399 lines
12 KiB
Go
399 lines
12 KiB
Go
/*
|
|
*
|
|
* 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 (
|
|
"fmt"
|
|
"sync"
|
|
|
|
"golang.org/x/net/context"
|
|
"google.golang.org/grpc/credentials"
|
|
"google.golang.org/grpc/grpclog"
|
|
"google.golang.org/grpc/naming"
|
|
)
|
|
|
|
// Address represents a server the client connects to.
|
|
// This is the EXPERIMENTAL API and may be changed or extended in the future.
|
|
type Address struct {
|
|
// Addr is the server address on which a connection will be established.
|
|
Addr string
|
|
// Metadata is the information associated with Addr, which may be used
|
|
// to make load balancing decision.
|
|
Metadata interface{}
|
|
}
|
|
|
|
// BalancerConfig specifies the configurations for Balancer.
|
|
type BalancerConfig struct {
|
|
// DialCreds is the transport credential the Balancer implementation can
|
|
// use to dial to a remote load balancer server. The Balancer implementations
|
|
// can ignore this if it does not need to talk to another party securely.
|
|
DialCreds credentials.TransportCredentials
|
|
}
|
|
|
|
// BalancerGetOptions configures a Get call.
|
|
// This is the EXPERIMENTAL API and may be changed or extended in the future.
|
|
type BalancerGetOptions struct {
|
|
// BlockingWait specifies whether Get should block when there is no
|
|
// connected address.
|
|
BlockingWait bool
|
|
}
|
|
|
|
// Balancer chooses network addresses for RPCs.
|
|
// This is the EXPERIMENTAL API and may be changed or extended in the future.
|
|
type Balancer interface {
|
|
// Start does the initialization work to bootstrap a Balancer. For example,
|
|
// this function may start the name resolution and watch the updates. It will
|
|
// be called when dialing.
|
|
Start(target string, config BalancerConfig) error
|
|
// Up informs the Balancer that gRPC has a connection to the server at
|
|
// addr. It returns down which is called once the connection to addr gets
|
|
// lost or closed.
|
|
// TODO: It is not clear how to construct and take advantage of the meaningful error
|
|
// parameter for down. Need realistic demands to guide.
|
|
Up(addr Address) (down func(error))
|
|
// Get gets the address of a server for the RPC corresponding to ctx.
|
|
// i) If it returns a connected address, gRPC internals issues the RPC on the
|
|
// connection to this address;
|
|
// ii) If it returns an address on which the connection is under construction
|
|
// (initiated by Notify(...)) but not connected, gRPC internals
|
|
// * fails RPC if the RPC is fail-fast and connection is in the TransientFailure or
|
|
// Shutdown state;
|
|
// or
|
|
// * issues RPC on the connection otherwise.
|
|
// iii) If it returns an address on which the connection does not exist, gRPC
|
|
// internals treats it as an error and will fail the corresponding RPC.
|
|
//
|
|
// Therefore, the following is the recommended rule when writing a custom Balancer.
|
|
// If opts.BlockingWait is true, it should return a connected address or
|
|
// block if there is no connected address. It should respect the timeout or
|
|
// cancellation of ctx when blocking. If opts.BlockingWait is false (for fail-fast
|
|
// RPCs), it should return an address it has notified via Notify(...) immediately
|
|
// instead of blocking.
|
|
//
|
|
// The function returns put which is called once the rpc has completed or failed.
|
|
// put can collect and report RPC stats to a remote load balancer.
|
|
//
|
|
// This function should only return the errors Balancer cannot recover by itself.
|
|
// gRPC internals will fail the RPC if an error is returned.
|
|
Get(ctx context.Context, opts BalancerGetOptions) (addr Address, put func(), err error)
|
|
// Notify returns a channel that is used by gRPC internals to watch the addresses
|
|
// gRPC needs to connect. The addresses might be from a name resolver or remote
|
|
// load balancer. gRPC internals will compare it with the existing connected
|
|
// addresses. If the address Balancer notified is not in the existing connected
|
|
// addresses, gRPC starts to connect the address. If an address in the existing
|
|
// connected addresses is not in the notification list, the corresponding connection
|
|
// is shutdown gracefully. Otherwise, there are no operations to take. Note that
|
|
// the Address slice must be the full list of the Addresses which should be connected.
|
|
// It is NOT delta.
|
|
Notify() <-chan []Address
|
|
// Close shuts down the balancer.
|
|
Close() error
|
|
}
|
|
|
|
// downErr implements net.Error. It is constructed by gRPC internals and passed to the down
|
|
// call of Balancer.
|
|
type downErr struct {
|
|
timeout bool
|
|
temporary bool
|
|
desc string
|
|
}
|
|
|
|
func (e downErr) Error() string { return e.desc }
|
|
func (e downErr) Timeout() bool { return e.timeout }
|
|
func (e downErr) Temporary() bool { return e.temporary }
|
|
|
|
func downErrorf(timeout, temporary bool, format string, a ...interface{}) downErr {
|
|
return downErr{
|
|
timeout: timeout,
|
|
temporary: temporary,
|
|
desc: fmt.Sprintf(format, a...),
|
|
}
|
|
}
|
|
|
|
// RoundRobin returns a Balancer that selects addresses round-robin. It uses r to watch
|
|
// the name resolution updates and updates the addresses available correspondingly.
|
|
func RoundRobin(r naming.Resolver) Balancer {
|
|
return &roundRobin{r: r}
|
|
}
|
|
|
|
type addrInfo struct {
|
|
addr Address
|
|
connected bool
|
|
}
|
|
|
|
type roundRobin struct {
|
|
r naming.Resolver
|
|
w naming.Watcher
|
|
addrs []*addrInfo // all the addresses the client should potentially connect
|
|
mu sync.Mutex
|
|
addrCh chan []Address // the channel to notify gRPC internals the list of addresses the client should connect to.
|
|
next int // index of the next address to return for Get()
|
|
waitCh chan struct{} // the channel to block when there is no connected address available
|
|
done bool // The Balancer is closed.
|
|
}
|
|
|
|
func (rr *roundRobin) watchAddrUpdates() error {
|
|
updates, err := rr.w.Next()
|
|
if err != nil {
|
|
grpclog.Printf("grpc: the naming watcher stops working due to %v.\n", err)
|
|
return err
|
|
}
|
|
rr.mu.Lock()
|
|
defer rr.mu.Unlock()
|
|
for _, update := range updates {
|
|
addr := Address{
|
|
Addr: update.Addr,
|
|
Metadata: update.Metadata,
|
|
}
|
|
switch update.Op {
|
|
case naming.Add:
|
|
var exist bool
|
|
for _, v := range rr.addrs {
|
|
if addr == v.addr {
|
|
exist = true
|
|
grpclog.Println("grpc: The name resolver wanted to add an existing address: ", addr)
|
|
break
|
|
}
|
|
}
|
|
if exist {
|
|
continue
|
|
}
|
|
rr.addrs = append(rr.addrs, &addrInfo{addr: addr})
|
|
case naming.Delete:
|
|
for i, v := range rr.addrs {
|
|
if addr == v.addr {
|
|
copy(rr.addrs[i:], rr.addrs[i+1:])
|
|
rr.addrs = rr.addrs[:len(rr.addrs)-1]
|
|
break
|
|
}
|
|
}
|
|
default:
|
|
grpclog.Println("Unknown update.Op ", update.Op)
|
|
}
|
|
}
|
|
// Make a copy of rr.addrs and write it onto rr.addrCh so that gRPC internals gets notified.
|
|
open := make([]Address, len(rr.addrs))
|
|
for i, v := range rr.addrs {
|
|
open[i] = v.addr
|
|
}
|
|
if rr.done {
|
|
return ErrClientConnClosing
|
|
}
|
|
rr.addrCh <- open
|
|
return nil
|
|
}
|
|
|
|
func (rr *roundRobin) Start(target string, config BalancerConfig) error {
|
|
rr.mu.Lock()
|
|
defer rr.mu.Unlock()
|
|
if rr.done {
|
|
return ErrClientConnClosing
|
|
}
|
|
if rr.r == nil {
|
|
// If there is no name resolver installed, it is not needed to
|
|
// do name resolution. In this case, target is added into rr.addrs
|
|
// as the only address available and rr.addrCh stays nil.
|
|
rr.addrs = append(rr.addrs, &addrInfo{addr: Address{Addr: target}})
|
|
return nil
|
|
}
|
|
w, err := rr.r.Resolve(target)
|
|
if err != nil {
|
|
return err
|
|
}
|
|
rr.w = w
|
|
rr.addrCh = make(chan []Address)
|
|
go func() {
|
|
for {
|
|
if err := rr.watchAddrUpdates(); err != nil {
|
|
return
|
|
}
|
|
}
|
|
}()
|
|
return nil
|
|
}
|
|
|
|
// Up sets the connected state of addr and sends notification if there are pending
|
|
// Get() calls.
|
|
func (rr *roundRobin) Up(addr Address) func(error) {
|
|
rr.mu.Lock()
|
|
defer rr.mu.Unlock()
|
|
var cnt int
|
|
for _, a := range rr.addrs {
|
|
if a.addr == addr {
|
|
if a.connected {
|
|
return nil
|
|
}
|
|
a.connected = true
|
|
}
|
|
if a.connected {
|
|
cnt++
|
|
}
|
|
}
|
|
// addr is only one which is connected. Notify the Get() callers who are blocking.
|
|
if cnt == 1 && rr.waitCh != nil {
|
|
close(rr.waitCh)
|
|
rr.waitCh = nil
|
|
}
|
|
return func(err error) {
|
|
rr.down(addr, err)
|
|
}
|
|
}
|
|
|
|
// down unsets the connected state of addr.
|
|
func (rr *roundRobin) down(addr Address, err error) {
|
|
rr.mu.Lock()
|
|
defer rr.mu.Unlock()
|
|
for _, a := range rr.addrs {
|
|
if addr == a.addr {
|
|
a.connected = false
|
|
break
|
|
}
|
|
}
|
|
}
|
|
|
|
// Get returns the next addr in the rotation.
|
|
func (rr *roundRobin) Get(ctx context.Context, opts BalancerGetOptions) (addr Address, put func(), err error) {
|
|
var ch chan struct{}
|
|
rr.mu.Lock()
|
|
if rr.done {
|
|
rr.mu.Unlock()
|
|
err = ErrClientConnClosing
|
|
return
|
|
}
|
|
|
|
if len(rr.addrs) > 0 {
|
|
if rr.next >= len(rr.addrs) {
|
|
rr.next = 0
|
|
}
|
|
next := rr.next
|
|
for {
|
|
a := rr.addrs[next]
|
|
next = (next + 1) % len(rr.addrs)
|
|
if a.connected {
|
|
addr = a.addr
|
|
rr.next = next
|
|
rr.mu.Unlock()
|
|
return
|
|
}
|
|
if next == rr.next {
|
|
// Has iterated all the possible address but none is connected.
|
|
break
|
|
}
|
|
}
|
|
}
|
|
if !opts.BlockingWait {
|
|
if len(rr.addrs) == 0 {
|
|
rr.mu.Unlock()
|
|
err = fmt.Errorf("there is no address available")
|
|
return
|
|
}
|
|
// Returns the next addr on rr.addrs for failfast RPCs.
|
|
addr = rr.addrs[rr.next].addr
|
|
rr.next++
|
|
rr.mu.Unlock()
|
|
return
|
|
}
|
|
// Wait on rr.waitCh for non-failfast RPCs.
|
|
if rr.waitCh == nil {
|
|
ch = make(chan struct{})
|
|
rr.waitCh = ch
|
|
} else {
|
|
ch = rr.waitCh
|
|
}
|
|
rr.mu.Unlock()
|
|
for {
|
|
select {
|
|
case <-ctx.Done():
|
|
err = ctx.Err()
|
|
return
|
|
case <-ch:
|
|
rr.mu.Lock()
|
|
if rr.done {
|
|
rr.mu.Unlock()
|
|
err = ErrClientConnClosing
|
|
return
|
|
}
|
|
|
|
if len(rr.addrs) > 0 {
|
|
if rr.next >= len(rr.addrs) {
|
|
rr.next = 0
|
|
}
|
|
next := rr.next
|
|
for {
|
|
a := rr.addrs[next]
|
|
next = (next + 1) % len(rr.addrs)
|
|
if a.connected {
|
|
addr = a.addr
|
|
rr.next = next
|
|
rr.mu.Unlock()
|
|
return
|
|
}
|
|
if next == rr.next {
|
|
// Has iterated all the possible address but none is connected.
|
|
break
|
|
}
|
|
}
|
|
}
|
|
// The newly added addr got removed by Down() again.
|
|
if rr.waitCh == nil {
|
|
ch = make(chan struct{})
|
|
rr.waitCh = ch
|
|
} else {
|
|
ch = rr.waitCh
|
|
}
|
|
rr.mu.Unlock()
|
|
}
|
|
}
|
|
}
|
|
|
|
func (rr *roundRobin) Notify() <-chan []Address {
|
|
return rr.addrCh
|
|
}
|
|
|
|
func (rr *roundRobin) Close() error {
|
|
rr.mu.Lock()
|
|
defer rr.mu.Unlock()
|
|
rr.done = true
|
|
if rr.w != nil {
|
|
rr.w.Close()
|
|
}
|
|
if rr.waitCh != nil {
|
|
close(rr.waitCh)
|
|
rr.waitCh = nil
|
|
}
|
|
if rr.addrCh != nil {
|
|
close(rr.addrCh)
|
|
}
|
|
return nil
|
|
}
|