// Attempts to claim a lock. If the overrideLock is set, any existing lock holder
// will be destroyed and one more attempt will be made to acquire the lock
func (r Replicator) lock(lock kp.Lock, lockPath string, overrideLock bool) error {
err := lock.Lock(lockPath)
if _, ok := err.(kp.AlreadyLockedError); ok {
holder, id, err := r.Store.LockHolder(lockPath)
if err != nil {
return util.Errorf("Lock already held for %q, could not determine holder due to error: %s", lockPath, err)
} else if holder == "" {
// we failed to acquire this lock, but there is no outstanding
// holder
// this indicates that the previous holder had a LockDelay,
// which prevents other parties from acquiring the lock for a
// limited time
return util.Errorf("Lock for %q is blocked due to delay by previous holder", lockPath)
} else if overrideLock {
err = r.Store.DestroyLockHolder(id)
if err != nil {
return util.Errorf("Unable to destroy the current lock holder (%s) for %q: %s", holder, lockPath, err)
}
// try acquiring the lock again, but this time don't destroy holders so we don't try forever
return r.lock(lock, lockPath, false)
} else {
return util.Errorf("Lock for %q already held by lock %q", lockPath, holder)
}
}
return err
}
// Listen for errors in lock renewal. If the lock can't be renewed, we need to
// 1) stop replication and 2) communicate the error up a level
// If replication finishes, destroy the lock
func (r replication) handleRenewalErrors(lock kp.Lock, renewalErrCh chan error) {
defer func() {
close(r.quitCh)
close(r.errCh)
lock.Destroy()
}()
select {
case <-r.replicationDoneCh:
case <-r.replicationCancelledCh:
case err := <-renewalErrCh:
// communicate the error to the caller.
r.errCh <- replicationError{
err: err,
isFatal: true,
}
return
}
}