[VOL-3860] redis client support in voltha-lib-go

redis client support has been added in this patch. There are two
types client `redis` and `redis-sentinel` to connect a redis instance.
redis-sentinel is required to be able to find the master redis
instance from a redis-sentinel process. See redis-sentinel usage
https://redis.io/topics/sentinel and
https://pkg.go.dev/github.com/go-redis/redis/v8#NewFailoverClient
for more information. If there is no need to have any failover
mechanism then the redis client type is the option to choose.

Change-Id: I997ed92115a9d565df632c6dd8184b9bab77b991
diff --git a/vendor/github.com/go-redis/redis/v8/options.go b/vendor/github.com/go-redis/redis/v8/options.go
new file mode 100644
index 0000000..f2c16c5
--- /dev/null
+++ b/vendor/github.com/go-redis/redis/v8/options.go
@@ -0,0 +1,317 @@
+package redis
+
+import (
+	"context"
+	"crypto/tls"
+	"errors"
+	"fmt"
+	"net"
+	"net/url"
+	"runtime"
+	"strconv"
+	"strings"
+	"time"
+
+	"github.com/go-redis/redis/v8/internal"
+	"github.com/go-redis/redis/v8/internal/pool"
+	"go.opentelemetry.io/otel/api/trace"
+	"go.opentelemetry.io/otel/label"
+)
+
+// Limiter is the interface of a rate limiter or a circuit breaker.
+type Limiter interface {
+	// Allow returns nil if operation is allowed or an error otherwise.
+	// If operation is allowed client must ReportResult of the operation
+	// whether it is a success or a failure.
+	Allow() error
+	// ReportResult reports the result of the previously allowed operation.
+	// nil indicates a success, non-nil error usually indicates a failure.
+	ReportResult(result error)
+}
+
+// Options keeps the settings to setup redis connection.
+type Options struct {
+	// The network type, either tcp or unix.
+	// Default is tcp.
+	Network string
+	// host:port address.
+	Addr string
+
+	// Dialer creates new network connection and has priority over
+	// Network and Addr options.
+	Dialer func(ctx context.Context, network, addr string) (net.Conn, error)
+
+	// Hook that is called when new connection is established.
+	OnConnect func(ctx context.Context, cn *Conn) error
+
+	// Use the specified Username to authenticate the current connection
+	// with one of the connections defined in the ACL list when connecting
+	// to a Redis 6.0 instance, or greater, that is using the Redis ACL system.
+	Username string
+	// Optional password. Must match the password specified in the
+	// requirepass server configuration option (if connecting to a Redis 5.0 instance, or lower),
+	// or the User Password when connecting to a Redis 6.0 instance, or greater,
+	// that is using the Redis ACL system.
+	Password string
+
+	// Database to be selected after connecting to the server.
+	DB int
+
+	// Maximum number of retries before giving up.
+	// Default is 3 retries.
+	MaxRetries int
+	// Minimum backoff between each retry.
+	// Default is 8 milliseconds; -1 disables backoff.
+	MinRetryBackoff time.Duration
+	// Maximum backoff between each retry.
+	// Default is 512 milliseconds; -1 disables backoff.
+	MaxRetryBackoff time.Duration
+
+	// Dial timeout for establishing new connections.
+	// Default is 5 seconds.
+	DialTimeout time.Duration
+	// Timeout for socket reads. If reached, commands will fail
+	// with a timeout instead of blocking. Use value -1 for no timeout and 0 for default.
+	// Default is 3 seconds.
+	ReadTimeout time.Duration
+	// Timeout for socket writes. If reached, commands will fail
+	// with a timeout instead of blocking.
+	// Default is ReadTimeout.
+	WriteTimeout time.Duration
+
+	// Maximum number of socket connections.
+	// Default is 10 connections per every CPU as reported by runtime.NumCPU.
+	PoolSize int
+	// Minimum number of idle connections which is useful when establishing
+	// new connection is slow.
+	MinIdleConns int
+	// Connection age at which client retires (closes) the connection.
+	// Default is to not close aged connections.
+	MaxConnAge time.Duration
+	// Amount of time client waits for connection if all connections
+	// are busy before returning an error.
+	// Default is ReadTimeout + 1 second.
+	PoolTimeout time.Duration
+	// Amount of time after which client closes idle connections.
+	// Should be less than server's timeout.
+	// Default is 5 minutes. -1 disables idle timeout check.
+	IdleTimeout time.Duration
+	// Frequency of idle checks made by idle connections reaper.
+	// Default is 1 minute. -1 disables idle connections reaper,
+	// but idle connections are still discarded by the client
+	// if IdleTimeout is set.
+	IdleCheckFrequency time.Duration
+
+	// Enables read only queries on slave nodes.
+	readOnly bool
+
+	// TLS Config to use. When set TLS will be negotiated.
+	TLSConfig *tls.Config
+
+	// Limiter interface used to implemented circuit breaker or rate limiter.
+	Limiter Limiter
+}
+
+func (opt *Options) init() {
+	if opt.Addr == "" {
+		opt.Addr = "localhost:6379"
+	}
+	if opt.Network == "" {
+		if strings.HasPrefix(opt.Addr, "/") {
+			opt.Network = "unix"
+		} else {
+			opt.Network = "tcp"
+		}
+	}
+	if opt.DialTimeout == 0 {
+		opt.DialTimeout = 5 * time.Second
+	}
+	if opt.Dialer == nil {
+		opt.Dialer = func(ctx context.Context, network, addr string) (net.Conn, error) {
+			netDialer := &net.Dialer{
+				Timeout:   opt.DialTimeout,
+				KeepAlive: 5 * time.Minute,
+			}
+			if opt.TLSConfig == nil {
+				return netDialer.DialContext(ctx, network, addr)
+			}
+			return tls.DialWithDialer(netDialer, network, addr, opt.TLSConfig)
+		}
+	}
+	if opt.PoolSize == 0 {
+		opt.PoolSize = 10 * runtime.NumCPU()
+	}
+	switch opt.ReadTimeout {
+	case -1:
+		opt.ReadTimeout = 0
+	case 0:
+		opt.ReadTimeout = 3 * time.Second
+	}
+	switch opt.WriteTimeout {
+	case -1:
+		opt.WriteTimeout = 0
+	case 0:
+		opt.WriteTimeout = opt.ReadTimeout
+	}
+	if opt.PoolTimeout == 0 {
+		opt.PoolTimeout = opt.ReadTimeout + time.Second
+	}
+	if opt.IdleTimeout == 0 {
+		opt.IdleTimeout = 5 * time.Minute
+	}
+	if opt.IdleCheckFrequency == 0 {
+		opt.IdleCheckFrequency = time.Minute
+	}
+
+	if opt.MaxRetries == -1 {
+		opt.MaxRetries = 0
+	} else if opt.MaxRetries == 0 {
+		opt.MaxRetries = 3
+	}
+	switch opt.MinRetryBackoff {
+	case -1:
+		opt.MinRetryBackoff = 0
+	case 0:
+		opt.MinRetryBackoff = 8 * time.Millisecond
+	}
+	switch opt.MaxRetryBackoff {
+	case -1:
+		opt.MaxRetryBackoff = 0
+	case 0:
+		opt.MaxRetryBackoff = 512 * time.Millisecond
+	}
+}
+
+func (opt *Options) clone() *Options {
+	clone := *opt
+	return &clone
+}
+
+// ParseURL parses an URL into Options that can be used to connect to Redis.
+// Scheme is required.
+// There are two connection types: by tcp socket and by unix socket.
+// Tcp connection:
+// 		redis://<user>:<password>@<host>:<port>/<db_number>
+// Unix connection:
+//		unix://<user>:<password>@</path/to/redis.sock>?db=<db_number>
+func ParseURL(redisURL string) (*Options, error) {
+	u, err := url.Parse(redisURL)
+	if err != nil {
+		return nil, err
+	}
+
+	switch u.Scheme {
+	case "redis", "rediss":
+		return setupTCPConn(u)
+	case "unix":
+		return setupUnixConn(u)
+	default:
+		return nil, fmt.Errorf("redis: invalid URL scheme: %s", u.Scheme)
+	}
+}
+
+func setupTCPConn(u *url.URL) (*Options, error) {
+	o := &Options{Network: "tcp"}
+
+	o.Username, o.Password = getUserPassword(u)
+
+	if len(u.Query()) > 0 {
+		return nil, errors.New("redis: no options supported")
+	}
+
+	h, p, err := net.SplitHostPort(u.Host)
+	if err != nil {
+		h = u.Host
+	}
+	if h == "" {
+		h = "localhost"
+	}
+	if p == "" {
+		p = "6379"
+	}
+	o.Addr = net.JoinHostPort(h, p)
+
+	f := strings.FieldsFunc(u.Path, func(r rune) bool {
+		return r == '/'
+	})
+	switch len(f) {
+	case 0:
+		o.DB = 0
+	case 1:
+		if o.DB, err = strconv.Atoi(f[0]); err != nil {
+			return nil, fmt.Errorf("redis: invalid database number: %q", f[0])
+		}
+	default:
+		return nil, fmt.Errorf("redis: invalid URL path: %s", u.Path)
+	}
+
+	if u.Scheme == "rediss" {
+		o.TLSConfig = &tls.Config{ServerName: h}
+	}
+
+	return o, nil
+}
+
+func setupUnixConn(u *url.URL) (*Options, error) {
+	o := &Options{
+		Network: "unix",
+	}
+
+	if strings.TrimSpace(u.Path) == "" { // path is required with unix connection
+		return nil, errors.New("redis: empty unix socket path")
+	}
+	o.Addr = u.Path
+
+	o.Username, o.Password = getUserPassword(u)
+
+	dbStr := u.Query().Get("db")
+	if dbStr == "" {
+		return o, nil // if database is not set, connect to 0 db.
+	}
+
+	db, err := strconv.Atoi(dbStr)
+	if err != nil {
+		return nil, fmt.Errorf("redis: invalid database number: %s", err)
+	}
+	o.DB = db
+
+	return o, nil
+}
+
+func getUserPassword(u *url.URL) (string, string) {
+	var user, password string
+	if u.User != nil {
+		user = u.User.Username()
+		if p, ok := u.User.Password(); ok {
+			password = p
+		}
+	}
+	return user, password
+}
+
+func newConnPool(opt *Options) *pool.ConnPool {
+	return pool.NewConnPool(&pool.Options{
+		Dialer: func(ctx context.Context) (net.Conn, error) {
+			var conn net.Conn
+			err := internal.WithSpan(ctx, "redis.dial", func(ctx context.Context, span trace.Span) error {
+				span.SetAttributes(
+					label.String("db.connection_string", opt.Addr),
+				)
+
+				var err error
+				conn, err = opt.Dialer(ctx, opt.Network, opt.Addr)
+				if err != nil {
+					_ = internal.RecordError(ctx, err)
+				}
+				return err
+			})
+			return conn, err
+		},
+		PoolSize:           opt.PoolSize,
+		MinIdleConns:       opt.MinIdleConns,
+		MaxConnAge:         opt.MaxConnAge,
+		PoolTimeout:        opt.PoolTimeout,
+		IdleTimeout:        opt.IdleTimeout,
+		IdleCheckFrequency: opt.IdleCheckFrequency,
+	})
+}