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ztransfer.go
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ztransfer.go
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package db
import (
"context"
"time"
"github.com/distributedio/titan/conf"
"github.com/distributedio/titan/metrics"
"github.com/pingcap/tidb/kv"
"go.uber.org/zap"
)
var (
sysZTLeader = []byte("$sys:0:ZTL:ZTLeader")
sysZTKeyPrefixLength = len(toZTKey([]byte{}))
sysZTLeaderFlushInterval = 10 * time.Second
ztQueue chan []byte
)
// loadZList is read only, so ZList did not call Destroy()
func loadZList(txn *Transaction, metaKey []byte) (*ZList, error) {
val, err := txn.t.Get(metaKey)
if err != nil {
return nil, err
}
obj, err := DecodeObject(val)
if err != nil {
return nil, err
}
if obj.Type != ObjectList {
return nil, ErrTypeMismatch
}
if obj.Encoding != ObjectEncodingZiplist {
zap.L().Error("[ZT] error in trans zlist, encoding type error", zap.Error(err))
return nil, ErrEncodingMismatch
}
if obj.ExpireAt != 0 && obj.ExpireAt < Now() {
return nil, ErrKeyNotFound
}
l := &ZList{
rawMetaKey: metaKey,
txn: txn,
}
if err = l.Unmarshal(obj, val); err != nil {
return nil, err
}
return l, nil
}
// toZTKey convert meta key to ZT key
// {sys.ns}:{sys.id}:{ZT}:{metakey}
// NOTE put this key to sys db.
func toZTKey(metakey []byte) []byte {
b := []byte{}
b = append(b, sysNamespace...)
b = append(b, ':', byte(sysDatabaseID))
b = append(b, ':', 'Z', 'T', ':')
b = append(b, metakey...)
return b
}
// PutZList should be called after ZList created
func PutZList(txn *Transaction, metakey []byte) error {
if logEnv := zap.L().Check(zap.DebugLevel, "[ZT] Zlist recorded in txn"); logEnv != nil {
logEnv.Write(zap.String("key", string(metakey)))
}
return txn.t.Set(toZTKey(metakey), []byte{0})
}
// RemoveZTKey remove an metakey from ZT
func RemoveZTKey(txn *Transaction, metakey []byte) error {
return txn.t.Delete(toZTKey(metakey))
}
// doZListTransfer get zt key, create zlist and transfer to llist, after that, delete zt key
func doZListTransfer(txn *Transaction, metakey []byte) (int, error) {
zlist, err := loadZList(txn, metakey)
if err != nil {
if err == ErrTypeMismatch || err == ErrEncodingMismatch || err == ErrKeyNotFound {
if err = RemoveZTKey(txn, metakey); err != nil {
zap.L().Error("[ZT] error in remove ZTKkey", zap.Error(err))
return 0, err
}
return 0, nil
}
zap.L().Error("[ZT] error in create zlist", zap.Error(err))
return 0, err
}
llist, err := zlist.TransferToLList(splitMetaKey(metakey))
if err != nil {
zap.L().Error("[ZT] error in convert zlist", zap.Error(err))
return 0, err
}
// clean the zt key, after success
if err = RemoveZTKey(txn, metakey); err != nil {
zap.L().Error("[ZT] error in remove ZTKkey", zap.Error(err))
return 0, err
}
return int(llist.Len), nil
}
func ztWorker(db *DB, batch int, interval time.Duration) {
var txn *Transaction
var err error
var n int
txnstart := false
batchCount := 0
sum := 0
commit := func(t *Transaction) {
if err = t.Commit(context.Background()); err != nil {
zap.L().Error("[ZT] error in commit transfer", zap.Error(err))
if err := txn.Rollback(); err != nil {
zap.L().Error("[ZT] rollback failed", zap.Error(err))
}
} else {
metrics.GetMetrics().ZTInfoCounterVec.WithLabelValues("zlist").Add(float64(batchCount))
metrics.GetMetrics().ZTInfoCounterVec.WithLabelValues("key").Add(float64(sum))
if logEnv := zap.L().Check(zap.DebugLevel, "[ZT] transfer zlist succeed"); logEnv != nil {
logEnv.Write(zap.Int("count", batchCount),
zap.Int("n", sum))
}
}
txnstart = false
batchCount = 0
sum = 0
}
// create zlist and transfer to llist, after that, delete zt key
for {
select {
case metakey := <-ztQueue:
if !txnstart {
if txn, err = db.Begin(); err != nil {
zap.L().Error("[ZT] zt worker error in kv begin", zap.Error(err))
continue
}
txnstart = true
}
if n, err = doZListTransfer(txn, metakey); err != nil {
if err := txn.Rollback(); err != nil {
zap.L().Error("[ZT] rollback failed", zap.Error(err))
}
txnstart = false
continue
}
sum += n
batchCount++
if batchCount >= batch {
commit(txn)
}
default:
if batchCount > 0 {
commit(txn)
} else {
time.Sleep(interval)
txnstart = false
}
}
}
}
func runZT(db *DB, prefix []byte, tick <-chan time.Time) ([]byte, error) {
txn, err := db.Begin()
if err != nil {
zap.L().Error("[ZT] error in kv begin", zap.Error(err))
return toZTKey(nil), nil
}
endPrefix := kv.Key(prefix).PrefixNext()
iter, err := txn.t.Iter(prefix, endPrefix)
if err != nil {
zap.L().Error("[ZT] error in seek", zap.ByteString("prefix", prefix), zap.Error(err))
return toZTKey(nil), err
}
for ; iter.Valid() && iter.Key().HasPrefix(prefix); err = iter.Next() {
if err != nil {
zap.L().Error("[ZT] error in iter next", zap.Error(err))
return toZTKey(nil), err
}
select {
case ztQueue <- iter.Key()[sysZTKeyPrefixLength:]:
case <-tick:
return iter.Key(), nil
default:
return iter.Key(), nil
}
}
if logEnv := zap.L().Check(zap.DebugLevel, "[ZT] no more ZT item, retrive iterator"); logEnv != nil {
logEnv.Write(zap.ByteString("prefix", prefix))
}
return toZTKey(nil), txn.Commit(context.Background())
}
// StartZT start ZT fill in the queue(channel), and start the worker to consume.
func StartZT(db *DB, conf *conf.ZT) {
ztQueue = make(chan []byte, conf.QueueDepth)
for i := 0; i < conf.Workers; i++ {
go ztWorker(db, conf.BatchCount, conf.Interval)
}
// check leader and fill the channel
prefix := toZTKey(nil)
ticker := time.NewTicker(conf.Interval)
defer ticker.Stop()
id := UUID()
for range ticker.C {
if conf.Disable {
continue
}
isLeader, err := isLeader(db, sysZTLeader, id, sysZTLeaderFlushInterval)
if err != nil {
zap.L().Error("[ZT] check ZT leader failed",
zap.Int64("dbid", int64(db.ID)),
zap.Error(err))
continue
}
if !isLeader {
if logEnv := zap.L().Check(zap.DebugLevel, "[ZT] not ZT leader"); logEnv != nil {
logEnv.Write(zap.ByteString("leader", sysZTLeader),
zap.ByteString("uuid", id),
zap.Int("workers", conf.Workers),
zap.Int("batchcount", conf.BatchCount),
zap.Int("queue-depth", conf.QueueDepth),
zap.Duration("interval", conf.Interval),
)
}
continue
}
if prefix, err = runZT(db, prefix, ticker.C); err != nil {
zap.L().Error("[ZT] error in run ZT",
zap.Int64("dbid", int64(db.ID)),
zap.ByteString("prefix", prefix),
zap.Error(err))
continue
}
}
}