datahub/shard.go

package datahub

import (
	"fmt"
	"math/big"
	"strings"
)

type ShardEntry struct {
	ShardId        string     `json:"ShardId"`
	State          ShardState `json:"State"`
	BeginHashKey   string     `json:"BeginHashKey"`
	EndHashKey     string     `json:"EndHashKey"`
	ClosedTime     int64      `json:"ClosedTime"`
	ParentShardIds []string   `json:"ParentShardIds"`
	LeftShardId    string     `json:"LeftShardId"`
	RightShardId   string     `json:"RightShardId"`
	Address        string     `json:"Address"`
}

func generateSpliteKey(projectName, topicName, shardId string, datahub DataHubApi) (string, error) {
	ls, err := datahub.ListShard(projectName, topicName)
	if err != nil {
		return "", err
	}
	shards := ls.Shards
	splitKey := ""
	for _, shard := range shards {
		if strings.EqualFold(shardId, shard.ShardId) {
			if shard.State != ACTIVE {
				return "", fmt.Errorf("only active shard can be split,the shard %s state is %s", shard.ShardId, shard.State)
			}
			splitKey, err = getSplitKey(shard.BeginHashKey, shard.EndHashKey)
			splitKey = strings.ToUpper(splitKey)
			if err != nil {
				return "", err
			}
		}
	}
	if splitKey == "" {
		return "", fmt.Errorf("shard not exist")
	}
	return splitKey, nil
}

func getSplitKey(beginHashKey, endHashKey string) (string, error) {
	var begin, end, sum, quo big.Int
	base := 16

	if len(beginHashKey) != 32 || len(endHashKey) != 32 {
		return "", fmt.Errorf("invalid Hash Key Range")
	}
	_, ok := begin.SetString(beginHashKey, base)
	if !ok {
		return "", fmt.Errorf("invalid Hash Key Range")
	}
	_, ok = end.SetString(endHashKey, base)
	if !ok {
		return "", fmt.Errorf("invalid Hash Key Range")
	}

	sum.Add(&begin, &end)
	quo.Quo(&sum, big.NewInt(2))
	return quo.Text(base), nil

}