ad54c5a278
Traefik should follow modern IT trends, and use manager/leader/worker/agent, etc. instead of "master/slave". e.g jenkinsci/jenkins#2007 (https://issues.jenkins-ci.org/browse/JENKINS-27268) NB: of course, it can only apply where possible, since backends like Mesos should retain their own concepts, and not add more confusion.
105 lines
2.6 KiB
Go
105 lines
2.6 KiB
Go
package cluster
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import (
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"context"
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"time"
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"github.com/cenk/backoff"
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"github.com/containous/traefik/log"
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"github.com/containous/traefik/safe"
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"github.com/containous/traefik/types"
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"github.com/docker/leadership"
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)
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// Leadership allows leadership election using a KV store
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type Leadership struct {
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*safe.Pool
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*types.Cluster
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candidate *leadership.Candidate
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leader *safe.Safe
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listeners []LeaderListener
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}
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// NewLeadership creates a leadership
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func NewLeadership(ctx context.Context, cluster *types.Cluster) *Leadership {
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return &Leadership{
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Pool: safe.NewPool(ctx),
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Cluster: cluster,
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candidate: leadership.NewCandidate(cluster.Store, cluster.Store.Prefix+"/leader", cluster.Node, 20*time.Second),
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listeners: []LeaderListener{},
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leader: safe.New(false),
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}
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}
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// LeaderListener is called when leadership has changed
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type LeaderListener func(elected bool) error
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// Participate tries to be a leader
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func (l *Leadership) Participate(pool *safe.Pool) {
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pool.GoCtx(func(ctx context.Context) {
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log.Debugf("Node %s running for election", l.Cluster.Node)
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defer log.Debugf("Node %s no more running for election", l.Cluster.Node)
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backOff := backoff.NewExponentialBackOff()
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operation := func() error {
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return l.run(ctx, l.candidate)
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}
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notify := func(err error, time time.Duration) {
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log.Errorf("Leadership election error %+v, retrying in %s", err, time)
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}
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err := backoff.RetryNotify(safe.OperationWithRecover(operation), backOff, notify)
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if err != nil {
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log.Errorf("Cannot elect leadership %+v", err)
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}
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})
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}
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// AddListener adds a leadership listener
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func (l *Leadership) AddListener(listener LeaderListener) {
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l.listeners = append(l.listeners, listener)
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}
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// Resign resigns from being a leader
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func (l *Leadership) Resign() {
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l.candidate.Resign()
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log.Infof("Node %s resigned", l.Cluster.Node)
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}
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func (l *Leadership) run(ctx context.Context, candidate *leadership.Candidate) error {
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electedCh, errCh := candidate.RunForElection()
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for {
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select {
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case elected := <-electedCh:
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l.onElection(elected)
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case err := <-errCh:
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return err
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case <-ctx.Done():
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l.candidate.Resign()
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return nil
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}
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}
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}
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func (l *Leadership) onElection(elected bool) {
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if elected {
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log.Infof("Node %s elected leader ♚", l.Cluster.Node)
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l.leader.Set(true)
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l.Start()
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} else {
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log.Infof("Node %s elected worker ♝", l.Cluster.Node)
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l.leader.Set(false)
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l.Stop()
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}
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for _, listener := range l.listeners {
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err := listener(elected)
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if err != nil {
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log.Errorf("Error calling Leadership listener: %s", err)
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}
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}
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}
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// IsLeader returns true if current node is leader
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func (l *Leadership) IsLeader() bool {
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return l.leader.Get().(bool)
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}
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