Redis 从入门到精通(十二):典型业务场景实战 ------ 排行榜、限流器、秒杀系统、Session 共享
一、排行榜系统(Sorted Set)
1.1 需求分析
实现一个游戏全服排行榜,支持:
- 玩家实时更新分数
- 查询 Top 100
- 查询某个玩家的排名和分数
- 查询某个玩家前后的竞争对手
1.2 完整实现
java
@Service
public class LeaderboardService {
private static final String RANK_KEY = "game:rank:global";
@Autowired
private StringRedisTemplate redisTemplate;
/**
* 更新玩家分数
*/
public void updateScore(String playerId, double score) {
redisTemplate.opsForZSet().add(RANK_KEY, playerId, score);
}
/**
* 增加分数(增量更新)
*/
public double addScore(String playerId, double delta) {
return redisTemplate.opsForZSet().incrementScore(RANK_KEY, playerId, delta);
}
/**
* 获取 Top N(降序,分数最高的在前)
*/
public List<RankEntry> getTopN(int n) {
Set<ZSetOperations.TypedTuple<String>> set =
redisTemplate.opsForZSet().reverseRangeWithScores(RANK_KEY, 0, n - 1);
if (set == null) return Collections.emptyList();
int rank = 1;
List<RankEntry> result = new ArrayList<>();
for (ZSetOperations.TypedTuple<String> tuple : set) {
result.add(new RankEntry(rank++, tuple.getValue(), tuple.getScore()));
}
return result;
}
/**
* 获取玩家排名(降序,第 1 名 rank 为 1)
*/
public Long getPlayerRank(String playerId) {
Long rank = redisTemplate.opsForZSet().reverseRank(RANK_KEY, playerId);
return rank == null ? null : rank + 1;
}
/**
* 获取玩家分数
*/
public Double getPlayerScore(String playerId) {
return redisTemplate.opsForZSet().score(RANK_KEY, playerId);
}
/**
* 获取玩家前后 N 名的竞争对手
*/
public List<RankEntry> getNearbyPlayers(String playerId, int n) {
Long rank = redisTemplate.opsForZSet().reverseRank(RANK_KEY, playerId);
if (rank == null) return Collections.emptyList();
long start = Math.max(0, rank - n);
long end = rank + n;
Set<ZSetOperations.TypedTuple<String>> set =
redisTemplate.opsForZSet().reverseRangeWithScores(RANK_KEY, start, end);
List<RankEntry> result = new ArrayList<>();
long currentRank = start + 1;
for (ZSetOperations.TypedTuple<String> tuple : set) {
result.add(new RankEntry((int) currentRank++, tuple.getValue(), tuple.getScore()));
}
return result;
}
@Data
@AllArgsConstructor
public static class RankEntry {
private int rank;
private String playerId;
private double score;
}
}
性能分析:
- 更新分数:O(log N),百万级数据毫秒级
- 查询 Top 100:O(log N + 100),恒定快速
- 查询排名:O(log N)
二、限流器:滑动窗口算法
2.1 需求分析
限制每个用户每分钟最多 100 次请求。使用滑动窗口算法,比固定窗口更平滑。
2.2 完整实现 ------ Lua 脚本版
lua
-- sliding_window_rate_limiter.lua
-- KEYS[1] = 限流 key(如 rate_limit:user:1001)
-- ARGV[1] = 窗口大小(毫秒,如 60000 表示 1 分钟)
-- ARGV[2] = 最大请求数(如 100)
local key = KEYS[1]
local window = tonumber(ARGV[1])
local max_requests = tonumber(ARGV[2])
local now = redis.call('TIME') -- 返回 {秒, 微秒}
local current = now[1] * 1000 + math.floor(now[2] / 1000)
-- 删除窗口外的旧记录
redis.call('ZREMRANGEBYSCORE', key, 0, current - window)
-- 统计当前窗口内的请求数
local count = redis.call('ZCARD', key)
if count < max_requests then
-- 允许通过,记录本次请求
redis.call('ZADD', key, current, current .. '-' .. math.random())
-- 设置 key 过期时间(窗口结束 + 缓冲)
redis.call('PEXPIRE', key, window + 1000)
return 1 -- 通过
else
return 0 -- 限流
end
java
@Component
public class SlidingWindowRateLimiter {
@Autowired
private StringRedisTemplate redisTemplate;
private String scriptSha;
@PostConstruct
public void init() {
String script = """
local key = KEYS[1]
local window = tonumber(ARGV[1])
local max_requests = tonumber(ARGV[2])
local now = redis.call('TIME')
local current = now[1] * 1000 + math.floor(now[2] / 1000)
redis.call('ZREMRANGEBYSCORE', key, 0, current - window)
local count = redis.call('ZCARD', key)
if count < max_requests then
redis.call('ZADD', key, current, current .. '-' .. math.random())
redis.call('PEXPIRE', key, window + 1000)
return 1
else
return 0
end
""";
scriptSha = redisTemplate.execute(
(RedisCallback<String>) conn -> conn.scriptLoad(script.getBytes())
);
}
/**
* @param key 限流标识
* @param windowSeconds 窗口大小(秒)
* @param maxRequests 最大请求数
* @return true=通过, false=限流
*/
public boolean isAllowed(String key, int windowSeconds, int maxRequests) {
String fullKey = "rate_limit:" + key;
Long result = redisTemplate.execute(
new DefaultRedisScript<>(scriptSha, Long.class),
Collections.singletonList(fullKey),
String.valueOf(windowSeconds * 1000L),
String.valueOf(maxRequests)
);
return result != null && result == 1;
}
}
java
// 拦截器中使用
@Component
public class RateLimitInterceptor implements HandlerInterceptor {
@Autowired
private SlidingWindowRateLimiter rateLimiter;
@Override
public boolean preHandle(HttpServletRequest request,
HttpServletResponse response, Object handler) {
String userId = getUserId(request);
boolean allowed = rateLimiter.isAllowed(userId, 60, 100);
if (!allowed) {
response.setStatus(429);
response.getWriter().write("Too Many Requests");
return false;
}
return true;
}
}
三、秒杀系统:库存扣减与超卖防护
3.1 需求分析
秒杀的核心难题:高并发下防止超卖。单纯的"查库存 → 减库存 → 写回"在并发下不可靠(读-改-写竞态)。
3.2 方案:Lua 脚本 + 原子扣减
lua
-- seckill.lua
-- KEYS[1] = 库存 key
-- KEYS[2] = 已购买用户集合 key
-- ARGV[1] = 用户 ID
local stock_key = KEYS[1]
local purchased_key = KEYS[2]
local user_id = ARGV[1]
-- 检查是否已经抢到过(防重复)
if redis.call('SISMEMBER', purchased_key, user_id) == 1 then
return -1 -- 已购买
end
-- 检查库存
local stock = tonumber(redis.call('GET', stock_key) or '0')
if stock <= 0 then
return 0 -- 库存不足
end
-- 扣减库存
redis.call('DECR', stock_key)
-- 记录购买用户
redis.call('SADD', purchased_key, user_id)
return 1 -- 秒杀成功
java
@Service
public class SeckillService {
@Autowired
private StringRedisTemplate redisTemplate;
private String seckillSha;
@PostConstruct
public void init() {
String script = """
local stock_key = KEYS[1]
local purchased_key = KEYS[2]
local user_id = ARGV[1]
if redis.call('SISMEMBER', purchased_key, user_id) == 1 then
return -1
end
local stock = tonumber(redis.call('GET', stock_key) or '0')
if stock <= 0 then
return 0
end
redis.call('DECR', stock_key)
redis.call('SADD', purchased_key, user_id)
return 1
""";
seckillSha = redisTemplate.execute(
(RedisCallback<String>) conn -> conn.scriptLoad(script.getBytes())
);
}
/**
* 执行秒杀
*/
public SeckillResult seckill(String productId, String userId) {
String stockKey = "seckill:stock:" + productId;
String purchasedKey = "seckill:purchased:" + productId;
Long result = redisTemplate.execute(
new DefaultRedisScript<>(seckillSha, Long.class),
Arrays.asList(stockKey, purchasedKey),
userId
);
if (result == null) {
return SeckillResult.ERROR;
}
return switch (result.intValue()) {
case 1 -> SeckillResult.SUCCESS;
case 0 -> SeckillResult.SOLD_OUT;
case -1 -> SeckillResult.ALREADY_PURCHASED;
default -> SeckillResult.ERROR;
};
}
/**
* 初始化秒杀库存
*/
public void initStock(String productId, int stock) {
redisTemplate.opsForValue().set(
"seckill:stock:" + productId, String.valueOf(stock));
redisTemplate.delete("seckill:purchased:" + productId);
}
public enum SeckillResult {
SUCCESS, SOLD_OUT, ALREADY_PURCHASED, ERROR
}
}
完整秒杀流程:
#mermaid-svg-9CcxWQ714luuATjY{font-family:"trebuchet ms",verdana,arial,sans-serif;font-size:16px;fill:#333;}@keyframes edge-animation-frame{from{stroke-dashoffset:0;}}@keyframes dash{to{stroke-dashoffset:0;}}#mermaid-svg-9CcxWQ714luuATjY .edge-animation-slow{stroke-dasharray:9,5!important;stroke-dashoffset:900;animation:dash 50s linear infinite;stroke-linecap:round;}#mermaid-svg-9CcxWQ714luuATjY .edge-animation-fast{stroke-dasharray:9,5!important;stroke-dashoffset:900;animation:dash 20s linear infinite;stroke-linecap:round;}#mermaid-svg-9CcxWQ714luuATjY .error-icon{fill:#552222;}#mermaid-svg-9CcxWQ714luuATjY .error-text{fill:#552222;stroke:#552222;}#mermaid-svg-9CcxWQ714luuATjY .edge-thickness-normal{stroke-width:1px;}#mermaid-svg-9CcxWQ714luuATjY .edge-thickness-thick{stroke-width:3.5px;}#mermaid-svg-9CcxWQ714luuATjY .edge-pattern-solid{stroke-dasharray:0;}#mermaid-svg-9CcxWQ714luuATjY .edge-thickness-invisible{stroke-width:0;fill:none;}#mermaid-svg-9CcxWQ714luuATjY .edge-pattern-dashed{stroke-dasharray:3;}#mermaid-svg-9CcxWQ714luuATjY .edge-pattern-dotted{stroke-dasharray:2;}#mermaid-svg-9CcxWQ714luuATjY .marker{fill:#333333;stroke:#333333;}#mermaid-svg-9CcxWQ714luuATjY .marker.cross{stroke:#333333;}#mermaid-svg-9CcxWQ714luuATjY svg{font-family:"trebuchet ms",verdana,arial,sans-serif;font-size:16px;}#mermaid-svg-9CcxWQ714luuATjY p{margin:0;}#mermaid-svg-9CcxWQ714luuATjY .label{font-family:"trebuchet ms",verdana,arial,sans-serif;color:#333;}#mermaid-svg-9CcxWQ714luuATjY .cluster-label text{fill:#333;}#mermaid-svg-9CcxWQ714luuATjY .cluster-label span{color:#333;}#mermaid-svg-9CcxWQ714luuATjY .cluster-label span p{background-color:transparent;}#mermaid-svg-9CcxWQ714luuATjY .label text,#mermaid-svg-9CcxWQ714luuATjY span{fill:#333;color:#333;}#mermaid-svg-9CcxWQ714luuATjY .node rect,#mermaid-svg-9CcxWQ714luuATjY .node circle,#mermaid-svg-9CcxWQ714luuATjY .node ellipse,#mermaid-svg-9CcxWQ714luuATjY .node polygon,#mermaid-svg-9CcxWQ714luuATjY .node path{fill:#ECECFF;stroke:#9370DB;stroke-width:1px;}#mermaid-svg-9CcxWQ714luuATjY .rough-node .label text,#mermaid-svg-9CcxWQ714luuATjY .node .label text,#mermaid-svg-9CcxWQ714luuATjY .image-shape .label,#mermaid-svg-9CcxWQ714luuATjY .icon-shape .label{text-anchor:middle;}#mermaid-svg-9CcxWQ714luuATjY .node .katex path{fill:#000;stroke:#000;stroke-width:1px;}#mermaid-svg-9CcxWQ714luuATjY .rough-node .label,#mermaid-svg-9CcxWQ714luuATjY .node .label,#mermaid-svg-9CcxWQ714luuATjY .image-shape .label,#mermaid-svg-9CcxWQ714luuATjY .icon-shape .label{text-align:center;}#mermaid-svg-9CcxWQ714luuATjY .node.clickable{cursor:pointer;}#mermaid-svg-9CcxWQ714luuATjY .root .anchor path{fill:#333333!important;stroke-width:0;stroke:#333333;}#mermaid-svg-9CcxWQ714luuATjY .arrowheadPath{fill:#333333;}#mermaid-svg-9CcxWQ714luuATjY .edgePath .path{stroke:#333333;stroke-width:2.0px;}#mermaid-svg-9CcxWQ714luuATjY .flowchart-link{stroke:#333333;fill:none;}#mermaid-svg-9CcxWQ714luuATjY .edgeLabel{background-color:rgba(232,232,232, 0.8);text-align:center;}#mermaid-svg-9CcxWQ714luuATjY .edgeLabel p{background-color:rgba(232,232,232, 0.8);}#mermaid-svg-9CcxWQ714luuATjY .edgeLabel rect{opacity:0.5;background-color:rgba(232,232,232, 0.8);fill:rgba(232,232,232, 0.8);}#mermaid-svg-9CcxWQ714luuATjY .labelBkg{background-color:rgba(232, 232, 232, 0.5);}#mermaid-svg-9CcxWQ714luuATjY .cluster rect{fill:#ffffde;stroke:#aaaa33;stroke-width:1px;}#mermaid-svg-9CcxWQ714luuATjY .cluster text{fill:#333;}#mermaid-svg-9CcxWQ714luuATjY .cluster span{color:#333;}#mermaid-svg-9CcxWQ714luuATjY div.mermaidTooltip{position:absolute;text-align:center;max-width:200px;padding:2px;font-family:"trebuchet ms",verdana,arial,sans-serif;font-size:12px;background:hsl(80, 100%, 96.2745098039%);border:1px solid #aaaa33;border-radius:2px;pointer-events:none;z-index:100;}#mermaid-svg-9CcxWQ714luuATjY .flowchartTitleText{text-anchor:middle;font-size:18px;fill:#333;}#mermaid-svg-9CcxWQ714luuATjY rect.text{fill:none;stroke-width:0;}#mermaid-svg-9CcxWQ714luuATjY .icon-shape,#mermaid-svg-9CcxWQ714luuATjY .image-shape{background-color:rgba(232,232,232, 0.8);text-align:center;}#mermaid-svg-9CcxWQ714luuATjY .icon-shape p,#mermaid-svg-9CcxWQ714luuATjY .image-shape p{background-color:rgba(232,232,232, 0.8);padding:2px;}#mermaid-svg-9CcxWQ714luuATjY .icon-shape .label rect,#mermaid-svg-9CcxWQ714luuATjY .image-shape .label rect{opacity:0.5;background-color:rgba(232,232,232, 0.8);fill:rgba(232,232,232, 0.8);}#mermaid-svg-9CcxWQ714luuATjY .label-icon{display:inline-block;height:1em;overflow:visible;vertical-align:-0.125em;}#mermaid-svg-9CcxWQ714luuATjY .node .label-icon path{fill:currentColor;stroke:revert;stroke-width:revert;}#mermaid-svg-9CcxWQ714luuATjY :root{--mermaid-font-family:"trebuchet ms",verdana,arial,sans-serif;} 返回1: 抢到
返回0: 售罄
返回-1: 已抢
用户请求秒杀
Lua 脚本
原子操作
发送 MQ 消息
异步创建订单
返回'已售罄'
返回'已参与'
MQ 消费者
写入数据库订单
返回用户
秒杀结果
关键设计原则:
- 库存扣减放在 Redis:原子操作,绝不超卖
- 订单创建异步化:MQ 削峰,不阻塞秒杀响应
- 前端防重:按钮置灰 + 验证码
- 网关限流:在秒杀接口上再加一层限流
四、Session 共享
4.1 问题
分布式系统中,用户请求可能被负载均衡到不同服务器。如果 Session 存在各服务器的本地内存中,用户会频繁"被登出"。
4.2 Spring Session + Redis 方案
xml
<!-- pom.xml -->
<dependency>
<groupId>org.springframework.session</groupId>
<artifactId>spring-session-data-redis</artifactId>
</dependency>
yaml
# application.yml
spring:
session:
store-type: redis
redis:
namespace: spring:session
timeout: 30m # Session 过期时间
data:
redis:
host: localhost
port: 6379
java
@Configuration
@EnableRedisHttpSession(maxInactiveIntervalInSeconds = 1800)
public class SessionConfig {
// 自定义 Session 序列化(可选)
@Bean
public RedisSerializer<Object> springSessionDefaultRedisSerializer() {
return new GenericJackson2JsonRedisSerializer();
}
// Cookie 配置
@Bean
public CookieSerializer cookieSerializer() {
DefaultCookieSerializer serializer = new DefaultCookieSerializer();
serializer.setCookieName("SESSIONID");
serializer.setCookiePath("/");
serializer.setDomainNamePattern("^.+?\\.(\\w+\\.[a-z]+)$");
return serializer;
}
}
使用方式完全不变,HttpSession 自动存入 Redis:
java
@RestController
public class LoginController {
@PostMapping("/login")
public String login(@RequestParam String username,
HttpSession session) {
// 自动存入 Redis
session.setAttribute("user", username);
return "OK";
}
@GetMapping("/user")
public String getUser(HttpSession session) {
// 自动从 Redis 读取
return (String) session.getAttribute("user");
}
}
五、附近的人(Geo 实现)
java
@Service
public class NearbyService {
@Autowired
private StringRedisTemplate redisTemplate;
private static final String LOCATION_KEY = "user:locations";
/**
* 更新用户位置
*/
public void updateLocation(String userId, double lng, double lat) {
redisTemplate.opsForGeo().add(LOCATION_KEY,
new Point(lng, lat), userId);
}
/**
* 查找附近的人
*/
public List<NearbyUser> findNearby(String userId, double radiusKm, int limit) {
// GeoSearchArgs 需要 Lettuce 或 Redisson 的原生 API
// 这里用通用 RedisTemplate 方式
// 先获取目标用户位置
List<Point> points = redisTemplate.opsForGeo()
.position(LOCATION_KEY, userId);
if (points == null || points.isEmpty()) return Collections.emptyList();
Point myPoint = points.get(0);
return findNearbyByPoint(myPoint.getX(), myPoint.getY(), radiusKm, limit);
}
/**
* 按坐标查找附近的人(Redis 6.2+)
*/
public List<NearbyUser> findNearbyByPoint(double lng, double lat,
double radiusKm, int limit) {
// GEOSEARCH 是 Redis 6.2+ 的命令
// 如果不支持,可以用 GEORADIUS
Distance radius = new Distance(radiusKm, Metrics.KILOMETERS);
RedisGeoCommands.GeoRadiusCommandArgs args =
RedisGeoCommands.GeoRadiusCommandArgs.newGeoRadiusArgs()
.includeDistance()
.includeCoordinates()
.sortAscending()
.limit(limit);
GeoResults<RedisGeoCommands.GeoLocation<String>> results =
redisTemplate.opsForGeo().radius(LOCATION_KEY,
new Circle(new Point(lng, lat), radius), args);
if (results == null) return Collections.emptyList();
return results.getContent().stream()
.map(geo -> new NearbyUser(
geo.getContent().getName(),
geo.getDistance().getValue(),
geo.getContent().getPoint().getX(),
geo.getContent().getPoint().getY()
))
.collect(Collectors.toList());
}
@Data
@AllArgsConstructor
public static class NearbyUser {
private String userId;
private double distanceKm;
private double lng;
private double lat;
}
}
六、消息已读未读(Bitmap)
java
@Service
public class MessageReadService {
@Autowired
private StringRedisTemplate redisTemplate;
/**
* 发送消息:为每个用户创建消息的已读标记位(初始为 0)
*/
public void sendMessage(long messageId, List<Long> receiverIds) {
for (Long userId : receiverIds) {
// 初始化为未读(0),GETBIT 获取不存在的位置返回 0,所以不显式设置也行
}
}
/**
* 标记已读
*/
public void markAsRead(long userId, long messageId) {
String key = "msg:read:" + userId;
redisTemplate.opsForValue()
.setBit(key, messageId, true);
}
/**
* 检查是否已读
*/
public boolean isRead(long userId, long messageId) {
String key = "msg:read:" + userId;
Boolean bit = redisTemplate.opsForValue().getBit(key, messageId);
return Boolean.TRUE.equals(bit);
}
/**
* 获取未读消息数量(群聊场景)
* 总消息数 - 已读数
*/
public long getUnreadCount(long userId, long totalMessages) {
String key = "msg:read:" + userId;
Long readCount = redisTemplate.execute(
(RedisCallback<Long>) conn -> conn.bitCount(key.getBytes())
);
return totalMessages - (readCount == null ? 0 : readCount);
}
/**
* 批量查询多条消息的已读状态
*/
public Map<Long, Boolean> batchCheckRead(long userId, List<Long> messageIds) {
String key = "msg:read:" + userId;
Map<Long, Boolean> result = new HashMap<>();
for (Long msgId : messageIds) {
Boolean bit = redisTemplate.opsForValue().getBit(key, msgId);
result.put(msgId, Boolean.TRUE.equals(bit));
}
return result;
}
}
七、总结
本文六个实战场景的核心技术选型:
| 场景 | 数据结构 | 关键技术 |
|---|---|---|
| 排行榜 | Sorted Set | ZADD / ZREVRANGE / ZREVRANK |
| 限流器 | Sorted Set + Lua | 滑动窗口算法 |
| 秒杀 | String + Set + Lua | 原子库存扣减 + MQ 异步下单 |
| Session 共享 | String(Hash) | Spring Session 自动管理 |
| 附近的人 | Geo | GEOADD / GEOSEARCH |
| 消息已读 | Bitmap | SETBIT / GETBIT / BITCOUNT |
如有疑问或指正,欢迎在评论区交流。