100 lines
2.6 KiB
Go
100 lines
2.6 KiB
Go
// Copyright 2017 The etcd Authors
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package grpcproxy
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import (
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"encoding/json"
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"os"
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"go.etcd.io/etcd/v3/clientv3"
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"go.etcd.io/etcd/v3/clientv3/concurrency"
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"go.etcd.io/etcd/v3/clientv3/naming"
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"go.uber.org/zap"
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"golang.org/x/time/rate"
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gnaming "google.golang.org/grpc/naming"
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)
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// allow maximum 1 retry per second
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const registerRetryRate = 1
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// Register registers itself as a grpc-proxy server by writing prefixed-key
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// with session of specified TTL (in seconds). The returned channel is closed
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// when the client's context is canceled.
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func Register(lg *zap.Logger, c *clientv3.Client, prefix string, addr string, ttl int) <-chan struct{} {
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rm := rate.NewLimiter(rate.Limit(registerRetryRate), registerRetryRate)
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donec := make(chan struct{})
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go func() {
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defer close(donec)
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for rm.Wait(c.Ctx()) == nil {
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ss, err := registerSession(lg, c, prefix, addr, ttl)
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if err != nil {
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lg.Warn("failed to create a session", zap.Error(err))
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continue
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}
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select {
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case <-c.Ctx().Done():
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ss.Close()
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return
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case <-ss.Done():
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lg.Warn("session expired; possible network partition or server restart")
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lg.Warn("creating a new session to rejoin")
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continue
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}
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}
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}()
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return donec
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}
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func registerSession(lg *zap.Logger, c *clientv3.Client, prefix string, addr string, ttl int) (*concurrency.Session, error) {
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ss, err := concurrency.NewSession(c, concurrency.WithTTL(ttl))
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if err != nil {
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return nil, err
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}
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gr := &naming.GRPCResolver{Client: c}
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if err = gr.Update(c.Ctx(), prefix, gnaming.Update{Op: gnaming.Add, Addr: addr, Metadata: getMeta()}, clientv3.WithLease(ss.Lease())); err != nil {
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return nil, err
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}
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lg.Info(
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"registered session with lease",
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zap.String("addr", addr),
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zap.Int("lease-ttl", ttl),
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)
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return ss, nil
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}
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// meta represents metadata of proxy register.
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type meta struct {
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Name string `json:"name"`
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}
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func getMeta() string {
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hostname, _ := os.Hostname()
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bts, _ := json.Marshal(meta{Name: hostname})
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return string(bts)
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}
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func decodeMeta(s string) (meta, error) {
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m := meta{}
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err := json.Unmarshal([]byte(s), &m)
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return m, err
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}
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