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base.go
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base.go
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// Copyright 2020 Douyu
//
// 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 balancer
import (
"errors"
"fmt"
"google.golang.org/grpc/attributes"
"google.golang.org/grpc/balancer"
"google.golang.org/grpc/balancer/base"
"google.golang.org/grpc/connectivity"
"google.golang.org/grpc/grpclog"
"google.golang.org/grpc/resolver"
)
// NewBalancerBuilderV2 returns a base balancer builder configured by the provided config.
func NewBalancerBuilderV2(name string, pb PickerBuilder, config base.Config) balancer.Builder {
return &baseBuilder{
name: name,
v2PickerBuilder: pb,
config: config,
}
}
type baseBuilder struct {
name string
v2PickerBuilder PickerBuilder
config base.Config
}
// Build ...
func (bb *baseBuilder) Build(cc balancer.ClientConn, opt balancer.BuildOptions) balancer.Balancer {
bal := &baseBalancer{
cc: cc,
v2PickerBuilder: bb.v2PickerBuilder,
subConns: make(map[resolver.Address]balancer.SubConn),
scStates: make(map[balancer.SubConn]connectivity.State),
csEvltr: &balancer.ConnectivityStateEvaluator{},
config: bb.config,
}
// Initialize picker to a picker that always returns
// ErrNoSubConnAvailable, because when state of a SubConn changes, we
// may call UpdateState with this picker.
bal.v2Picker = NewErrPickerV2(balancer.ErrNoSubConnAvailable)
return bal
}
// Name ...
func (bb *baseBuilder) Name() string {
return bb.name
}
var _ balancer.Balancer = (*baseBalancer)(nil) // Assert that we implement V2Balancer
type baseBalancer struct {
cc balancer.ClientConn
v2PickerBuilder PickerBuilder
csEvltr *balancer.ConnectivityStateEvaluator
state connectivity.State
subConns map[resolver.Address]balancer.SubConn
scStates map[balancer.SubConn]connectivity.State
v2Picker balancer.Picker
config base.Config
attributes *attributes.Attributes
}
// HandleResolvedAddrs ...
func (b *baseBalancer) HandleResolvedAddrs(addrs []resolver.Address, err error) {
panic("not implemented")
}
// ResolverError ...
func (b *baseBalancer) ResolverError(err error) {
switch b.state {
case connectivity.TransientFailure, connectivity.Idle, connectivity.Connecting:
b.v2Picker = NewErrPickerV2(err)
}
}
// UpdateClientConnState ...
func (b *baseBalancer) UpdateClientConnState(s balancer.ClientConnState) error {
// TODO: handle s.ResolverState.Err (log if not nil) once implemented.
// TODO: handle s.ResolverState.ServiceConfig?
if grpclog.V(2) {
grpclog.Infoln("base.baseBalancer: got new ClientConn state: ", s)
}
// addrsSet is the set converted from addrs, it's used for quick lookup of an address.
addrsSet := make(map[resolver.Address]struct{})
fmt.Printf("s.ResolverState.Addresses = %+v\n", s.ResolverState.Addresses)
fmt.Printf("s.ResolverState.Attributes = %+v\n", s.ResolverState.Attributes)
for _, a := range s.ResolverState.Addresses {
addrsSet[a] = struct{}{}
if _, ok := b.subConns[a]; !ok {
// a is a new address (not existing in b.subConns).
sc, err := b.cc.NewSubConn(
[]resolver.Address{a},
balancer.NewSubConnOptions{HealthCheckEnabled: b.config.HealthCheck},
)
if err != nil {
grpclog.Warningf("base.baseBalancer: failed to create new SubConn: %v", err)
continue
}
b.subConns[a] = sc
b.scStates[sc] = connectivity.Idle
sc.Connect()
}
}
b.attributes = s.ResolverState.Attributes
for a, sc := range b.subConns {
// a was removed by resolver.
if _, ok := addrsSet[a]; !ok {
b.cc.RemoveSubConn(sc)
delete(b.subConns, a)
// Keep the state of this sc in b.scStates until sc's state becomes Shutdown.
// The entry will be deleted in HandleSubConnStateChange.
}
}
return nil
}
// regeneratePicker takes a snapshot of the balancer, and generates a picker
// from it. The picker is
// - errPicker with ErrTransientFailure if the balancer is in TransientFailure,
// - built by the pickerBuilder with all READY SubConns otherwise.
func (b *baseBalancer) regeneratePicker(err error) {
if b.state == connectivity.TransientFailure {
if err != nil {
b.v2Picker = NewErrPickerV2(balancer.TransientFailureError(err))
} else {
// This means the last subchannel transition was not to
// TransientFailure (otherwise err must be set), but the
// aggregate state of the balancer is TransientFailure, meaning
// there are no other addresses.
b.v2Picker = NewErrPickerV2(balancer.TransientFailureError(errors.New("resolver returned no addresses")))
}
return
}
readySCs := make(map[balancer.SubConn]base.SubConnInfo)
// Filter out all ready SCs from full subConn map.
for addr, sc := range b.subConns {
if st, ok := b.scStates[sc]; ok && st == connectivity.Ready {
readySCs[sc] = base.SubConnInfo{Address: addr}
}
}
b.v2Picker = b.v2PickerBuilder.Build(
PickerBuildInfo{
ReadySCs: readySCs,
Attributes: b.attributes,
},
)
}
// HandleSubConnStateChange ...
func (b *baseBalancer) HandleSubConnStateChange(sc balancer.SubConn, s connectivity.State) {
panic("not implemented")
}
// UpdateSubConnState ...
func (b *baseBalancer) UpdateSubConnState(sc balancer.SubConn, state balancer.SubConnState) {
s := state.ConnectivityState
if grpclog.V(2) {
grpclog.Infof("base.baseBalancer: handle SubConn state change: %p, %v", sc, s)
}
oldS, ok := b.scStates[sc]
if !ok {
if grpclog.V(2) {
grpclog.Infof("base.baseBalancer: got state changes for an unknown SubConn: %p, %v", sc, s)
}
return
}
b.scStates[sc] = s
switch s {
case connectivity.Idle:
sc.Connect()
case connectivity.Shutdown:
// When an address was removed by resolver, b called RemoveSubConn but
// kept the sc's state in scStates. Remove state for this sc here.
delete(b.scStates, sc)
}
oldAggrState := b.state
b.state = b.csEvltr.RecordTransition(oldS, s)
// Regenerate picker when one of the following happens:
// - this sc became ready from not-ready
// - this sc became not-ready from ready
// - the aggregated state of balancer became TransientFailure from non-TransientFailure
// - the aggregated state of balancer became non-TransientFailure from TransientFailure
if (s == connectivity.Ready) != (oldS == connectivity.Ready) ||
(b.state == connectivity.TransientFailure) != (oldAggrState == connectivity.TransientFailure) {
b.regeneratePicker(state.ConnectionError)
}
b.cc.UpdateState(balancer.State{ConnectivityState: b.state, Picker: b.v2Picker})
}
// Close is a nop because base balancer doesn't have internal state to clean up,
// and it doesn't need to call RemoveSubConn for the SubConns.
func (b *baseBalancer) Close() {
}
// NewErrPickerV2 returns a V2Picker that always returns err on Pick().
func NewErrPickerV2(err error) balancer.Picker {
return &errPickerV2{err: err}
}
type errPickerV2 struct {
err error // Pick() always returns this err.
}
// Pick ...
func (p *errPickerV2) Pick(info balancer.PickInfo) (balancer.PickResult, error) {
return balancer.PickResult{}, p.err
}