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state.go
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state.go
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package meta
import (
"bytes"
"encoding/json"
"errors"
"fmt"
"io/ioutil"
"math/rand"
"os"
"path/filepath"
"sync"
"time"
"github.com/hashicorp/raft"
"github.com/hashicorp/raft-boltdb"
)
// raftState abstracts the interaction of the raft consensus layer
// across local or remote nodes. It is a form of the state design pattern and allows
// the meta.Store to change its behavior with the raft layer at runtime.
type raftState interface {
open() error
remove() error
initialize() error
leader() string
isLeader() bool
sync(index uint64, timeout time.Duration) error
setPeers(addrs []string) error
addPeer(addr string) error
removePeer(addr string) error
peers() ([]string, error)
invalidate() error
close() error
lastIndex() uint64
apply(b []byte) error
snapshot() error
isLocal() bool
}
// localRaft is a consensus strategy that uses a local raft implementation for
// consensus operations.
type localRaft struct {
wg sync.WaitGroup
closing chan struct{}
store *Store
raft *raft.Raft
transport *raft.NetworkTransport
peerStore raft.PeerStore
raftStore *raftboltdb.BoltStore
raftLayer *raftLayer
}
func (r *localRaft) remove() error {
if err := os.RemoveAll(filepath.Join(r.store.path, "raft.db")); err != nil {
return err
}
if err := os.RemoveAll(filepath.Join(r.store.path, "peers.json")); err != nil {
return err
}
if err := os.RemoveAll(filepath.Join(r.store.path, "snapshots")); err != nil {
return err
}
return nil
}
func (r *localRaft) updateMetaData(ms *Data) {
if ms == nil {
return
}
updated := false
r.store.mu.RLock()
if ms.Index > r.store.data.Index {
updated = true
}
r.store.mu.RUnlock()
if updated {
r.store.Logger.Printf("Updating metastore to term=%v index=%v", ms.Term, ms.Index)
r.store.mu.Lock()
r.store.data = ms
// Signal any blocked goroutines that the meta store has been updated
r.store.notifyChanged()
r.store.mu.Unlock()
}
}
func (r *localRaft) invalidate() error {
if r.store.IsLeader() {
return nil
}
ms, err := r.store.rpc.fetchMetaData(false)
if err != nil {
return fmt.Errorf("error fetching meta data: %s", err)
}
r.updateMetaData(ms)
return nil
}
func (r *localRaft) open() error {
r.closing = make(chan struct{})
s := r.store
// Setup raft configuration.
config := raft.DefaultConfig()
config.LogOutput = ioutil.Discard
if s.clusterTracingEnabled {
config.Logger = s.Logger
}
config.HeartbeatTimeout = s.HeartbeatTimeout
config.ElectionTimeout = s.ElectionTimeout
config.LeaderLeaseTimeout = s.LeaderLeaseTimeout
config.CommitTimeout = s.CommitTimeout
// Since we actually never call `removePeer` this is safe.
// If in the future we decide to call remove peer we have to re-evaluate how to handle this
config.ShutdownOnRemove = false
// If no peers are set in the config or there is one and we are it, then start as a single server.
if len(s.peers) <= 1 {
config.EnableSingleNode = true
// Ensure we can always become the leader
config.DisableBootstrapAfterElect = false
}
// Build raft layer to multiplex listener.
r.raftLayer = newRaftLayer(s.RaftListener, s.RemoteAddr)
// Create a transport layer
r.transport = raft.NewNetworkTransport(r.raftLayer, 3, 10*time.Second, config.LogOutput)
// Create peer storage.
r.peerStore = raft.NewJSONPeers(s.path, r.transport)
peers, err := r.peerStore.Peers()
if err != nil {
return err
}
// For single-node clusters, we can update the raft peers before we start the cluster if the hostname
// has changed.
if config.EnableSingleNode {
if err := r.peerStore.SetPeers([]string{s.RemoteAddr.String()}); err != nil {
return err
}
peers = []string{s.RemoteAddr.String()}
}
// If we have multiple nodes in the cluster, make sure our address is in the raft peers or
// we won't be able to boot into the cluster because the other peers will reject our new hostname. This
// is difficult to resolve automatically because we need to have all the raft peers agree on the current members
// of the cluster before we can change them.
if len(peers) > 0 && !raft.PeerContained(peers, s.RemoteAddr.String()) {
s.Logger.Printf("%s is not in the list of raft peers. Please update %v/peers.json on all raft nodes to have the same contents.", s.RemoteAddr.String(), s.Path())
return fmt.Errorf("peers out of sync: %v not in %v", s.RemoteAddr.String(), peers)
}
// Create the log store and stable store.
store, err := raftboltdb.NewBoltStore(filepath.Join(s.path, "raft.db"))
if err != nil {
return fmt.Errorf("new bolt store: %s", err)
}
r.raftStore = store
// Create the snapshot store.
snapshots, err := raft.NewFileSnapshotStore(s.path, raftSnapshotsRetained, os.Stderr)
if err != nil {
return fmt.Errorf("file snapshot store: %s", err)
}
// Create raft log.
ra, err := raft.NewRaft(config, (*storeFSM)(s), store, store, snapshots, r.peerStore, r.transport)
if err != nil {
return fmt.Errorf("new raft: %s", err)
}
r.raft = ra
r.wg.Add(1)
go r.logLeaderChanges()
return nil
}
func (r *localRaft) logLeaderChanges() {
defer r.wg.Done()
// Logs our current state (Node at 1.2.3.4:8088 [Follower])
r.store.Logger.Printf(r.raft.String())
for {
select {
case <-r.closing:
return
case <-r.raft.LeaderCh():
peers, err := r.peers()
if err != nil {
r.store.Logger.Printf("failed to lookup peers: %v", err)
}
r.store.Logger.Printf("%v. peers=%v", r.raft.String(), peers)
}
}
}
func (r *localRaft) close() error {
close(r.closing)
r.wg.Wait()
if r.transport != nil {
r.transport.Close()
r.transport = nil
}
// Shutdown raft.
if r.raft != nil {
if err := r.raft.Shutdown().Error(); err != nil {
return err
}
r.raft = nil
}
if r.raftStore != nil {
r.raftStore.Close()
r.raftStore = nil
}
return nil
}
func (r *localRaft) initialize() error {
s := r.store
// If we have committed entries then the store is already in the cluster.
if index, err := r.raftStore.LastIndex(); err != nil {
return fmt.Errorf("last index: %s", err)
} else if index > 0 {
return nil
}
// Force set peers.
if err := r.setPeers(s.peers); err != nil {
return fmt.Errorf("set raft peers: %s", err)
}
return nil
}
// apply applies a serialized command to the raft log.
func (r *localRaft) apply(b []byte) error {
// Apply to raft log.
f := r.raft.Apply(b, 0)
if err := f.Error(); err != nil {
return err
}
// Return response if it's an error.
// No other non-nil objects should be returned.
resp := f.Response()
if err, ok := resp.(error); ok {
return lookupError(err)
}
assert(resp == nil, "unexpected response: %#v", resp)
return nil
}
func (r *localRaft) lastIndex() uint64 {
return r.raft.LastIndex()
}
func (r *localRaft) sync(index uint64, timeout time.Duration) error {
ticker := time.NewTicker(100 * time.Millisecond)
defer ticker.Stop()
timer := time.NewTimer(timeout)
defer timer.Stop()
for {
// Wait for next tick or timeout.
select {
case <-ticker.C:
case <-timer.C:
return errors.New("timeout")
}
// Compare index against current metadata.
r.store.mu.Lock()
ok := (r.store.data.Index >= index)
r.store.mu.Unlock()
// Exit if we are at least at the given index.
if ok {
return nil
}
}
}
func (r *localRaft) snapshot() error {
future := r.raft.Snapshot()
return future.Error()
}
// addPeer adds addr to the list of peers in the cluster.
func (r *localRaft) addPeer(addr string) error {
peers, err := r.peerStore.Peers()
if err != nil {
return err
}
if len(peers) >= 3 {
return nil
}
if fut := r.raft.AddPeer(addr); fut.Error() != nil {
return fut.Error()
}
return nil
}
// removePeer removes addr from the list of peers in the cluster.
func (r *localRaft) removePeer(addr string) error {
// Only do this on the leader
if !r.isLeader() {
return errors.New("not the leader")
}
if fut := r.raft.RemovePeer(addr); fut.Error() != nil {
return fut.Error()
}
return nil
}
// setPeers sets a list of peers in the cluster.
func (r *localRaft) setPeers(addrs []string) error {
return r.raft.SetPeers(addrs).Error()
}
func (r *localRaft) peers() ([]string, error) {
return r.peerStore.Peers()
}
func (r *localRaft) leader() string {
if r.raft == nil {
return ""
}
return r.raft.Leader()
}
func (r *localRaft) isLeader() bool {
if r.raft == nil {
return false
}
return r.raft.State() == raft.Leader
}
func (r *localRaft) isLocal() bool {
return true
}
// remoteRaft is a consensus strategy that uses a remote raft cluster for
// consensus operations.
type remoteRaft struct {
store *Store
}
func (r *remoteRaft) remove() error {
return nil
}
func (r *remoteRaft) updateMetaData(ms *Data) {
if ms == nil {
return
}
updated := false
r.store.mu.RLock()
if ms.Index > r.store.data.Index {
updated = true
}
r.store.mu.RUnlock()
if updated {
r.store.Logger.Printf("Updating metastore to term=%v index=%v", ms.Term, ms.Index)
r.store.mu.Lock()
r.store.data = ms
// Signal any blocked goroutines that the meta store has been updated
r.store.notifyChanged()
r.store.mu.Unlock()
}
}
func (r *remoteRaft) invalidate() error {
ms, err := r.store.rpc.fetchMetaData(false)
if err != nil {
return fmt.Errorf("error fetching meta data: %s", err)
}
r.updateMetaData(ms)
return nil
}
func (r *remoteRaft) setPeers(addrs []string) error {
// Convert to JSON
var buf bytes.Buffer
enc := json.NewEncoder(&buf)
if err := enc.Encode(addrs); err != nil {
return err
}
// Write out as JSON
return ioutil.WriteFile(filepath.Join(r.store.path, "peers.json"), buf.Bytes(), 0755)
}
// addPeer adds addr to the list of peers in the cluster.
func (r *remoteRaft) addPeer(addr string) error {
return fmt.Errorf("cannot add peer using remote raft")
}
// removePeer does nothing for remoteRaft.
func (r *remoteRaft) removePeer(addr string) error {
return nil
}
func (r *remoteRaft) peers() ([]string, error) {
return readPeersJSON(filepath.Join(r.store.path, "peers.json"))
}
func (r *remoteRaft) open() error {
if err := r.setPeers(r.store.peers); err != nil {
return err
}
go func() {
for {
select {
case <-r.store.closing:
return
default:
}
ms, err := r.store.rpc.fetchMetaData(true)
if err != nil {
r.store.Logger.Printf("fetch metastore: %v", err)
time.Sleep(time.Second)
continue
}
r.updateMetaData(ms)
}
}()
return nil
}
func (r *remoteRaft) close() error {
return nil
}
// apply applies a serialized command to the raft log.
func (r *remoteRaft) apply(b []byte) error {
return fmt.Errorf("cannot apply log while in remote raft state")
}
func (r *remoteRaft) initialize() error {
return nil
}
func (r *remoteRaft) leader() string {
if len(r.store.peers) == 0 {
return ""
}
return r.store.peers[rand.Intn(len(r.store.peers))]
}
func (r *remoteRaft) isLeader() bool {
return false
}
func (r *remoteRaft) isLocal() bool {
return false
}
func (r *remoteRaft) lastIndex() uint64 {
return r.store.cachedData().Index
}
func (r *remoteRaft) sync(index uint64, timeout time.Duration) error {
//FIXME: jwilder: check index and timeout
return r.store.invalidate()
}
func (r *remoteRaft) snapshot() error {
return fmt.Errorf("cannot snapshot while in remote raft state")
}
func readPeersJSON(path string) ([]string, error) {
// Read the file
buf, err := ioutil.ReadFile(path)
if err != nil && !os.IsNotExist(err) {
return nil, err
}
// Check for no peers
if len(buf) == 0 {
return nil, nil
}
// Decode the peers
var peers []string
dec := json.NewDecoder(bytes.NewReader(buf))
if err := dec.Decode(&peers); err != nil {
return nil, err
}
return peers, nil
}