Created
May 8, 2020 15:00
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Basic idea on how to use memberlist, serf, and raft all together. Last example I found had a few bugs to work out.
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package main | |
import ( | |
"fmt" | |
"github.com/hashicorp/memberlist" | |
"github.com/hashicorp/raft" | |
"github.com/hashicorp/raft-boltdb" | |
"github.com/hashicorp/serf/serf" | |
"io" | |
"log" | |
"os" | |
"os/signal" | |
"path/filepath" | |
"syscall" | |
"time" | |
) | |
const ( | |
raftState = "raft/" | |
snapshotsRetained = 2 | |
raftLogCacheSize = 512 | |
) | |
func obtainStores(dataDir string, logOutput io.Writer) (raft.LogStore, raft.StableStore, raft.SnapshotStore, error) { | |
path := filepath.Join(dataDir, raftState) | |
if err := os.MkdirAll(path, 0755); err != nil { | |
return nil, nil, nil, err | |
} | |
stable, err := raftboltdb.NewBoltStore(filepath.Join(path, "raft.db")) | |
if err != nil { | |
return nil, nil, nil, err | |
} | |
logs, err := raft.NewLogCache(raftLogCacheSize, stable) | |
if err != nil { | |
return nil, nil, nil, err | |
} | |
snaps, err := raft.NewFileSnapshotStore(path, snapshotsRetained, logOutput) | |
if err != nil { | |
return nil, nil, nil, err | |
} | |
return logs, stable, snaps, nil | |
} | |
func mainE() error { | |
// assumed to run on the same port, just different hosts | |
peers := []string{ | |
"localhost", | |
} | |
bindAddress := "localhost" | |
serfPort := 7946 | |
raftPort := 1235 | |
dataDir := "data" | |
logOutput := os.Stdout | |
serfCh := make(chan serf.Event, 16) | |
defer close(serfCh) | |
memberlistConfig := memberlist.DefaultLANConfig() | |
memberlistConfig.BindPort = serfPort | |
memberlistConfig.LogOutput = logOutput | |
serfConfig := serf.DefaultConfig() | |
serfConfig.EventCh = serfCh | |
serfConfig.MemberlistConfig = memberlistConfig | |
serfConfig.LogOutput = logOutput | |
s, err := serf.Create(serfConfig) | |
if err != nil { | |
return err | |
} | |
serfPeers := make([]string, len(peers)) | |
for i, peer := range peers { | |
serfPeers[i] = fmt.Sprintf("%s:%d", peer, serfPort) | |
} | |
if len(serfPeers) > 0 { | |
_, err := s.Join(serfPeers, false) | |
if err != nil { | |
return err | |
} | |
} | |
raftAddress := fmt.Sprintf("%s:%d", bindAddress, raftPort) | |
transport, err := raft.NewTCPTransport(raftAddress, nil, 3, 10*time.Second, logOutput) | |
if err != nil { | |
return err | |
} | |
logs, stable, snaps, err := obtainStores(dataDir, logOutput) | |
if err != nil { | |
return err | |
} | |
if closer, ok := stable.(io.Closer); ok { | |
defer func() { | |
err := closer.Close() | |
if err != nil { | |
log.Fatal(err) | |
} | |
}() | |
} | |
hasState, err := raft.HasExistingState(logs, stable, snaps) | |
if err != nil { | |
return err | |
} | |
raftConfig := raft.DefaultConfig() | |
raftConfig.LocalID = raft.ServerID(raftAddress) | |
if !hasState { | |
raftPeers := make([]raft.Server, len(peers)) | |
for i, peer := range peers { | |
p := fmt.Sprintf("%s:%d", peer, raftPort) | |
raftPeers[i] = raft.Server{ | |
Suffrage: raft.Voter, | |
ID: raft.ServerID(p), | |
Address: raft.ServerAddress(p), | |
} | |
} | |
bootstrapConfig := raft.Configuration{ | |
Servers: raftPeers, | |
} | |
err := raft.BootstrapCluster(raftConfig, logs, stable, snaps, transport, bootstrapConfig) | |
if err != nil { | |
return err | |
} | |
} | |
r, err := raft.NewRaft(raftConfig, &fsm{}, logs, stable, snaps, transport) | |
if err != nil { | |
return err | |
} | |
defer func(){ | |
future := r.Shutdown() | |
if err := future.Error(); err != nil { | |
log.Fatal(err) | |
} | |
}() | |
done := false | |
ch := make(chan os.Signal) | |
signal.Notify(ch, syscall.SIGTERM, syscall.SIGINT) | |
ticker := time.NewTicker(3 * time.Second) | |
for !done { | |
select { | |
case <-ch: | |
done = true | |
case <-ticker.C: | |
future := r.VerifyLeader() | |
if err := future.Error(); err != nil { | |
fmt.Println("node is a follower") | |
} else { | |
fmt.Println("node is a leader") | |
} | |
case ev := <-serfCh: | |
leader := r.VerifyLeader() | |
if memberEvent, ok := ev.(serf.MemberEvent); ok { | |
for _, member := range memberEvent.Members { | |
eventType := memberEvent.EventType() | |
changedPeer := fmt.Sprintf("%s:%d", member.Addr.String(), raftPort) | |
if leader.Error() != nil { | |
continue | |
} | |
if eventType == serf.EventMemberJoin { | |
future := r.AddVoter(raft.ServerID(changedPeer), raft.ServerAddress(changedPeer), 0, 0) | |
if err := future.Error(); err != nil { | |
// log | |
} | |
} else if eventType == serf.EventMemberLeave || eventType == serf.EventMemberFailed { | |
future := r.RemoveServer(raft.ServerID(changedPeer), 0, 0) | |
if err := future.Error(); err != nil { | |
// log | |
} | |
} | |
} | |
} | |
} | |
} | |
fmt.Println("shutting down") | |
return nil | |
} | |
func main() { | |
if err := mainE(); err != nil { | |
panic(err) | |
} | |
} | |
type fsm struct {} | |
func (*fsm) Apply(l *raft.Log) interface{} { | |
return nil | |
} | |
func (*fsm) Snapshot() (raft.FSMSnapshot, error) { | |
return nil, nil | |
} | |
func (*fsm) Restore(read io.ReadCloser) error { | |
return nil | |
} | |
var _ raft.FSM = &fsm{} |
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