示例#1
0
// NewTransaction creates a new transaction. The transaction key is
// composed using the specified baseKey (for locality with data
// affected by the transaction) and a random UUID to guarantee
// uniqueness. The specified user-level priority is combined with
// a randomly chosen value to yield a final priority, used to settle
// write conflicts in a way that avoids starvation of long-running
// transactions (see Range.InternalPushTxn).
func NewTransaction(baseKey engine.Key, userPriority int32,
	isolation proto.IsolationType, clock *hlc.Clock) *proto.Transaction {
	// Compute priority by adjusting based on userPriority factor.
	if userPriority < 1 {
		userPriority = 1
	}
	priority := math.MaxInt32 - util.CachedRand.Int31n(math.MaxInt32/userPriority)
	// Compute timestamp and max timestamp.
	now := clock.Now()
	max := now
	max.WallTime += clock.MaxDrift().Nanoseconds()

	return &proto.Transaction{
		ID:           append(baseKey, []byte(uuid.New())...),
		Priority:     priority,
		Isolation:    isolation,
		Timestamp:    now,
		MaxTimestamp: max,
	}
}
示例#2
0
// Clear clears the cache and resets the high water mark to the
// current time plus the maximum clock skew.
func (tc *TimestampCache) Clear(clock *hlc.Clock) {
	tc.cache.Clear()
	tc.highWater = clock.Now()
	tc.highWater.WallTime += clock.MaxDrift().Nanoseconds()
	tc.latest = tc.highWater
}