khenaidoo | ffe076b | 2019-01-15 16:08:08 -0500 | [diff] [blame^] | 1 | // Copyright 2017 The etcd Authors |
| 2 | // |
| 3 | // Licensed under the Apache License, Version 2.0 (the "License"); |
| 4 | // you may not use this file except in compliance with the License. |
| 5 | // You may obtain a copy of the License at |
| 6 | // |
| 7 | // http://www.apache.org/licenses/LICENSE-2.0 |
| 8 | // |
| 9 | // Unless required by applicable law or agreed to in writing, software |
| 10 | // distributed under the License is distributed on an "AS IS" BASIS, |
| 11 | // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| 12 | // See the License for the specific language governing permissions and |
| 13 | // limitations under the License. |
| 14 | |
| 15 | package grpcproxy |
| 16 | |
| 17 | import ( |
| 18 | "encoding/json" |
| 19 | "os" |
| 20 | |
| 21 | "github.com/coreos/etcd/clientv3" |
| 22 | "github.com/coreos/etcd/clientv3/concurrency" |
| 23 | "github.com/coreos/etcd/clientv3/naming" |
| 24 | |
| 25 | "golang.org/x/time/rate" |
| 26 | gnaming "google.golang.org/grpc/naming" |
| 27 | ) |
| 28 | |
| 29 | // allow maximum 1 retry per second |
| 30 | const registerRetryRate = 1 |
| 31 | |
| 32 | // Register registers itself as a grpc-proxy server by writing prefixed-key |
| 33 | // with session of specified TTL (in seconds). The returned channel is closed |
| 34 | // when the client's context is canceled. |
| 35 | func Register(c *clientv3.Client, prefix string, addr string, ttl int) <-chan struct{} { |
| 36 | rm := rate.NewLimiter(rate.Limit(registerRetryRate), registerRetryRate) |
| 37 | |
| 38 | donec := make(chan struct{}) |
| 39 | go func() { |
| 40 | defer close(donec) |
| 41 | |
| 42 | for rm.Wait(c.Ctx()) == nil { |
| 43 | ss, err := registerSession(c, prefix, addr, ttl) |
| 44 | if err != nil { |
| 45 | plog.Warningf("failed to create a session %v", err) |
| 46 | continue |
| 47 | } |
| 48 | select { |
| 49 | case <-c.Ctx().Done(): |
| 50 | ss.Close() |
| 51 | return |
| 52 | |
| 53 | case <-ss.Done(): |
| 54 | plog.Warning("session expired; possible network partition or server restart") |
| 55 | plog.Warning("creating a new session to rejoin") |
| 56 | continue |
| 57 | } |
| 58 | } |
| 59 | }() |
| 60 | |
| 61 | return donec |
| 62 | } |
| 63 | |
| 64 | func registerSession(c *clientv3.Client, prefix string, addr string, ttl int) (*concurrency.Session, error) { |
| 65 | ss, err := concurrency.NewSession(c, concurrency.WithTTL(ttl)) |
| 66 | if err != nil { |
| 67 | return nil, err |
| 68 | } |
| 69 | |
| 70 | gr := &naming.GRPCResolver{Client: c} |
| 71 | if err = gr.Update(c.Ctx(), prefix, gnaming.Update{Op: gnaming.Add, Addr: addr, Metadata: getMeta()}, clientv3.WithLease(ss.Lease())); err != nil { |
| 72 | return nil, err |
| 73 | } |
| 74 | |
| 75 | plog.Infof("registered %q with %d-second lease", addr, ttl) |
| 76 | return ss, nil |
| 77 | } |
| 78 | |
| 79 | // meta represents metadata of proxy register. |
| 80 | type meta struct { |
| 81 | Name string `json:"name"` |
| 82 | } |
| 83 | |
| 84 | func getMeta() string { |
| 85 | hostname, _ := os.Hostname() |
| 86 | bts, _ := json.Marshal(meta{Name: hostname}) |
| 87 | return string(bts) |
| 88 | } |
| 89 | |
| 90 | func decodeMeta(s string) (meta, error) { |
| 91 | m := meta{} |
| 92 | err := json.Unmarshal([]byte(s), &m) |
| 93 | return m, err |
| 94 | } |