Package org.apache.cassandra.transport

Interface QueueBackpressure

public interface QueueBackpressure

Native Queue Backpressure mechanism. If the queue fills up above DatabaseDescriptor.getNativeTransportQueueMaxItemAgeThreshold(). In other words, request has been sitting more than a % of DatabaseDescriptor.getNativeTransportQueueMaxItemAgeThreshold() in the queue, we start an incident.

Incident starts by marking the incident time and raising severity level to 1. Each time we observe an old item in the head of the queue, we first bump then number of times we have applied the backpressure. After bumping it 10 times, we increase severity level by 1.

Backpressure delay applied to the client socket is computed by multiplying the severity level by the minimum delay.

If we have not seen old requests in the head of the queue for 1 second, we close the incident.

If the queue remains saturated for a prolonged period (meaning returns false), the amount of delay will increase in proportion to the request rate as appliedTimes & severityLevel are incremented. If no new requests are considered overloaded in this way for a second, the incident will be reset and so the delay will drop back down to {@link Impl#minDelayNanos()}.

Nested Class Summary

Nested Classes

Modifier and Type	Interface	Description
static class	QueueBackpressure.Impl

Field Summary

Fields

Modifier and Type	Field	Description
static QueueBackpressure	DEFAULT
static QueueBackpressure	NO_OP

Method Summary

Modifier and Type	Method	Description
long	markAndGetDelay(java.util.concurrent.TimeUnit timeUnit)
static QueueBackpressure.Impl	noBackpressure(java.util.function.LongSupplier minDelayNanos, java.util.function.LongSupplier maxDelayNanos)

Field Detail

NO_OP

static final QueueBackpressure NO_OP

DEFAULT

static final QueueBackpressure DEFAULT

Method Detail

markAndGetDelay

long markAndGetDelay(java.util.concurrent.TimeUnit timeUnit)

noBackpressure

static QueueBackpressure.Impl noBackpressure(java.util.function.LongSupplier minDelayNanos,
                                             java.util.function.LongSupplier maxDelayNanos)