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package raft
import (
"sync"
"time"
)
// Future is used to represent an action that may occur in the future.
type Future interface {
Error() error
}
// ApplyFuture is used for Apply() and can returns the FSM response.
type ApplyFuture interface {
Future
Response() interface{}
Index() uint64
}
// errorFuture is used to return a static error.
type errorFuture struct {
err error
}
func (e errorFuture) Error() error {
return e.err
}
func (e errorFuture) Response() interface{} {
return nil
}
func (e errorFuture) Index() uint64 {
return 0
}
// deferError can be embedded to allow a future
// to provide an error in the future.
type deferError struct {
err error
errCh chan error
responded bool
}
func (d *deferError) init() {
d.errCh = make(chan error, 1)
}
func (d *deferError) Error() error {
if d.err != nil {
return d.err
}
if d.errCh == nil {
panic("waiting for response on nil channel")
}
d.err = <-d.errCh
return d.err
}
func (d *deferError) respond(err error) {
if d.errCh == nil {
return
}
if d.responded {
return
}
d.errCh <- err
close(d.errCh)
d.responded = true
}
// logFuture is used to apply a log entry and waits until
// the log is considered committed.
type logFuture struct {
deferError
log Log
policy quorumPolicy
response interface{}
dispatch time.Time
}
func (l *logFuture) Response() interface{} {
return l.response
}
func (l *logFuture) Index() uint64 {
return l.log.Index
}
type peerFuture struct {
deferError
peers []string
}
type shutdownFuture struct {
raft *Raft
}
func (s *shutdownFuture) Error() error {
for s.raft.getRoutines() > 0 {
time.Sleep(5 * time.Millisecond)
}
return nil
}
// snapshotFuture is used for waiting on a snapshot to complete.
type snapshotFuture struct {
deferError
}
// reqSnapshotFuture is used for requesting a snapshot start.
// It is only used internally.
type reqSnapshotFuture struct {
deferError
// snapshot details provided by the FSM runner before responding
index uint64
term uint64
peers []string
snapshot FSMSnapshot
}
// restoreFuture is used for requesting an FSM to perform a
// snapshot restore. Used internally only.
type restoreFuture struct {
deferError
ID string
}
// verifyFuture is used to verify the current node is still
// the leader. This is to prevent a stale read.
type verifyFuture struct {
deferError
notifyCh chan *verifyFuture
quorumSize int
votes int
voteLock sync.Mutex
}
// vote is used to respond to a verifyFuture.
// This may block when responding on the notifyCh.
func (v *verifyFuture) vote(leader bool) {
v.voteLock.Lock()
defer v.voteLock.Unlock()
// Guard against having notified already
if v.notifyCh == nil {
return
}
if leader {
v.votes++
if v.votes >= v.quorumSize {
v.notifyCh <- v
v.notifyCh = nil
}
} else {
v.notifyCh <- v
v.notifyCh = nil
}
}
// appendFuture is used for waiting on a pipelined append
// entries RPC.
type appendFuture struct {
deferError
start time.Time
args *AppendEntriesRequest
resp *AppendEntriesResponse
}
func (a *appendFuture) Start() time.Time {
return a.start
}
func (a *appendFuture) Request() *AppendEntriesRequest {
return a.args
}
func (a *appendFuture) Response() *AppendEntriesResponse {
return a.resp
}
|
