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raft.go
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raft.go
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package registry
import (
"bufio"
"context"
"encoding/json"
"fmt"
"io"
stdlog "log"
"strings"
"time"
"go.uber.org/zap"
"github.com/spf13/viper"
"github.com/pydio/cells/common/log"
defaults "github.com/pydio/cells/common/micro"
"github.com/hashicorp/raft"
"github.com/nats-io/nats"
natslog "github.com/pydio/nats-on-a-log"
)
type Cluster interface {
Join(nodeId string) error
Leave() error
Close() error
LeadershipAcquired() chan bool
}
type NullFSM struct{}
type NullSnapshot struct{}
func (n *NullSnapshot) Persist(sink raft.SnapshotSink) error {
sink.Close()
return nil
}
func (n *NullSnapshot) Release() {}
func (n *NullFSM) Apply(*raft.Log) interface{} {
return nil
}
func (n *NullFSM) Snapshot() (raft.FSMSnapshot, error) {
return &NullSnapshot{}, nil
}
func (n *NullFSM) Restore(rc io.ReadCloser) error {
rc.Close()
return nil
}
type joinRequest struct {
ID string `json:"id"`
Leave bool `json:"leave"`
}
type joinResponse struct {
OK bool `json:"ok"`
Error string `json:"error"`
}
type pingResponse struct {
OK bool `json:"ok"`
}
const (
defaultJoinRaftGroupTimeout = time.Second
defaultRaftHBTimeout = 2 * time.Second
defaultRaftElectionTimeout = 2 * time.Second
defaultRaftLeaseTimeout = time.Second
defaultRaftCommitTimeout = 100 * time.Millisecond
timeoutForDialAndFlush = 2 * time.Second
)
type raftNatsCluster struct {
ctx context.Context
serviceName string
fsm raft.FSM
config *raft.Config
localId string
leadership chan bool
logOutput io.Writer
conn *nats.Conn
raft *raft.Raft
subs []*nats.Subscription
}
func GetCluster(ctx context.Context, serviceName string, fsm raft.FSM) Cluster {
c := raft.DefaultConfig()
c.ElectionTimeout = defaultRaftElectionTimeout
c.HeartbeatTimeout = defaultRaftHBTimeout
c.LeaderLeaseTimeout = defaultRaftLeaseTimeout
c.CommitTimeout = defaultRaftCommitTimeout
return &raftNatsCluster{
ctx: ctx,
serviceName: serviceName,
fsm: fsm,
leadership: make(chan bool),
config: c,
}
}
func (r *raftNatsCluster) logger() io.Writer {
if r.logOutput == nil {
re, wr := io.Pipe()
r.logOutput = wr
scanner := bufio.NewScanner(re)
scanner.Split(bufio.ScanLines)
go func() {
for scanner.Scan() {
line := scanner.Text()
line = strings.Replace(line, "raft: ", "[raft] ", 1)
line = strings.Replace(line, "raft-net: ", "[raft-net] ", 1)
if strings.HasPrefix(line, "[WARN] ") {
log.Logger(r.ctx).Debug(strings.TrimPrefix(line, "[WARN] "))
} else if strings.HasPrefix(line, "[DEBUG] ") {
log.Logger(r.ctx).Debug(strings.TrimPrefix(line, "[DEBUG] "))
} else if strings.HasPrefix(line, "[INFO] ") {
log.Logger(r.ctx).Info(strings.TrimPrefix(line, "[INFO] "))
} else if strings.HasPrefix(line, "[ERR] ") {
log.Logger(r.ctx).Warn(strings.TrimPrefix(line, "[ERR] "))
} else {
log.Logger(r.ctx).Info(line)
}
}
}()
}
return r.logOutput
}
func (r *raftNatsCluster) Join(nodeId string) error {
r.localId = r.serviceName + "-" + nodeId
r.config.LocalID = raft.ServerID(r.localId)
r.config.Logger = stdlog.New(r.logger(), "", 0)
natsOpts := nats.GetDefaultOptions()
natsOpts.Timeout = defaultJoinRaftGroupTimeout
natsOpts.FlusherTimeout = timeoutForDialAndFlush
addr := viper.GetString("registry_address")
natsOpts.Url = addr
var err error
r.conn, err = natsOpts.Connect()
if err != nil {
return err
}
transport, err := natslog.NewNATSTransportWithLogger(r.localId, r.conn, defaultJoinRaftGroupTimeout, r.config.Logger)
if err != nil {
return err
}
// Create the log store and stable store.
logStore := raft.NewInmemStore()
stableStore := raft.NewInmemStore()
snStore := raft.NewInmemSnapshotStore()
// Instantiate the Raft cluster.
ra, err := raft.NewRaft(r.config, r.fsm, logStore, stableStore, snStore, transport)
if err != nil {
return fmt.Errorf("cannot init raft cluster: %s", err)
}
r.raft = ra
// create subscriptions
e := r.subscribe()
if e != nil {
return e
}
// start ticker for pruning dead nodes
go func() {
ticker := time.Tick(30 * time.Second)
for range ticker {
if ra.State() == raft.Leader {
r.prune()
}
}
}()
nn := r.listExistingNodes()
// No nodes found, bootstraping now
if len(nn) == 0 {
return r.bootstrap(transport)
}
// Try to join existing cluster
var joined bool
for _, joinId := range nn {
log.Logger(r.ctx).Debug("[raft] Trying to join node " + joinId)
req, _ := json.Marshal(&joinRequest{ID: r.localId})
resp, err := r.conn.Request(fmt.Sprintf("%s.join", joinId), req, 10*time.Second)
if err != nil {
continue
}
var r joinResponse
if err := json.Unmarshal(resp.Data, &r); err != nil {
continue
}
if r.OK {
joined = true
break
}
}
// Cannot join any nodes, bootstrap
if !joined {
return r.bootstrap(transport)
}
return nil
}
func (r *raftNatsCluster) LeadershipAcquired() chan bool {
return r.leadership
}
func (r *raftNatsCluster) Leave() error {
log.Logger(r.ctx).Info("[raft] Leaving cluster now")
configFuture := r.raft.GetConfiguration()
if e := configFuture.Error(); e == nil {
if r.raft.State() == raft.Leader {
// For leader, remove from conf directly
log.Logger(r.ctx).Debug("[raft] Removing from configuration")
f := r.raft.RemoveServer(raft.ServerID(r.localId), configFuture.Index(), 1*time.Second)
f.Error()
} else {
// For follower, call leader
leader := r.raft.Leader()
var leaderId raft.ServerID
for _, s := range configFuture.Configuration().Servers {
if s.Address == leader {
leaderId = s.ID
}
}
if leaderId != "" {
log.Logger(r.ctx).Debug("[raft] Informing leader of removal")
req, _ := json.Marshal(&joinRequest{ID: r.localId, Leave: true})
_, err := r.conn.Request(fmt.Sprintf("%s.join", leaderId), req, 5*time.Second)
if err != nil {
log.Logger(r.ctx).Error("[raft] could not send leave request", zap.Error(err))
}
}
}
}
for _, s := range r.subs {
s.Unsubscribe()
}
return nil
}
func (r *raftNatsCluster) Close() error {
return nil
}
func (r *raftNatsCluster) listExistingNodes() (ids []string) {
ss, err := defaults.StartupRegistry().GetService(r.serviceName)
if err == nil && len(ss) > 0 {
for _, n := range ss[0].Nodes {
ids = append(ids, n.Id)
}
}
return
}
func (r *raftNatsCluster) bootstrap(t raft.Transport) error {
conf := raft.Configuration{
Servers: []raft.Server{{
ID: r.config.LocalID,
Address: t.LocalAddr(),
}},
}
return r.raft.BootstrapCluster(conf).Error()
}
func (r *raftNatsCluster) subscribe() error {
// HANDLE JOIN REQUESTS
sub, err := r.conn.Subscribe(fmt.Sprintf("%s.join", r.localId), func(msg *nats.Msg) {
var req joinRequest
if err := json.Unmarshal(msg.Data, &req); err != nil {
resp, _ := json.Marshal(&joinResponse{OK: false, Error: err.Error()})
r.conn.Publish(msg.Reply, resp)
return
}
if r.raft.State() != raft.Leader {
resp, _ := json.Marshal(&joinResponse{OK: false, Error: raft.ErrNotLeader.Error()})
r.conn.Publish(msg.Reply, resp)
return
}
configFuture := r.raft.GetConfiguration()
if err := configFuture.Error(); err != nil {
log.Logger(r.ctx).Error("[raft] failed to get raft configuration:", zap.Error(err))
resp, _ := json.Marshal(&joinResponse{OK: false, Error: err.Error()})
r.conn.Publish(msg.Reply, resp)
return
}
for _, srv := range configFuture.Configuration().Servers {
// However if *both* the ID and the address are the same, then nothing -- not even
// a join operation -- is needed.
if !req.Leave && srv.ID == raft.ServerID(req.ID) {
//fmt.Println("node already member of cluster, ignoring join request", req.ID)
return
}
}
resp := &joinResponse{OK: true}
if !req.Leave {
log.Logger(r.ctx).Info("[raft] Adding new node to raft cluster " + req.ID)
future := r.raft.AddVoter(raft.ServerID(req.ID), raft.ServerAddress(req.ID), 0, 0)
if err := future.Error(); err != nil {
resp.OK = false
resp.Error = err.Error()
}
} else {
future := r.raft.RemoveServer(raft.ServerID(req.ID), configFuture.Index(), 2*time.Second)
if err := future.Error(); err != nil {
resp.OK = false
resp.Error = err.Error()
}
}
rs, _ := json.Marshal(resp)
r.conn.Publish(msg.Reply, rs)
})
if err != nil {
return err
} else {
r.subs = append(r.subs, sub)
}
// HANDLE PING FOR PRUNING DEAD NODES
sub2, err2 := r.conn.Subscribe(fmt.Sprintf("%s.ping", r.localId), func(msg *nats.Msg) {
re, _ := json.Marshal(&pingResponse{OK: true})
r.conn.Publish(msg.Reply, re)
})
if err2 != nil {
return err
} else {
r.subs = append(r.subs, sub2)
}
// LISTEN TO LEADER ACQUISITION
go func() {
for isLeader := range r.raft.LeaderCh() {
if isLeader {
log.Logger(r.ctx).Info("[raft] #### Leadership Acquired for service " + r.serviceName + " ####")
r.leadership <- true
r.prune()
} else {
log.Logger(r.ctx).Info("[raft] #### Leadership Lost on service " + r.serviceName + " ####")
}
}
}()
return nil
}
func (r *raftNatsCluster) prune() {
// Leader changed, so someone must have been lost, ping cluster and remove dead servers
configFuture := r.raft.GetConfiguration()
if err := configFuture.Error(); err != nil {
log.Logger(r.ctx).Error("[raft] failed to get raft configuration: %v\n", zap.Error(err))
} else {
for _, srv := range configFuture.Configuration().Servers {
if srv.ID == raft.ServerID(r.localId) {
continue
}
req, _ := json.Marshal(map[string]interface{}{})
if _, e := r.conn.Request(fmt.Sprintf("%s.ping", srv.ID), req, 10*time.Second); e != nil {
log.Logger(r.ctx).Debug("[raft] Removing server from cluster now " + string(srv.ID))
f := r.raft.RemoveServer(srv.ID, configFuture.Index(), 1*time.Second)
if er := f.Error(); er != nil {
log.Logger(r.ctx).Error("[raft] Error while removing server from cluster", zap.Error(err))
}
}
}
}
}