/*
*
* Copyright 2017 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 grpc
import (
"fmt"
"sync"
"google.golang.org/grpc/balancer"
"google.golang.org/grpc/connectivity"
"google.golang.org/grpc/grpclog"
"google.golang.org/grpc/resolver"
)
// scStateUpdate contains the subConn and the new state it changed to.
type scStateUpdate struct {
sc balancer.SubConn
state connectivity.State
}
// scStateUpdateBuffer is an unbounded channel for scStateChangeTuple.
// TODO make a general purpose buffer that uses interface{}.
type scStateUpdateBuffer struct {
c chan *scStateUpdate
mu sync.Mutex
backlog []*scStateUpdate
}
func newSCStateUpdateBuffer() *scStateUpdateBuffer {
return &scStateUpdateBuffer{
c: make(chan *scStateUpdate, 1),
}
}
func (b *scStateUpdateBuffer) put(t *scStateUpdate) {
b.mu.Lock()
defer b.mu.Unlock()
if len(b.backlog) == 0 {
select {
case b.c <- t:
return
default:
}
}
b.backlog = append(b.backlog, t)
}
func (b *scStateUpdateBuffer) load() {
b.mu.Lock()
defer b.mu.Unlock()
if len(b.backlog) > 0 {
select {
case b.c <- b.backlog[0]:
b.backlog[0] = nil
b.backlog = b.backlog[1:]
default:
}
}
}
// get returns the channel that the scStateUpdate will be sent to.
//
// Upon receiving, the caller should call load to send another
// scStateChangeTuple onto the channel if there is any.
func (b *scStateUpdateBuffer) get() <-chan *scStateUpdate {
return b.c
}
// resolverUpdate contains the new resolved addresses or error if there's
// any.
type resolverUpdate struct {
addrs []resolver.Address
err error
}
// ccBalancerWrapper is a wrapper on top of cc for balancers.
// It implements balancer.ClientConn interface.
type ccBalancerWrapper struct {
cc *ClientConn
balancer balancer.Balancer
stateChangeQueue *scStateUpdateBuffer
resolverUpdateCh chan *resolverUpdate
done chan struct{}
mu sync.Mutex
subConns map[*acBalancerWrapper]struct{}
}
func newCCBalancerWrapper(cc *ClientConn, b balancer.Builder, bopts balancer.BuildOptions) *ccBalancerWrapper {
ccb := &ccBalancerWrapper{
cc: cc,
stateChangeQueue: newSCStateUpdateBuffer(),
resolverUpdateCh: make(chan *resolverUpdate, 1),
done: make(chan struct{}),
subConns: make(map[*acBalancerWrapper]struct{}),
}
go ccb.watcher()
ccb.balancer = b.Build(ccb, bopts)
return ccb
}
// watcher balancer functions sequentially, so the balancer can be implemented
// lock-free.
func (ccb *ccBalancerWrapper) watcher() {
for {
select {
case t := <-ccb.stateChangeQueue.get():
ccb.stateChangeQueue.load()
select {
case <-ccb.done:
ccb.balancer.Close()
return
default:
}
ccb.balancer.HandleSubConnStateChange(t.sc, t.state)
case t := <-ccb.resolverUpdateCh:
select {
case <-ccb.done:
ccb.balancer.Close()
return
default:
}
ccb.balancer.HandleResolvedAddrs(t.addrs, t.err)
case <-ccb.done:
}
select {
case <-ccb.done:
ccb.balancer.Close()
ccb.mu.Lock()
scs := ccb.subConns
ccb.subConns = nil
ccb.mu.Unlock()
for acbw := range scs {
ccb.cc.removeAddrConn(acbw.getAddrConn(), errConnDrain)
}
return
default:
}
}
}
func (ccb *ccBalancerWrapper) close() {
close(ccb.done)
}
func (ccb *ccBalancerWrapper) handleSubConnStateChange(sc balancer.SubConn, s connectivity.State) {
// When updating addresses for a SubConn, if the address in use is not in
// the new addresses, the old ac will be tearDown() and a new ac will be
// created. tearDown() generates a state change with Shutdown state, we
// don't want the balancer to receive this state change. So before
// tearDown() on the old ac, ac.acbw (acWrapper) will be set to nil, and
// this function will be called with (nil, Shutdown). We don't need to call
// balancer method in this case.
if sc == nil {
return
}
ccb.stateChangeQueue.put(&scStateUpdate{
sc: sc,
state: s,
})
}
func (ccb *ccBalancerWrapper) handleResolvedAddrs(addrs []resolver.Address, err error) {
if ccb.cc.curBalancerName != grpclbName {
var containsGRPCLB bool
for _, a := range addrs {
if a.Type == resolver.GRPCLB {
containsGRPCLB = true
break
}
}
if containsGRPCLB {
// The current balancer is not grpclb, but addresses contain grpclb
// address. This means we failed to switch to grpclb, most likely
// because grpclb is not registered. Filter out all grpclb addresses
// from addrs before sending to balancer.
tempAddrs := make([]resolver.Address, 0, len(addrs))
for _, a := range addrs {
if a.Type != resolver.GRPCLB {
tempAddrs = append(tempAddrs, a)
}
}
addrs = tempAddrs
}
}
select {
case <-ccb.resolverUpdateCh:
default:
}
ccb.resolverUpdateCh <- &resolverUpdate{
addrs: addrs,
err: err,
}
}
func (ccb *ccBalancerWrapper) NewSubConn(addrs []resolver.Address, opts balancer.NewSubConnOptions) (balancer.SubConn, error) {
if len(addrs) <= 0 {
return nil, fmt.Errorf("grpc: cannot create SubConn with empty address list")
}
ccb.mu.Lock()
defer ccb.mu.Unlock()
if ccb.subConns == nil {
return nil, fmt.Errorf("grpc: ClientConn balancer wrapper was closed")
}
ac, err := ccb.cc.newAddrConn(addrs, opts)
if err != nil {
return nil, err
}
acbw := &acBalancerWrapper{ac: ac}
acbw.ac.mu.Lock()
ac.acbw = acbw
acbw.ac.mu.Unlock()
ccb.subConns[acbw] = struct{}{}
return acbw, nil
}
func (ccb *ccBalancerWrapper) RemoveSubConn(sc balancer.SubConn) {
acbw, ok := sc.(*acBalancerWrapper)
if !ok {
return
}
ccb.mu.Lock()
defer ccb.mu.Unlock()
if ccb.subConns == nil {
return
}
delete(ccb.subConns, acbw)
ccb.cc.removeAddrConn(acbw.getAddrConn(), errConnDrain)
}
func (ccb *ccBalancerWrapper) UpdateBalancerState(s connectivity.State, p balancer.Picker) {
ccb.mu.Lock()
defer ccb.mu.Unlock()
if ccb.subConns == nil {
return
}
// Update picker before updating state. Even though the ordering here does
// not matter, it can lead to multiple calls of Pick in the common start-up
// case where we wait for ready and then perform an RPC. If the picker is
// updated later, we could call the "connecting" picker when the state is
// updated, and then call the "ready" picker after the picker gets updated.
ccb.cc.blockingpicker.updatePicker(p)
ccb.cc.csMgr.updateState(s)
}
func (ccb *ccBalancerWrapper) ResolveNow(o resolver.ResolveNowOption) {
ccb.cc.resolveNow(o)
}
func (ccb *ccBalancerWrapper) Target() string {
return ccb.cc.target
}
// acBalancerWrapper is a wrapper on top of ac for balancers.
// It implements balancer.SubConn interface.
type acBalancerWrapper struct {
mu sync.Mutex
ac *addrConn
}
func (acbw *acBalancerWrapper) UpdateAddresses(addrs []resolver.Address) {
acbw.mu.Lock()
defer acbw.mu.Unlock()
if len(addrs) <= 0 {
acbw.ac.tearDown(errConnDrain)
return
}
if !acbw.ac.tryUpdateAddrs(addrs) {
cc := acbw.ac.cc
opts := acbw.ac.scopts
acbw.ac.mu.Lock()
// Set old ac.acbw to nil so the Shutdown state update will be ignored
// by balancer.
//
// TODO(bar) the state transition could be wrong when tearDown() old ac
// and creating new ac, fix the transition.
acbw.ac.acbw = nil
acbw.ac.mu.Unlock()
acState := acbw.ac.getState()
acbw.ac.tearDown(errConnDrain)
if acState == connectivity.Shutdown {
return
}
ac, err := cc.newAddrConn(addrs, opts)
if err != nil {
grpclog.Warningf("acBalancerWrapper: UpdateAddresses: failed to newAddrConn: %v", err)
return
}
acbw.ac = ac
ac.mu.Lock()
ac.acbw = acbw
ac.mu.Unlock()
if acState != connectivity.Idle {
ac.connect()
}
}
}
func (acbw *acBalancerWrapper) Connect() {
acbw.mu.Lock()
defer acbw.mu.Unlock()
acbw.ac.connect()
}
func (acbw *acBalancerWrapper) getAddrConn() *addrConn {
acbw.mu.Lock()
defer acbw.mu.Unlock()
return acbw.ac
}
