/
eds.go
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/
eds.go
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/*
*
* Copyright 2019 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 edsbalancer contains EDS balancer implementation.
package edsbalancer
import (
"context"
"encoding/json"
"fmt"
"time"
"github.com/google/go-cmp/cmp"
"google.golang.org/grpc/balancer"
"google.golang.org/grpc/balancer/roundrobin"
"google.golang.org/grpc/connectivity"
"google.golang.org/grpc/internal/buffer"
"google.golang.org/grpc/internal/grpclog"
"google.golang.org/grpc/resolver"
"google.golang.org/grpc/serviceconfig"
"google.golang.org/grpc/xds/internal/balancer/lrs"
xdsclient "google.golang.org/grpc/xds/internal/client"
)
const (
defaultTimeout = 10 * time.Second
edsName = "eds_experimental"
)
var (
newEDSBalancer = func(cc balancer.ClientConn, enqueueState func(priorityType, balancer.State), loadStore lrs.Store, logger *grpclog.PrefixLogger) edsBalancerImplInterface {
return newEDSBalancerImpl(cc, enqueueState, loadStore, logger)
}
)
func init() {
balancer.Register(&edsBalancerBuilder{})
}
type edsBalancerBuilder struct{}
// Build helps implement the balancer.Builder interface.
func (b *edsBalancerBuilder) Build(cc balancer.ClientConn, opts balancer.BuildOptions) balancer.Balancer {
ctx, cancel := context.WithCancel(context.Background())
x := &edsBalancer{
ctx: ctx,
cancel: cancel,
cc: cc,
buildOpts: opts,
grpcUpdate: make(chan interface{}),
xdsClientUpdate: make(chan interface{}),
childPolicyUpdate: buffer.NewUnbounded(),
}
loadStore := lrs.NewStore()
x.logger = grpclog.NewPrefixLogger(loggingPrefix(x))
x.edsImpl = newEDSBalancer(x.cc, x.enqueueChildBalancerState, loadStore, x.logger)
x.client = newXDSClientWrapper(x.handleEDSUpdate, x.loseContact, x.buildOpts, loadStore, x.logger)
x.logger.Infof("Created")
go x.run()
return x
}
func (b *edsBalancerBuilder) Name() string {
return edsName
}
func (b *edsBalancerBuilder) ParseConfig(c json.RawMessage) (serviceconfig.LoadBalancingConfig, error) {
var cfg EDSConfig
if err := json.Unmarshal(c, &cfg); err != nil {
return nil, fmt.Errorf("unable to unmarshal balancer config %s into EDSConfig, error: %v", string(c), err)
}
return &cfg, nil
}
// edsBalancerImplInterface defines the interface that edsBalancerImpl must
// implement to communicate with edsBalancer.
//
// It's implemented by the real eds balancer and a fake testing eds balancer.
//
// TODO: none of the methods in this interface needs to be exported.
type edsBalancerImplInterface interface {
// HandleEDSResponse passes the received EDS message from traffic director to eds balancer.
HandleEDSResponse(edsResp *xdsclient.EDSUpdate)
// HandleChildPolicy updates the eds balancer the intra-cluster load balancing policy to use.
HandleChildPolicy(name string, config json.RawMessage)
// HandleSubConnStateChange handles state change for SubConn.
HandleSubConnStateChange(sc balancer.SubConn, state connectivity.State)
// updateState handle a balancer state update from the priority.
updateState(priority priorityType, s balancer.State)
// Close closes the eds balancer.
Close()
}
var _ balancer.V2Balancer = (*edsBalancer)(nil) // Assert that we implement V2Balancer
// edsBalancer manages xdsClient and the actual EDS balancer implementation that
// does load balancing.
//
// It currently has only an edsBalancer. Later, we may add fallback.
type edsBalancer struct {
cc balancer.ClientConn // *xdsClientConn
buildOpts balancer.BuildOptions
ctx context.Context
cancel context.CancelFunc
logger *grpclog.PrefixLogger
// edsBalancer continuously monitor the channels below, and will handle events from them in sync.
grpcUpdate chan interface{}
xdsClientUpdate chan interface{}
childPolicyUpdate *buffer.Unbounded
client *xdsclientWrapper // may change when passed a different service config
config *EDSConfig // may change when passed a different service config
edsImpl edsBalancerImplInterface
}
// run gets executed in a goroutine once edsBalancer is created. It monitors updates from grpc,
// xdsClient and load balancer. It synchronizes the operations that happen inside edsBalancer. It
// exits when edsBalancer is closed.
func (x *edsBalancer) run() {
for {
select {
case update := <-x.grpcUpdate:
x.handleGRPCUpdate(update)
case update := <-x.xdsClientUpdate:
x.handleXDSClientUpdate(update)
case update := <-x.childPolicyUpdate.Get():
x.childPolicyUpdate.Load()
u := update.(*balancerStateWithPriority)
x.edsImpl.updateState(u.priority, u.s)
case <-x.ctx.Done():
if x.client != nil {
x.client.close()
}
if x.edsImpl != nil {
x.edsImpl.Close()
}
return
}
}
}
func (x *edsBalancer) handleGRPCUpdate(update interface{}) {
switch u := update.(type) {
case *subConnStateUpdate:
if x.edsImpl != nil {
x.edsImpl.HandleSubConnStateChange(u.sc, u.state.ConnectivityState)
}
case *balancer.ClientConnState:
x.logger.Infof("Receive update from resolver, balancer config: %+v", u.BalancerConfig)
cfg, _ := u.BalancerConfig.(*EDSConfig)
if cfg == nil {
// service config parsing failed. should never happen.
return
}
x.client.handleUpdate(cfg, u.ResolverState.Attributes)
if x.config == nil {
x.config = cfg
return
}
// We will update the edsImpl with the new child policy, if we got a
// different one.
if x.edsImpl != nil && !cmp.Equal(cfg.ChildPolicy, x.config.ChildPolicy) {
if cfg.ChildPolicy != nil {
x.edsImpl.HandleChildPolicy(cfg.ChildPolicy.Name, cfg.ChildPolicy.Config)
} else {
x.edsImpl.HandleChildPolicy(roundrobin.Name, nil)
}
}
x.config = cfg
default:
// unreachable path
panic("wrong update type")
}
}
func (x *edsBalancer) handleXDSClientUpdate(update interface{}) {
switch u := update.(type) {
// TODO: this func should accept (*xdsclient.EDSUpdate, error), and process
// the error, instead of having a separate loseContact signal.
case *xdsclient.EDSUpdate:
x.edsImpl.HandleEDSResponse(u)
case *loseContact:
// loseContact can be useful for going into fallback.
default:
panic("unexpected xds client update type")
}
}
type subConnStateUpdate struct {
sc balancer.SubConn
state balancer.SubConnState
}
func (x *edsBalancer) HandleSubConnStateChange(sc balancer.SubConn, state connectivity.State) {
x.logger.Errorf("UpdateSubConnState should be called instead of HandleSubConnStateChange")
}
func (x *edsBalancer) HandleResolvedAddrs(addrs []resolver.Address, err error) {
x.logger.Errorf("UpdateResolverState should be called instead of HandleResolvedAddrs")
}
func (x *edsBalancer) UpdateSubConnState(sc balancer.SubConn, state balancer.SubConnState) {
update := &subConnStateUpdate{
sc: sc,
state: state,
}
select {
case x.grpcUpdate <- update:
case <-x.ctx.Done():
}
}
func (x *edsBalancer) ResolverError(error) {
// TODO: Need to distinguish between connection errors and resource removed
// errors. For the former, we will need to handle it later on for fallback.
// For the latter, handle it by stopping the watch, closing sub-balancers
// and pickers.
}
func (x *edsBalancer) UpdateClientConnState(s balancer.ClientConnState) error {
select {
case x.grpcUpdate <- &s:
case <-x.ctx.Done():
}
return nil
}
func (x *edsBalancer) handleEDSUpdate(resp *xdsclient.EDSUpdate) error {
// TODO: this function should take (resp, error), and send them together on
// the channel. There doesn't need to be a separate `loseContact` function.
select {
case x.xdsClientUpdate <- resp:
case <-x.ctx.Done():
}
return nil
}
type loseContact struct {
}
// TODO: delete loseContact when handleEDSUpdate takes (resp, error).
func (x *edsBalancer) loseContact() {
select {
case x.xdsClientUpdate <- &loseContact{}:
case <-x.ctx.Done():
}
}
type balancerStateWithPriority struct {
priority priorityType
s balancer.State
}
func (x *edsBalancer) enqueueChildBalancerState(p priorityType, s balancer.State) {
x.childPolicyUpdate.Put(&balancerStateWithPriority{
priority: p,
s: s,
})
}
func (x *edsBalancer) Close() {
x.cancel()
x.logger.Infof("Shutdown")
}