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/*
*
* 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 (
"sync"
"sync/atomic"
"golang.org/x/net/context"
"google.golang.org/grpc/balancer"
"google.golang.org/grpc/codes"
lbpb "google.golang.org/grpc/grpclb/grpc_lb_v1/messages"
"google.golang.org/grpc/status"
)
type rpcStats struct {
NumCallsStarted int64
NumCallsFinished int64
NumCallsFinishedWithDropForRateLimiting int64
NumCallsFinishedWithDropForLoadBalancing int64
NumCallsFinishedWithClientFailedToSend int64
NumCallsFinishedKnownReceived int64
}
// toClientStats converts rpcStats to lbpb.ClientStats, and clears rpcStats.
func (s *rpcStats) toClientStats() *lbpb.ClientStats {
stats := &lbpb.ClientStats{
NumCallsStarted: atomic.SwapInt64(&s.NumCallsStarted, 0),
NumCallsFinished: atomic.SwapInt64(&s.NumCallsFinished, 0),
NumCallsFinishedWithDropForRateLimiting: atomic.SwapInt64(&s.NumCallsFinishedWithDropForRateLimiting, 0),
NumCallsFinishedWithDropForLoadBalancing: atomic.SwapInt64(&s.NumCallsFinishedWithDropForLoadBalancing, 0),
NumCallsFinishedWithClientFailedToSend: atomic.SwapInt64(&s.NumCallsFinishedWithClientFailedToSend, 0),
NumCallsFinishedKnownReceived: atomic.SwapInt64(&s.NumCallsFinishedKnownReceived, 0),
}
return stats
}
func (s *rpcStats) dropForRateLimiting() {
atomic.AddInt64(&s.NumCallsStarted, 1)
atomic.AddInt64(&s.NumCallsFinishedWithDropForRateLimiting, 1)
atomic.AddInt64(&s.NumCallsFinished, 1)
}
func (s *rpcStats) dropForLoadBalancing() {
atomic.AddInt64(&s.NumCallsStarted, 1)
atomic.AddInt64(&s.NumCallsFinishedWithDropForLoadBalancing, 1)
atomic.AddInt64(&s.NumCallsFinished, 1)
}
func (s *rpcStats) failedToSend() {
atomic.AddInt64(&s.NumCallsStarted, 1)
atomic.AddInt64(&s.NumCallsFinishedWithClientFailedToSend, 1)
atomic.AddInt64(&s.NumCallsFinished, 1)
}
func (s *rpcStats) knownReceived() {
atomic.AddInt64(&s.NumCallsStarted, 1)
atomic.AddInt64(&s.NumCallsFinishedKnownReceived, 1)
atomic.AddInt64(&s.NumCallsFinished, 1)
}
type errPicker struct {
// Pick always returns this err.
err error
}
func (p *errPicker) Pick(ctx context.Context, opts balancer.PickOptions) (balancer.SubConn, func(balancer.DoneInfo), error) {
return nil, nil, p.err
}
// rrPicker does roundrobin on subConns. It's typically used when there's no
// response from remote balancer, and grpclb falls back to the resolved
// backends.
//
// It guaranteed that len(subConns) > 0.
type rrPicker struct {
mu sync.Mutex
subConns []balancer.SubConn // The subConns that were READY when taking the snapshot.
subConnsNext int
}
func (p *rrPicker) Pick(ctx context.Context, opts balancer.PickOptions) (balancer.SubConn, func(balancer.DoneInfo), error) {
p.mu.Lock()
defer p.mu.Unlock()
sc := p.subConns[p.subConnsNext]
p.subConnsNext = (p.subConnsNext + 1) % len(p.subConns)
return sc, nil, nil
}
// lbPicker does two layers of picks:
//
// First layer: roundrobin on all servers in serverList, including drops and backends.
// - If it picks a drop, the RPC will fail as being dropped.
// - If it picks a backend, do a second layer pick to pick the real backend.
//
// Second layer: roundrobin on all READY backends.
//
// It's guaranteed that len(serverList) > 0.
type lbPicker struct {
mu sync.Mutex
serverList []*lbpb.Server
serverListNext int
subConns []balancer.SubConn // The subConns that were READY when taking the snapshot.
subConnsNext int
stats *rpcStats
}
func (p *lbPicker) Pick(ctx context.Context, opts balancer.PickOptions) (balancer.SubConn, func(balancer.DoneInfo), error) {
p.mu.Lock()
defer p.mu.Unlock()
// Layer one roundrobin on serverList.
s := p.serverList[p.serverListNext]
p.serverListNext = (p.serverListNext + 1) % len(p.serverList)
// If it's a drop, return an error and fail the RPC.
if s.DropForRateLimiting {
p.stats.dropForRateLimiting()
return nil, nil, status.Errorf(codes.Unavailable, "request dropped by grpclb")
}
if s.DropForLoadBalancing {
p.stats.dropForLoadBalancing()
return nil, nil, status.Errorf(codes.Unavailable, "request dropped by grpclb")
}
// If not a drop but there's no ready subConns.
if len(p.subConns) <= 0 {
return nil, nil, balancer.ErrNoSubConnAvailable
}
// Return the next ready subConn in the list, also collect rpc stats.
sc := p.subConns[p.subConnsNext]
p.subConnsNext = (p.subConnsNext + 1) % len(p.subConns)
done := func(info balancer.DoneInfo) {
if !info.BytesSent {
p.stats.failedToSend()
} else if info.BytesReceived {
p.stats.knownReceived()
}
}
return sc, done, nil
}
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