1 files changed, 296 insertions, 0 deletions
diff --git a/weed/sequence/etcd_sequencer.go b/weed/sequence/etcd_sequencer.go
new file mode 100644
index 000000000..1fc378640
--- /dev/null
+++ b/weed/sequence/etcd_sequencer.go
@@ -0,0 +1,296 @@
+package sequence
+
+/*
+Note :
+(1) store the sequence in the ETCD cluster, and local file(sequence.dat)
+(2) batch get the sequences from ETCD cluster, and store the max sequence id in the local file
+(3) the sequence range is : [currentSeqId, maxSeqId), when the currentSeqId >= maxSeqId, fetch the new maxSeqId.
+*/
+
+import (
+	"context"
+	"fmt"
+	"sync"
+	"time"
+
+	"io"
+	"os"
+	"strconv"
+	"strings"
+
+	"github.com/chrislusf/seaweedfs/weed/glog"
+	"go.etcd.io/etcd/client"
+)
+
+const (
+	// EtcdKeyPrefix                   = "/seaweedfs"
+	EtcdKeySequence                 = "/master/sequence"
+	EtcdContextTimeoutSecond        = 100 * time.Second
+	DefaultEtcdSteps         uint64 = 500 // internal counter
+	SequencerFileName               = "sequencer.dat"
+	FileMaxSequenceLength           = 128
+)
+
+type EtcdSequencer struct {
+	sequenceLock sync.Mutex
+
+	// available sequence range : [currentSeqId, maxSeqId)
+	currentSeqId uint64
+	maxSeqId     uint64
+
+	keysAPI client.KeysAPI
+	seqFile *os.File
+}
+
+func NewEtcdSequencer(etcdUrls string, metaFolder string) (*EtcdSequencer, error) {
+	file, err := openSequenceFile(metaFolder + "/" + SequencerFileName)
+	if nil != err {
+		return nil, fmt.Errorf("open sequence file fialed, %v", err)
+	}
+
+	cli, err := client.New(client.Config{
+		Endpoints: strings.Split(etcdUrls, ","),
+		Username:  "",
+		Password:  "",
+	})
+	if err != nil {
+		return nil, err
+	}
+	keysApi := client.NewKeysAPI(cli)
+
+	// TODO: the current sequence id in local file is not used
+	maxValue, _, err := readSequenceFile(file)
+	if err != nil {
+		return nil, fmt.Errorf("read sequence from file failed, %v", err)
+	}
+	glog.V(4).Infof("read sequence from file : %d", maxValue)
+
+	newSeq, err := setMaxSequenceToEtcd(keysApi, maxValue)
+	if err != nil {
+		return nil, err
+	}
+
+	sequencer := &EtcdSequencer{maxSeqId: newSeq,
+		currentSeqId: newSeq,
+		keysAPI:      keysApi,
+		seqFile:      file,
+	}
+	return sequencer, nil
+}
+
+func (es *EtcdSequencer) NextFileId(count uint64) uint64 {
+	es.sequenceLock.Lock()
+	defer es.sequenceLock.Unlock()
+
+	if (es.currentSeqId + count) >= es.maxSeqId {
+		reqSteps := DefaultEtcdSteps
+		if count > DefaultEtcdSteps {
+			reqSteps += count
+		}
+		maxId, err := batchGetSequenceFromEtcd(es.keysAPI, reqSteps)
+		glog.V(4).Infof("get max sequence id from etcd, %d", maxId)
+		if err != nil {
+			glog.Error(err)
+			return 0
+		}
+		es.currentSeqId, es.maxSeqId = maxId-reqSteps, maxId
+		glog.V(4).Infof("current id : %d, max id : %d", es.currentSeqId, es.maxSeqId)
+
+		if err := writeSequenceFile(es.seqFile, es.maxSeqId, es.currentSeqId); err != nil {
+			glog.Errorf("flush sequence to file failed, %v", err)
+		}
+	}
+
+	ret := es.currentSeqId
+	es.currentSeqId += count
+	return ret
+}
+
+/**
+instead of collecting the max value from volume server,
+the max value should be saved in local config file and ETCD cluster
+*/
+func (es *EtcdSequencer) SetMax(seenValue uint64) {
+	es.sequenceLock.Lock()
+	defer es.sequenceLock.Unlock()
+	if seenValue > es.maxSeqId {
+		maxId, err := setMaxSequenceToEtcd(es.keysAPI, seenValue)
+		if err != nil {
+			glog.Errorf("set Etcd Max sequence failed : %v", err)
+			return
+		}
+		es.currentSeqId, es.maxSeqId = maxId, maxId
+
+		if err := writeSequenceFile(es.seqFile, maxId, maxId); err != nil {
+			glog.Errorf("flush sequence to file failed, %v", err)
+		}
+	}
+}
+
+func (es *EtcdSequencer) GetMax() uint64 {
+	return es.maxSeqId
+}
+
+func (es *EtcdSequencer) Peek() uint64 {
+	return es.currentSeqId
+}
+
+func batchGetSequenceFromEtcd(kvApi client.KeysAPI, step uint64) (uint64, error) {
+	if step <= 0 {
+		return 0, fmt.Errorf("the step must be large than 1")
+	}
+
+	ctx, cancel := context.WithTimeout(context.Background(), EtcdContextTimeoutSecond)
+	var endSeqValue uint64 = 0
+	defer cancel()
+	for {
+		getResp, err := kvApi.Get(ctx, EtcdKeySequence, &client.GetOptions{Recursive: false, Quorum: true})
+		if err != nil {
+			return 0, err
+		}
+		if getResp.Node == nil {
+			continue
+		}
+
+		prevValue := getResp.Node.Value
+		prevSeqValue, err := strconv.ParseUint(prevValue, 10, 64)
+		if err != nil {
+			return 0, fmt.Errorf("get sequence from etcd failed, %v", err)
+		}
+		endSeqValue = prevSeqValue + step
+		endSeqStr := strconv.FormatUint(endSeqValue, 10)
+
+		_, err = kvApi.Set(ctx, EtcdKeySequence, endSeqStr, &client.SetOptions{PrevValue: prevValue})
+		if err == nil {
+			break
+		}
+		glog.Error(err)
+	}
+
+	return endSeqValue, nil
+}
+
+/**
+update the value of the key EtcdKeySequence in ETCD cluster with the parameter of maxSeq,
+when the value of the key EtcdKeySequence is equal to or large than the parameter maxSeq,
+return the value of EtcdKeySequence in the ETCD cluster;
+when the value of the EtcdKeySequence is less than the parameter maxSeq,
+return the value of the parameter maxSeq
+*/
+func setMaxSequenceToEtcd(kvApi client.KeysAPI, maxSeq uint64) (uint64, error) {
+	maxSeqStr := strconv.FormatUint(maxSeq, 10)
+	ctx, cancel := context.WithTimeout(context.Background(), EtcdContextTimeoutSecond)
+	defer cancel()
+
+	for {
+		getResp, err := kvApi.Get(ctx, EtcdKeySequence, &client.GetOptions{Recursive: false, Quorum: true})
+		if err != nil {
+			if ce, ok := err.(client.Error); ok && (ce.Code == client.ErrorCodeKeyNotFound) {
+				_, err := kvApi.Create(ctx, EtcdKeySequence, maxSeqStr)
+				if err == nil {
+					continue
+				}
+				if ce, ok = err.(client.Error); ok && (ce.Code == client.ErrorCodeNodeExist) {
+					continue
+				}
+				return 0, err
+			} else {
+				return 0, err
+			}
+		}
+
+		if getResp.Node == nil {
+			continue
+		}
+		prevSeqStr := getResp.Node.Value
+		prevSeq, err := strconv.ParseUint(prevSeqStr, 10, 64)
+		if err != nil {
+			return 0, err
+		}
+		if prevSeq >= maxSeq {
+			return prevSeq, nil
+		}
+
+		_, err = kvApi.Set(ctx, EtcdKeySequence, maxSeqStr, &client.SetOptions{PrevValue: prevSeqStr})
+		if err != nil {
+			return 0, err
+		}
+	}
+}
+
+func openSequenceFile(file string) (*os.File, error) {
+	_, err := os.Stat(file)
+	if os.IsNotExist(err) {
+		fid, err := os.OpenFile(file, os.O_RDWR|os.O_CREATE, 0644)
+		if err != nil {
+			return nil, err
+		}
+		if err := writeSequenceFile(fid, 1, 0); err != nil {
+			return nil, err
+		}
+		return fid, nil
+	} else {
+		return os.OpenFile(file, os.O_RDWR|os.O_CREATE, 0644)
+	}
+}
+
+/*
+read sequence and step from sequence file
+*/
+func readSequenceFile(file *os.File) (uint64, uint64, error) {
+	sequence := make([]byte, FileMaxSequenceLength)
+	size, err := file.ReadAt(sequence, 0)
+	if (err != nil) && (err != io.EOF) {
+		err := fmt.Errorf("cannot read file %s, %v", file.Name(), err)
+		return 0, 0, err
+	}
+	sequence = sequence[0:size]
+	seqs := strings.Split(string(sequence), ":")
+	maxId, err := strconv.ParseUint(seqs[0], 10, 64)
+	if err != nil {
+		return 0, 0, fmt.Errorf("parse sequence from file failed, %v", err)
+	}
+
+	if len(seqs) > 1 {
+		step, err := strconv.ParseUint(seqs[1], 10, 64)
+		if err != nil {
+			return 0, 0, fmt.Errorf("parse sequence from file failed, %v", err)
+		}
+		return maxId, step, nil
+	}
+
+	return maxId, 0, nil
+}
+
+/**
+write the sequence and step to sequence file
+*/
+func writeSequenceFile(file *os.File, sequence, step uint64) error {
+	_ = step
+	seqStr := fmt.Sprintf("%d:%d", sequence, sequence)
+	if _, err := file.Seek(0, 0); err != nil {
+		err = fmt.Errorf("cannot seek to the beginning of %s: %v", file.Name(), err)
+		return err
+	}
+	if err := file.Truncate(0); err != nil {
+		return fmt.Errorf("truncate sequence file faield : %v", err)
+	}
+	if _, err := file.WriteString(seqStr); err != nil {
+		return fmt.Errorf("write file %s failed, %v", file.Name(), err)
+	}
+	if err := file.Sync(); err != nil {
+		return fmt.Errorf("flush file %s failed, %v", file.Name(), err)
+	}
+	return nil
+}
+
+// the UT helper method
+// func deleteEtcdKey(kvApi client.KeysAPI, key string) error {
+// 	ctx, cancel := context.WithTimeout(context.Background(), EtcdContextTimeoutSecond)
+// 	defer cancel()
+// 	_, err := kvApi.Delete(ctx, key, &client.DeleteOptions{Dir: false})
+// 	if err != nil {
+// 		return err
+// 	}
+// 	return nil
+// }