Add new Resolver and Balancer APIs (gRFC L9) (#1408)
- Add package balancer and resolver. - Change ClientConn internals to new APIs and adds a wrapper for v1 balancer.
This commit is contained in:
Menghan Li
303
balancer_v1_wrapper.go
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303
balancer_v1_wrapper.go
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/*
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*
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* Copyright 2017 gRPC 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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*/
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package grpc
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import (
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"sync"
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"golang.org/x/net/context"
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"google.golang.org/grpc/balancer"
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"google.golang.org/grpc/connectivity"
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"google.golang.org/grpc/grpclog"
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"google.golang.org/grpc/resolver"
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)
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type balancerWrapperBuilder struct {
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b Balancer // The v1 balancer.
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}
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func (bwb *balancerWrapperBuilder) Build(cc balancer.ClientConn, opts balancer.BuildOptions) balancer.Balancer {
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bwb.b.Start(cc.Target(), BalancerConfig{
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DialCreds: opts.DialCreds,
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Dialer: opts.Dialer,
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})
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_, pickfirst := bwb.b.(*pickFirst)
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bw := &balancerWrapper{
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balancer: bwb.b,
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pickfirst: pickfirst,
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cc: cc,
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startCh: make(chan struct{}),
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conns: make(map[resolver.Address]balancer.SubConn),
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connSt: make(map[balancer.SubConn]*scState),
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}
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cc.UpdateBalancerState(connectivity.Idle, bw)
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go bw.lbWatcher()
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return bw
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}
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func (bwb *balancerWrapperBuilder) Name() string {
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return "wrapper"
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}
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type scState struct {
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addr Address // The v1 address type.
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s connectivity.State
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down func(error)
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}
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type balancerWrapper struct {
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balancer Balancer // The v1 balancer.
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pickfirst bool
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cc balancer.ClientConn
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mu sync.Mutex
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conns map[resolver.Address]balancer.SubConn
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connSt map[balancer.SubConn]*scState
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// This channel is closed when handling the first resolver result.
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// lbWatcher blocks until this is closed, to avoid race between
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// - NewSubConn is created, cc wants to notify balancer of state changes;
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// - Build hasn't return, cc doesn't have access to balancer.
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startCh chan struct{}
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}
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// lbWatcher watches the Notify channel of the balancer and manages
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// connections accordingly.
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func (bw *balancerWrapper) lbWatcher() {
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<-bw.startCh
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grpclog.Infof("balancerWrapper: is pickfirst: %v\n", bw.pickfirst)
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notifyCh := bw.balancer.Notify()
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if notifyCh == nil {
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// There's no resolver in the balancer. Connect directly.
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a := resolver.Address{
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Addr: bw.cc.Target(),
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Type: resolver.Backend,
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}
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sc, err := bw.cc.NewSubConn([]resolver.Address{a}, balancer.NewSubConnOptions{})
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if err != nil {
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grpclog.Warningf("Error creating connection to %v. Err: %v", a, err)
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} else {
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bw.mu.Lock()
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bw.conns[a] = sc
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bw.connSt[sc] = &scState{
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addr: Address{Addr: bw.cc.Target()},
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s: connectivity.Idle,
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}
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bw.mu.Unlock()
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sc.Connect()
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}
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return
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}
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for addrs := range notifyCh {
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grpclog.Infof("balancerWrapper: got update addr from Notify: %v\n", addrs)
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if bw.pickfirst {
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var (
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oldA resolver.Address
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oldSC balancer.SubConn
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)
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bw.mu.Lock()
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for oldA, oldSC = range bw.conns {
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break
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}
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bw.mu.Unlock()
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if len(addrs) <= 0 {
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if oldSC != nil {
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// Teardown old sc.
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bw.mu.Lock()
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delete(bw.conns, oldA)
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delete(bw.connSt, oldSC)
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bw.mu.Unlock()
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bw.cc.RemoveSubConn(oldSC)
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}
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continue
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}
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var newAddrs []resolver.Address
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for _, a := range addrs {
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newAddr := resolver.Address{
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Addr: a.Addr,
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Type: resolver.Backend, // All addresses from balancer are all backends.
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ServerName: "", // TODO(bar) support servername.
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Metadata: a.Metadata,
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}
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newAddrs = append(newAddrs, newAddr)
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}
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if oldSC == nil {
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// Create new sc.
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sc, err := bw.cc.NewSubConn(newAddrs, balancer.NewSubConnOptions{})
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if err != nil {
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grpclog.Warningf("Error creating connection to %v. Err: %v", newAddrs, err)
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} else {
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bw.mu.Lock()
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// For pickfirst, there should be only one SubConn, so the
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// address doesn't matter. All states updating (up and down)
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// and picking should all happen on that only SubConn.
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bw.conns[resolver.Address{}] = sc
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bw.connSt[sc] = &scState{
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addr: addrs[0], // Use the first address.
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s: connectivity.Idle,
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}
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bw.mu.Unlock()
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sc.Connect()
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}
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} else {
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oldSC.UpdateAddresses(newAddrs)
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bw.mu.Lock()
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bw.connSt[oldSC].addr = addrs[0]
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bw.mu.Unlock()
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}
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} else {
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var (
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add []resolver.Address // Addresses need to setup connections.
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del []balancer.SubConn // Connections need to tear down.
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)
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resAddrs := make(map[resolver.Address]Address)
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for _, a := range addrs {
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resAddrs[resolver.Address{
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Addr: a.Addr,
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Type: resolver.Backend, // All addresses from balancer are all backends.
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ServerName: "", // TODO(bar) support servername.
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Metadata: a.Metadata,
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}] = a
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}
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bw.mu.Lock()
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for a := range resAddrs {
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if _, ok := bw.conns[a]; !ok {
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add = append(add, a)
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}
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}
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for a, c := range bw.conns {
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if _, ok := resAddrs[a]; !ok {
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del = append(del, c)
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delete(bw.conns, a)
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delete(bw.connSt, c)
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}
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}
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bw.mu.Unlock()
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for _, a := range add {
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sc, err := bw.cc.NewSubConn([]resolver.Address{a}, balancer.NewSubConnOptions{})
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if err != nil {
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grpclog.Warningf("Error creating connection to %v. Err: %v", a, err)
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} else {
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bw.mu.Lock()
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bw.conns[a] = sc
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bw.connSt[sc] = &scState{
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addr: resAddrs[a],
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s: connectivity.Idle,
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}
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bw.mu.Unlock()
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sc.Connect()
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}
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}
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for _, c := range del {
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bw.cc.RemoveSubConn(c)
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}
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}
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}
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}
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func (bw *balancerWrapper) HandleSubConnStateChange(sc balancer.SubConn, s connectivity.State) {
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grpclog.Infof("balancerWrapper: handle subconn state change: %p, %v", sc, s)
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bw.mu.Lock()
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defer bw.mu.Unlock()
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scSt, ok := bw.connSt[sc]
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if !ok {
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return
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}
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if s == connectivity.Idle {
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sc.Connect()
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}
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oldS := scSt.s
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scSt.s = s
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grpclog.Infof("balancerWrapper: handle state change addr: %v, old state: %v, new state: %v", sc.(*acBalancerWrapper).getAddrConn().addrs, oldS, s)
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if oldS != connectivity.Ready && s == connectivity.Ready {
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scSt.down = bw.balancer.Up(scSt.addr)
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} else if oldS == connectivity.Ready && s != connectivity.Ready {
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if scSt.down != nil {
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scSt.down(errConnClosing) // TODO(bar) what error to use?
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}
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}
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// The connectivity state is ignored by clientConn now.
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// TODO(bar) use the aggregated connectivity state.
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bw.cc.UpdateBalancerState(connectivity.Ready, bw)
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return
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}
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func (bw *balancerWrapper) HandleResolvedAddrs([]resolver.Address, error) {
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bw.mu.Lock()
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defer bw.mu.Unlock()
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select {
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case <-bw.startCh:
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default:
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close(bw.startCh)
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}
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// There should be a resolver inside the balancer.
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// All updates here, if any, are ignored.
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return
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}
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func (bw *balancerWrapper) Close() {
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bw.mu.Lock()
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defer bw.mu.Unlock()
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select {
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case <-bw.startCh:
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default:
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close(bw.startCh)
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}
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bw.balancer.Close()
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return
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}
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// The picker is the balancerWrapper itself.
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// Pick should never return ErrNoSubConnAvailable.
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// It either blocks or returns error, consistent with v1 balancer Get().
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func (bw *balancerWrapper) Pick(ctx context.Context, opts balancer.PickOptions) (balancer.SubConn, func(balancer.DoneInfo), error) {
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failfast := true // Default failfast is true.
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if ss, ok := rpcInfoFromContext(ctx); ok {
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failfast = ss.failfast
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}
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a, p, err := bw.balancer.Get(ctx, BalancerGetOptions{BlockingWait: !failfast})
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if err != nil {
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return nil, nil, err
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}
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var put func(balancer.DoneInfo)
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if p != nil {
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put = func(i balancer.DoneInfo) { p() }
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}
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var sc balancer.SubConn
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if bw.pickfirst {
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bw.mu.Lock()
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// Get the first sc in conns.
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for _, sc = range bw.conns {
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break
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}
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bw.mu.Unlock()
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} else {
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bw.mu.Lock()
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sc = bw.conns[resolver.Address{
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Addr: a.Addr,
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Type: resolver.Backend,
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ServerName: "", // TODO(bar) support servername.
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Metadata: a.Metadata,
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}]
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bw.mu.Unlock()
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}
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return sc, put, nil
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}
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