Playing around with mid write crashing.

test.go

package main

import (
	"encoding/json"
	"fmt"
	"log"
	"math/rand"
	"os"
	"time"
)

func genNumbers(n int) []int {
	words := make([]int, n)
	for i := 0; i < n; i++ {
		words[i] = rand.Intn(n)
	}
	return words
}

func writeFile(data []byte, filename string) error {
	file, err := os.Create(filename)
	if err != nil {
		return err
	}
	defer file.Close()
	fmt.Println("@@@ commencing file write @@@")
	_, err = file.Write(data)
	return err
}

var lastTime time.Time

func printTime(msg string) {
	current := time.Now()
	fmt.Println(msg, "took", current.Sub(lastTime))
	lastTime = current
}

func spawnRandomCrash(n int) {
	timeUntilCrash := rand.Intn(n)
	<-time.After(time.Duration(timeUntilCrash) * time.Millisecond)
	os.Exit(1)
}

// Test for failures with the following:
// go build test.go && ./test; cat test.json | json_verify
//
// Which should produce somtthing like this:
//
// $ go build test.go && ./test; cat test.json | json_verify
// genNumbers took 341.819596ms
// marshal took 560.629396ms
// @@@ commencing file write @@@
// lexical error: invalid char in json text.
//                                         931774,5077342,4984661,1921838
//                      (right here) ------^
// JSON is invalid
//
// If JSON is valid, you will likely want to tweak the param to spawnRandomCrash to be
// close to the time to took to run writeFile.

func main() {
	lastTime = time.Now()
	words := genNumbers(10000000)
	printTime("genNumbers")

	data, err := json.Marshal(words)
	if err != nil {
		log.Fatal(err)
	}
	printTime("marshal")

	go spawnRandomCrash(30)

	err = writeFile(data, "test.json")
	if err != nil {
		log.Fatal(err)
	}
	printTime("writeFile")
}