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/*
*
* Copyright 2017 gRPC 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 grpc
import (
"context"
"google.golang.org/grpc/balancer"
"google.golang.org/grpc/connectivity"
"google.golang.org/grpc/grpclog"
"google.golang.org/grpc/resolver"
)
// PickFirstBalancerName is the name of the pick_first balancer.
const PickFirstBalancerName = "pick_first"
func newPickfirstBuilder() balancer.Builder {
return &pickfirstBuilder{}
}
type pickfirstBuilder struct{}
func (*pickfirstBuilder) Build(cc balancer.ClientConn, opt balancer.BuildOptions) balancer.Balancer {
return &pickfirstBalancer{cc: cc}
}
func (*pickfirstBuilder) Name() string {
return PickFirstBalancerName
}
type pickfirstBalancer struct {
cc balancer.ClientConn
sc balancer.SubConn
}
func (b *pickfirstBalancer) HandleResolvedAddrs(addrs []resolver.Address, err error) {
if err != nil {
grpclog.Infof("pickfirstBalancer: HandleResolvedAddrs called with error %v", err)
return
}
if b.sc == nil {
b.sc, err = b.cc.NewSubConn(addrs, balancer.NewSubConnOptions{})
if err != nil {
//TODO(yuxuanli): why not change the cc state to Idle?
grpclog.Errorf("pickfirstBalancer: failed to NewSubConn: %v", err)
return
}
b.cc.UpdateBalancerState(connectivity.Idle, &picker{sc: b.sc})
b.sc.Connect()
} else {
b.sc.UpdateAddresses(addrs)
b.sc.Connect()
}
}
func (b *pickfirstBalancer) HandleSubConnStateChange(sc balancer.SubConn, s connectivity.State) {
grpclog.Infof("pickfirstBalancer: HandleSubConnStateChange: %p, %v", sc, s)
if b.sc != sc {
grpclog.Infof("pickfirstBalancer: ignored state change because sc is not recognized")
return
}
if s == connectivity.Shutdown {
b.sc = nil
return
}
switch s {
case connectivity.Ready, connectivity.Idle:
b.cc.UpdateBalancerState(s, &picker{sc: sc})
case connectivity.Connecting:
b.cc.UpdateBalancerState(s, &picker{err: balancer.ErrNoSubConnAvailable})
case connectivity.TransientFailure:
b.cc.UpdateBalancerState(s, &picker{err: balancer.ErrTransientFailure})
}
}
func (b *pickfirstBalancer) Close() {
}
type picker struct {
err error
sc balancer.SubConn
}
func (p *picker) Pick(ctx context.Context, opts balancer.PickOptions) (balancer.SubConn, func(balancer.DoneInfo), error) {
if p.err != nil {
return nil, nil, p.err
}
return p.sc, nil, nil
}
func init() {
balancer.Register(newPickfirstBuilder())
}