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// Copyright (c) 2020 The Jaeger 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 utils
import (
"fmt"
"net"
"sync"
"sync/atomic"
"time"
"github.com/uber/jaeger-client-go/log"
)
// reconnectingUDPConn is an implementation of udpConn that resolves hostPort every resolveTimeout, if the resolved address is
// different than the current conn then the new address is dialed and the conn is swapped.
type reconnectingUDPConn struct {
hostPort string
resolveFunc resolveFunc
dialFunc dialFunc
logger log.Logger
bufferBytes int64
connMtx sync.RWMutex
conn *net.UDPConn
destAddr *net.UDPAddr
closeChan chan struct{}
}
type resolveFunc func(network string, hostPort string) (*net.UDPAddr, error)
type dialFunc func(network string, laddr, raddr *net.UDPAddr) (*net.UDPConn, error)
// newReconnectingUDPConn returns a new udpConn that resolves hostPort every resolveTimeout, if the resolved address is
// different than the current conn then the new address is dialed and the conn is swapped.
func newReconnectingUDPConn(hostPort string, resolveTimeout time.Duration, resolveFunc resolveFunc, dialFunc dialFunc, logger log.Logger) (*reconnectingUDPConn, error) {
conn := &reconnectingUDPConn{
hostPort: hostPort,
resolveFunc: resolveFunc,
dialFunc: dialFunc,
logger: logger,
closeChan: make(chan struct{}),
}
if err := conn.attemptResolveAndDial(); err != nil {
logger.Error(fmt.Sprintf("failed resolving destination address on connection startup, with err: %q. retrying in %s", err.Error(), resolveTimeout))
}
go conn.reconnectLoop(resolveTimeout)
return conn, nil
}
func (c *reconnectingUDPConn) reconnectLoop(resolveTimeout time.Duration) {
ticker := time.NewTicker(resolveTimeout)
defer ticker.Stop()
for {
select {
case <-c.closeChan:
return
case <-ticker.C:
if err := c.attemptResolveAndDial(); err != nil {
c.logger.Error(err.Error())
}
}
}
}
func (c *reconnectingUDPConn) attemptResolveAndDial() error {
newAddr, err := c.resolveFunc("udp", c.hostPort)
if err != nil {
return fmt.Errorf("failed to resolve new addr for host %q, with err: %w", c.hostPort, err)
}
c.connMtx.RLock()
curAddr := c.destAddr
c.connMtx.RUnlock()
// dont attempt dial if an addr was successfully dialed previously and, resolved addr is the same as current conn
if curAddr != nil && newAddr.String() == curAddr.String() {
return nil
}
if err := c.attemptDialNewAddr(newAddr); err != nil {
return fmt.Errorf("failed to dial newly resolved addr '%s', with err: %w", newAddr, err)
}
return nil
}
func (c *reconnectingUDPConn) attemptDialNewAddr(newAddr *net.UDPAddr) error {
connUDP, err := c.dialFunc(newAddr.Network(), nil, newAddr)
if err != nil {
return err
}
if bufferBytes := int(atomic.LoadInt64(&c.bufferBytes)); bufferBytes != 0 {
if err = connUDP.SetWriteBuffer(bufferBytes); err != nil {
return err
}
}
c.connMtx.Lock()
c.destAddr = newAddr
// store prev to close later
prevConn := c.conn
c.conn = connUDP
c.connMtx.Unlock()
if prevConn != nil {
return prevConn.Close()
}
return nil
}
// 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
func (c *reconnectingUDPConn) Write(b []byte) (int, error) {
var bytesWritten int
var err error
c.connMtx.RLock()
if c.conn == nil {
// if connection is not initialized indicate this with err in order to hook into retry logic
err = fmt.Errorf("UDP connection not yet initialized, an address has not been resolved")
} else {
bytesWritten, err = c.conn.Write(b)
}
c.connMtx.RUnlock()
if err == nil {
return bytesWritten, nil
}
// attempt to resolve and dial new address in case that's the problem, if resolve and dial succeeds, try write again
if reconnErr := c.attemptResolveAndDial(); reconnErr == nil {
c.connMtx.RLock()
defer c.connMtx.RUnlock()
return c.conn.Write(b)
}
// return original error if reconn fails
return bytesWritten, err
}
// Close stops the reconnectLoop, then closes the connection via net.udpConn 's implementation
func (c *reconnectingUDPConn) Close() error {
close(c.closeChan)
// acquire rw lock before closing conn to ensure calls to Write drain
c.connMtx.Lock()
defer c.connMtx.Unlock()
if c.conn != nil {
return c.conn.Close()
}
return nil
}
// SetWriteBuffer defers to the net.udpConn SetWriteBuffer implementation wrapped with a RLock. if no conn is currently held
// and SetWriteBuffer is called store bufferBytes to be set for new conns
func (c *reconnectingUDPConn) SetWriteBuffer(bytes int) error {
var err error
c.connMtx.RLock()
if c.conn != nil {
err = c.conn.SetWriteBuffer(bytes)
}
c.connMtx.RUnlock()
if err == nil {
atomic.StoreInt64(&c.bufferBytes, int64(bytes))
}
return err
}
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