本篇内容介绍了“dubbo-go中ConsistentHashLoadBalance的用法”的有关知识，在实际案例的操作过程中，不少人都会遇到这样的困境，接下来就让小编带领大家学习一下如何处理这些情况吧！希望大家仔细阅读，能够学有所成！
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本文主要研究一下dubbo-go的ConsistentHashLoadBalance
dubbo-go-v1.4.2/cluster/loadbalance/consistent_hash.go
const (
// ConsistentHash ...
ConsistentHash = "consistenthash"
// HashNodes ...
HashNodes = "hash.nodes"
// HashArguments ...
HashArguments = "hash.arguments"
)
var (
selectors = make(map[string]*ConsistentHashSelector)
re = regexp.MustCompile(constant.COMMA_SPLIT_PATTERN)
)
func init() {
extension.SetLoadbalance(ConsistentHash, NewConsistentHashLoadBalance)
}
// ConsistentHashLoadBalance ...
type ConsistentHashLoadBalance struct {
}
// NewConsistentHashLoadBalance ...
func NewConsistentHashLoadBalance() cluster.LoadBalance {
return &ConsistentHashLoadBalance{}
}ConsistentHashLoadBalance的init方法设置了名为consistenthash的ConsistentHashLoadBalance到extension中
dubbo-go-v1.4.2/cluster/loadbalance/consistent_hash.go
// Select ...
func (lb *ConsistentHashLoadBalance) Select(invokers []protocol.Invoker, invocation protocol.Invocation) protocol.Invoker {
methodName := invocation.MethodName()
key := invokers[0].GetUrl().ServiceKey() + "." + methodName
// hash the invokers
bs := make([]byte, 0)
for _, invoker := range invokers {
b, err := json.Marshal(invoker)
if err != nil {
return nil
}
bs = append(bs, b...)
}
hashCode := crc32.ChecksumIEEE(bs)
selector, ok := selectors[key]
if !ok || selector.hashCode != hashCode {
selectors[key] = newConsistentHashSelector(invokers, methodName, hashCode)
selector = selectors[key]
}
return selector.Select(invocation)
}Select方法遍历invokers挨个执行json.Marshal(invoker)，将bytes[]添加到bs中，之后通过crc32.ChecksumIEEE(bs)计算hashCode，然后对比selectors[key]的hashCode与计算出来的hashCode是否一致，不一致则通过newConsistentHashSelector重新设置一个，最后执行selector.Select(invocation)
dubbo-go-v1.4.2/cluster/loadbalance/consistent_hash.go
// ConsistentHashSelector ...
type ConsistentHashSelector struct {
hashCode uint32
replicaNum int
virtualInvokers map[uint32]protocol.Invoker
keys Uint32Slice
argumentIndex []int
}ConsistentHashSelector定义了hashCode、replicaNum、virtualInvokers、keys、argumentIndex属性
dubbo-go-v1.4.2/cluster/loadbalance/consistent_hash.go
func newConsistentHashSelector(invokers []protocol.Invoker, methodName string,
hashCode uint32) *ConsistentHashSelector {
selector := &ConsistentHashSelector{}
selector.virtualInvokers = make(map[uint32]protocol.Invoker)
selector.hashCode = hashCode
url := invokers[0].GetUrl()
selector.replicaNum = int(url.GetMethodParamInt(methodName, HashNodes, 160))
indices := re.Split(url.GetMethodParam(methodName, HashArguments, "0"), -1)
for _, index := range indices {
i, err := strconv.Atoi(index)
if err != nil {
return nil
}
selector.argumentIndex = append(selector.argumentIndex, i)
}
for _, invoker := range invokers {
u := invoker.GetUrl()
address := u.Ip + ":" + u.Port
for i := 0; i < selector.replicaNum/4; i++ {
digest := md5.Sum([]byte(address + strconv.Itoa(i)))
for j := 0; j < 4; j++ {
key := selector.hash(digest, j)
selector.keys = append(selector.keys, key)
selector.virtualInvokers[key] = invoker
}
}
}
sort.Sort(selector.keys)
return selector
}newConsistentHashSelector方法实例化ConsistentHashSelector，并初始化virtualInvokers、hashCode、argumentIndex、keys、virtualInvokers属性
dubbo-go-v1.4.2/cluster/loadbalance/consistent_hash.go
// Select ...
func (c *ConsistentHashSelector) Select(invocation protocol.Invocation) protocol.Invoker {
key := c.toKey(invocation.Arguments())
digest := md5.Sum([]byte(key))
return c.selectForKey(c.hash(digest, 0))
}
func (c *ConsistentHashSelector) toKey(args []interface{}) string {
var sb strings.Builder
for i := range c.argumentIndex {
if i >= 0 && i < len(args) {
fmt.Fprint(&sb, args[i].(string))
}
}
return sb.String()
}
func (c *ConsistentHashSelector) selectForKey(hash uint32) protocol.Invoker {
idx := sort.Search(len(c.keys), func(i int) bool {
return c.keys[i] >= hash
})
if idx == len(c.keys) {
idx = 0
}
return c.virtualInvokers[c.keys[idx]]
}
func (c *ConsistentHashSelector) hash(digest [16]byte, i int) uint32 {
return uint32((digest[3+i*4]&0xFF)<<24) | uint32((digest[2+i*4]&0xFF)<<16) |
uint32((digest[1+i*4]&0xFF)<<8) | uint32(digest[i*4]&0xFF)&0xFFFFFFF
}Select方法通过c.toKey(invocation.Arguments())获取key，再通过md5.Sum([]byte(key))计算digest，最后通过c.selectForKey(c.hash(digest, 0))选取Invoker
ConsistentHashLoadBalance的Select方法遍历invokers挨个执行json.Marshal(invoker)，将bytes[]添加到bs中，之后通过crc32.ChecksumIEEE(bs)计算hashCode，然后对比selectors[key]的hashCode与计算出来的hashCode是否一致，不一致则通过newConsistentHashSelector重新设置一个，最后执行selector.Select(invocation)
“dubbo-go中ConsistentHashLoadBalance的用法”的内容就介绍到这里了，感谢大家的阅读。如果想了解更多行业相关的知识可以关注创新互联网站，小编将为大家输出更多高质量的实用文章！
