modelRT/diagram/redis_client.go

// Package diagram provide diagram data structure and operation
package diagram

import (
	"context"
	"fmt"
	"sort"
	"strconv"

	"github.com/redis/go-redis/v9"
)

// RedisClient define struct to accessing redis data that does not require the use of distributed locks
type RedisClient struct {
	Client *redis.Client
}

// QueryLatestMeasurementValue returns the score whose member contains the
// greatest numeric timestamp. Measurement ZSets currently store timestamp in
// member and measurement value in score.
func (rc *RedisClient) QueryLatestMeasurementValue(ctx context.Context, key string) (float64, error) {
	values, err := rc.QueryLatestMeasurementValues(ctx, key, 1)
	if err != nil {
		return 0, err
	}
	return values[0], nil
}

// QueryLatestMeasurementValues returns up to size scores ordered by their
// numeric member timestamps from newest to oldest.
func (rc *RedisClient) QueryLatestMeasurementValues(ctx context.Context, key string, size int) ([]float64, error) {
	if rc.Client == nil {
		return nil, fmt.Errorf("redis client is not initialized")
	}
	if size <= 0 {
		return nil, fmt.Errorf("measurement window size must be greater than 0, got %d", size)
	}

	members, err := rc.Client.ZRangeWithScores(ctx, key, 0, -1).Result()
	if err != nil {
		return nil, err
	}
	return latestMeasurementValues(members, key, size)
}

func latestMeasurementValue(members []redis.Z, key string) (float64, error) {
	values, err := latestMeasurementValues(members, key, 1)
	if err != nil {
		return 0, err
	}
	return values[0], nil
}

func latestMeasurementValues(members []redis.Z, key string, size int) ([]float64, error) {
	if size <= 0 {
		return nil, fmt.Errorf("measurement window size must be greater than 0, got %d", size)
	}
	if len(members) == 0 {
		return nil, fmt.Errorf("real-time measurement value not found for key %q", key)
	}

	type timestampedValue struct {
		timestamp int64
		value     float64
	}
	values := make([]timestampedValue, 0, len(members))
	for _, member := range members {
		timestamp, err := strconv.ParseInt(fmt.Sprint(member.Member), 10, 64)
		if err != nil {
			continue
		}
		values = append(values, timestampedValue{timestamp: timestamp, value: member.Score})
	}
	if len(values) == 0 {
		return nil, fmt.Errorf("real-time measurement timestamps are invalid for key %q", key)
	}

	sort.Slice(values, func(i, j int) bool {
		return values[i].timestamp > values[j].timestamp
	})
	if size > len(values) {
		size = len(values)
	}
	result := make([]float64, size)
	for index := range size {
		result[index] = values[index].value
	}
	return result, nil
}

// NewRedisClient define func of new redis client instance
func NewRedisClient() *RedisClient {
	return &RedisClient{
		Client: GetRedisClientInstance(),
	}
}

// QueryByZRange define func to query real time data from redis zset
func (rc *RedisClient) QueryByZRange(ctx context.Context, key string, size int64) ([]redis.Z, error) {
	client := rc.Client
	args := redis.ZRangeArgs{
		Key:     key,
		Start:   0,
		Stop:    size,
		ByScore: false,
		ByLex:   false,
		Rev:     false,
		Offset:  0,
		Count:   0,
	}
	return client.ZRangeArgsWithScores(ctx, args).Result()
}