divyadesai | 81bb7ba | 2020-03-11 11:45:23 +0000 | [diff] [blame] | 1 | // Copyright 2018 The etcd Authors |
| 2 | // |
| 3 | // Licensed under the Apache License, Version 2.0 (the "License"); |
| 4 | // you may not use this file except in compliance with the License. |
| 5 | // You may obtain a copy of the License at |
| 6 | // |
| 7 | // http://www.apache.org/licenses/LICENSE-2.0 |
| 8 | // |
| 9 | // Unless required by applicable law or agreed to in writing, software |
| 10 | // distributed under the License is distributed on an "AS IS" BASIS, |
| 11 | // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| 12 | // See the License for the specific language governing permissions and |
| 13 | // limitations under the License. |
| 14 | |
| 15 | // Package balancer implements client balancer. |
| 16 | package balancer |
| 17 | |
| 18 | import ( |
| 19 | "strconv" |
| 20 | "sync" |
| 21 | "time" |
| 22 | |
David K. Bainbridge | e05cf0c | 2021-08-19 03:16:50 +0000 | [diff] [blame] | 23 | "github.com/coreos/etcd/clientv3/balancer/connectivity" |
| 24 | "github.com/coreos/etcd/clientv3/balancer/picker" |
divyadesai | 81bb7ba | 2020-03-11 11:45:23 +0000 | [diff] [blame] | 25 | |
| 26 | "go.uber.org/zap" |
| 27 | "google.golang.org/grpc/balancer" |
| 28 | grpcconnectivity "google.golang.org/grpc/connectivity" |
| 29 | "google.golang.org/grpc/resolver" |
| 30 | _ "google.golang.org/grpc/resolver/dns" // register DNS resolver |
| 31 | _ "google.golang.org/grpc/resolver/passthrough" // register passthrough resolver |
| 32 | ) |
| 33 | |
| 34 | // Config defines balancer configurations. |
| 35 | type Config struct { |
| 36 | // Policy configures balancer policy. |
| 37 | Policy picker.Policy |
| 38 | |
| 39 | // Picker implements gRPC picker. |
| 40 | // Leave empty if "Policy" field is not custom. |
| 41 | // TODO: currently custom policy is not supported. |
| 42 | // Picker picker.Picker |
| 43 | |
| 44 | // Name defines an additional name for balancer. |
| 45 | // Useful for balancer testing to avoid register conflicts. |
| 46 | // If empty, defaults to policy name. |
| 47 | Name string |
| 48 | |
| 49 | // Logger configures balancer logging. |
| 50 | // If nil, logs are discarded. |
| 51 | Logger *zap.Logger |
| 52 | } |
| 53 | |
| 54 | // RegisterBuilder creates and registers a builder. Since this function calls balancer.Register, it |
| 55 | // must be invoked at initialization time. |
| 56 | func RegisterBuilder(cfg Config) { |
| 57 | bb := &builder{cfg} |
| 58 | balancer.Register(bb) |
| 59 | |
| 60 | bb.cfg.Logger.Debug( |
| 61 | "registered balancer", |
| 62 | zap.String("policy", bb.cfg.Policy.String()), |
| 63 | zap.String("name", bb.cfg.Name), |
| 64 | ) |
| 65 | } |
| 66 | |
| 67 | type builder struct { |
| 68 | cfg Config |
| 69 | } |
| 70 | |
| 71 | // Build is called initially when creating "ccBalancerWrapper". |
| 72 | // "grpc.Dial" is called to this client connection. |
| 73 | // Then, resolved addresses will be handled via "HandleResolvedAddrs". |
| 74 | func (b *builder) Build(cc balancer.ClientConn, opt balancer.BuildOptions) balancer.Balancer { |
| 75 | bb := &baseBalancer{ |
| 76 | id: strconv.FormatInt(time.Now().UnixNano(), 36), |
| 77 | policy: b.cfg.Policy, |
| 78 | name: b.cfg.Name, |
| 79 | lg: b.cfg.Logger, |
| 80 | |
| 81 | addrToSc: make(map[resolver.Address]balancer.SubConn), |
| 82 | scToAddr: make(map[balancer.SubConn]resolver.Address), |
| 83 | scToSt: make(map[balancer.SubConn]grpcconnectivity.State), |
| 84 | |
| 85 | currentConn: nil, |
| 86 | connectivityRecorder: connectivity.New(b.cfg.Logger), |
| 87 | |
| 88 | // initialize picker always returns "ErrNoSubConnAvailable" |
| 89 | picker: picker.NewErr(balancer.ErrNoSubConnAvailable), |
| 90 | } |
| 91 | |
| 92 | // TODO: support multiple connections |
| 93 | bb.mu.Lock() |
| 94 | bb.currentConn = cc |
| 95 | bb.mu.Unlock() |
| 96 | |
| 97 | bb.lg.Info( |
| 98 | "built balancer", |
| 99 | zap.String("balancer-id", bb.id), |
| 100 | zap.String("policy", bb.policy.String()), |
| 101 | zap.String("resolver-target", cc.Target()), |
| 102 | ) |
| 103 | return bb |
| 104 | } |
| 105 | |
| 106 | // Name implements "grpc/balancer.Builder" interface. |
| 107 | func (b *builder) Name() string { return b.cfg.Name } |
| 108 | |
| 109 | // Balancer defines client balancer interface. |
| 110 | type Balancer interface { |
| 111 | // Balancer is called on specified client connection. Client initiates gRPC |
| 112 | // connection with "grpc.Dial(addr, grpc.WithBalancerName)", and then those resolved |
| 113 | // addresses are passed to "grpc/balancer.Balancer.HandleResolvedAddrs". |
| 114 | // For each resolved address, balancer calls "balancer.ClientConn.NewSubConn". |
| 115 | // "grpc/balancer.Balancer.HandleSubConnStateChange" is called when connectivity state |
| 116 | // changes, thus requires failover logic in this method. |
| 117 | balancer.Balancer |
| 118 | |
| 119 | // Picker calls "Pick" for every client request. |
| 120 | picker.Picker |
| 121 | } |
| 122 | |
| 123 | type baseBalancer struct { |
| 124 | id string |
| 125 | policy picker.Policy |
| 126 | name string |
| 127 | lg *zap.Logger |
| 128 | |
| 129 | mu sync.RWMutex |
| 130 | |
| 131 | addrToSc map[resolver.Address]balancer.SubConn |
| 132 | scToAddr map[balancer.SubConn]resolver.Address |
| 133 | scToSt map[balancer.SubConn]grpcconnectivity.State |
| 134 | |
| 135 | currentConn balancer.ClientConn |
| 136 | connectivityRecorder connectivity.Recorder |
| 137 | |
| 138 | picker picker.Picker |
| 139 | } |
| 140 | |
| 141 | // HandleResolvedAddrs implements "grpc/balancer.Balancer" interface. |
| 142 | // gRPC sends initial or updated resolved addresses from "Build". |
| 143 | func (bb *baseBalancer) HandleResolvedAddrs(addrs []resolver.Address, err error) { |
| 144 | if err != nil { |
| 145 | bb.lg.Warn("HandleResolvedAddrs called with error", zap.String("balancer-id", bb.id), zap.Error(err)) |
| 146 | return |
| 147 | } |
| 148 | bb.lg.Info("resolved", |
| 149 | zap.String("picker", bb.picker.String()), |
| 150 | zap.String("balancer-id", bb.id), |
| 151 | zap.Strings("addresses", addrsToStrings(addrs)), |
| 152 | ) |
| 153 | |
| 154 | bb.mu.Lock() |
| 155 | defer bb.mu.Unlock() |
| 156 | |
| 157 | resolved := make(map[resolver.Address]struct{}) |
| 158 | for _, addr := range addrs { |
| 159 | resolved[addr] = struct{}{} |
| 160 | if _, ok := bb.addrToSc[addr]; !ok { |
| 161 | sc, err := bb.currentConn.NewSubConn([]resolver.Address{addr}, balancer.NewSubConnOptions{}) |
| 162 | if err != nil { |
| 163 | bb.lg.Warn("NewSubConn failed", zap.String("picker", bb.picker.String()), zap.String("balancer-id", bb.id), zap.Error(err), zap.String("address", addr.Addr)) |
| 164 | continue |
| 165 | } |
| 166 | bb.lg.Info("created subconn", zap.String("address", addr.Addr)) |
| 167 | bb.addrToSc[addr] = sc |
| 168 | bb.scToAddr[sc] = addr |
| 169 | bb.scToSt[sc] = grpcconnectivity.Idle |
| 170 | sc.Connect() |
| 171 | } |
| 172 | } |
| 173 | |
| 174 | for addr, sc := range bb.addrToSc { |
| 175 | if _, ok := resolved[addr]; !ok { |
| 176 | // was removed by resolver or failed to create subconn |
| 177 | bb.currentConn.RemoveSubConn(sc) |
| 178 | delete(bb.addrToSc, addr) |
| 179 | |
| 180 | bb.lg.Info( |
| 181 | "removed subconn", |
| 182 | zap.String("picker", bb.picker.String()), |
| 183 | zap.String("balancer-id", bb.id), |
| 184 | zap.String("address", addr.Addr), |
| 185 | zap.String("subconn", scToString(sc)), |
| 186 | ) |
| 187 | |
| 188 | // Keep the state of this sc in bb.scToSt until sc's state becomes Shutdown. |
| 189 | // The entry will be deleted in HandleSubConnStateChange. |
| 190 | // (DO NOT) delete(bb.scToAddr, sc) |
| 191 | // (DO NOT) delete(bb.scToSt, sc) |
| 192 | } |
| 193 | } |
| 194 | } |
| 195 | |
| 196 | // HandleSubConnStateChange implements "grpc/balancer.Balancer" interface. |
| 197 | func (bb *baseBalancer) HandleSubConnStateChange(sc balancer.SubConn, s grpcconnectivity.State) { |
| 198 | bb.mu.Lock() |
| 199 | defer bb.mu.Unlock() |
| 200 | |
| 201 | old, ok := bb.scToSt[sc] |
| 202 | if !ok { |
| 203 | bb.lg.Warn( |
| 204 | "state change for an unknown subconn", |
| 205 | zap.String("picker", bb.picker.String()), |
| 206 | zap.String("balancer-id", bb.id), |
| 207 | zap.String("subconn", scToString(sc)), |
| 208 | zap.Int("subconn-size", len(bb.scToAddr)), |
| 209 | zap.String("state", s.String()), |
| 210 | ) |
| 211 | return |
| 212 | } |
| 213 | |
| 214 | bb.lg.Info( |
| 215 | "state changed", |
| 216 | zap.String("picker", bb.picker.String()), |
| 217 | zap.String("balancer-id", bb.id), |
| 218 | zap.Bool("connected", s == grpcconnectivity.Ready), |
| 219 | zap.String("subconn", scToString(sc)), |
| 220 | zap.Int("subconn-size", len(bb.scToAddr)), |
| 221 | zap.String("address", bb.scToAddr[sc].Addr), |
| 222 | zap.String("old-state", old.String()), |
| 223 | zap.String("new-state", s.String()), |
| 224 | ) |
| 225 | |
| 226 | bb.scToSt[sc] = s |
| 227 | switch s { |
| 228 | case grpcconnectivity.Idle: |
| 229 | sc.Connect() |
| 230 | case grpcconnectivity.Shutdown: |
| 231 | // When an address was removed by resolver, b called RemoveSubConn but |
| 232 | // kept the sc's state in scToSt. Remove state for this sc here. |
| 233 | delete(bb.scToAddr, sc) |
| 234 | delete(bb.scToSt, sc) |
| 235 | } |
| 236 | |
| 237 | oldAggrState := bb.connectivityRecorder.GetCurrentState() |
| 238 | bb.connectivityRecorder.RecordTransition(old, s) |
| 239 | |
| 240 | // Update balancer picker when one of the following happens: |
| 241 | // - this sc became ready from not-ready |
| 242 | // - this sc became not-ready from ready |
| 243 | // - the aggregated state of balancer became TransientFailure from non-TransientFailure |
| 244 | // - the aggregated state of balancer became non-TransientFailure from TransientFailure |
| 245 | if (s == grpcconnectivity.Ready) != (old == grpcconnectivity.Ready) || |
| 246 | (bb.connectivityRecorder.GetCurrentState() == grpcconnectivity.TransientFailure) != (oldAggrState == grpcconnectivity.TransientFailure) { |
| 247 | bb.updatePicker() |
| 248 | } |
| 249 | |
| 250 | bb.currentConn.UpdateBalancerState(bb.connectivityRecorder.GetCurrentState(), bb.picker) |
| 251 | } |
| 252 | |
| 253 | func (bb *baseBalancer) updatePicker() { |
| 254 | if bb.connectivityRecorder.GetCurrentState() == grpcconnectivity.TransientFailure { |
| 255 | bb.picker = picker.NewErr(balancer.ErrTransientFailure) |
| 256 | bb.lg.Info( |
| 257 | "updated picker to transient error picker", |
| 258 | zap.String("picker", bb.picker.String()), |
| 259 | zap.String("balancer-id", bb.id), |
| 260 | zap.String("policy", bb.policy.String()), |
| 261 | ) |
| 262 | return |
| 263 | } |
| 264 | |
| 265 | // only pass ready subconns to picker |
| 266 | scToAddr := make(map[balancer.SubConn]resolver.Address) |
| 267 | for addr, sc := range bb.addrToSc { |
| 268 | if st, ok := bb.scToSt[sc]; ok && st == grpcconnectivity.Ready { |
| 269 | scToAddr[sc] = addr |
| 270 | } |
| 271 | } |
| 272 | |
| 273 | bb.picker = picker.New(picker.Config{ |
| 274 | Policy: bb.policy, |
| 275 | Logger: bb.lg, |
| 276 | SubConnToResolverAddress: scToAddr, |
| 277 | }) |
| 278 | bb.lg.Info( |
| 279 | "updated picker", |
| 280 | zap.String("picker", bb.picker.String()), |
| 281 | zap.String("balancer-id", bb.id), |
| 282 | zap.String("policy", bb.policy.String()), |
| 283 | zap.Strings("subconn-ready", scsToStrings(scToAddr)), |
| 284 | zap.Int("subconn-size", len(scToAddr)), |
| 285 | ) |
| 286 | } |
| 287 | |
| 288 | // Close implements "grpc/balancer.Balancer" interface. |
| 289 | // Close is a nop because base balancer doesn't have internal state to clean up, |
| 290 | // and it doesn't need to call RemoveSubConn for the SubConns. |
| 291 | func (bb *baseBalancer) Close() { |
| 292 | // TODO |
| 293 | } |