Better handling of moving sentinel servers
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d51e77efdd
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236
main.go
236
main.go
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@ -1,119 +1,181 @@
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package main
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import (
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"errors"
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"flag"
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"fmt"
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"io"
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"log"
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"net"
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"strings"
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"time"
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"errors"
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"flag"
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"fmt"
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"io"
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"log"
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"net"
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"strings"
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"sync"
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"time"
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)
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var (
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masterAddr *net.TCPAddr
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raddr *net.TCPAddr
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saddr *net.TCPAddr
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saddr *net.TCPAddr // Address of the sentinel service
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slock *sync.Mutex // Guard for above var
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localAddr = flag.String("listen", ":9999", "local address")
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sentinelAddr = flag.String("sentinel", ":26379", "remote address")
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masterName = flag.String("master", "", "name of the master redis node")
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masterAddr *net.TCPAddr // Address of the redis master
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mlock *sync.Mutex // Guard for above var
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localAddr = flag.String("listen", ":9999", "local address")
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sentinelAddr = flag.String("sentinel", ":26379", "remote address")
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masterName = flag.String("master", "", "name of the master redis node")
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)
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func main() {
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flag.Parse()
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flag.Parse()
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laddr, err := net.ResolveTCPAddr("tcp", *localAddr)
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if err != nil {
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log.Fatal("Failed to resolve local address: %s", err)
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}
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saddr, err = net.ResolveTCPAddr("tcp", *sentinelAddr)
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if err != nil {
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log.Fatal("Failed to resolve sentinel address: %s", err)
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}
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slock = &sync.Mutex{}
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mlock = &sync.Mutex{}
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go master()
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laddr, err := net.ResolveTCPAddr("tcp", *localAddr)
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if err != nil {
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log.Fatalf("Failed to resolve local address: %s", err.Error())
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}
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resolveSentinel(*sentinelAddr)
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listener, err := net.ListenTCP("tcp", laddr)
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if err != nil {
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log.Fatal(err)
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}
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// If sentinel's address is set to nil, this goroutine will resolve it and set the var again
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go sentinelUpdater(*sentinelAddr)
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for {
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conn, err := listener.AcceptTCP()
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if err != nil {
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log.Println(err)
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continue
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}
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// Continuously query sentinel for the master address, updating masterAddr when needed
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go master()
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go proxy(conn, masterAddr)
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}
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listener, err := net.ListenTCP("tcp", laddr)
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if err != nil {
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log.Fatal(err)
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}
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for {
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conn, err := listener.AcceptTCP()
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if err != nil {
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log.Println(err)
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continue
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}
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go proxy(conn, masterAddr)
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}
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}
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func sentinelUpdater(sentinelAddr string) {
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// Resolve the address of sentinel when needed
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for {
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if saddr == nil {
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log.Print("Resolving sentinel address")
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resolveSentinel(sentinelAddr)
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}
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time.Sleep(1 * time.Second)
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}
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}
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func resolveSentinel(sentinelAddr string) {
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// var err error
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addr, err := net.ResolveTCPAddr("tcp", sentinelAddr)
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if err != nil {
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log.Printf("Failed to resolve sentinel address: %s", err.Error())
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return
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}
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slock.Lock()
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saddr = addr
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slock.Unlock()
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// TODO other cases when saddr isn't valid
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}
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func master() {
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var err error
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for {
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masterAddr, err = getMasterAddr(saddr, *masterName)
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if err != nil {
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log.Println(err)
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}
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time.Sleep(1 * time.Second)
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}
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var err error
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var tempAddr *net.TCPAddr
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for {
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tempAddr, err = getMasterAddr()
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if err != nil {
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log.Printf("Failed to get master addres: %s", err.Error())
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} else {
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mlock.Lock()
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masterAddr = tempAddr
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mlock.Unlock()
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}
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time.Sleep(1 * time.Second)
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}
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}
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func pipe(r io.Reader, w io.WriteCloser) {
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io.Copy(w, r)
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w.Close()
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io.Copy(w, r)
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w.Close()
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}
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func proxy(local io.ReadWriteCloser, remoteAddr *net.TCPAddr) {
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remote, err := net.DialTCP("tcp", nil, remoteAddr)
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if err != nil {
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log.Println(err)
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local.Close()
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return
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}
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go pipe(local, remote)
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go pipe(remote, local)
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remote, err := net.DialTCP("tcp", nil, remoteAddr)
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if err != nil {
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log.Println(err)
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local.Close()
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return
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}
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go pipe(local, remote)
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go pipe(remote, local)
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}
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func getMasterAddr(sentinelAddress *net.TCPAddr, masterName string) (*net.TCPAddr, error) {
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conn, err := net.DialTCP("tcp", nil, sentinelAddress)
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if err != nil {
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return nil, err
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}
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// Connect to Sentinel and query it to find the redis master
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func getMasterAddr() (*net.TCPAddr, error) {
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// Connect to sentinel
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// If the connection times out, that master is probably gone.
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// Mark saddr as nil so that the resolver thread will update it later.
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// Create a local copy of the sentinel address, it can change under our feet
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slock.Lock()
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if saddr == nil {
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defer slock.Unlock()
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return nil, errors.New("Sentinel address not available")
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}
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local_saddr := *saddr
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slock.Unlock()
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defer conn.Close()
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sentConn, err := dialTimeout(&local_saddr, 5*time.Second)
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if err != nil {
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log.Printf("Connecting to sentinel master timed out/failed: %s\n", err.Error())
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slock.Lock()
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saddr = nil
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slock.Unlock()
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return nil, err
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}
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defer sentConn.Close()
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conn.Write([]byte(fmt.Sprintf("sentinel get-master-addr-by-name %s\n", masterName)))
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// We connected to the master, ask for the redis master
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sentConn.Write([]byte(fmt.Sprintf("sentinel get-master-addr-by-name %s\n", *masterName)))
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b := make([]byte, 256)
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_, err = conn.Read(b)
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if err != nil {
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log.Fatal(err)
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}
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b := make([]byte, 256)
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_, err = sentConn.Read(b)
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if err != nil {
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return nil, err
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}
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parts := strings.Split(string(b), "\r\n")
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if len(parts) < 5 {
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err = errors.New("Couldn't get master address from sentinel")
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return nil, err
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}
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parts := strings.Split(string(b), "\r\n")
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// Parse the address for the master node
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stringaddr := fmt.Sprintf("%s:%s", parts[2], parts[4])
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addr, err := net.ResolveTCPAddr("tcp", stringaddr)
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if err != nil {
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return nil, err
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}
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if len(parts) < 5 {
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err = errors.New("Couldn't get master address from sentinel")
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return nil, err
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}
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//getting the string address for the master node
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stringaddr := fmt.Sprintf("%s:%s", parts[2], parts[4])
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addr, err := net.ResolveTCPAddr("tcp", stringaddr)
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if err != nil {
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return nil, err
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}
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//check that there's actually someone listening on that address
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conn2, err := net.DialTCP("tcp", nil, addr)
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if err == nil {
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defer conn2.Close()
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}
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return addr, err
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// Verify the returned address is actually listening
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// TODO is this really needed?
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conn2, err := dialTimeout(addr, 5*time.Second)
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if err != nil {
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return nil, err
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}
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defer conn2.Close()
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return addr, err
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}
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// Connect to a TCPAddr, failing if a timeout is exceeded or other error encountered
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func dialTimeout(destAddr *net.TCPAddr, timeout time.Duration) (*net.TCPConn, error) {
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d := net.Dialer{Timeout: timeout}
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netcon, err := d.Dial("tcp", fmt.Sprintf("%s:%d", destAddr.IP, destAddr.Port))
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if err != nil {
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return nil, err
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}
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conn, _ := netcon.(*net.TCPConn)
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return conn, nil
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}
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