snapshot of https://github.com/grpc/grpc-go.git (master, 2026-09-15; blobs > 131072B omitted)

internal/xds/balancer/priority/balancer_child.go

@@ -0,0 +1,186 @@
+/*
+ *
+ * Copyright 2021 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 priority
+
+import (
+	"time"
+
+	"google.golang.org/grpc/balancer"
+	"google.golang.org/grpc/balancer/base"
+	"google.golang.org/grpc/connectivity"
+	"google.golang.org/grpc/resolver"
+	"google.golang.org/grpc/serviceconfig"
+)
+
+var timeAfterFunc = time.AfterFunc
+
+type childBalancer struct {
+	name         string
+	parent       *priorityBalancer
+	parentCC     balancer.ClientConn
+	balancerName string
+	cc           *ignoreResolveNowClientConn
+
+	ignoreReresolutionRequests bool
+	config                     serviceconfig.LoadBalancingConfig
+	rState                     resolver.State
+
+	started bool
+	// This is set when the child reports TransientFailure, and unset when it
+	// reports Ready or Idle. It is used to decide whether the failover timer
+	// should start when the child is transitioning into Connecting. The timer
+	// will be restarted if the child has not reported TF more recently than it
+	// reported Ready or Idle.
+	reportedTF bool
+	// The latest state the child balancer provided.
+	state balancer.State
+	// The timer to give a priority some time to connect. And if the priority
+	// doesn't go into Ready/Failure, the next priority will be started.
+	initTimer *timerWrapper
+}
+
+// newChildBalancer creates a child balancer place holder, but doesn't
+// build/start the child balancer.
+func newChildBalancer(name string, parent *priorityBalancer, balancerName string, cc balancer.ClientConn) *childBalancer {
+	return &childBalancer{
+		name:         name,
+		parent:       parent,
+		parentCC:     cc,
+		balancerName: balancerName,
+		cc:           newIgnoreResolveNowClientConn(cc, false),
+		started:      false,
+		// Start with the connecting state and picker with re-pick error, so
+		// that when a priority switch causes this child picked before it's
+		// balancing policy is created, a re-pick will happen.
+		state: balancer.State{
+			ConnectivityState: connectivity.Connecting,
+			Picker:            base.NewErrPicker(balancer.ErrNoSubConnAvailable),
+		},
+	}
+}
+
+// updateBalancerName updates balancer name for the child, but doesn't build a
+// new one. The parent priority LB always closes the child policy before
+// updating the balancer name, and the new balancer is built when it gets added
+// to the balancergroup as part of start().
+func (cb *childBalancer) updateBalancerName(balancerName string) {
+	cb.balancerName = balancerName
+	cb.cc = newIgnoreResolveNowClientConn(cb.parentCC, cb.ignoreReresolutionRequests)
+}
+
+// updateConfig sets childBalancer's config and state, but doesn't send update to
+// the child balancer unless it is started.
+func (cb *childBalancer) updateConfig(child *Child, rState resolver.State) {
+	cb.ignoreReresolutionRequests = child.IgnoreReresolutionRequests
+	cb.config = child.Config.Config
+	cb.rState = rState
+	if cb.started {
+		cb.sendUpdate()
+	}
+}
+
+// start builds the child balancer if it's not already started.
+//
+// It doesn't do it directly. It asks the balancer group to build it.
+func (cb *childBalancer) start() {
+	if cb.started {
+		return
+	}
+	cb.started = true
+	cb.parent.bg.AddWithClientConn(cb.name, cb.balancerName, cb.cc)
+	cb.startInitTimer()
+	cb.sendUpdate()
+}
+
+// sendUpdate sends the addresses and config to the child balancer.
+func (cb *childBalancer) sendUpdate() {
+	cb.cc.updateIgnoreResolveNow(cb.ignoreReresolutionRequests)
+	// TODO: return and aggregate the returned error in the parent.
+	err := cb.parent.bg.UpdateClientConnState(cb.name, balancer.ClientConnState{
+		ResolverState:  cb.rState,
+		BalancerConfig: cb.config,
+	})
+	// Report TF if update to the child fails.
+	if err != nil {
+		cb.parent.logger.Warningf("Failed to update state for child policy %q: %v", cb.name, err)
+		cb.reportedTF = true
+		cb.state = balancer.State{
+			ConnectivityState: connectivity.TransientFailure,
+			Picker:            base.NewErrPicker(err),
+		}
+		cb.parent.handleChildStateUpdate(cb.name, cb.state)
+	}
+}
+
+// stop stops the child balancer and resets the state.
+//
+// It doesn't do it directly. It asks the balancer group to remove it.
+//
+// Note that the underlying balancer group could keep the child in a cache.
+func (cb *childBalancer) stop(immediate bool) {
+	if !cb.started {
+		return
+	}
+	cb.stopInitTimer()
+	if immediate {
+		cb.parent.bg.RemoveImmediately(cb.name)
+	} else {
+		cb.parent.bg.Remove(cb.name)
+	}
+	cb.started = false
+	cb.state = balancer.State{
+		ConnectivityState: connectivity.Connecting,
+		Picker:            base.NewErrPicker(balancer.ErrNoSubConnAvailable),
+	}
+	// Clear child.reportedTF, so that if this child is started later, it will
+	// be given time to connect.
+	cb.reportedTF = false
+}
+
+func (cb *childBalancer) startInitTimer() {
+	if cb.initTimer != nil {
+		return
+	}
+	// Need this local variable to capture timerW in the AfterFunc closure
+	// to check the stopped boolean.
+	timerW := &timerWrapper{}
+	cb.initTimer = timerW
+	timerW.timer = timeAfterFunc(DefaultPriorityInitTimeout, func() {
+		cb.parent.mu.Lock()
+		defer cb.parent.mu.Unlock()
+		if timerW.stopped {
+			return
+		}
+		cb.initTimer = nil
+		// Re-sync the priority. This will switch to the next priority if
+		// there's any. Note that it's important sync() is called after setting
+		// initTimer to nil.
+		cb.parent.syncPriority("")
+	})
+}
+
+func (cb *childBalancer) stopInitTimer() {
+	timerW := cb.initTimer
+	if timerW == nil {
+		return
+	}
+	cb.initTimer = nil
+	timerW.stopped = true
+	timerW.timer.Stop()
+}