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// Copyright 2017 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 grpcproxy
import (
"encoding/json"
"os"
"go.etcd.io/etcd/client/v3"
"go.etcd.io/etcd/client/v3/concurrency"
"go.etcd.io/etcd/client/v3/naming/endpoints"
"go.uber.org/zap"
"golang.org/x/time/rate"
)
// allow maximum 1 retry per second
const registerRetryRate = 1
// Register registers itself as a grpc-proxy server by writing prefixed-key
// with session of specified TTL (in seconds). The returned channel is closed
// when the client's context is canceled.
func Register(lg *zap.Logger, c *clientv3.Client, prefix string, addr string, ttl int) <-chan struct{} {
rm := rate.NewLimiter(rate.Limit(registerRetryRate), registerRetryRate)
donec := make(chan struct{})
go func() {
defer close(donec)
for rm.Wait(c.Ctx()) == nil {
ss, err := registerSession(lg, c, prefix, addr, ttl)
if err != nil {
lg.Warn("failed to create a session", zap.Error(err))
continue
}
select {
case <-c.Ctx().Done():
ss.Close()
return
case <-ss.Done():
lg.Warn("session expired; possible network partition or server restart")
lg.Warn("creating a new session to rejoin")
continue
}
}
}()
return donec
}
func registerSession(lg *zap.Logger, c *clientv3.Client, prefix string, addr string, ttl int) (*concurrency.Session, error) {
ss, err := concurrency.NewSession(c, concurrency.WithTTL(ttl))
if err != nil {
return nil, err
}
em, err := endpoints.NewManager(c, prefix)
if err != nil {
return nil, err
}
endpoint := endpoints.Endpoint{Addr: addr, Metadata: getMeta()}
if err = em.AddEndpoint(c.Ctx(), prefix+"/"+addr, endpoint, clientv3.WithLease(ss.Lease())); err != nil {
return nil, err
}
lg.Info(
"registered session with lease",
zap.String("addr", addr),
zap.Int("lease-ttl", ttl),
)
return ss, nil
}
// meta represents metadata of proxy register.
type meta struct {
Name string `json:"name"`
}
func getMeta() string {
hostname, _ := os.Hostname()
bts, _ := json.Marshal(meta{Name: hostname})
return string(bts)
}
func decodeMeta(s string) (meta, error) {
m := meta{}
err := json.Unmarshal([]byte(s), &m)
return m, err
}
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