redisproxy/main.go

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4.7 KiB
Go
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package main
import (
"errors"
"flag"
"fmt"
"io"
"log"
"net"
"strings"
"sync"
"time"
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)
var (
saddr *net.TCPAddr // Address of the sentinel service
slock *sync.Mutex // Guard for above var
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masterAddr *net.TCPAddr // Address of the redis master
mlock *sync.Mutex // Guard for above var
localAddr = flag.String("listen", ":9999", "local address")
sentinelAddr = flag.String("sentinel", ":26379", "remote address")
masterName = flag.String("master", "", "name of the master redis node")
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)
func main() {
flag.Parse()
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slock = &sync.Mutex{}
mlock = &sync.Mutex{}
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laddr, err := net.ResolveTCPAddr("tcp", *localAddr)
if err != nil {
log.Fatalf("Failed to resolve local address: %s", err.Error())
}
resolveSentinel(*sentinelAddr)
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// If sentinel's address is set to nil, this goroutine will resolve it and set the var again
go sentinelUpdater(*sentinelAddr)
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// Continuously query sentinel for the master address, updating masterAddr when needed
go master()
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listener, err := net.ListenTCP("tcp", laddr)
if err != nil {
log.Fatal(err)
}
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for {
conn, err := listener.AcceptTCP()
if err != nil {
log.Println(err)
continue
}
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go proxy(conn, masterAddr)
}
}
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func sentinelUpdater(sentinelAddr string) {
// Resolve the address of sentinel when needed
for {
if saddr == nil {
log.Print("Resolving sentinel address")
resolveSentinel(sentinelAddr)
}
time.Sleep(1 * time.Second)
}
}
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func resolveSentinel(sentinelAddr string) {
// var err error
addr, err := net.ResolveTCPAddr("tcp", sentinelAddr)
if err != nil {
log.Printf("Failed to resolve sentinel address: %s", err.Error())
return
}
slock.Lock()
saddr = addr
slock.Unlock()
// TODO other cases when saddr isn't valid
}
func master() {
var err error
var tempAddr *net.TCPAddr
for {
tempAddr, err = getMasterAddr()
if err != nil {
log.Printf("Failed to get master addres: %s", err.Error())
} else {
mlock.Lock()
masterAddr = tempAddr
mlock.Unlock()
}
time.Sleep(1 * time.Second)
}
}
func pipe(r io.Reader, w io.WriteCloser) {
io.Copy(w, r)
w.Close()
}
func proxy(local io.ReadWriteCloser, remoteAddr *net.TCPAddr) {
remote, err := net.DialTCP("tcp", nil, remoteAddr)
if err != nil {
log.Println(err)
local.Close()
return
}
go pipe(local, remote)
go pipe(remote, local)
}
// Connect to Sentinel and query it to find the redis master
func getMasterAddr() (*net.TCPAddr, error) {
// Connect to sentinel
// If the connection times out, that master is probably gone.
// Mark saddr as nil so that the resolver thread will update it later.
// Create a local copy of the sentinel address, it can change under our feet
slock.Lock()
if saddr == nil {
defer slock.Unlock()
return nil, errors.New("Sentinel address not available")
}
local_saddr := *saddr
slock.Unlock()
sentConn, err := dialTimeout(&local_saddr, 5*time.Second)
if err != nil {
log.Printf("Connecting to sentinel master timed out/failed: %s\n", err.Error())
slock.Lock()
saddr = nil
slock.Unlock()
return nil, err
}
defer sentConn.Close()
// We connected to the master, ask for the redis master
sentConn.Write([]byte(fmt.Sprintf("sentinel get-master-addr-by-name %s\n", *masterName)))
b := make([]byte, 256)
_, err = sentConn.Read(b)
if err != nil {
return nil, err
}
parts := strings.Split(string(b), "\r\n")
if len(parts) < 5 {
err = errors.New("Couldn't get master address from sentinel")
return nil, err
}
// Parse the address for the master node
stringaddr := fmt.Sprintf("%s:%s", parts[2], parts[4])
addr, err := net.ResolveTCPAddr("tcp", stringaddr)
if err != nil {
return nil, err
}
// Verify the returned address is actually listening
// TODO is this really needed?
conn2, err := dialTimeout(addr, 5*time.Second)
if err != nil {
return nil, err
}
defer conn2.Close()
return addr, err
}
// Connect to a TCPAddr, failing if a timeout is exceeded or other error encountered
func dialTimeout(destAddr *net.TCPAddr, timeout time.Duration) (*net.TCPConn, error) {
d := net.Dialer{Timeout: timeout}
netcon, err := d.Dial("tcp", fmt.Sprintf("%s:%d", destAddr.IP, destAddr.Port))
if err != nil {
return nil, err
}
conn, _ := netcon.(*net.TCPConn)
return conn, nil
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}