/
registrator.go
168 lines (141 loc) · 4.09 KB
/
registrator.go
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// Copyright 2016 IBM Corporation
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package cluster
import (
"errors"
"sync"
"time"
"github.com/Sirupsen/logrus"
"github.com/amalgam8/amalgam8/registry/utils/logging"
)
// Registrator enables a member node to join and leave the cluster
type Registrator interface {
// Self returns the associated member node.
Self() Member
// Join adds the associated member node to the cluster.
// Returns a non-nil error if and only if the member node could not be added to the cluster.
Join() error
// Leave removes the associated member node from the cluster.
// Returns a non-nil error if and only if the member node could not be removed from the cluster.
Leave() error
}
func newRegistrator(backend backend, member Member, membership Membership, interval time.Duration) *registrator {
reg := ®istrator{
backend: backend,
member: member,
membership: membership,
interval: interval,
rejoin: make(chan struct{}),
done: make(chan struct{}),
logger: logging.GetLogger(module),
}
reg.listener = &ongoingListener{reg: reg}
return reg
}
// registration is a Registration implementation that actively rejoins
// the cluster as long as not explicitly stopped.
type registrator struct {
backend backend
member Member
membership Membership
interval time.Duration
rejoin chan struct{}
done chan struct{}
renewer *time.Ticker
listener *ongoingListener
mutex sync.Mutex
logger *logrus.Entry
}
func (r *registrator) Self() Member {
return r.member
}
func (r *registrator) Join() error {
r.mutex.Lock()
defer r.mutex.Unlock()
if r.renewer != nil {
err := errors.New("Already joined")
r.logger.WithField("error", err).Warning()
return err
}
r.membership.RegisterListener(r.listener)
r.renewer = time.NewTicker(r.interval)
go r.maintainRegistration(r.renewer.C, r.rejoin, r.done)
r.writeSelf()
return nil
}
func (r *registrator) Leave() error {
r.mutex.Lock()
defer r.mutex.Unlock()
if r.renewer == nil {
err := errors.New("Already left or never joined")
r.logger.WithField("error", err).Warning()
return err
}
r.membership.DeregisterListener(r.listener)
r.renewer.Stop()
r.renewer = nil
r.done <- struct{}{}
return r.deleteSelf()
}
func (r *registrator) maintainRegistration(tick <-chan time.Time, left <-chan struct{}, done <-chan struct{}) {
for {
select {
// race condition: Leave() and then deleteSelf()
// might be called just prior to calling writeSelf().
// this is both rare and self-healing, so not guarded
case <-tick:
r.writeSelf()
case <-left:
r.writeSelf()
case <-done:
return
}
}
}
func (r *registrator) writeSelf() {
self := &member{
MemberIP: r.member.IP(),
MemberPort: r.member.Port(),
Timestamp: time.Now(),
}
err := r.backend.WriteMember(self)
if err != nil {
_, joined := r.membership.Members()[r.member]
if joined {
r.logger.WithField("error", err).Warningf("Error renewing member %v", self.ID())
} else {
r.logger.WithField("error", err).Warningf("Error joining member %v", self.ID())
}
}
return
}
func (r *registrator) deleteSelf() error {
err := r.backend.DeleteMember(r.member.ID())
if err != nil {
r.logger.WithField("error", err).Warningf("Error leaving member %v", r.member.ID())
}
return err
}
type ongoingListener struct {
reg *registrator
}
func (l *ongoingListener) OnJoin(m Member) {
// Do nothing
}
func (l *ongoingListener) OnLeave(m Member) {
if m.ID() == l.reg.member.ID() {
l.reg.logger.Warningf("Attempting to rejoin the cluster: %v", m.ID())
l.reg.rejoin <- struct{}{}
}
}