| // Licensed to Apache Software Foundation (ASF) under one or more contributor |
| // license agreements. See the NOTICE file distributed with |
| // this work for additional information regarding copyright |
| // ownership. Apache Software Foundation (ASF) licenses this file to you 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 lb |
| |
| import ( |
| "hash/crc32" |
| "sync" |
| |
| "google.golang.org/grpc/balancer" |
| "google.golang.org/grpc/balancer/base" |
| "google.golang.org/grpc/grpclog" |
| ) |
| |
| const Name = "satellite_lb" |
| |
| var logger = grpclog.Component(Name) |
| |
| func newBuilder() balancer.Builder { |
| return base.NewBalancerBuilder(Name, &satelliteDynamicPickerBuilder{}, base.Config{HealthCheck: true}) |
| } |
| |
| func init() { |
| balancer.Register(newBuilder()) |
| } |
| |
| type satelliteDynamicPickerBuilder struct { |
| } |
| |
| func (s *satelliteDynamicPickerBuilder) Build(info base.PickerBuildInfo) balancer.Picker { |
| logger.Infof("ready to build a new picker: %v", info) |
| if len(info.ReadySCs) == 0 { |
| return base.NewErrPicker(balancer.ErrNoSubConnAvailable) |
| } |
| |
| addrToConn := make(map[string]balancer.SubConn) |
| cons := make([]*connectionWrap, 0) |
| for conn, connInfo := range info.ReadySCs { |
| addrToConn[connInfo.Address.Addr] = conn |
| cons = append(cons, &connectionWrap{ |
| addr: connInfo.Address.Addr, |
| conn: conn, |
| }) |
| } |
| |
| return &satelliteDynamicPicker{ |
| cons: cons, |
| addrToConn: addrToConn, |
| connCount: len(cons), |
| } |
| } |
| |
| type satelliteDynamicPicker struct { |
| cons []*connectionWrap |
| addrToConn map[string]balancer.SubConn |
| connCount int |
| |
| mu sync.Mutex |
| next int |
| } |
| |
| type connectionWrap struct { |
| addr string |
| conn balancer.SubConn |
| } |
| |
| func (s *satelliteDynamicPicker) Pick(info balancer.PickInfo) (balancer.PickResult, error) { |
| // only one connection |
| if s.connCount == 1 { |
| return balancer.PickResult{SubConn: s.cons[0].conn}, nil |
| } |
| |
| config := queryConfig(info.Ctx) |
| // if not exists config just round-robin the connection |
| if config == nil { |
| return s.roundRobinConnection(), nil |
| } |
| |
| // check exists appoint address |
| if config.appointAddr != "" { |
| if con := s.addrToConn[config.appointAddr]; con != nil { |
| return balancer.PickResult{SubConn: con}, nil |
| } |
| } |
| |
| // hash the route key |
| routeIndex := hashCode(config.routeKey) % s.connCount |
| connWrap := s.cons[routeIndex] |
| // update the address to the config |
| config.appointAddr = connWrap.addr |
| return balancer.PickResult{SubConn: connWrap.conn}, nil |
| } |
| |
| func (s *satelliteDynamicPicker) roundRobinConnection() balancer.PickResult { |
| s.mu.Lock() |
| sc := s.cons[s.next] |
| s.next = (s.next + 1) % s.connCount |
| s.mu.Unlock() |
| return balancer.PickResult{SubConn: sc.conn} |
| } |
| |
| func hashCode(s string) int { |
| v := int(crc32.ChecksumIEEE([]byte(s))) |
| if v >= 0 { |
| return v |
| } |
| if -v >= 0 { |
| return -v |
| } |
| return 0 |
| } |