feat(platform): report redis online key health

vehicle-data-platform/apps/api/internal/platform/redis_online.go

@@ -0,0 +1,165 @@
+package platform
+
+import (
+	"bufio"
+	"context"
+	"errors"
+	"fmt"
+	"io"
+	"net"
+	"strconv"
+	"strings"
+	"time"
+)
+
+type RedisOnlineKeyCounter struct {
+	addr     string
+	username string
+	password string
+	db       int
+}
+
+func NewRedisOnlineKeyCounter(addr, username, password string, db int) *RedisOnlineKeyCounter {
+	return &RedisOnlineKeyCounter{addr: strings.TrimSpace(addr), username: username, password: password, db: db}
+}
+
+func (c *RedisOnlineKeyCounter) CountOnlineKeys(ctx context.Context) (int, error) {
+	if c.addr == "" {
+		return 0, errors.New("redis addr is empty")
+	}
+	dialer := net.Dialer{Timeout: 2 * time.Second}
+	conn, err := dialer.DialContext(ctx, "tcp", c.addr)
+	if err != nil {
+		return 0, err
+	}
+	defer conn.Close()
+	if deadline, ok := ctx.Deadline(); ok {
+		_ = conn.SetDeadline(deadline)
+	} else {
+		_ = conn.SetDeadline(time.Now().Add(3 * time.Second))
+	}
+	reader := bufio.NewReader(conn)
+	if c.password != "" {
+		args := []string{"AUTH"}
+		if c.username != "" {
+			args = append(args, c.username)
+		}
+		args = append(args, c.password)
+		if _, err := redisCommand(conn, reader, args...); err != nil {
+			return 0, err
+		}
+	}
+	if _, err := redisCommand(conn, reader, "PING"); err != nil {
+		return 0, err
+	}
+	if c.db >= 0 {
+		if _, err := redisCommand(conn, reader, "SELECT", strconv.Itoa(c.db)); err != nil {
+			return 0, err
+		}
+	}
+	total := 0
+	cursor := "0"
+	for {
+		value, err := redisCommand(conn, reader, "SCAN", cursor, "MATCH", "vehicle:online:*", "COUNT", "1000")
+		if err != nil {
+			return 0, err
+		}
+		reply, ok := value.([]any)
+		if !ok || len(reply) != 2 {
+			return 0, fmt.Errorf("unexpected redis scan reply: %#v", value)
+		}
+		nextCursor, ok := reply[0].(string)
+		if !ok {
+			return 0, fmt.Errorf("unexpected redis scan cursor: %#v", reply[0])
+		}
+		keys, ok := reply[1].([]any)
+		if !ok {
+			return 0, fmt.Errorf("unexpected redis scan keys: %#v", reply[1])
+		}
+		total += len(keys)
+		if nextCursor == "0" {
+			return total, nil
+		}
+		cursor = nextCursor
+	}
+}
+
+func redisCommand(conn net.Conn, reader *bufio.Reader, args ...string) (any, error) {
+	if _, err := fmt.Fprintf(conn, "*%d\r\n", len(args)); err != nil {
+		return nil, err
+	}
+	for _, arg := range args {
+		if _, err := fmt.Fprintf(conn, "$%d\r\n%s\r\n", len(arg), arg); err != nil {
+			return nil, err
+		}
+	}
+	return readRedisReply(reader)
+}
+
+func readRedisReply(reader *bufio.Reader) (any, error) {
+	prefix, err := reader.ReadByte()
+	if err != nil {
+		return nil, err
+	}
+	switch prefix {
+	case '+':
+		return readRedisLine(reader)
+	case '-':
+		line, err := readRedisLine(reader)
+		if err != nil {
+			return nil, err
+		}
+		return nil, errors.New(line)
+	case ':':
+		line, err := readRedisLine(reader)
+		if err != nil {
+			return nil, err
+		}
+		return strconv.Atoi(line)
+	case '$':
+		line, err := readRedisLine(reader)
+		if err != nil {
+			return nil, err
+		}
+		size, err := strconv.Atoi(line)
+		if err != nil {
+			return nil, err
+		}
+		if size < 0 {
+			return "", nil
+		}
+		buf := make([]byte, size+2)
+		if _, err := io.ReadFull(reader, buf); err != nil {
+			return nil, err
+		}
+		return string(buf[:size]), nil
+	case '*':
+		line, err := readRedisLine(reader)
+		if err != nil {
+			return nil, err
+		}
+		count, err := strconv.Atoi(line)
+		if err != nil {
+			return nil, err
+		}
+		values := make([]any, 0, count)
+		for i := 0; i < count; i++ {
+			value, err := readRedisReply(reader)
+			if err != nil {
+				return nil, err
+			}
+			values = append(values, value)
+		}
+		return values, nil
+	default:
+		return nil, fmt.Errorf("unexpected redis reply prefix %q", prefix)
+	}
+}
+
+func readRedisLine(reader *bufio.Reader) (string, error) {
+	line, err := reader.ReadString('\n')
+	if err != nil {
+		return "", err
+	}
+	return strings.TrimSuffix(strings.TrimSuffix(line, "\n"), "\r"), nil
+}