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