Add proper SingleConnPool implementation

error.go

@@ -0,0 +1,95 @@
+package redis
+
+import (
+	"context"
+	"io"
+	"net"
+	"strings"
+
+	"github.com/go-redis/redis/internal/pool"
+	"github.com/go-redis/redis/internal/proto"
+)
+
+func isRetryableError(err error, retryTimeout bool) bool {
+	switch err {
+	case nil, context.Canceled, context.DeadlineExceeded, pool.ErrBadConn:
+		return false
+	case io.EOF:
+		return true
+	}
+	if netErr, ok := err.(net.Error); ok {
+		if netErr.Timeout() {
+			return retryTimeout
+		}
+		return true
+	}
+
+	s := err.Error()
+	if s == "ERR max number of clients reached" {
+		return true
+	}
+	if strings.HasPrefix(s, "LOADING ") {
+		return true
+	}
+	if strings.HasPrefix(s, "READONLY ") {
+		return true
+	}
+	if strings.HasPrefix(s, "CLUSTERDOWN ") {
+		return true
+	}
+	return false
+}
+
+func isRedisError(err error) bool {
+	_, ok := err.(proto.RedisError)
+	return ok
+}
+
+func isBadConn(err error, allowTimeout bool) bool {
+	switch err {
+	case nil:
+		return false
+	case pool.ErrBadConn:
+		return true
+	}
+	if isRedisError(err) {
+		return isReadOnlyError(err) // #790
+	}
+	if allowTimeout {
+		if netErr, ok := err.(net.Error); ok && netErr.Timeout() {
+			return false
+		}
+	}
+	return true
+}
+
+func isMovedError(err error) (moved bool, ask bool, addr string) {
+	if !isRedisError(err) {
+		return
+	}
+
+	s := err.Error()
+	switch {
+	case strings.HasPrefix(s, "MOVED "):
+		moved = true
+	case strings.HasPrefix(s, "ASK "):
+		ask = true
+	default:
+		return
+	}
+
+	ind := strings.LastIndex(s, " ")
+	if ind == -1 {
+		return false, false, ""
+	}
+	addr = s[ind+1:]
+	return
+}
+
+func isLoadingError(err error) bool {
+	return strings.HasPrefix(err.Error(), "LOADING ")
+}
+
+func isReadOnlyError(err error) bool {
+	return strings.HasPrefix(err.Error(), "READONLY ")
+}