peridot/vendor/google.golang.org/grpc/balancer/pickfirst/pickfirst.go

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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 pickfirst contains the pick_first load balancing policy.
package pickfirst
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import (
"encoding/json"
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"errors"
"fmt"
"math/rand"
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"google.golang.org/grpc/balancer"
"google.golang.org/grpc/connectivity"
"google.golang.org/grpc/grpclog"
"google.golang.org/grpc/internal"
internalgrpclog "google.golang.org/grpc/internal/grpclog"
"google.golang.org/grpc/internal/pretty"
"google.golang.org/grpc/resolver"
"google.golang.org/grpc/serviceconfig"
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)
func init() {
balancer.Register(pickfirstBuilder{})
internal.ShuffleAddressListForTesting = func(n int, swap func(i, j int)) { rand.Shuffle(n, swap) }
}
var logger = grpclog.Component("pick-first-lb")
const (
// Name is the name of the pick_first balancer.
Name = "pick_first"
logPrefix = "[pick-first-lb %p] "
)
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type pickfirstBuilder struct{}
func (pickfirstBuilder) Build(cc balancer.ClientConn, opt balancer.BuildOptions) balancer.Balancer {
b := &pickfirstBalancer{cc: cc}
b.logger = internalgrpclog.NewPrefixLogger(logger, fmt.Sprintf(logPrefix, b))
return b
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}
func (pickfirstBuilder) Name() string {
return Name
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}
type pfConfig struct {
serviceconfig.LoadBalancingConfig `json:"-"`
// If set to true, instructs the LB policy to shuffle the order of the list
// of endpoints received from the name resolver before attempting to
// connect to them.
ShuffleAddressList bool `json:"shuffleAddressList"`
}
func (pickfirstBuilder) ParseConfig(js json.RawMessage) (serviceconfig.LoadBalancingConfig, error) {
var cfg pfConfig
if err := json.Unmarshal(js, &cfg); err != nil {
return nil, fmt.Errorf("pickfirst: unable to unmarshal LB policy config: %s, error: %v", string(js), err)
}
return cfg, nil
}
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type pickfirstBalancer struct {
logger *internalgrpclog.PrefixLogger
state connectivity.State
cc balancer.ClientConn
subConn balancer.SubConn
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}
func (b *pickfirstBalancer) ResolverError(err error) {
if b.logger.V(2) {
b.logger.Infof("Received error from the name resolver: %v", err)
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}
if b.subConn == nil {
b.state = connectivity.TransientFailure
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}
if b.state != connectivity.TransientFailure {
// The picker will not change since the balancer does not currently
// report an error.
return
}
b.cc.UpdateState(balancer.State{
ConnectivityState: connectivity.TransientFailure,
Picker: &picker{err: fmt.Errorf("name resolver error: %v", err)},
})
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}
type Shuffler interface {
ShuffleAddressListForTesting(n int, swap func(i, j int))
}
func ShuffleAddressListForTesting(n int, swap func(i, j int)) { rand.Shuffle(n, swap) }
func (b *pickfirstBalancer) UpdateClientConnState(state balancer.ClientConnState) error {
if len(state.ResolverState.Addresses) == 0 && len(state.ResolverState.Endpoints) == 0 {
// The resolver reported an empty address list. Treat it like an error by
// calling b.ResolverError.
if b.subConn != nil {
// Shut down the old subConn. All addresses were removed, so it is
// no longer valid.
b.subConn.Shutdown()
b.subConn = nil
}
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b.ResolverError(errors.New("produced zero addresses"))
return balancer.ErrBadResolverState
}
// We don't have to guard this block with the env var because ParseConfig
// already does so.
cfg, ok := state.BalancerConfig.(pfConfig)
if state.BalancerConfig != nil && !ok {
return fmt.Errorf("pickfirst: received illegal BalancerConfig (type %T): %v", state.BalancerConfig, state.BalancerConfig)
}
if b.logger.V(2) {
b.logger.Infof("Received new config %s, resolver state %s", pretty.ToJSON(cfg), pretty.ToJSON(state.ResolverState))
}
var addrs []resolver.Address
if endpoints := state.ResolverState.Endpoints; len(endpoints) != 0 {
// Perform the optional shuffling described in gRFC A62. The shuffling will
// change the order of endpoints but not touch the order of the addresses
// within each endpoint. - A61
if cfg.ShuffleAddressList {
endpoints = append([]resolver.Endpoint{}, endpoints...)
internal.ShuffleAddressListForTesting.(func(int, func(int, int)))(len(endpoints), func(i, j int) { endpoints[i], endpoints[j] = endpoints[j], endpoints[i] })
}
// "Flatten the list by concatenating the ordered list of addresses for each
// of the endpoints, in order." - A61
for _, endpoint := range endpoints {
// "In the flattened list, interleave addresses from the two address
// families, as per RFC-8304 section 4." - A61
// TODO: support the above language.
addrs = append(addrs, endpoint.Addresses...)
}
} else {
// Endpoints not set, process addresses until we migrate resolver
// emissions fully to Endpoints. The top channel does wrap emitted
// addresses with endpoints, however some balancers such as weighted
// target do not forwarrd the corresponding correct endpoints down/split
// endpoints properly. Once all balancers correctly forward endpoints
// down, can delete this else conditional.
addrs = state.ResolverState.Addresses
if cfg.ShuffleAddressList {
addrs = append([]resolver.Address{}, addrs...)
rand.Shuffle(len(addrs), func(i, j int) { addrs[i], addrs[j] = addrs[j], addrs[i] })
}
}
if b.subConn != nil {
b.cc.UpdateAddresses(b.subConn, addrs)
return nil
}
var subConn balancer.SubConn
subConn, err := b.cc.NewSubConn(addrs, balancer.NewSubConnOptions{
StateListener: func(state balancer.SubConnState) {
b.updateSubConnState(subConn, state)
},
})
if err != nil {
if b.logger.V(2) {
b.logger.Infof("Failed to create new SubConn: %v", err)
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}
b.state = connectivity.TransientFailure
b.cc.UpdateState(balancer.State{
ConnectivityState: connectivity.TransientFailure,
Picker: &picker{err: fmt.Errorf("error creating connection: %v", err)},
})
return balancer.ErrBadResolverState
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}
b.subConn = subConn
b.state = connectivity.Idle
b.cc.UpdateState(balancer.State{
ConnectivityState: connectivity.Connecting,
Picker: &picker{err: balancer.ErrNoSubConnAvailable},
})
b.subConn.Connect()
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return nil
}
// UpdateSubConnState is unused as a StateListener is always registered when
// creating SubConns.
func (b *pickfirstBalancer) UpdateSubConnState(subConn balancer.SubConn, state balancer.SubConnState) {
b.logger.Errorf("UpdateSubConnState(%v, %+v) called unexpectedly", subConn, state)
}
func (b *pickfirstBalancer) updateSubConnState(subConn balancer.SubConn, state balancer.SubConnState) {
if b.logger.V(2) {
b.logger.Infof("Received SubConn state update: %p, %+v", subConn, state)
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}
if b.subConn != subConn {
if b.logger.V(2) {
b.logger.Infof("Ignored state change because subConn is not recognized")
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}
return
}
if state.ConnectivityState == connectivity.Shutdown {
b.subConn = nil
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return
}
switch state.ConnectivityState {
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case connectivity.Ready:
b.cc.UpdateState(balancer.State{
ConnectivityState: state.ConnectivityState,
Picker: &picker{result: balancer.PickResult{SubConn: subConn}},
})
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case connectivity.Connecting:
if b.state == connectivity.TransientFailure {
// We stay in TransientFailure until we are Ready. See A62.
return
}
b.cc.UpdateState(balancer.State{
ConnectivityState: state.ConnectivityState,
Picker: &picker{err: balancer.ErrNoSubConnAvailable},
})
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case connectivity.Idle:
if b.state == connectivity.TransientFailure {
// We stay in TransientFailure until we are Ready. Also kick the
// subConn out of Idle into Connecting. See A62.
b.subConn.Connect()
return
}
b.cc.UpdateState(balancer.State{
ConnectivityState: state.ConnectivityState,
Picker: &idlePicker{subConn: subConn},
})
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case connectivity.TransientFailure:
b.cc.UpdateState(balancer.State{
ConnectivityState: state.ConnectivityState,
Picker: &picker{err: state.ConnectionError},
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})
}
b.state = state.ConnectivityState
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}
func (b *pickfirstBalancer) Close() {
}
func (b *pickfirstBalancer) ExitIdle() {
if b.subConn != nil && b.state == connectivity.Idle {
b.subConn.Connect()
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}
}
type picker struct {
result balancer.PickResult
err error
}
func (p *picker) Pick(balancer.PickInfo) (balancer.PickResult, error) {
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return p.result, p.err
}
// idlePicker is used when the SubConn is IDLE and kicks the SubConn into
// CONNECTING when Pick is called.
type idlePicker struct {
subConn balancer.SubConn
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}
func (i *idlePicker) Pick(balancer.PickInfo) (balancer.PickResult, error) {
i.subConn.Connect()
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return balancer.PickResult{}, balancer.ErrNoSubConnAvailable
}