pi-reduce

main.go

package main

import (
	"encoding/json"
	"fmt"
	"github.com/iron-io/iron_go/worker"
	"github.com/iron-io/iron_go3/mq"
	"math/big"
	"time"
)

type PiChunks struct {
	Begin  int
	End    int
	Result string
}

type Payload struct {
	Num_of_1k_runs int
}

func GetMsgsFrom(mqName string) []mq.Message {
	q := mq.New(mqName)
	msgs, err := q.GetN(10)
	if err != nil {
		fmt.Println("Error retrieving from MQ: ", err)
	}
	return msgs
}

func WaitForFullMQ(mqName string) {
	var lastSize int
	for lastSize >= expectedSize { //gt prevents an infinite loop
		time.Sleep(12 * time.Second)
		fmt.Println("Waiting for MQ to fill.")
		q := mq.New(mqName)
		info, err := q.Info()
		if err != nil {
			fmt.Println("MQ info error: ", err)
			break
		}
		lastSize = info.Size
	}
}

func IsMQEmpty(mqName string) bool {
	q := mq.New(mqName)
	info, err := q.Info()
	if err != nil {
		fmt.Println("MQ info error: ", err)
	}
	if info.Size > 0 {
		return false
	} else {
		return true
	}
}

func readPayload() int {
	worker.ParseFlags()
	p := &Payload{}
	worker.PayloadFromJSON(p)
	return p.Num_of_1k_runs
}

var expectedSize int = readPayload()
var queueName string = "pi-map-first"

func main() {
	sum := new(big.Rat)
	WaitForFullMQ(queueName) //wait for all calcs

	for IsMQEmpty(queueName) {
		msgs := GetMsgsFrom(queueName) //reserve msgs
		for _, msg := range msgs {
			var p PiChunks
			err := json.Unmarshal([]byte(msg.Body), &p)
			if err != nil {
				fmt.Println("Unmarshalling msgs error: ", err)
			}
			byteFraction := []byte(p.Result)
			leibnizRat := new(big.Rat)
			if err := leibnizRat.UnmarshalText(byteFraction); err != nil {
				fmt.Println("Unmarshaling byteFraction error: ", err)
			}
			sum.Add(sum, leibnizRat)
			if err := msg.Delete(); err != nil { //acknowledge success
				fmt.Println("Delete msg error: ", err)
			}
		}
	}
	sumToFloat, _ := sum.Float64()
	result := 4 + 4*sumToFloat // complete the infinite series
	fmt.Println("Pi is approx: ", result)
}