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clusterimpl.go
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clusterimpl.go
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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 clusterimpl implements the xds_cluster_impl balancing policy. It
// handles the cluster features (e.g. circuit_breaking, RPC dropping).
//
// Note that it doesn't handle name resolution, which is done by policy
// xds_cluster_resolver.
package clusterimpl
import (
"encoding/json"
"fmt"
"sync"
"sync/atomic"
"google.golang.org/grpc/balancer"
"google.golang.org/grpc/connectivity"
"google.golang.org/grpc/internal/balancer/gracefulswitch"
"google.golang.org/grpc/internal/buffer"
"google.golang.org/grpc/internal/grpclog"
"google.golang.org/grpc/internal/grpcsync"
"google.golang.org/grpc/internal/pretty"
"google.golang.org/grpc/internal/xds"
"google.golang.org/grpc/resolver"
"google.golang.org/grpc/serviceconfig"
xdsinternal "google.golang.org/grpc/xds/internal"
"google.golang.org/grpc/xds/internal/balancer/loadstore"
"google.golang.org/grpc/xds/internal/xdsclient"
"google.golang.org/grpc/xds/internal/xdsclient/bootstrap"
"google.golang.org/grpc/xds/internal/xdsclient/load"
)
const (
// Name is the name of the cluster_impl balancer.
Name = "xds_cluster_impl_experimental"
defaultRequestCountMax = 1024
)
func init() {
balancer.Register(bb{})
}
type bb struct{}
func (bb) Build(cc balancer.ClientConn, bOpts balancer.BuildOptions) balancer.Balancer {
b := &clusterImplBalancer{
ClientConn: cc,
bOpts: bOpts,
closed: grpcsync.NewEvent(),
done: grpcsync.NewEvent(),
loadWrapper: loadstore.NewWrapper(),
pickerUpdateCh: buffer.NewUnbounded(),
requestCountMax: defaultRequestCountMax,
}
b.logger = prefixLogger(b)
b.child = gracefulswitch.NewBalancer(b, bOpts)
go b.run()
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 clusterImplBalancer struct {
balancer.ClientConn
// mu guarantees mutual exclusion between Close() and handling of picker
// update to the parent ClientConn in run(). It's to make sure that the
// run() goroutine doesn't send picker update to parent after the balancer
// is closed.
//
// It's only used by the run() goroutine, but not the other exported
// functions. Because the exported functions are guaranteed to be
// synchronized with Close().
mu sync.Mutex
closed *grpcsync.Event
done *grpcsync.Event
bOpts balancer.BuildOptions
logger *grpclog.PrefixLogger
xdsClient xdsclient.XDSClient
config *LBConfig
child *gracefulswitch.Balancer
cancelLoadReport func()
edsServiceName string
lrsServer *bootstrap.ServerConfig
loadWrapper *loadstore.Wrapper
clusterNameMu sync.Mutex
clusterName string
// childState/drops/requestCounter keeps the state used by the most recently
// generated picker. All fields can only be accessed in run(). And run() is
// the only goroutine that sends picker to the parent ClientConn. All
// requests to update picker need to be sent to pickerUpdateCh.
childState balancer.State
dropCategories []DropConfig // The categories for drops.
drops []*dropper
requestCounterCluster string // The cluster name for the request counter.
requestCounterService string // The service name for the request counter.
requestCounter *xdsclient.ClusterRequestsCounter
requestCountMax uint32
pickerUpdateCh *buffer.Unbounded
}
// updateLoadStore checks the config for load store, and decides whether it
// needs to restart the load reporting stream.
func (b *clusterImplBalancer) updateLoadStore(newConfig *LBConfig) error {
var updateLoadClusterAndService bool
// ClusterName is different, restart. ClusterName is from ClusterName and
// EDSServiceName.
clusterName := b.getClusterName()
if clusterName != newConfig.Cluster {
updateLoadClusterAndService = true
b.setClusterName(newConfig.Cluster)
clusterName = newConfig.Cluster
}
if b.edsServiceName != newConfig.EDSServiceName {
updateLoadClusterAndService = true
b.edsServiceName = newConfig.EDSServiceName
}
if updateLoadClusterAndService {
// This updates the clusterName and serviceName that will be reported
// for the loads. The update here is too early, the perfect timing is
// when the picker is updated with the new connection. But from this
// balancer's point of view, it's impossible to tell.
//
// On the other hand, this will almost never happen. Each LRS policy
// shouldn't get updated config. The parent should do a graceful switch
// when the clusterName or serviceName is changed.
b.loadWrapper.UpdateClusterAndService(clusterName, b.edsServiceName)
}
var (
stopOldLoadReport bool
startNewLoadReport bool
)
// Check if it's necessary to restart load report.
if b.lrsServer == nil {
if newConfig.LoadReportingServer != nil {
// Old is nil, new is not nil, start new LRS.
b.lrsServer = newConfig.LoadReportingServer
startNewLoadReport = true
}
// Old is nil, new is nil, do nothing.
} else if newConfig.LoadReportingServer == nil {
// Old is not nil, new is nil, stop old, don't start new.
b.lrsServer = newConfig.LoadReportingServer
stopOldLoadReport = true
} else {
// Old is not nil, new is not nil, compare string values, if
// different, stop old and start new.
if !b.lrsServer.Equal(newConfig.LoadReportingServer) {
b.lrsServer = newConfig.LoadReportingServer
stopOldLoadReport = true
startNewLoadReport = true
}
}
if stopOldLoadReport {
if b.cancelLoadReport != nil {
b.cancelLoadReport()
b.cancelLoadReport = nil
if !startNewLoadReport {
// If a new LRS stream will be started later, no need to update
// it to nil here.
b.loadWrapper.UpdateLoadStore(nil)
}
}
}
if startNewLoadReport {
var loadStore *load.Store
if b.xdsClient != nil {
loadStore, b.cancelLoadReport = b.xdsClient.ReportLoad(b.lrsServer)
}
b.loadWrapper.UpdateLoadStore(loadStore)
}
return nil
}
func (b *clusterImplBalancer) UpdateClientConnState(s balancer.ClientConnState) error {
if b.closed.HasFired() {
b.logger.Warningf("xds: received ClientConnState {%+v} after clusterImplBalancer was closed", s)
return nil
}
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)
}
// Need to check for potential errors at the beginning of this function, so
// that on errors, we reject the whole config, instead of applying part of
// it.
bb := balancer.Get(newConfig.ChildPolicy.Name)
if bb == nil {
return fmt.Errorf("balancer %q not registered", newConfig.ChildPolicy.Name)
}
if b.xdsClient == nil {
c := xdsclient.FromResolverState(s.ResolverState)
if c == nil {
return balancer.ErrBadResolverState
}
b.xdsClient = c
}
// Update load reporting config. This needs to be done before updating the
// child policy because we need the loadStore from the updated client to be
// passed to the ccWrapper, so that the next picker from the child policy
// will pick up the new loadStore.
if err := b.updateLoadStore(newConfig); err != nil {
return err
}
if b.config == nil || b.config.ChildPolicy.Name != newConfig.ChildPolicy.Name {
if err := b.child.SwitchTo(bb); err != nil {
return fmt.Errorf("error switching to child of type %q: %v", newConfig.ChildPolicy.Name, err)
}
}
b.config = newConfig
// Notify run() of this new config, in case drop and request counter need
// update (which means a new picker needs to be generated).
b.pickerUpdateCh.Put(newConfig)
// Addresses and sub-balancer config are sent to sub-balancer.
return b.child.UpdateClientConnState(balancer.ClientConnState{
ResolverState: s.ResolverState,
BalancerConfig: b.config.ChildPolicy.Config,
})
}
func (b *clusterImplBalancer) ResolverError(err error) {
if b.closed.HasFired() {
b.logger.Warningf("xds: received resolver error {%+v} after clusterImplBalancer was closed", err)
return
}
b.child.ResolverError(err)
}
func (b *clusterImplBalancer) updateSubConnState(sc balancer.SubConn, s balancer.SubConnState, cb func(balancer.SubConnState)) {
if b.closed.HasFired() {
b.logger.Warningf("xds: received subconn state change {%+v, %+v} after clusterImplBalancer was closed", sc, s)
return
}
// Trigger re-resolution when a SubConn turns transient failure. This is
// necessary for the LogicalDNS in cluster_resolver policy to re-resolve.
//
// Note that this happens not only for the addresses from DNS, but also for
// EDS (cluster_impl doesn't know if it's DNS or EDS, only the parent
// knows). The parent priority policy is configured to ignore re-resolution
// signal from the EDS children.
if s.ConnectivityState == connectivity.TransientFailure {
b.ClientConn.ResolveNow(resolver.ResolveNowOptions{})
}
if cb != nil {
cb(s)
}
}
func (b *clusterImplBalancer) UpdateSubConnState(sc balancer.SubConn, s balancer.SubConnState) {
b.logger.Errorf("UpdateSubConnState(%v, %+v) called unexpectedly", sc, s)
}
func (b *clusterImplBalancer) Close() {
b.mu.Lock()
b.closed.Fire()
b.mu.Unlock()
b.child.Close()
b.childState = balancer.State{}
b.pickerUpdateCh.Close()
<-b.done.Done()
b.logger.Infof("Shutdown")
}
func (b *clusterImplBalancer) ExitIdle() {
b.child.ExitIdle()
}
// Override methods to accept updates from the child LB.
func (b *clusterImplBalancer) UpdateState(state balancer.State) {
// Instead of updating parent ClientConn inline, send state to run().
b.pickerUpdateCh.Put(state)
}
func (b *clusterImplBalancer) setClusterName(n string) {
b.clusterNameMu.Lock()
defer b.clusterNameMu.Unlock()
b.clusterName = n
}
func (b *clusterImplBalancer) getClusterName() string {
b.clusterNameMu.Lock()
defer b.clusterNameMu.Unlock()
return b.clusterName
}
// scWrapper is a wrapper of SubConn with locality ID. The locality ID can be
// retrieved from the addresses when creating SubConn.
//
// All SubConns passed to the child policies are wrapped in this, so that the
// picker can get the localityID from the picked SubConn, and do load reporting.
//
// After wrapping, all SubConns to and from the parent ClientConn (e.g. for
// SubConn state update, update/remove SubConn) must be the original SubConns.
// All SubConns to and from the child policy (NewSubConn, forwarding SubConn
// state update) must be the wrapper. The balancer keeps a map from the original
// SubConn to the wrapper for this purpose.
type scWrapper struct {
balancer.SubConn
// locality needs to be atomic because it can be updated while being read by
// the picker.
locality atomic.Value // type xdsinternal.LocalityID
}
func (scw *scWrapper) updateLocalityID(lID xdsinternal.LocalityID) {
scw.locality.Store(lID)
}
func (scw *scWrapper) localityID() xdsinternal.LocalityID {
lID, _ := scw.locality.Load().(xdsinternal.LocalityID)
return lID
}
func (b *clusterImplBalancer) NewSubConn(addrs []resolver.Address, opts balancer.NewSubConnOptions) (balancer.SubConn, error) {
clusterName := b.getClusterName()
newAddrs := make([]resolver.Address, len(addrs))
var lID xdsinternal.LocalityID
for i, addr := range addrs {
newAddrs[i] = xds.SetXDSHandshakeClusterName(addr, clusterName)
lID = xdsinternal.GetLocalityID(newAddrs[i])
}
var sc balancer.SubConn
oldListener := opts.StateListener
opts.StateListener = func(state balancer.SubConnState) { b.updateSubConnState(sc, state, oldListener) }
sc, err := b.ClientConn.NewSubConn(newAddrs, opts)
if err != nil {
return nil, err
}
// Wrap this SubConn in a wrapper, and add it to the map.
ret := &scWrapper{SubConn: sc}
ret.updateLocalityID(lID)
return ret, nil
}
func (b *clusterImplBalancer) RemoveSubConn(sc balancer.SubConn) {
b.logger.Errorf("RemoveSubConn(%v) called unexpectedly", sc)
}
func (b *clusterImplBalancer) UpdateAddresses(sc balancer.SubConn, addrs []resolver.Address) {
clusterName := b.getClusterName()
newAddrs := make([]resolver.Address, len(addrs))
var lID xdsinternal.LocalityID
for i, addr := range addrs {
newAddrs[i] = xds.SetXDSHandshakeClusterName(addr, clusterName)
lID = xdsinternal.GetLocalityID(newAddrs[i])
}
if scw, ok := sc.(*scWrapper); ok {
scw.updateLocalityID(lID)
// Need to get the original SubConn from the wrapper before calling
// parent ClientConn.
sc = scw.SubConn
}
b.ClientConn.UpdateAddresses(sc, newAddrs)
}
type dropConfigs struct {
drops []*dropper
requestCounter *xdsclient.ClusterRequestsCounter
requestCountMax uint32
}
// handleDropAndRequestCount compares drop and request counter in newConfig with
// the one currently used by picker. It returns a new dropConfigs if a new
// picker needs to be generated, otherwise it returns nil.
func (b *clusterImplBalancer) handleDropAndRequestCount(newConfig *LBConfig) *dropConfigs {
// Compare new drop config. And update picker if it's changed.
var updatePicker bool
if !equalDropCategories(b.dropCategories, newConfig.DropCategories) {
b.dropCategories = newConfig.DropCategories
b.drops = make([]*dropper, 0, len(newConfig.DropCategories))
for _, c := range newConfig.DropCategories {
b.drops = append(b.drops, newDropper(c))
}
updatePicker = true
}
// Compare cluster name. And update picker if it's changed, because circuit
// breaking's stream counter will be different.
if b.requestCounterCluster != newConfig.Cluster || b.requestCounterService != newConfig.EDSServiceName {
b.requestCounterCluster = newConfig.Cluster
b.requestCounterService = newConfig.EDSServiceName
b.requestCounter = xdsclient.GetClusterRequestsCounter(newConfig.Cluster, newConfig.EDSServiceName)
updatePicker = true
}
// Compare upper bound of stream count. And update picker if it's changed.
// This is also for circuit breaking.
var newRequestCountMax uint32 = 1024
if newConfig.MaxConcurrentRequests != nil {
newRequestCountMax = *newConfig.MaxConcurrentRequests
}
if b.requestCountMax != newRequestCountMax {
b.requestCountMax = newRequestCountMax
updatePicker = true
}
if !updatePicker {
return nil
}
return &dropConfigs{
drops: b.drops,
requestCounter: b.requestCounter,
requestCountMax: b.requestCountMax,
}
}
func (b *clusterImplBalancer) run() {
defer b.done.Fire()
for {
select {
case update, ok := <-b.pickerUpdateCh.Get():
if !ok {
return
}
b.pickerUpdateCh.Load()
b.mu.Lock()
if b.closed.HasFired() {
b.mu.Unlock()
return
}
switch u := update.(type) {
case balancer.State:
b.childState = u
b.ClientConn.UpdateState(balancer.State{
ConnectivityState: b.childState.ConnectivityState,
Picker: newPicker(b.childState, &dropConfigs{
drops: b.drops,
requestCounter: b.requestCounter,
requestCountMax: b.requestCountMax,
}, b.loadWrapper),
})
case *LBConfig:
dc := b.handleDropAndRequestCount(u)
if dc != nil && b.childState.Picker != nil {
b.ClientConn.UpdateState(balancer.State{
ConnectivityState: b.childState.ConnectivityState,
Picker: newPicker(b.childState, dc, b.loadWrapper),
})
}
}
b.mu.Unlock()
case <-b.closed.Done():
if b.cancelLoadReport != nil {
b.cancelLoadReport()
b.cancelLoadReport = nil
}
return
}
}
}