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interceptor.go
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/
interceptor.go
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// Copyright 2016 The etcd 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 v3rpc
import (
"sync"
"time"
"github.com/coreos/etcd/etcdserver"
"github.com/coreos/etcd/etcdserver/api"
"github.com/coreos/etcd/etcdserver/api/v3rpc/rpctypes"
"github.com/coreos/etcd/pkg/types"
"github.com/coreos/etcd/raft"
prometheus "github.com/grpc-ecosystem/go-grpc-prometheus"
"golang.org/x/net/context"
"google.golang.org/grpc"
"google.golang.org/grpc/metadata"
)
const (
maxNoLeaderCnt = 3
)
type streamsMap struct {
mu sync.Mutex
streams map[grpc.ServerStream]struct{}
}
func newUnaryInterceptor(s *etcdserver.EtcdServer) grpc.UnaryServerInterceptor {
return func(ctx context.Context, req interface{}, info *grpc.UnaryServerInfo, handler grpc.UnaryHandler) (resp interface{}, err error) {
if !api.IsCapabilityEnabled(api.V3rpcCapability) {
return nil, rpctypes.ErrGRPCNotCapable
}
md, ok := metadata.FromContext(ctx)
if ok {
if ks := md[rpctypes.MetadataRequireLeaderKey]; len(ks) > 0 && ks[0] == rpctypes.MetadataHasLeader {
if s.Leader() == types.ID(raft.None) {
return nil, rpctypes.ErrGRPCNoLeader
}
}
}
return prometheus.UnaryServerInterceptor(ctx, req, info, handler)
}
}
func newStreamInterceptor(s *etcdserver.EtcdServer) grpc.StreamServerInterceptor {
smap := monitorLeader(s)
return func(srv interface{}, ss grpc.ServerStream, info *grpc.StreamServerInfo, handler grpc.StreamHandler) error {
if !api.IsCapabilityEnabled(api.V3rpcCapability) {
return rpctypes.ErrGRPCNotCapable
}
md, ok := metadata.FromContext(ss.Context())
if ok {
if ks := md[rpctypes.MetadataRequireLeaderKey]; len(ks) > 0 && ks[0] == rpctypes.MetadataHasLeader {
if s.Leader() == types.ID(raft.None) {
return rpctypes.ErrGRPCNoLeader
}
cctx, cancel := context.WithCancel(ss.Context())
ss = serverStreamWithCtx{ctx: cctx, cancel: &cancel, ServerStream: ss}
smap.mu.Lock()
smap.streams[ss] = struct{}{}
smap.mu.Unlock()
defer func() {
smap.mu.Lock()
delete(smap.streams, ss)
smap.mu.Unlock()
cancel()
}()
}
}
return prometheus.StreamServerInterceptor(srv, ss, info, handler)
}
}
type serverStreamWithCtx struct {
grpc.ServerStream
ctx context.Context
cancel *context.CancelFunc
}
func (ssc serverStreamWithCtx) Context() context.Context { return ssc.ctx }
func monitorLeader(s *etcdserver.EtcdServer) *streamsMap {
smap := &streamsMap{
streams: make(map[grpc.ServerStream]struct{}),
}
go func() {
election := time.Duration(s.Cfg.TickMs) * time.Duration(s.Cfg.ElectionTicks) * time.Millisecond
noLeaderCnt := 0
for {
select {
case <-s.StopNotify():
return
case <-time.After(election):
if s.Leader() == types.ID(raft.None) {
noLeaderCnt++
} else {
noLeaderCnt = 0
}
// We are more conservative on canceling existing streams. Reconnecting streams
// cost much more than just rejecting new requests. So we wait until the member
// cannot find a leader for maxNoLeaderCnt election timeouts to cancel existing streams.
if noLeaderCnt >= maxNoLeaderCnt {
smap.mu.Lock()
for ss := range smap.streams {
if ssWithCtx, ok := ss.(serverStreamWithCtx); ok {
(*ssWithCtx.cancel)()
<-ss.Context().Done()
}
}
smap.streams = make(map[grpc.ServerStream]struct{})
smap.mu.Unlock()
}
}
}
}()
return smap
}