smegmesh/pkg/crdt/two_phase_map_syncer.go
Tim Beatham 815c4484ee 47-default-routing
Implemented default routing and improved size of gossip. Using 64 bit
hash funciton to identify vector.
2023-12-08 20:02:57 +00:00

188 lines
3.8 KiB
Go

package crdt
import (
"bytes"
"encoding/gob"
logging "github.com/tim-beatham/wgmesh/pkg/log"
)
type SyncState int
const (
HASH SyncState = iota
PREPARE
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 TwoPhaseHash struct {
Hash uint64
}
type SyncFSM map[SyncState]func(*TwoPhaseSyncer) ([]byte, bool)
func hash(syncer *TwoPhaseSyncer) ([]byte, bool) {
hash := TwoPhaseHash{
Hash: syncer.manager.store.Clock.GetHash(),
}
var buffer bytes.Buffer
enc := gob.NewEncoder(&buffer)
err := enc.Encode(hash)
if err != nil {
logging.Log.WriteErrorf(err.Error())
}
syncer.IncrementState()
return buffer.Bytes(), true
}
func prepare(syncer *TwoPhaseSyncer) ([]byte, bool) {
var recvBuffer = bytes.NewBuffer(syncer.peerMsg)
dec := gob.NewDecoder(recvBuffer)
var hash TwoPhaseHash
err := dec.Decode(&hash)
if err != nil {
logging.Log.WriteErrorf(err.Error())
}
// If vector clocks are equal then no need to merge state
// Helps to reduce bandwidth by detecting early
if hash.Hash == syncer.manager.store.Clock.GetHash() {
return nil, false
}
var buffer bytes.Buffer
enc := gob.NewEncoder(&buffer)
err = enc.Encode(*syncer.mapState)
if err != nil {
logging.Log.WriteErrorf(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.WriteErrorf(err.Error())
}
difference := syncer.mapState.Difference(&mapState)
syncer.manager.store.Clock.Merge(mapState.Vectors)
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")
if t.state >= MERGE {
t.manager.store.Clock.IncrementClock()
}
}
func NewTwoPhaseSyncer(manager *TwoPhaseStoreMeshManager) *TwoPhaseSyncer {
var generateMessageFsm SyncFSM = SyncFSM{
HASH: hash,
PREPARE: prepare,
PRESENT: present,
EXCHANGE: exchange,
MERGE: merge,
}
return &TwoPhaseSyncer{
manager: manager,
state: HASH,
mapState: manager.store.GenerateMessage(),
generateMessageFSM: generateMessageFsm,
}
}