Connect to Redis with Senitel (#180)

docs/en/redis_best_practices.md

@@ -29,6 +29,15 @@ There're some [fundamental things](https://redis.io/topics/sentinel#fundamental-
 
 Please read the [official documentation](https://redis.io/topics/sentinel) for more information.
 
+Once Redis servers and Sentinels are deployed, the `REDIS-URL` can be specified as `[redis[s]://][USER:PASSWORD@]MASTERNAME,SENTINEL_ADDRS:SENTINEL_PORT[/DB]`, for example,
+
+```
+$ ./juicefs mount rediss://:sentinelPass@masterName,1.2.3.4,1.2.5.6:5000/2
+```
+**Note** The default port for Sentinel is 26379, but the above URL use 6379 (default port for Redis server) as the default, so the port for Sentinel is not optional.
+
+**Note** When the password is provided in the URL, it will also be used to connect Redis server. If they have different passwords, the passwords should be specified by enviroment viarables (`SENTINEL_PASSWORD` and `REDIS_PASSWORD`) separately.
+
 ## Data Durability
 
 Redis provides a different range of [persistence](https://redis.io/topics/persistence) options:

pkg/meta/redis.go

@@ -23,6 +23,7 @@ import (
 	"fmt"
 	"hash/fnv"
 	"math/rand"
+	"net"
 	"os"
 	"strconv"
 	"strings"
@@ -114,13 +115,46 @@ func NewRedisMeta(url string, conf *RedisConfig) (Meta, error) {
 	if err != nil {
 		return nil, fmt.Errorf("parse %s: %s", url, err)
 	}
-	if opt.Password == "" && os.Getenv("REDIS_PASSWORD") != "" {
-		opt.Password = os.Getenv("REDIS_PASSWORD")
+	var rdb *redis.Client
+	if strings.Contains(opt.Addr, ",") {
+		var fopt redis.FailoverOptions
+		ps := strings.Split(opt.Addr, ",")
+		fopt.MasterName = ps[0]
+		fopt.SentinelAddrs = ps[1:]
+		_, port, _ := net.SplitHostPort(fopt.SentinelAddrs[len(fopt.SentinelAddrs)-1])
+		if port != "" {
+			for i := range fopt.SentinelAddrs {
+				h, p, _ := net.SplitHostPort(fopt.SentinelAddrs[i])
+				if p == "" {
+					fopt.SentinelAddrs[i] = net.JoinHostPort(h, port)
+				}
+			}
+		}
+		// Assume Redis server and sentinel have the same password.
+		fopt.SentinelPassword = opt.Password
+		fopt.Username = opt.Username
+		fopt.Password = opt.Password
+		if fopt.SentinelPassword == "" && os.Getenv("SENTINEL_PASSWORD") != "" {
+			fopt.SentinelPassword = os.Getenv("SENTINEL_PASSWORD")
+		}
+		if fopt.Password == "" && os.Getenv("REDIS_PASSWORD") != "" {
+			fopt.Password = os.Getenv("REDIS_PASSWORD")
+		}
+		fopt.DB = opt.DB
+		fopt.TLSConfig = opt.TLSConfig
+		fopt.MaxRetries = conf.Retries
+		fopt.MinRetryBackoff = time.Millisecond * 100
+		fopt.MaxRetryBackoff = time.Minute * 1
+		rdb = redis.NewFailoverClient(&fopt)
+	} else {
+		if opt.Password == "" && os.Getenv("REDIS_PASSWORD") != "" {
+			opt.Password = os.Getenv("REDIS_PASSWORD")
+		}
+		opt.MaxRetries = conf.Retries
+		opt.MinRetryBackoff = time.Millisecond * 100
+		opt.MaxRetryBackoff = time.Minute * 1
+		rdb = redis.NewClient(opt)
 	}
-	opt.MaxRetries = conf.Retries
-	opt.MinRetryBackoff = time.Millisecond * 100
-	opt.MaxRetryBackoff = time.Minute * 1
-	rdb := redis.NewClient(opt)
 	m := &redisMeta{
 		conf:         conf,
 		rdb:          rdb,