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/*
*
* Copyright 2016, Google Inc.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are
* met:
*
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above
* copyright notice, this list of conditions and the following disclaimer
* in the documentation and/or other materials provided with the
* distribution.
* * Neither the name of Google Inc. nor the names of its
* contributors may be used to endorse or promote products derived from
* this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
*/
package grpc
import (
"errors"
"fmt"
"math/rand"
"net"
"sync"
"time"
"golang.org/x/net/context"
"google.golang.org/grpc/codes"
lbpb "google.golang.org/grpc/grpclb/grpc_lb_v1"
"google.golang.org/grpc/grpclog"
"google.golang.org/grpc/metadata"
"google.golang.org/grpc/naming"
)
// Client API for LoadBalancer service.
// Mostly copied from generated pb.go file.
// To avoid circular dependency.
type loadBalancerClient struct {
cc *ClientConn
}
func (c *loadBalancerClient) BalanceLoad(ctx context.Context, opts ...CallOption) (*balanceLoadClientStream, error) {
desc := &StreamDesc{
StreamName: "BalanceLoad",
ServerStreams: true,
ClientStreams: true,
}
stream, err := NewClientStream(ctx, desc, c.cc, "/grpc.lb.v1.LoadBalancer/BalanceLoad", opts...)
if err != nil {
return nil, err
}
x := &balanceLoadClientStream{stream}
return x, nil
}
type balanceLoadClientStream struct {
ClientStream
}
func (x *balanceLoadClientStream) Send(m *lbpb.LoadBalanceRequest) error {
return x.ClientStream.SendMsg(m)
}
func (x *balanceLoadClientStream) Recv() (*lbpb.LoadBalanceResponse, error) {
m := new(lbpb.LoadBalanceResponse)
if err := x.ClientStream.RecvMsg(m); err != nil {
return nil, err
}
return m, nil
}
// AddressType indicates the address type returned by name resolution.
type AddressType uint8
const (
// Backend indicates the server is a backend server.
Backend AddressType = iota
// GRPCLB indicates the server is a grpclb load balancer.
GRPCLB
)
// AddrMetadataGRPCLB contains the information the name resolution for grpclb should provide. The
// name resolver used by grpclb balancer is required to provide this type of metadata in
// its address updates.
type AddrMetadataGRPCLB struct {
// AddrType is the type of server (grpc load balancer or backend).
AddrType AddressType
// ServerName is the name of the grpc load balancer. Used for authentication.
ServerName string
}
// NewGRPCLBBalancer creates a grpclb load balancer.
func NewGRPCLBBalancer(r naming.Resolver) Balancer {
return &balancer{
r: r,
}
}
type remoteBalancerInfo struct {
addr string
// the server name used for authentication with the remote LB server.
name string
}
// grpclbAddrInfo consists of the information of a backend server.
type grpclbAddrInfo struct {
addr Address
connected bool
// dropForRateLimiting indicates whether this particular request should be
// dropped by the client for rate limiting.
dropForRateLimiting bool
// dropForLoadBalancing indicates whether this particular request should be
// dropped by the client for load balancing.
dropForLoadBalancing bool
}
type balancer struct {
r naming.Resolver
target string
mu sync.Mutex
seq int // a sequence number to make sure addrCh does not get stale addresses.
w naming.Watcher
addrCh chan []Address
rbs []remoteBalancerInfo
addrs []*grpclbAddrInfo
next int
waitCh chan struct{}
done bool
expTimer *time.Timer
rand *rand.Rand
clientStats lbpb.ClientStats
}
func (b *balancer) watchAddrUpdates(w naming.Watcher, ch chan []remoteBalancerInfo) error {
updates, err := w.Next()
if err != nil {
return err
}
b.mu.Lock()
defer b.mu.Unlock()
if b.done {
return ErrClientConnClosing
}
for _, update := range updates {
switch update.Op {
case naming.Add:
var exist bool
for _, v := range b.rbs {
// TODO: Is the same addr with different server name a different balancer?
if update.Addr == v.addr {
exist = true
break
}
}
if exist {
continue
}
md, ok := update.Metadata.(*AddrMetadataGRPCLB)
if !ok {
// TODO: Revisit the handling here and may introduce some fallback mechanism.
grpclog.Printf("The name resolution contains unexpected metadata %v", update.Metadata)
continue
}
switch md.AddrType {
case Backend:
// TODO: Revisit the handling here and may introduce some fallback mechanism.
grpclog.Printf("The name resolution does not give grpclb addresses")
continue
case GRPCLB:
b.rbs = append(b.rbs, remoteBalancerInfo{
addr: update.Addr,
name: md.ServerName,
})
default:
grpclog.Printf("Received unknow address type %d", md.AddrType)
continue
}
case naming.Delete:
for i, v := range b.rbs {
if update.Addr == v.addr {
copy(b.rbs[i:], b.rbs[i+1:])
b.rbs = b.rbs[:len(b.rbs)-1]
break
}
}
default:
grpclog.Println("Unknown update.Op ", update.Op)
}
}
// TODO: Fall back to the basic round-robin load balancing if the resulting address is
// not a load balancer.
select {
case <-ch:
default:
}
ch <- b.rbs
return nil
}
func (b *balancer) serverListExpire(seq int) {
b.mu.Lock()
defer b.mu.Unlock()
// TODO: gRPC interanls do not clear the connections when the server list is stale.
// This means RPCs will keep using the existing server list until b receives new
// server list even though the list is expired. Revisit this behavior later.
if b.done || seq < b.seq {
return
}
b.next = 0
b.addrs = nil
// Ask grpc internals to close all the corresponding connections.
b.addrCh <- nil
}
func convertDuration(d *lbpb.Duration) time.Duration {
if d == nil {
return 0
}
return time.Duration(d.Seconds)*time.Second + time.Duration(d.Nanos)*time.Nanosecond
}
func (b *balancer) processServerList(l *lbpb.ServerList, seq int) {
if l == nil {
return
}
servers := l.GetServers()
expiration := convertDuration(l.GetExpirationInterval())
var (
sl []*grpclbAddrInfo
addrs []Address
)
for _, s := range servers {
md := metadata.Pairs("lb-token", s.LoadBalanceToken)
addr := Address{
Addr: fmt.Sprintf("%s:%d", net.IP(s.IpAddress), s.Port),
Metadata: &md,
}
sl = append(sl, &grpclbAddrInfo{
addr: addr,
dropForRateLimiting: s.DropForRateLimiting,
dropForLoadBalancing: s.DropForLoadBalancing,
})
addrs = append(addrs, addr)
}
b.mu.Lock()
defer b.mu.Unlock()
if b.done || seq < b.seq {
return
}
if len(sl) > 0 {
// reset b.next to 0 when replacing the server list.
b.next = 0
b.addrs = sl
b.addrCh <- addrs
if b.expTimer != nil {
b.expTimer.Stop()
b.expTimer = nil
}
if expiration > 0 {
b.expTimer = time.AfterFunc(expiration, func() {
b.serverListExpire(seq)
})
}
}
return
}
func (b *balancer) sendLoadReport(s *balanceLoadClientStream, interval time.Duration, done <-chan struct{}) {
ticker := time.NewTicker(interval)
defer ticker.Stop()
for {
select {
case <-ticker.C:
case <-done:
return
}
b.mu.Lock()
stats := b.clientStats
b.clientStats = lbpb.ClientStats{} // Clear the stats.
b.mu.Unlock()
t := time.Now()
stats.Timestamp = &lbpb.Timestamp{
Seconds: t.Unix(),
Nanos: int32(t.Nanosecond()),
}
if err := s.Send(&lbpb.LoadBalanceRequest{
LoadBalanceRequestType: &lbpb.LoadBalanceRequest_ClientStats{
ClientStats: &stats,
},
}); err != nil {
return
}
}
}
func (b *balancer) callRemoteBalancer(lbc *loadBalancerClient, seq int) (retry bool) {
ctx, cancel := context.WithCancel(context.Background())
defer cancel()
stream, err := lbc.BalanceLoad(ctx)
if err != nil {
grpclog.Printf("Failed to perform RPC to the remote balancer %v", err)
return
}
b.mu.Lock()
if b.done {
b.mu.Unlock()
return
}
b.mu.Unlock()
initReq := &lbpb.LoadBalanceRequest{
LoadBalanceRequestType: &lbpb.LoadBalanceRequest_InitialRequest{
InitialRequest: &lbpb.InitialLoadBalanceRequest{
Name: b.target,
},
},
}
if err := stream.Send(initReq); err != nil {
// TODO: backoff on retry?
return true
}
reply, err := stream.Recv()
if err != nil {
// TODO: backoff on retry?
return true
}
initResp := reply.GetInitialResponse()
if initResp == nil {
grpclog.Println("Failed to receive the initial response from the remote balancer.")
return
}
// TODO: Support delegation.
if initResp.LoadBalancerDelegate != "" {
// delegation
grpclog.Println("TODO: Delegation is not supported yet.")
return
}
streamDone := make(chan struct{})
defer close(streamDone)
b.mu.Lock()
b.clientStats = lbpb.ClientStats{} // Clear client stats.
b.mu.Unlock()
if d := convertDuration(initResp.ClientStatsReportInterval); d > 0 {
go b.sendLoadReport(stream, d, streamDone)
}
// Retrieve the server list.
for {
reply, err := stream.Recv()
if err != nil {
break
}
b.mu.Lock()
if b.done || seq < b.seq {
b.mu.Unlock()
return
}
b.seq++ // tick when receiving a new list of servers.
seq = b.seq
b.mu.Unlock()
if serverList := reply.GetServerList(); serverList != nil {
b.processServerList(serverList, seq)
}
}
return true
}
func (b *balancer) Start(target string, config BalancerConfig) error {
b.rand = rand.New(rand.NewSource(time.Now().Unix()))
// TODO: Fall back to the basic direct connection if there is no name resolver.
if b.r == nil {
return errors.New("there is no name resolver installed")
}
b.target = target
b.mu.Lock()
if b.done {
b.mu.Unlock()
return ErrClientConnClosing
}
b.addrCh = make(chan []Address)
w, err := b.r.Resolve(target)
if err != nil {
b.mu.Unlock()
return err
}
b.w = w
b.mu.Unlock()
balancerAddrsCh := make(chan []remoteBalancerInfo, 1)
// Spawn a goroutine to monitor the name resolution of remote load balancer.
go func() {
for {
if err := b.watchAddrUpdates(w, balancerAddrsCh); err != nil {
grpclog.Printf("grpc: the naming watcher stops working due to %v.\n", err)
close(balancerAddrsCh)
return
}
}
}()
// Spawn a goroutine to talk to the remote load balancer.
go func() {
var (
cc *ClientConn
// ccError is closed when there is an error in the current cc.
// A new rb should be picked from rbs and connected.
ccError chan struct{}
rb *remoteBalancerInfo
rbs []remoteBalancerInfo
rbIdx int
)
defer func() {
if ccError != nil {
select {
case <-ccError:
default:
close(ccError)
}
}
if cc != nil {
cc.Close()
}
}()
for {
var ok bool
select {
case rbs, ok = <-balancerAddrsCh:
if !ok {
return
}
foundIdx := -1
if rb != nil {
for i, trb := range rbs {
if trb == *rb {
foundIdx = i
break
}
}
}
if foundIdx >= 0 {
if foundIdx >= 1 {
// Move the address in use to the beginning of the list.
b.rbs[0], b.rbs[foundIdx] = b.rbs[foundIdx], b.rbs[0]
rbIdx = 0
}
continue // If found, don't dial new cc.
} else if len(rbs) > 0 {
// Pick a random one from the list, instead of always using the first one.
if l := len(rbs); l > 1 && rb != nil {
tmpIdx := b.rand.Intn(l - 1)
b.rbs[0], b.rbs[tmpIdx] = b.rbs[tmpIdx], b.rbs[0]
}
rbIdx = 0
rb = &rbs[0]
} else {
// foundIdx < 0 && len(rbs) <= 0.
rb = nil
}
case <-ccError:
ccError = nil
if rbIdx < len(rbs)-1 {
rbIdx++
rb = &rbs[rbIdx]
} else {
rb = nil
}
}
if rb == nil {
continue
}
if cc != nil {
cc.Close()
}
// Talk to the remote load balancer to get the server list.
var err error
creds := config.DialCreds
ccError = make(chan struct{})
if creds == nil {
cc, err = Dial(rb.addr, WithInsecure())
} else {
if rb.name != "" {
if err := creds.OverrideServerName(rb.name); err != nil {
grpclog.Printf("Failed to override the server name in the credentials: %v", err)
continue
}
}
cc, err = Dial(rb.addr, WithTransportCredentials(creds))
}
if err != nil {
grpclog.Printf("Failed to setup a connection to the remote balancer %v: %v", rb.addr, err)
close(ccError)
continue
}
b.mu.Lock()
b.seq++ // tick when getting a new balancer address
seq := b.seq
b.next = 0
b.mu.Unlock()
go func(cc *ClientConn, ccError chan struct{}) {
lbc := &loadBalancerClient{cc}
b.callRemoteBalancer(lbc, seq)
cc.Close()
select {
case <-ccError:
default:
close(ccError)
}
}(cc, ccError)
}
}()
return nil
}
func (b *balancer) down(addr Address, err error) {
b.mu.Lock()
defer b.mu.Unlock()
for _, a := range b.addrs {
if addr == a.addr {
a.connected = false
break
}
}
}
func (b *balancer) Up(addr Address) func(error) {
b.mu.Lock()
defer b.mu.Unlock()
if b.done {
return nil
}
var cnt int
for _, a := range b.addrs {
if a.addr == addr {
if a.connected {
return nil
}
a.connected = true
}
if a.connected && !a.dropForRateLimiting && !a.dropForLoadBalancing {
cnt++
}
}
// addr is the only one which is connected. Notify the Get() callers who are blocking.
if cnt == 1 && b.waitCh != nil {
close(b.waitCh)
b.waitCh = nil
}
return func(err error) {
b.down(addr, err)
}
}
func (b *balancer) Get(ctx context.Context, opts BalancerGetOptions) (addr Address, put func(), err error) {
var ch chan struct{}
b.mu.Lock()
if b.done {
b.mu.Unlock()
err = ErrClientConnClosing
return
}
seq := b.seq
defer func() {
if err != nil {
return
}
put = func() {
s, ok := rpcInfoFromContext(ctx)
if !ok {
return
}
b.mu.Lock()
defer b.mu.Unlock()
if b.done || seq < b.seq {
return
}
b.clientStats.NumCallsFinished++
if !s.bytesSent {
b.clientStats.NumCallsFinishedWithClientFailedToSend++
} else if s.bytesReceived {
b.clientStats.NumCallsFinishedKnownReceived++
}
}
}()
b.clientStats.NumCallsStarted++
if len(b.addrs) > 0 {
if b.next >= len(b.addrs) {
b.next = 0
}
next := b.next
for {
a := b.addrs[next]
next = (next + 1) % len(b.addrs)
if a.connected {
if !a.dropForRateLimiting && !a.dropForLoadBalancing {
addr = a.addr
b.next = next
b.mu.Unlock()
return
}
if !opts.BlockingWait {
b.next = next
if a.dropForLoadBalancing {
b.clientStats.NumCallsFinished++
b.clientStats.NumCallsFinishedWithDropForLoadBalancing++
} else if a.dropForRateLimiting {
b.clientStats.NumCallsFinished++
b.clientStats.NumCallsFinishedWithDropForRateLimiting++
}
b.mu.Unlock()
err = Errorf(codes.Unavailable, "%s drops requests", a.addr.Addr)
return
}
}
if next == b.next {
// Has iterated all the possible address but none is connected.
break
}
}
}
if !opts.BlockingWait {
if len(b.addrs) == 0 {
b.clientStats.NumCallsFinished++
b.clientStats.NumCallsFinishedWithClientFailedToSend++
b.mu.Unlock()
err = Errorf(codes.Unavailable, "there is no address available")
return
}
// Returns the next addr on b.addrs for a failfast RPC.
addr = b.addrs[b.next].addr
b.next++
b.mu.Unlock()
return
}
// Wait on b.waitCh for non-failfast RPCs.
if b.waitCh == nil {
ch = make(chan struct{})
b.waitCh = ch
} else {
ch = b.waitCh
}
b.mu.Unlock()
for {
select {
case <-ctx.Done():
b.mu.Lock()
b.clientStats.NumCallsFinished++
b.clientStats.NumCallsFinishedWithClientFailedToSend++
b.mu.Unlock()
err = ctx.Err()
return
case <-ch:
b.mu.Lock()
if b.done {
b.clientStats.NumCallsFinished++
b.clientStats.NumCallsFinishedWithClientFailedToSend++
b.mu.Unlock()
err = ErrClientConnClosing
return
}
if len(b.addrs) > 0 {
if b.next >= len(b.addrs) {
b.next = 0
}
next := b.next
for {
a := b.addrs[next]
next = (next + 1) % len(b.addrs)
if a.connected {
if !a.dropForRateLimiting && !a.dropForLoadBalancing {
addr = a.addr
b.next = next
b.mu.Unlock()
return
}
if !opts.BlockingWait {
b.next = next
if a.dropForLoadBalancing {
b.clientStats.NumCallsFinished++
b.clientStats.NumCallsFinishedWithDropForLoadBalancing++
} else if a.dropForRateLimiting {
b.clientStats.NumCallsFinished++
b.clientStats.NumCallsFinishedWithDropForRateLimiting++
}
b.mu.Unlock()
err = Errorf(codes.Unavailable, "drop requests for the addreess %s", a.addr.Addr)
return
}
}
if next == b.next {
// Has iterated all the possible address but none is connected.
break
}
}
}
// The newly added addr got removed by Down() again.
if b.waitCh == nil {
ch = make(chan struct{})
b.waitCh = ch
} else {
ch = b.waitCh
}
b.mu.Unlock()
}
}
}
func (b *balancer) Notify() <-chan []Address {
return b.addrCh
}
func (b *balancer) Close() error {
b.mu.Lock()
defer b.mu.Unlock()
b.done = true
if b.expTimer != nil {
b.expTimer.Stop()
}
if b.waitCh != nil {
close(b.waitCh)
}
if b.addrCh != nil {
close(b.addrCh)
}
if b.w != nil {
b.w.Close()
}
return nil
}