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eds_impl.go
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/
eds_impl.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
import (
"encoding/json"
"reflect"
"sync"
"time"
"github.com/google/go-cmp/cmp"
"github.com/seacomandor/grpc-go/balancer"
"github.com/seacomandor/grpc-go/balancer/base"
"github.com/seacomandor/grpc-go/balancer/roundrobin"
"github.com/seacomandor/grpc-go/balancer/weightedroundrobin"
"github.com/seacomandor/grpc-go/codes"
"github.com/seacomandor/grpc-go/connectivity"
"github.com/seacomandor/grpc-go/internal/grpclog"
"github.com/seacomandor/grpc-go/resolver"
"github.com/seacomandor/grpc-go/status"
"github.com/seacomandor/grpc-go/xds/internal"
"github.com/seacomandor/grpc-go/xds/internal/balancer/balancergroup"
"github.com/seacomandor/grpc-go/xds/internal/balancer/lrs"
xdsclient "github.com/seacomandor/grpc-go/xds/internal/client"
)
// TODO: make this a environment variable?
var defaultPriorityInitTimeout = 10 * time.Second
type localityConfig struct {
weight uint32
addrs []resolver.Address
}
// balancerGroupWithConfig contains the localities with the same priority. It
// manages all localities using a balancerGroup.
type balancerGroupWithConfig struct {
bg *balancergroup.BalancerGroup
configs map[internal.LocalityID]*localityConfig
}
// edsBalancerImpl does load balancing based on the EDS responses. Note that it
// doesn't implement the balancer interface. It's intended to be used by a high
// level balancer implementation.
//
// The localities are picked as weighted round robin. A configurable child
// policy is used to manage endpoints in each locality.
type edsBalancerImpl struct {
cc balancer.ClientConn
logger *grpclog.PrefixLogger
enqueueChildBalancerStateUpdate func(priorityType, balancer.State)
subBalancerBuilder balancer.Builder
loadStore lrs.Store
priorityToLocalities map[priorityType]*balancerGroupWithConfig
respReceived bool
// There's no need to hold any mutexes at the same time. The order to take
// mutex should be: priorityMu > subConnMu, but this is implicit via
// balancers (starting balancer with next priority while holding priorityMu,
// and the balancer may create new SubConn).
priorityMu sync.Mutex
// priorities are pointers, and will be nil when EDS returns empty result.
priorityInUse priorityType
priorityLowest priorityType
priorityToState map[priorityType]*balancer.State
// The timer to give a priority 10 seconds to connect. And if the priority
// doesn't go into Ready/Failure, start the next priority.
//
// One timer is enough because there can be at most one priority in init
// state.
priorityInitTimer *time.Timer
subConnMu sync.Mutex
subConnToPriority map[balancer.SubConn]priorityType
pickerMu sync.Mutex
dropConfig []xdsclient.OverloadDropConfig
drops []*dropper
innerState balancer.State // The state of the picker without drop support.
}
// newEDSBalancerImpl create a new edsBalancerImpl.
func newEDSBalancerImpl(cc balancer.ClientConn, enqueueState func(priorityType, balancer.State), loadStore lrs.Store, logger *grpclog.PrefixLogger) *edsBalancerImpl {
edsImpl := &edsBalancerImpl{
cc: cc,
logger: logger,
subBalancerBuilder: balancer.Get(roundrobin.Name),
enqueueChildBalancerStateUpdate: enqueueState,
priorityToLocalities: make(map[priorityType]*balancerGroupWithConfig),
priorityToState: make(map[priorityType]*balancer.State),
subConnToPriority: make(map[balancer.SubConn]priorityType),
loadStore: loadStore,
}
// Don't start balancer group here. Start it when handling the first EDS
// response. Otherwise the balancer group will be started with round-robin,
// and if users specify a different sub-balancer, all balancers in balancer
// group will be closed and recreated when sub-balancer update happens.
return edsImpl
}
// handleChildPolicy updates the child balancers handling endpoints. Child
// policy is roundrobin by default. If the specified balancer is not installed,
// the old child balancer will be used.
//
// HandleChildPolicy and HandleEDSResponse must be called by the same goroutine.
func (edsImpl *edsBalancerImpl) handleChildPolicy(name string, config json.RawMessage) {
if edsImpl.subBalancerBuilder.Name() == name {
return
}
newSubBalancerBuilder := balancer.Get(name)
if newSubBalancerBuilder == nil {
edsImpl.logger.Infof("edsBalancerImpl: failed to find balancer with name %q, keep using %q", name, edsImpl.subBalancerBuilder.Name())
return
}
edsImpl.subBalancerBuilder = newSubBalancerBuilder
for _, bgwc := range edsImpl.priorityToLocalities {
if bgwc == nil {
continue
}
for id, config := range bgwc.configs {
// TODO: (eds) add support to balancer group to support smoothly
// switching sub-balancers (keep old balancer around until new
// balancer becomes ready).
bgwc.bg.Remove(id)
bgwc.bg.Add(id, config.weight, edsImpl.subBalancerBuilder)
bgwc.bg.UpdateClientConnState(id, balancer.ClientConnState{
ResolverState: resolver.State{Addresses: config.addrs},
})
}
}
}
// updateDrops compares new drop policies with the old. If they are different,
// it updates the drop policies and send ClientConn an updated picker.
func (edsImpl *edsBalancerImpl) updateDrops(dropConfig []xdsclient.OverloadDropConfig) {
if cmp.Equal(dropConfig, edsImpl.dropConfig) {
return
}
edsImpl.pickerMu.Lock()
edsImpl.dropConfig = dropConfig
var newDrops []*dropper
for _, c := range edsImpl.dropConfig {
newDrops = append(newDrops, newDropper(c))
}
edsImpl.drops = newDrops
if edsImpl.innerState.Picker != nil {
// Update picker with old inner picker, new drops.
edsImpl.cc.UpdateState(balancer.State{
ConnectivityState: edsImpl.innerState.ConnectivityState,
Picker: newDropPicker(edsImpl.innerState.Picker, newDrops, edsImpl.loadStore)},
)
}
edsImpl.pickerMu.Unlock()
}
// handleEDSResponse handles the EDS response and creates/deletes localities and
// SubConns. It also handles drops.
//
// HandleChildPolicy and HandleEDSResponse must be called by the same goroutine.
func (edsImpl *edsBalancerImpl) handleEDSResponse(edsResp xdsclient.EndpointsUpdate) {
// TODO: Unhandled fields from EDS response:
// - edsResp.GetPolicy().GetOverprovisioningFactor()
// - locality.GetPriority()
// - lbEndpoint.GetMetadata(): contains BNS name, send to sub-balancers
// - as service config or as resolved address
// - if socketAddress is not ip:port
// - socketAddress.GetNamedPort(), socketAddress.GetResolverName()
// - resolve endpoint's name with another resolver
// If the first EDS update is an empty update, nothing is changing from the
// previous update (which is the default empty value). We need to explicitly
// handle first update being empty, and send a transient failure picker.
//
// TODO: define Equal() on type EndpointUpdate to avoid DeepEqual. And do
// the same for the other types.
if !edsImpl.respReceived && reflect.DeepEqual(edsResp, xdsclient.EndpointsUpdate{}) {
edsImpl.cc.UpdateState(balancer.State{ConnectivityState: connectivity.TransientFailure, Picker: base.NewErrPicker(errAllPrioritiesRemoved)})
}
edsImpl.respReceived = true
edsImpl.updateDrops(edsResp.Drops)
// Filter out all localities with weight 0.
//
// Locality weighted load balancer can be enabled by setting an option in
// CDS, and the weight of each locality. Currently, without the guarantee
// that CDS is always sent, we assume locality weighted load balance is
// always enabled, and ignore all weight 0 localities.
//
// In the future, we should look at the config in CDS response and decide
// whether locality weight matters.
newLocalitiesWithPriority := make(map[priorityType][]xdsclient.Locality)
for _, locality := range edsResp.Localities {
if locality.Weight == 0 {
continue
}
priority := newPriorityType(locality.Priority)
newLocalitiesWithPriority[priority] = append(newLocalitiesWithPriority[priority], locality)
}
var (
priorityLowest priorityType
priorityChanged bool
)
for priority, newLocalities := range newLocalitiesWithPriority {
if !priorityLowest.isSet() || priorityLowest.higherThan(priority) {
priorityLowest = priority
}
bgwc, ok := edsImpl.priorityToLocalities[priority]
if !ok {
// Create balancer group if it's never created (this is the first
// time this priority is received). We don't start it here. It may
// be started when necessary (e.g. when higher is down, or if it's a
// new lowest priority).
bgwc = &balancerGroupWithConfig{
bg: balancergroup.New(edsImpl.ccWrapperWithPriority(priority), edsImpl.loadStore, edsImpl.logger),
configs: make(map[internal.LocalityID]*localityConfig),
}
edsImpl.priorityToLocalities[priority] = bgwc
priorityChanged = true
edsImpl.logger.Infof("New priority %v added", priority)
}
edsImpl.handleEDSResponsePerPriority(bgwc, newLocalities)
}
edsImpl.priorityLowest = priorityLowest
// Delete priorities that are removed in the latest response, and also close
// the balancer group.
for p, bgwc := range edsImpl.priorityToLocalities {
if _, ok := newLocalitiesWithPriority[p]; !ok {
delete(edsImpl.priorityToLocalities, p)
bgwc.bg.Close()
delete(edsImpl.priorityToState, p)
priorityChanged = true
edsImpl.logger.Infof("Priority %v deleted", p)
}
}
// If priority was added/removed, it may affect the balancer group to use.
// E.g. priorityInUse was removed, or all priorities are down, and a new
// lower priority was added.
if priorityChanged {
edsImpl.handlePriorityChange()
}
}
func (edsImpl *edsBalancerImpl) handleEDSResponsePerPriority(bgwc *balancerGroupWithConfig, newLocalities []xdsclient.Locality) {
// newLocalitiesSet contains all names of localities in the new EDS response
// for the same priority. It's used to delete localities that are removed in
// the new EDS response.
newLocalitiesSet := make(map[internal.LocalityID]struct{})
for _, locality := range newLocalities {
// One balancer for each locality.
lid := locality.ID
newLocalitiesSet[lid] = struct{}{}
newWeight := locality.Weight
var newAddrs []resolver.Address
for _, lbEndpoint := range locality.Endpoints {
// Filter out all "unhealthy" endpoints (unknown and
// healthy are both considered to be healthy:
// https://www.envoyproxy.io/docs/envoy/latest/api-v2/api/v2/core/health_check.proto#envoy-api-enum-core-healthstatus).
if lbEndpoint.HealthStatus != xdsclient.EndpointHealthStatusHealthy &&
lbEndpoint.HealthStatus != xdsclient.EndpointHealthStatusUnknown {
continue
}
address := resolver.Address{
Addr: lbEndpoint.Address,
}
if edsImpl.subBalancerBuilder.Name() == weightedroundrobin.Name && lbEndpoint.Weight != 0 {
ai := weightedroundrobin.AddrInfo{Weight: lbEndpoint.Weight}
address = weightedroundrobin.SetAddrInfo(address, ai)
// Metadata field in resolver.Address is deprecated. The
// attributes field should be used to specify arbitrary
// attributes about the address. We still need to populate the
// Metadata field here to allow users of this field to migrate
// to the new one.
// TODO(easwars): Remove this once all users have migrated.
// See https://github.com/grpc/grpc-go/issues/3563.
address.Metadata = &ai
}
newAddrs = append(newAddrs, address)
}
var weightChanged, addrsChanged bool
config, ok := bgwc.configs[lid]
if !ok {
// A new balancer, add it to balancer group and balancer map.
bgwc.bg.Add(lid, newWeight, edsImpl.subBalancerBuilder)
config = &localityConfig{
weight: newWeight,
}
bgwc.configs[lid] = config
// weightChanged is false for new locality, because there's no need
// to update weight in bg.
addrsChanged = true
edsImpl.logger.Infof("New locality %v added", lid)
} else {
// Compare weight and addrs.
if config.weight != newWeight {
weightChanged = true
}
if !cmp.Equal(config.addrs, newAddrs) {
addrsChanged = true
}
edsImpl.logger.Infof("Locality %v updated, weightedChanged: %v, addrsChanged: %v", lid, weightChanged, addrsChanged)
}
if weightChanged {
config.weight = newWeight
bgwc.bg.ChangeWeight(lid, newWeight)
}
if addrsChanged {
config.addrs = newAddrs
bgwc.bg.UpdateClientConnState(lid, balancer.ClientConnState{
ResolverState: resolver.State{Addresses: newAddrs},
})
}
}
// Delete localities that are removed in the latest response.
for lid := range bgwc.configs {
if _, ok := newLocalitiesSet[lid]; !ok {
bgwc.bg.Remove(lid)
delete(bgwc.configs, lid)
edsImpl.logger.Infof("Locality %v deleted", lid)
}
}
}
// handleSubConnStateChange handles the state change and update pickers accordingly.
func (edsImpl *edsBalancerImpl) handleSubConnStateChange(sc balancer.SubConn, s connectivity.State) {
edsImpl.subConnMu.Lock()
var bgwc *balancerGroupWithConfig
if p, ok := edsImpl.subConnToPriority[sc]; ok {
if s == connectivity.Shutdown {
// Only delete sc from the map when state changed to Shutdown.
delete(edsImpl.subConnToPriority, sc)
}
bgwc = edsImpl.priorityToLocalities[p]
}
edsImpl.subConnMu.Unlock()
if bgwc == nil {
edsImpl.logger.Infof("edsBalancerImpl: priority not found for sc state change")
return
}
if bg := bgwc.bg; bg != nil {
bg.UpdateSubConnState(sc, balancer.SubConnState{ConnectivityState: s})
}
}
// updateState first handles priority, and then wraps picker in a drop picker
// before forwarding the update.
func (edsImpl *edsBalancerImpl) updateState(priority priorityType, s balancer.State) {
_, ok := edsImpl.priorityToLocalities[priority]
if !ok {
edsImpl.logger.Infof("eds: received picker update from unknown priority")
return
}
if edsImpl.handlePriorityWithNewState(priority, s) {
edsImpl.pickerMu.Lock()
defer edsImpl.pickerMu.Unlock()
edsImpl.innerState = s
// Don't reset drops when it's a state change.
edsImpl.cc.UpdateState(balancer.State{ConnectivityState: s.ConnectivityState, Picker: newDropPicker(s.Picker, edsImpl.drops, edsImpl.loadStore)})
}
}
func (edsImpl *edsBalancerImpl) ccWrapperWithPriority(priority priorityType) *edsBalancerWrapperCC {
return &edsBalancerWrapperCC{
ClientConn: edsImpl.cc,
priority: priority,
parent: edsImpl,
}
}
// edsBalancerWrapperCC implements the balancer.ClientConn API and get passed to
// each balancer group. It contains the locality priority.
type edsBalancerWrapperCC struct {
balancer.ClientConn
priority priorityType
parent *edsBalancerImpl
}
func (ebwcc *edsBalancerWrapperCC) NewSubConn(addrs []resolver.Address, opts balancer.NewSubConnOptions) (balancer.SubConn, error) {
return ebwcc.parent.newSubConn(ebwcc.priority, addrs, opts)
}
func (ebwcc *edsBalancerWrapperCC) UpdateState(state balancer.State) {
ebwcc.parent.enqueueChildBalancerStateUpdate(ebwcc.priority, state)
}
func (edsImpl *edsBalancerImpl) newSubConn(priority priorityType, addrs []resolver.Address, opts balancer.NewSubConnOptions) (balancer.SubConn, error) {
sc, err := edsImpl.cc.NewSubConn(addrs, opts)
if err != nil {
return nil, err
}
edsImpl.subConnMu.Lock()
edsImpl.subConnToPriority[sc] = priority
edsImpl.subConnMu.Unlock()
return sc, nil
}
// close closes the balancer.
func (edsImpl *edsBalancerImpl) close() {
for _, bgwc := range edsImpl.priorityToLocalities {
if bg := bgwc.bg; bg != nil {
bg.Close()
}
}
}
type dropPicker struct {
drops []*dropper
p balancer.Picker
loadStore lrs.Store
}
func newDropPicker(p balancer.Picker, drops []*dropper, loadStore lrs.Store) *dropPicker {
return &dropPicker{
drops: drops,
p: p,
loadStore: loadStore,
}
}
func (d *dropPicker) Pick(info balancer.PickInfo) (balancer.PickResult, error) {
var (
drop bool
category string
)
for _, dp := range d.drops {
if dp.drop() {
drop = true
category = dp.c.Category
break
}
}
if drop {
if d.loadStore != nil {
d.loadStore.CallDropped(category)
}
return balancer.PickResult{}, status.Errorf(codes.Unavailable, "RPC is dropped")
}
// TODO: (eds) don't drop unless the inner picker is READY. Similar to
// https://github.com/grpc/grpc-go/issues/2622.
return d.p.Pick(info)
}