338 lines
11 KiB
Go
338 lines
11 KiB
Go
/*
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*
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* Copyright 2017 gRPC authors.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*
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*/
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package grpc
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import (
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"context"
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"fmt"
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"sync"
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"google.golang.org/grpc/balancer"
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"google.golang.org/grpc/connectivity"
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"google.golang.org/grpc/internal/balancer/gracefulswitch"
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"google.golang.org/grpc/internal/channelz"
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"google.golang.org/grpc/internal/grpcsync"
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"google.golang.org/grpc/resolver"
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)
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// ccBalancerWrapper sits between the ClientConn and the Balancer.
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//
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// ccBalancerWrapper implements methods corresponding to the ones on the
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// balancer.Balancer interface. The ClientConn is free to call these methods
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// concurrently and the ccBalancerWrapper ensures that calls from the ClientConn
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// to the Balancer happen in order by performing them in the serializer, without
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// any mutexes held.
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//
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// ccBalancerWrapper also implements the balancer.ClientConn interface and is
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// passed to the Balancer implementations. It invokes unexported methods on the
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// ClientConn to handle these calls from the Balancer.
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//
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// It uses the gracefulswitch.Balancer internally to ensure that balancer
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// switches happen in a graceful manner.
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type ccBalancerWrapper struct {
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// The following fields are initialized when the wrapper is created and are
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// read-only afterwards, and therefore can be accessed without a mutex.
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cc *ClientConn
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opts balancer.BuildOptions
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serializer *grpcsync.CallbackSerializer
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serializerCancel context.CancelFunc
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// The following fields are only accessed within the serializer or during
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// initialization.
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curBalancerName string
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balancer *gracefulswitch.Balancer
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// The following field is protected by mu. Caller must take cc.mu before
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// taking mu.
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mu sync.Mutex
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closed bool
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}
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// newCCBalancerWrapper creates a new balancer wrapper in idle state. The
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// underlying balancer is not created until the updateClientConnState() method
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// is invoked.
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func newCCBalancerWrapper(cc *ClientConn) *ccBalancerWrapper {
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ctx, cancel := context.WithCancel(cc.ctx)
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ccb := &ccBalancerWrapper{
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cc: cc,
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opts: balancer.BuildOptions{
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DialCreds: cc.dopts.copts.TransportCredentials,
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CredsBundle: cc.dopts.copts.CredsBundle,
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Dialer: cc.dopts.copts.Dialer,
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Authority: cc.authority,
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CustomUserAgent: cc.dopts.copts.UserAgent,
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ChannelzParent: cc.channelz,
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Target: cc.parsedTarget,
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},
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serializer: grpcsync.NewCallbackSerializer(ctx),
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serializerCancel: cancel,
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}
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ccb.balancer = gracefulswitch.NewBalancer(ccb, ccb.opts)
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return ccb
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}
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// updateClientConnState is invoked by grpc to push a ClientConnState update to
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// the underlying balancer. This is always executed from the serializer, so
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// it is safe to call into the balancer here.
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func (ccb *ccBalancerWrapper) updateClientConnState(ccs *balancer.ClientConnState) error {
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errCh := make(chan error)
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ok := ccb.serializer.Schedule(func(ctx context.Context) {
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defer close(errCh)
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if ctx.Err() != nil || ccb.balancer == nil {
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return
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}
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name := gracefulswitch.ChildName(ccs.BalancerConfig)
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if ccb.curBalancerName != name {
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ccb.curBalancerName = name
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channelz.Infof(logger, ccb.cc.channelz, "Channel switches to new LB policy %q", name)
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}
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err := ccb.balancer.UpdateClientConnState(*ccs)
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if logger.V(2) && err != nil {
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logger.Infof("error from balancer.UpdateClientConnState: %v", err)
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}
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errCh <- err
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})
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if !ok {
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return nil
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}
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return <-errCh
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}
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// resolverError is invoked by grpc to push a resolver error to the underlying
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// balancer. The call to the balancer is executed from the serializer.
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func (ccb *ccBalancerWrapper) resolverError(err error) {
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ccb.serializer.Schedule(func(ctx context.Context) {
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if ctx.Err() != nil || ccb.balancer == nil {
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return
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}
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ccb.balancer.ResolverError(err)
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})
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}
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// close initiates async shutdown of the wrapper. cc.mu must be held when
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// calling this function. To determine the wrapper has finished shutting down,
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// the channel should block on ccb.serializer.Done() without cc.mu held.
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func (ccb *ccBalancerWrapper) close() {
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ccb.mu.Lock()
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ccb.closed = true
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ccb.mu.Unlock()
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channelz.Info(logger, ccb.cc.channelz, "ccBalancerWrapper: closing")
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ccb.serializer.Schedule(func(context.Context) {
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if ccb.balancer == nil {
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return
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}
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ccb.balancer.Close()
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ccb.balancer = nil
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})
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ccb.serializerCancel()
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}
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// exitIdle invokes the balancer's exitIdle method in the serializer.
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func (ccb *ccBalancerWrapper) exitIdle() {
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ccb.serializer.Schedule(func(ctx context.Context) {
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if ctx.Err() != nil || ccb.balancer == nil {
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return
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}
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ccb.balancer.ExitIdle()
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})
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}
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func (ccb *ccBalancerWrapper) NewSubConn(addrs []resolver.Address, opts balancer.NewSubConnOptions) (balancer.SubConn, error) {
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ccb.cc.mu.Lock()
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defer ccb.cc.mu.Unlock()
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ccb.mu.Lock()
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if ccb.closed {
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ccb.mu.Unlock()
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return nil, fmt.Errorf("balancer is being closed; no new SubConns allowed")
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}
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ccb.mu.Unlock()
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if len(addrs) == 0 {
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return nil, fmt.Errorf("grpc: cannot create SubConn with empty address list")
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}
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ac, err := ccb.cc.newAddrConnLocked(addrs, opts)
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if err != nil {
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channelz.Warningf(logger, ccb.cc.channelz, "acBalancerWrapper: NewSubConn: failed to newAddrConn: %v", err)
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return nil, err
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}
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acbw := &acBalancerWrapper{
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ccb: ccb,
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ac: ac,
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producers: make(map[balancer.ProducerBuilder]*refCountedProducer),
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stateListener: opts.StateListener,
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}
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ac.acbw = acbw
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return acbw, nil
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}
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func (ccb *ccBalancerWrapper) RemoveSubConn(sc balancer.SubConn) {
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// The graceful switch balancer will never call this.
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logger.Errorf("ccb RemoveSubConn(%v) called unexpectedly, sc")
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}
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func (ccb *ccBalancerWrapper) UpdateAddresses(sc balancer.SubConn, addrs []resolver.Address) {
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acbw, ok := sc.(*acBalancerWrapper)
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if !ok {
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return
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}
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acbw.UpdateAddresses(addrs)
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}
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func (ccb *ccBalancerWrapper) UpdateState(s balancer.State) {
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ccb.cc.mu.Lock()
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defer ccb.cc.mu.Unlock()
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ccb.mu.Lock()
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if ccb.closed {
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ccb.mu.Unlock()
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return
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}
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ccb.mu.Unlock()
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// Update picker before updating state. Even though the ordering here does
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// not matter, it can lead to multiple calls of Pick in the common start-up
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// case where we wait for ready and then perform an RPC. If the picker is
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// updated later, we could call the "connecting" picker when the state is
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// updated, and then call the "ready" picker after the picker gets updated.
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// Note that there is no need to check if the balancer wrapper was closed,
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// as we know the graceful switch LB policy will not call cc if it has been
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// closed.
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ccb.cc.pickerWrapper.updatePicker(s.Picker)
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ccb.cc.csMgr.updateState(s.ConnectivityState)
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}
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func (ccb *ccBalancerWrapper) ResolveNow(o resolver.ResolveNowOptions) {
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ccb.cc.mu.RLock()
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defer ccb.cc.mu.RUnlock()
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ccb.mu.Lock()
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if ccb.closed {
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ccb.mu.Unlock()
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return
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}
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ccb.mu.Unlock()
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ccb.cc.resolveNowLocked(o)
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}
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func (ccb *ccBalancerWrapper) Target() string {
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return ccb.cc.target
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}
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// acBalancerWrapper is a wrapper on top of ac for balancers.
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// It implements balancer.SubConn interface.
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type acBalancerWrapper struct {
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ac *addrConn // read-only
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ccb *ccBalancerWrapper // read-only
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stateListener func(balancer.SubConnState)
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mu sync.Mutex
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producers map[balancer.ProducerBuilder]*refCountedProducer
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}
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// updateState is invoked by grpc to push a subConn state update to the
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// underlying balancer.
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func (acbw *acBalancerWrapper) updateState(s connectivity.State, err error) {
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acbw.ccb.serializer.Schedule(func(ctx context.Context) {
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if ctx.Err() != nil || acbw.ccb.balancer == nil {
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return
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}
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// Even though it is optional for balancers, gracefulswitch ensures
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// opts.StateListener is set, so this cannot ever be nil.
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// TODO: delete this comment when UpdateSubConnState is removed.
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acbw.stateListener(balancer.SubConnState{ConnectivityState: s, ConnectionError: err})
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})
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}
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func (acbw *acBalancerWrapper) String() string {
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return fmt.Sprintf("SubConn(id:%d)", acbw.ac.channelz.ID)
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}
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func (acbw *acBalancerWrapper) UpdateAddresses(addrs []resolver.Address) {
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acbw.ac.updateAddrs(addrs)
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}
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func (acbw *acBalancerWrapper) Connect() {
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go acbw.ac.connect()
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}
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func (acbw *acBalancerWrapper) Shutdown() {
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acbw.ccb.cc.removeAddrConn(acbw.ac, errConnDrain)
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}
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// NewStream begins a streaming RPC on the addrConn. If the addrConn is not
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// ready, blocks until it is or ctx expires. Returns an error when the context
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// expires or the addrConn is shut down.
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func (acbw *acBalancerWrapper) NewStream(ctx context.Context, desc *StreamDesc, method string, opts ...CallOption) (ClientStream, error) {
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transport, err := acbw.ac.getTransport(ctx)
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if err != nil {
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return nil, err
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}
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return newNonRetryClientStream(ctx, desc, method, transport, acbw.ac, opts...)
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}
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// Invoke performs a unary RPC. If the addrConn is not ready, returns
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// errSubConnNotReady.
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func (acbw *acBalancerWrapper) Invoke(ctx context.Context, method string, args any, reply any, opts ...CallOption) error {
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cs, err := acbw.NewStream(ctx, unaryStreamDesc, method, opts...)
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if err != nil {
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return err
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}
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if err := cs.SendMsg(args); err != nil {
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return err
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}
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return cs.RecvMsg(reply)
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}
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type refCountedProducer struct {
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producer balancer.Producer
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refs int // number of current refs to the producer
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close func() // underlying producer's close function
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}
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func (acbw *acBalancerWrapper) GetOrBuildProducer(pb balancer.ProducerBuilder) (balancer.Producer, func()) {
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acbw.mu.Lock()
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defer acbw.mu.Unlock()
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// Look up existing producer from this builder.
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pData := acbw.producers[pb]
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if pData == nil {
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// Not found; create a new one and add it to the producers map.
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p, close := pb.Build(acbw)
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pData = &refCountedProducer{producer: p, close: close}
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acbw.producers[pb] = pData
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}
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// Account for this new reference.
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pData.refs++
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// Return a cleanup function wrapped in a OnceFunc to remove this reference
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// and delete the refCountedProducer from the map if the total reference
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// count goes to zero.
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unref := func() {
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acbw.mu.Lock()
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pData.refs--
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if pData.refs == 0 {
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defer pData.close() // Run outside the acbw mutex
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delete(acbw.producers, pb)
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}
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acbw.mu.Unlock()
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}
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return pData.producer, grpcsync.OnceFunc(unref)
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}
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