mirror of https://github.com/hashicorp/consul
141 lines
2.7 KiB
Go
141 lines
2.7 KiB
Go
package controller
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import (
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"context"
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"time"
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"github.com/hashicorp/consul/lib/retry"
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)
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// flapThreshold is the minimum amount of time between restarts for us *not* to
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// consider a controller to be stuck in a crash-loop.
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const flapThreshold = 2 * time.Second
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// supervisor keeps a task running, restarting it on-error, for as long as the
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// given lease is held. When the lease is lost, the context given to the task
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// will be canceled. If the task persistently fails (i.e. the controller is in
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// a crash-loop) supervisor will use exponential backoff to delay restarts.
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type supervisor struct {
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task task
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lease Lease
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running bool
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startedAt time.Time
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errCh chan error
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cancelTask context.CancelFunc
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backoff *retry.Waiter
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backoffUntil time.Time
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backoffTimerCh <-chan time.Time
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}
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func newSupervisor(task task, lease Lease) *supervisor {
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return &supervisor{
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task: task,
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lease: lease,
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errCh: make(chan error),
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backoff: &retry.Waiter{
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MinFailures: 1,
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MinWait: 500 * time.Millisecond,
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MaxWait: time.Minute,
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Jitter: retry.NewJitter(25),
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},
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}
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}
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type task func(context.Context) error
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func (s *supervisor) run(ctx context.Context) {
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for {
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if s.shouldStart() {
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s.startTask(ctx)
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} else if s.shouldStop() {
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s.stopTask()
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}
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select {
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// Outer context canceled.
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case <-ctx.Done():
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if s.cancelTask != nil {
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s.cancelTask()
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}
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return
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// Task stopped running.
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case <-s.errCh:
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stopBackoffTimer := s.handleError()
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if stopBackoffTimer != nil {
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defer stopBackoffTimer()
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}
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// Unblock when the lease is acquired/lost, or the backoff timer fires.
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case <-s.lease.Changed():
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case <-s.backoffTimerCh:
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}
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}
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}
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func (s *supervisor) shouldStart() bool {
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if s.running {
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return false
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}
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if !s.lease.Held() {
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return false
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}
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if time.Now().Before(s.backoffUntil) {
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return false
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}
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return true
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}
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func (s *supervisor) startTask(ctx context.Context) {
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if s.cancelTask != nil {
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s.cancelTask()
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}
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taskCtx, cancelTask := context.WithCancel(ctx)
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s.cancelTask = cancelTask
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s.startedAt = time.Now()
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s.running = true
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go func() {
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err := s.task(taskCtx)
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select {
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case s.errCh <- err:
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case <-ctx.Done():
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}
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}()
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}
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func (s *supervisor) shouldStop() bool {
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return s.running && !s.lease.Held()
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}
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func (s *supervisor) stopTask() {
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s.cancelTask()
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s.backoff.Reset()
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s.running = false
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}
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func (s *supervisor) handleError() func() bool {
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s.running = false
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if time.Since(s.startedAt) > flapThreshold {
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s.backoff.Reset()
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s.backoffUntil = time.Time{}
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} else {
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delay := s.backoff.WaitDuration()
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s.backoffUntil = time.Now().Add(delay)
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timer := time.NewTimer(delay)
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s.backoffTimerCh = timer.C
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return timer.Stop
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}
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return nil
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}
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