example/main.go

package main

import (
	"fmt"
	"runtime"
	"time"

	"github.com/smartystreets/go-disruptor"
)

const (
	BufferSize = 1024 * 64
	BufferMask = BufferSize - 1
	Iterations = 1000000 * 100
)

var ringBuffer = [BufferSize]int64{}

func main() {
	runtime.GOMAXPROCS(2)

	written, read := disruptor.NewCursor(), disruptor.NewCursor()
	started := time.Now()

	go consume(written, read, SampleConsumer{})
	publish(written, read)

	finished := time.Now()
	fmt.Println(Iterations, finished.Sub(started))

	time.Sleep(time.Millisecond * 10)
}

func publish(written, read *disruptor.Cursor) {
	previous := disruptor.InitialSequenceValue
	gate := disruptor.InitialSequenceValue

	for previous <= Iterations {
		next := previous + 1
		wrap := next - BufferSize

		for wrap > gate {
			gate = read.Sequence
		}

		ringBuffer[next&BufferMask] = next
		written.Sequence = next
		previous = next
	}
}

func consume(written, read *disruptor.Cursor, consumer disruptor.Consumer) {
	previous := int64(-1)
	upstream := disruptor.Barrier(written)
	idling, gating := 0, 0

	for {
		lower := previous + 1
		upper := upstream.Read(lower)

		if lower <= upper {
			consumer.Consume(lower, upper)
			read.Sequence = upper
			previous = upper
		} else if upper = written.Load(); lower <= upper {
			// Gating--TODO: wait strategy (provide gating count to wait strategy for phased backoff)
			gating++
			idling = 0
		} else if previous < Iterations {
			// Idling--TODO: wait strategy (provide idling count to wait strategy for phased backoff)
			idling++
			gating = 0
		} else {
			break
		}

		time.Sleep(time.Nanosecond)
	}

	// for previous < Iterations {
	// 	lower := previous + 1
	// 	upper := upstream.Read(lower)

	// 	if lower <= upper {
	// 		consumer.Consume(lower, upper)
	// 		read.Sequence = upper
	// 		previous = upper
	// 	} else if upper = written.Sequence; lower <= upper {
	// 		// TODO: gating strategy
	// 	} else {
	// 		// TODO: idling strategy
	// 		idling++
	// 	}

	// 	time.Sleep(time.Nanosecond)
	// }

	fmt.Println("Consumer idling/gating", idling, gating)
}

type SampleConsumer struct{}

func (this SampleConsumer) Consume(lower, upper int64) {
	for lower <= upper {
		message := ringBuffer[lower&BufferMask]
		if message != lower {
			fmt.Println("Race condition", message, lower)
			panic("Race condition")
		}
		lower++
	}
}