khenaidoo | 7d3c558 | 2021-08-11 18:09:44 -0400 | [diff] [blame] | 1 | // Copyright (c) 2020 The Jaeger 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 utils |
| 16 | |
| 17 | import ( |
| 18 | "fmt" |
| 19 | "net" |
| 20 | "sync" |
| 21 | "sync/atomic" |
| 22 | "time" |
| 23 | |
| 24 | "github.com/uber/jaeger-client-go/log" |
| 25 | ) |
| 26 | |
| 27 | // reconnectingUDPConn is an implementation of udpConn that resolves hostPort every resolveTimeout, if the resolved address is |
| 28 | // different than the current conn then the new address is dialed and the conn is swapped. |
| 29 | type reconnectingUDPConn struct { |
| 30 | hostPort string |
| 31 | resolveFunc resolveFunc |
| 32 | dialFunc dialFunc |
| 33 | logger log.Logger |
| 34 | bufferBytes int64 |
| 35 | |
| 36 | connMtx sync.RWMutex |
| 37 | conn *net.UDPConn |
| 38 | destAddr *net.UDPAddr |
| 39 | closeChan chan struct{} |
| 40 | } |
| 41 | |
| 42 | type resolveFunc func(network string, hostPort string) (*net.UDPAddr, error) |
| 43 | type dialFunc func(network string, laddr, raddr *net.UDPAddr) (*net.UDPConn, error) |
| 44 | |
| 45 | // newReconnectingUDPConn returns a new udpConn that resolves hostPort every resolveTimeout, if the resolved address is |
| 46 | // different than the current conn then the new address is dialed and the conn is swapped. |
| 47 | func newReconnectingUDPConn(hostPort string, resolveTimeout time.Duration, resolveFunc resolveFunc, dialFunc dialFunc, logger log.Logger) (*reconnectingUDPConn, error) { |
| 48 | conn := &reconnectingUDPConn{ |
| 49 | hostPort: hostPort, |
| 50 | resolveFunc: resolveFunc, |
| 51 | dialFunc: dialFunc, |
| 52 | logger: logger, |
| 53 | closeChan: make(chan struct{}), |
| 54 | } |
| 55 | |
| 56 | if err := conn.attemptResolveAndDial(); err != nil { |
| 57 | logger.Error(fmt.Sprintf("failed resolving destination address on connection startup, with err: %q. retrying in %s", err.Error(), resolveTimeout)) |
| 58 | } |
| 59 | |
| 60 | go conn.reconnectLoop(resolveTimeout) |
| 61 | |
| 62 | return conn, nil |
| 63 | } |
| 64 | |
| 65 | func (c *reconnectingUDPConn) reconnectLoop(resolveTimeout time.Duration) { |
| 66 | ticker := time.NewTicker(resolveTimeout) |
| 67 | defer ticker.Stop() |
| 68 | |
| 69 | for { |
| 70 | select { |
| 71 | case <-c.closeChan: |
| 72 | return |
| 73 | case <-ticker.C: |
| 74 | if err := c.attemptResolveAndDial(); err != nil { |
| 75 | c.logger.Error(err.Error()) |
| 76 | } |
| 77 | } |
| 78 | } |
| 79 | } |
| 80 | |
| 81 | func (c *reconnectingUDPConn) attemptResolveAndDial() error { |
| 82 | newAddr, err := c.resolveFunc("udp", c.hostPort) |
| 83 | if err != nil { |
| 84 | return fmt.Errorf("failed to resolve new addr for host %q, with err: %w", c.hostPort, err) |
| 85 | } |
| 86 | |
| 87 | c.connMtx.RLock() |
| 88 | curAddr := c.destAddr |
| 89 | c.connMtx.RUnlock() |
| 90 | |
| 91 | // dont attempt dial if an addr was successfully dialed previously and, resolved addr is the same as current conn |
| 92 | if curAddr != nil && newAddr.String() == curAddr.String() { |
| 93 | return nil |
| 94 | } |
| 95 | |
| 96 | if err := c.attemptDialNewAddr(newAddr); err != nil { |
| 97 | return fmt.Errorf("failed to dial newly resolved addr '%s', with err: %w", newAddr, err) |
| 98 | } |
| 99 | |
| 100 | return nil |
| 101 | } |
| 102 | |
| 103 | func (c *reconnectingUDPConn) attemptDialNewAddr(newAddr *net.UDPAddr) error { |
| 104 | connUDP, err := c.dialFunc(newAddr.Network(), nil, newAddr) |
| 105 | if err != nil { |
| 106 | return err |
| 107 | } |
| 108 | |
| 109 | if bufferBytes := int(atomic.LoadInt64(&c.bufferBytes)); bufferBytes != 0 { |
| 110 | if err = connUDP.SetWriteBuffer(bufferBytes); err != nil { |
| 111 | return err |
| 112 | } |
| 113 | } |
| 114 | |
| 115 | c.connMtx.Lock() |
| 116 | c.destAddr = newAddr |
| 117 | // store prev to close later |
| 118 | prevConn := c.conn |
| 119 | c.conn = connUDP |
| 120 | c.connMtx.Unlock() |
| 121 | |
| 122 | if prevConn != nil { |
| 123 | return prevConn.Close() |
| 124 | } |
| 125 | |
| 126 | return nil |
| 127 | } |
| 128 | |
| 129 | // Write calls net.udpConn.Write, if it fails an attempt is made to connect to a new addr, if that succeeds the write is retried before returning |
| 130 | func (c *reconnectingUDPConn) Write(b []byte) (int, error) { |
| 131 | var bytesWritten int |
| 132 | var err error |
| 133 | |
| 134 | c.connMtx.RLock() |
| 135 | if c.conn == nil { |
| 136 | // if connection is not initialized indicate this with err in order to hook into retry logic |
| 137 | err = fmt.Errorf("UDP connection not yet initialized, an address has not been resolved") |
| 138 | } else { |
| 139 | bytesWritten, err = c.conn.Write(b) |
| 140 | } |
| 141 | c.connMtx.RUnlock() |
| 142 | |
| 143 | if err == nil { |
| 144 | return bytesWritten, nil |
| 145 | } |
| 146 | |
| 147 | // attempt to resolve and dial new address in case that's the problem, if resolve and dial succeeds, try write again |
| 148 | if reconnErr := c.attemptResolveAndDial(); reconnErr == nil { |
| 149 | c.connMtx.RLock() |
| 150 | defer c.connMtx.RUnlock() |
| 151 | return c.conn.Write(b) |
| 152 | } |
| 153 | |
| 154 | // return original error if reconn fails |
| 155 | return bytesWritten, err |
| 156 | } |
| 157 | |
| 158 | // Close stops the reconnectLoop, then closes the connection via net.udpConn 's implementation |
| 159 | func (c *reconnectingUDPConn) Close() error { |
| 160 | close(c.closeChan) |
| 161 | |
| 162 | // acquire rw lock before closing conn to ensure calls to Write drain |
| 163 | c.connMtx.Lock() |
| 164 | defer c.connMtx.Unlock() |
| 165 | |
| 166 | if c.conn != nil { |
| 167 | return c.conn.Close() |
| 168 | } |
| 169 | |
| 170 | return nil |
| 171 | } |
| 172 | |
| 173 | // SetWriteBuffer defers to the net.udpConn SetWriteBuffer implementation wrapped with a RLock. if no conn is currently held |
| 174 | // and SetWriteBuffer is called store bufferBytes to be set for new conns |
| 175 | func (c *reconnectingUDPConn) SetWriteBuffer(bytes int) error { |
| 176 | var err error |
| 177 | |
| 178 | c.connMtx.RLock() |
| 179 | if c.conn != nil { |
| 180 | err = c.conn.SetWriteBuffer(bytes) |
| 181 | } |
| 182 | c.connMtx.RUnlock() |
| 183 | |
| 184 | if err == nil { |
| 185 | atomic.StoreInt64(&c.bufferBytes, int64(bytes)) |
| 186 | } |
| 187 | |
| 188 | return err |
| 189 | } |