Scenario

In an online game, it is required to count players' scores in real time and display the rankings to facilitate competition and comparison between players. To meet the real-time and high concurrency requirements, Redis is used to implement leaderboard ranking.

Business Requirements

l Player scores are counted in real time and their rankings are generated based on their scores.

l Provides the function to query the ranking of specified players so that players can see their position in the leaderboard.

Analysis

l The leaderboard needs to be updated in real time and able to handle high concurrent requests.

l Ranking data needs to be persistent to prevent data loss.

Implementation Solution

Using DCS Redis, you can implement the function of a bestselling product ranking list. Its advantage is that the data is stored in memory with good performance and fast read-write speed, and provides a variety of convenient data types such as String, List, Set, Hash, and so on.

The specific implementation solution is as follows:

l Use Redis's Sorted Set to store player scores and sort them based on the scores.

l Each player's score is used as the score value of the sorted set, and the player ID is used as a member of the sorted set.

l Use the sorted set-related commands provided by Redis to implement functions such as updating, querying, and ranking.

l Use the persistence function of Redis, such as AOF or RDB, to ensure the persistence of the ranking data.

Core Code

Here is a simplified sample code that shows how to implement the key parts of the leaderboard using Redis:

// Player score increases
public void increasePlayerScore(String playerId, int score) {
    Jedis jedis = new Jedis("localhost");
    jedis.zincrby("player_scores", score, playerId);
    jedis.close();
}

// Obtain player rank
public long getPlayerRank(String playerId) {
    Jedis jedis = new Jedis("localhost");
    long rank = jedis.zrevrank("player_scores", playerId);
    jedis.close();
    return rank != null ? rank + 1 : -1;  // Return rank (starting from 1); if not found, return -1
}

// Obtain the first N players in the leaderboard
public List<String> getTopPlayers(int count) {
    Jedis jedis = new Jedis("localhost");
    Set<String> players = jedis.zrevrange("player_scores", 0, count - 1);
    jedis.close();
    return new ArrayList<>(players);
}

The sample code uses Redis's ordered sets to store players' scores, the zincrby command to increase the players' scores, and the zrevrank command to obtain ranking information.

DCS Redis Help Documentation

Ranking Function