Couchbase work out a set of keys that are guaranteed to write to all vBuckets

vbmap_test.go

// from github.com/go-couchbase
// Copyright (c) 2013  Couchbase, Inc.
//
package couchbase

import (
	"fmt"
	"testing"
	"unsafe"
)

func testBucket() Bucket {
	b := Bucket{vBucketServerMap: unsafe.Pointer(&VBucketServerMap{
		VBucketMap: make([][]int, 2048),
	})}
	return b
}

/*
key: k0 master: 10.1.7.1:11210 vBucketId: 9 couchApiBase: http://10.1.7.1:8092/default replicas: 10.1.7.2:11210
key: k1 master: 10.1.7.1:11210 vBucketId: 14 couchApiBase: http://10.1.7.1:8092/default replicas: 10.1.7.3:11210
key: k2 master: 10.1.7.1:11210 vBucketId: 7 couchApiBase: http://10.1.7.1:8092/default replicas: 10.1.7.2:11210
key: k3 master: 10.1.7.1:11210 vBucketId: 0 couchApiBase: http://10.1.7.1:8092/default replicas: 10.1.7.2:11210
key: k4 master: 10.1.7.2:11210 vBucketId: 100 couchApiBase: http://10.1.7.2:8092/default replicas: 10.1.7.5:11210
key: k5 master: 10.1.7.2:11210 vBucketId: 99 couchApiBase: http://10.1.7.2:8092/default replicas: 10.1.7.5:11210
*/

func TestVBHash(t *testing.T) {
	b := testBucket()
	// m := map[string]uint32{
	// 	"k0": 9,
	// 	"k1": 14,
	// 	"k2": 7,
	// 	"k3": 0,
	// 	"k4": 100,
	// 	"k5": 99,
	// }

	// for k, v := range m {
	// 	assert(t, k, b.VBHash(k), v)
	// }

	hit := map[uint32]string{}

	for n := 0; n < 100000000; n++ {
		key := fmt.Sprintf("vbfill-%d", n)
		bid := b.VBHash(key)
		_, ok := hit[bid]
		if !ok {
			hit[bid] = key
			// fmt.Println("another", key)
			if len(hit) == 2048 {
				break
			}
			// fmt.Println("len", len(hit))
		}
	}

	if len(hit) != 2048 {
		t.Error("not enough")
	}

	for _, v := range hit {
		fmt.Printf("\"%v\",\n", v)
	}
}

because of this...
https://issues.couchbase.com/browse/MB-12931