140 lines
3.8 KiB
Go
140 lines
3.8 KiB
Go
/*
|
|
* Copyright 2022 The Dragonfly Authors
|
|
*
|
|
* Licensed under the Apache License, Version 2.0 (the "License");
|
|
* you may not use this file except in compliance with the License.
|
|
* You may obtain a copy of the License at
|
|
*
|
|
* http://www.apache.org/licenses/LICENSE-2.0
|
|
*
|
|
* Unless required by applicable law or agreed to in writing, software
|
|
* distributed under the License is distributed on an "AS IS" BASIS,
|
|
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
|
|
* See the License for the specific language governing permissions and
|
|
* limitations under the License.
|
|
*/
|
|
|
|
package balancer
|
|
|
|
import (
|
|
"errors"
|
|
"fmt"
|
|
"reflect"
|
|
|
|
"google.golang.org/grpc/balancer"
|
|
"google.golang.org/grpc/balancer/base"
|
|
"google.golang.org/grpc/grpclog"
|
|
"stathat.com/c/consistent"
|
|
)
|
|
|
|
type ContextKeyType string
|
|
|
|
const (
|
|
// BalancerName is the name of consistent-hashing balancer.
|
|
BalancerName = "consistent-hashing"
|
|
|
|
// BalancerServiceConfig is a service config that sets the default balancer
|
|
// to the consistent-hashing balancer.
|
|
BalancerServiceConfig = `{"loadBalancingPolicy":"consistent-hashing"}`
|
|
|
|
// ContextKey is the key for the grpc request's context.Context which points to
|
|
// the key to hash for the request.
|
|
ContextKey = ContextKeyType("consistent-hashing-key")
|
|
)
|
|
|
|
// searchCircleLimit is the limit of searching circle.
|
|
const searchCircleLimit = 10
|
|
|
|
var logger = grpclog.Component("consistenthashing")
|
|
|
|
// NewConsistentHashingBuilder creates a new consistent-hashing balancer builder.
|
|
func NewConsistentHashingBuilder() (balancer.Builder, *ConsistentHashingPickerBuilder) {
|
|
pickerBuilder := &ConsistentHashingPickerBuilder{}
|
|
return base.NewBalancerBuilder(
|
|
BalancerName,
|
|
pickerBuilder,
|
|
base.Config{HealthCheck: true},
|
|
), pickerBuilder
|
|
}
|
|
|
|
type ConsistentHashingPickerBuilder struct {
|
|
hashring *consistent.Consistent
|
|
members []string
|
|
circle map[string]string
|
|
}
|
|
|
|
func (b *ConsistentHashingPickerBuilder) Build(info base.PickerBuildInfo) balancer.Picker {
|
|
logger.Infof("consistentHashingPicker: newPicker called with info: %v", info)
|
|
if len(info.ReadySCs) == 0 {
|
|
return base.NewErrPicker(balancer.ErrNoSubConnAvailable)
|
|
}
|
|
|
|
// Build hashring and init sub connections map.
|
|
b.hashring = consistent.New()
|
|
scs := make(map[string]balancer.SubConn, len(info.ReadySCs))
|
|
for sc, scInfo := range info.ReadySCs {
|
|
element := fmt.Sprintf("%s:%s", scInfo.Address.Addr, scInfo.Address.ServerName)
|
|
b.hashring.Add(element)
|
|
scs[element] = sc
|
|
}
|
|
|
|
return &consistentHashingPicker{
|
|
subConns: scs,
|
|
hashring: b.hashring,
|
|
}
|
|
}
|
|
|
|
func (b *ConsistentHashingPickerBuilder) GetCircle() (map[string]string, error) {
|
|
if b.hashring == nil {
|
|
return nil, errors.New("invalid hashring")
|
|
}
|
|
|
|
members := b.hashring.Members()
|
|
if reflect.DeepEqual(b.members, members) {
|
|
return b.circle, nil
|
|
}
|
|
|
|
circle := make(map[string]string, len(members))
|
|
for i := 0; i <= len(members)*searchCircleLimit; i++ {
|
|
key := fmt.Sprint(i)
|
|
member, err := b.hashring.Get(key)
|
|
if err != nil {
|
|
logger.Errorf("hashring get member failed: %s", err.Error())
|
|
continue
|
|
}
|
|
|
|
if _, ok := circle[member]; !ok {
|
|
circle[member] = key
|
|
if len(circle) == len(members) {
|
|
b.members = members
|
|
b.circle = circle
|
|
return circle, nil
|
|
}
|
|
}
|
|
}
|
|
|
|
return nil, errors.New("can not generate circle")
|
|
}
|
|
|
|
type consistentHashingPicker struct {
|
|
subConns map[string]balancer.SubConn
|
|
hashring *consistent.Consistent
|
|
}
|
|
|
|
func (p *consistentHashingPicker) Pick(info balancer.PickInfo) (balancer.PickResult, error) {
|
|
taskID, ok := info.Ctx.Value(ContextKey).(string)
|
|
if !ok {
|
|
return balancer.PickResult{}, errors.New("picker can not found task id")
|
|
}
|
|
|
|
element, err := p.hashring.Get(taskID)
|
|
if err != nil {
|
|
return balancer.PickResult{}, err
|
|
}
|
|
logger.Infof("task %s picks connection %s", taskID, element)
|
|
|
|
return balancer.PickResult{
|
|
SubConn: p.subConns[element],
|
|
}, nil
|
|
}
|