBuffer.Bytes(), true
}
func merge(syncer *TwoPhaseSyncer) ([]byte, bool) {
if syncer.peerMsg == nil {
panic("peer msg is nil")
}
var recvBuffer = bytes.NewBuffer(syncer.peerMsg)
dec := gob.NewDecoder(recvBuffer)
var snapshot TwoPhaseMapSnapshot[string, MeshNode]
dec.Decode(&snapshot)
syncer.manager.store.Merge(snapshot)
return nil, false
}
func (t *TwoPhaseSyncer) IncrementState() {
t.state = min(t.state+1, FINISHED)
}
func (t *TwoPhaseSyncer) GenerateMessage() ([]byte, bool) {
fsmFunc, ok := t.generateMessageFSM[t.state]
if !ok {
panic("state not handled")
}
return fsmFunc(t)
}
func (t *TwoPhaseSyncer) RecvMessage(msg []byte) error {
t.peerMsg = msg
return nil
}
func (t *TwoPhaseSyncer) Complete() {
logging.Log.WriteInfof("SYNC COMPLETED")
}
func NewTwoPhaseSyncer(manager *TwoPhaseStoreMeshManager) *TwoPhaseSyncer {
var generateMessageFsm SyncFSM = SyncFSM{
PREPARE: prepare,
PRESENT: present,
EXCHANGE: exchange,
MERGE: merge,
}
return &TwoPhaseSyncer{
manager: manager,
state: PREPARE,
mapState: manager.store.GenerateMessage(),
generateMessageFSM: generateMessageFsm,
}
}