khenaidoo | ffe076b | 2019-01-15 16:08:08 -0500 | [diff] [blame^] | 1 | // Copyright 2016 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 tcpproxy |
| 16 | |
| 17 | import ( |
| 18 | "fmt" |
| 19 | "io" |
| 20 | "math/rand" |
| 21 | "net" |
| 22 | "sync" |
| 23 | "time" |
| 24 | |
| 25 | "github.com/coreos/pkg/capnslog" |
| 26 | ) |
| 27 | |
| 28 | var ( |
| 29 | plog = capnslog.NewPackageLogger("github.com/coreos/etcd", "proxy/tcpproxy") |
| 30 | ) |
| 31 | |
| 32 | type remote struct { |
| 33 | mu sync.Mutex |
| 34 | srv *net.SRV |
| 35 | addr string |
| 36 | inactive bool |
| 37 | } |
| 38 | |
| 39 | func (r *remote) inactivate() { |
| 40 | r.mu.Lock() |
| 41 | defer r.mu.Unlock() |
| 42 | r.inactive = true |
| 43 | } |
| 44 | |
| 45 | func (r *remote) tryReactivate() error { |
| 46 | conn, err := net.Dial("tcp", r.addr) |
| 47 | if err != nil { |
| 48 | return err |
| 49 | } |
| 50 | conn.Close() |
| 51 | r.mu.Lock() |
| 52 | defer r.mu.Unlock() |
| 53 | r.inactive = false |
| 54 | return nil |
| 55 | } |
| 56 | |
| 57 | func (r *remote) isActive() bool { |
| 58 | r.mu.Lock() |
| 59 | defer r.mu.Unlock() |
| 60 | return !r.inactive |
| 61 | } |
| 62 | |
| 63 | type TCPProxy struct { |
| 64 | Listener net.Listener |
| 65 | Endpoints []*net.SRV |
| 66 | MonitorInterval time.Duration |
| 67 | |
| 68 | donec chan struct{} |
| 69 | |
| 70 | mu sync.Mutex // guards the following fields |
| 71 | remotes []*remote |
| 72 | pickCount int // for round robin |
| 73 | } |
| 74 | |
| 75 | func (tp *TCPProxy) Run() error { |
| 76 | tp.donec = make(chan struct{}) |
| 77 | if tp.MonitorInterval == 0 { |
| 78 | tp.MonitorInterval = 5 * time.Minute |
| 79 | } |
| 80 | for _, srv := range tp.Endpoints { |
| 81 | addr := fmt.Sprintf("%s:%d", srv.Target, srv.Port) |
| 82 | tp.remotes = append(tp.remotes, &remote{srv: srv, addr: addr}) |
| 83 | } |
| 84 | |
| 85 | eps := []string{} |
| 86 | for _, ep := range tp.Endpoints { |
| 87 | eps = append(eps, fmt.Sprintf("%s:%d", ep.Target, ep.Port)) |
| 88 | } |
| 89 | plog.Printf("ready to proxy client requests to %+v", eps) |
| 90 | |
| 91 | go tp.runMonitor() |
| 92 | for { |
| 93 | in, err := tp.Listener.Accept() |
| 94 | if err != nil { |
| 95 | return err |
| 96 | } |
| 97 | |
| 98 | go tp.serve(in) |
| 99 | } |
| 100 | } |
| 101 | |
| 102 | func (tp *TCPProxy) pick() *remote { |
| 103 | var weighted []*remote |
| 104 | var unweighted []*remote |
| 105 | |
| 106 | bestPr := uint16(65535) |
| 107 | w := 0 |
| 108 | // find best priority class |
| 109 | for _, r := range tp.remotes { |
| 110 | switch { |
| 111 | case !r.isActive(): |
| 112 | case r.srv.Priority < bestPr: |
| 113 | bestPr = r.srv.Priority |
| 114 | w = 0 |
| 115 | weighted = nil |
| 116 | unweighted = []*remote{r} |
| 117 | fallthrough |
| 118 | case r.srv.Priority == bestPr: |
| 119 | if r.srv.Weight > 0 { |
| 120 | weighted = append(weighted, r) |
| 121 | w += int(r.srv.Weight) |
| 122 | } else { |
| 123 | unweighted = append(unweighted, r) |
| 124 | } |
| 125 | } |
| 126 | } |
| 127 | if weighted != nil { |
| 128 | if len(unweighted) > 0 && rand.Intn(100) == 1 { |
| 129 | // In the presence of records containing weights greater |
| 130 | // than 0, records with weight 0 should have a very small |
| 131 | // chance of being selected. |
| 132 | r := unweighted[tp.pickCount%len(unweighted)] |
| 133 | tp.pickCount++ |
| 134 | return r |
| 135 | } |
| 136 | // choose a uniform random number between 0 and the sum computed |
| 137 | // (inclusive), and select the RR whose running sum value is the |
| 138 | // first in the selected order |
| 139 | choose := rand.Intn(w) |
| 140 | for i := 0; i < len(weighted); i++ { |
| 141 | choose -= int(weighted[i].srv.Weight) |
| 142 | if choose <= 0 { |
| 143 | return weighted[i] |
| 144 | } |
| 145 | } |
| 146 | } |
| 147 | if unweighted != nil { |
| 148 | for i := 0; i < len(tp.remotes); i++ { |
| 149 | picked := tp.remotes[tp.pickCount%len(tp.remotes)] |
| 150 | tp.pickCount++ |
| 151 | if picked.isActive() { |
| 152 | return picked |
| 153 | } |
| 154 | } |
| 155 | } |
| 156 | return nil |
| 157 | } |
| 158 | |
| 159 | func (tp *TCPProxy) serve(in net.Conn) { |
| 160 | var ( |
| 161 | err error |
| 162 | out net.Conn |
| 163 | ) |
| 164 | |
| 165 | for { |
| 166 | tp.mu.Lock() |
| 167 | remote := tp.pick() |
| 168 | tp.mu.Unlock() |
| 169 | if remote == nil { |
| 170 | break |
| 171 | } |
| 172 | // TODO: add timeout |
| 173 | out, err = net.Dial("tcp", remote.addr) |
| 174 | if err == nil { |
| 175 | break |
| 176 | } |
| 177 | remote.inactivate() |
| 178 | plog.Warningf("deactivated endpoint [%s] due to %v for %v", remote.addr, err, tp.MonitorInterval) |
| 179 | } |
| 180 | |
| 181 | if out == nil { |
| 182 | in.Close() |
| 183 | return |
| 184 | } |
| 185 | |
| 186 | go func() { |
| 187 | io.Copy(in, out) |
| 188 | in.Close() |
| 189 | out.Close() |
| 190 | }() |
| 191 | |
| 192 | io.Copy(out, in) |
| 193 | out.Close() |
| 194 | in.Close() |
| 195 | } |
| 196 | |
| 197 | func (tp *TCPProxy) runMonitor() { |
| 198 | for { |
| 199 | select { |
| 200 | case <-time.After(tp.MonitorInterval): |
| 201 | tp.mu.Lock() |
| 202 | for _, rem := range tp.remotes { |
| 203 | if rem.isActive() { |
| 204 | continue |
| 205 | } |
| 206 | go func(r *remote) { |
| 207 | if err := r.tryReactivate(); err != nil { |
| 208 | plog.Warningf("failed to activate endpoint [%s] due to %v (stay inactive for another %v)", r.addr, err, tp.MonitorInterval) |
| 209 | } else { |
| 210 | plog.Printf("activated %s", r.addr) |
| 211 | } |
| 212 | }(rem) |
| 213 | } |
| 214 | tp.mu.Unlock() |
| 215 | case <-tp.donec: |
| 216 | return |
| 217 | } |
| 218 | } |
| 219 | } |
| 220 | |
| 221 | func (tp *TCPProxy) Stop() { |
| 222 | // graceful shutdown? |
| 223 | // shutdown current connections? |
| 224 | tp.Listener.Close() |
| 225 | close(tp.donec) |
| 226 | } |