stats.go

package hedgedhttp

import "sync/atomic"

// atomicCounter is a false sharing safe counter.
type atomicCounter struct {
	count uint64
	_     [7]uint64
}

type cacheLine [64]byte

// Stats object that can be queried to obtain certain metrics and get better observability.
type Stats struct {
	_                        cacheLine
	requestedRoundTrips      atomicCounter
	actualRoundTrips         atomicCounter
	failedRoundTrips         atomicCounter
	originalRequestWins      atomicCounter
	hedgedRequestWins        atomicCounter
	canceledByUserRoundTrips atomicCounter
	canceledSubRequests      atomicCounter
	_                        cacheLine
}

func (s *Stats) requestedRoundTripsInc()      { atomic.AddUint64(&s.requestedRoundTrips.count, 1) }
func (s *Stats) actualRoundTripsInc()         { atomic.AddUint64(&s.actualRoundTrips.count, 1) }
func (s *Stats) failedRoundTripsInc()         { atomic.AddUint64(&s.failedRoundTrips.count, 1) }
func (s *Stats) originalRequestWinsInc()      { atomic.AddUint64(&s.originalRequestWins.count, 1) }
func (s *Stats) hedgedRequestWinsInc()        { atomic.AddUint64(&s.hedgedRequestWins.count, 1) }
func (s *Stats) canceledByUserRoundTripsInc() { atomic.AddUint64(&s.canceledByUserRoundTrips.count, 1) }
func (s *Stats) canceledSubRequestsInc()      { atomic.AddUint64(&s.canceledSubRequests.count, 1) }

// RequestedRoundTrips returns count of requests that were requested by client.
func (s *Stats) RequestedRoundTrips() uint64 {
	return atomic.LoadUint64(&s.requestedRoundTrips.count)
}

// ActualRoundTrips returns count of requests that were actually sent.
func (s *Stats) ActualRoundTrips() uint64 {
	return atomic.LoadUint64(&s.actualRoundTrips.count)
}

// FailedRoundTrips returns count of requests that failed.
func (s *Stats) FailedRoundTrips() uint64 {
	return atomic.LoadUint64(&s.failedRoundTrips.count)
}

// OriginalRequestWins returns count of original requests that were faster than the original.
func (s *Stats) OriginalRequestWins() uint64 {
	return atomic.LoadUint64(&s.originalRequestWins.count)
}

// HedgedRequestWins returns count of hedged requests that were faster than the original.
func (s *Stats) HedgedRequestWins() uint64 {
	return atomic.LoadUint64(&s.hedgedRequestWins.count)
}

// CanceledByUserRoundTrips returns count of requests that were canceled by user, using request context.
func (s *Stats) CanceledByUserRoundTrips() uint64 {
	return atomic.LoadUint64(&s.canceledByUserRoundTrips.count)
}

// CanceledSubRequests returns count of hedged sub-requests that were canceled by transport.
func (s *Stats) CanceledSubRequests() uint64 {
	return atomic.LoadUint64(&s.canceledSubRequests.count)
}