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/*
*
* Copyright 2020 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 weightedtarget implements the weighted_target balancer.
//
// All APIs in this package are experimental.
package weightedtarget
import (
"encoding/json"
"fmt"
"google.golang.org/grpc/balancer"
"google.golang.org/grpc/balancer/weightedtarget/weightedaggregator"
"google.golang.org/grpc/internal/balancergroup"
"google.golang.org/grpc/internal/grpclog"
"google.golang.org/grpc/internal/hierarchy"
"google.golang.org/grpc/internal/pretty"
"google.golang.org/grpc/internal/wrr"
"google.golang.org/grpc/resolver"
"google.golang.org/grpc/serviceconfig"
)
// Name is the name of the weighted_target balancer.
const Name = "weighted_target_experimental"
// NewRandomWRR is the WRR constructor used to pick sub-pickers from
// sub-balancers. It's to be modified in tests.
var NewRandomWRR = wrr.NewRandom
func init() {
balancer.Register(bb{})
}
type bb struct{}
func (bb) Build(cc balancer.ClientConn, bOpts balancer.BuildOptions) balancer.Balancer {
b := &weightedTargetBalancer{}
b.logger = prefixLogger(b)
b.stateAggregator = weightedaggregator.New(cc, b.logger, NewRandomWRR)
b.stateAggregator.Start()
b.bg = balancergroup.New(cc, bOpts, b.stateAggregator, b.logger)
b.bg.Start()
b.logger.Infof("Created")
return b
}
func (bb) Name() string {
return Name
}
func (bb) ParseConfig(c json.RawMessage) (serviceconfig.LoadBalancingConfig, error) {
return parseConfig(c)
}
type weightedTargetBalancer struct {
logger *grpclog.PrefixLogger
bg *balancergroup.BalancerGroup
stateAggregator *weightedaggregator.Aggregator
targets map[string]Target
}
// UpdateClientConnState takes the new targets in balancer group,
// creates/deletes sub-balancers and sends them update. addresses are split into
// groups based on hierarchy path.
func (b *weightedTargetBalancer) UpdateClientConnState(s balancer.ClientConnState) error {
b.logger.Infof("Received update from resolver, balancer config: %+v", pretty.ToJSON(s.BalancerConfig))
newConfig, ok := s.BalancerConfig.(*LBConfig)
if !ok {
return fmt.Errorf("unexpected balancer config with type: %T", s.BalancerConfig)
}
addressesSplit := hierarchy.Group(s.ResolverState.Addresses)
b.stateAggregator.PauseStateUpdates()
defer b.stateAggregator.ResumeStateUpdates()
// Remove sub-pickers and sub-balancers that are not in the new config.
for name := range b.targets {
if _, ok := newConfig.Targets[name]; !ok {
b.stateAggregator.Remove(name)
b.bg.Remove(name)
}
}
// For sub-balancers in the new config
// - if it's new. add to balancer group,
// - if it's old, but has a new weight, update weight in balancer group.
//
// For all sub-balancers, forward the address/balancer config update.
for name, newT := range newConfig.Targets {
oldT, ok := b.targets[name]
if !ok {
// If this is a new sub-balancer, add weights to the picker map.
b.stateAggregator.Add(name, newT.Weight)
// Then add to the balancer group.
b.bg.Add(name, balancer.Get(newT.ChildPolicy.Name))
// Not trigger a state/picker update. Wait for the new sub-balancer
// to send its updates.
} else if newT.ChildPolicy.Name != oldT.ChildPolicy.Name {
// If the child policy name is different, remove from balancer group
// and re-add.
b.stateAggregator.Remove(name)
b.bg.Remove(name)
b.stateAggregator.Add(name, newT.Weight)
b.bg.Add(name, balancer.Get(newT.ChildPolicy.Name))
} else if newT.Weight != oldT.Weight {
// If this is an existing sub-balancer, update weight if necessary.
b.stateAggregator.UpdateWeight(name, newT.Weight)
}
// Forwards all the update:
// - addresses are from the map after splitting with hierarchy path,
// - Top level service config and attributes are the same,
// - Balancer config comes from the targets map.
//
// TODO: handle error? How to aggregate errors and return?
_ = b.bg.UpdateClientConnState(name, balancer.ClientConnState{
ResolverState: resolver.State{
Addresses: addressesSplit[name],
ServiceConfig: s.ResolverState.ServiceConfig,
Attributes: s.ResolverState.Attributes,
},
BalancerConfig: newT.ChildPolicy.Config,
})
}
b.targets = newConfig.Targets
// If the targets length is zero, it means we have removed all child
// policies from the balancer group and aggregator.
// At the start of this UpdateClientConnState() operation, a call to
// b.stateAggregator.ResumeStateUpdates() is deferred. Thus, setting the
// needUpdateStateOnResume bool to true here will ensure a new picker is
// built as part of that deferred function. Since there are now no child
// policies, the aggregated connectivity state reported form the Aggregator
// will be TRANSIENT_FAILURE.
if len(b.targets) == 0 {
b.stateAggregator.NeedUpdateStateOnResume()
}
return nil
}
func (b *weightedTargetBalancer) ResolverError(err error) {
b.bg.ResolverError(err)
}
func (b *weightedTargetBalancer) UpdateSubConnState(sc balancer.SubConn, state balancer.SubConnState) {
b.bg.UpdateSubConnState(sc, state)
}
func (b *weightedTargetBalancer) Close() {
b.stateAggregator.Stop()
b.bg.Close()
}
func (b *weightedTargetBalancer) ExitIdle() {
b.bg.ExitIdle()
}
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