public class SegmentIDGen {
    privatefinal AtomicLong currentId = new AtomicLong(0);
    privatevolatilelong maxId;
    privatefinal ExecutorService loader = Executors.newSingleThreadExecutor();

    public void init() {
        loadSegment();
        loader.submit(this::daemonLoad);
    }

    private void loadSegment() {
        // 從DB獲取號(hào)段：SELECT max_id FROM alloc WHERE biz_tag='short_url'
        this.maxId = dbMaxId + 10000; // 每次取1萬個(gè)號(hào)
        currentId.set(dbMaxId);
    }

    private void daemonLoad() {
        while (currentId.get() > maxId * 0.8) {
            loadSegment(); // 號(hào)段使用80%時(shí)異步加載
        }
    }

    public long nextId() {
        if (currentId.get() >= maxId) thrownew BusyException();
        return currentId.incrementAndGet();
    }
}

2000000000 = 2×62^4 + 17×62^3 + 35×62^2 + 10×62 + 8 
           = "Cdz9a"

// Base62編碼（0-9a-zA-Z）
publicclass Base62Encoder {
    privatestaticfinal String BASE62 = 
        "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";
    
    public static String encode(long id) {
        StringBuilder sb = new StringBuilder();
        while (id > 0) {
            sb.append(BASE62.charAt((int)(id % 62)));
            id /= 62;
        }
        return sb.reverse().toString();
    }
    
    // 測(cè)試：生成8位短碼
    public static void main(String[] args) {
        long id = 1_000_000_000L;
        System.out.println(encode(id)); // 輸出：BFp3qQ
    }
}

// Redis緩存擊穿防護(hù)
public String getLongUrl(String shortCode) {
    // 1. 布隆過濾器預(yù)檢
    if (!bloomFilter.mightContain(shortCode)) {
        returnnull;
    }
    
    // 2. 查Redis
    String cacheKey = "url:" + shortCode;
    String longUrl = redis.get(cacheKey);
    if (longUrl != null) {
        return longUrl;
    }
    
    // 3. 獲取分布式鎖
    String lockKey = "lock:" + shortCode;
    if (redis.setnx(lockKey, "1", 10)) { // 10秒超時(shí)
        try {
            // 4. 二次檢查緩存
            longUrl = redis.get(cacheKey);
            if (longUrl != null) return longUrl;
            
            // 5. 查數(shù)據(jù)庫
            longUrl = db.queryLongUrl(shortCode);
            if (longUrl != null) {
                // 6. 回填Redis
                redis.setex(cacheKey, 3600, longUrl);
            }
            return longUrl;
        } finally {
            redis.del(lockKey);
        }
    } else {
        // 7. 等待重試
        Thread.sleep(50);
        return getLongUrl(shortCode);
    }
}

server {
    listen 80;
    server_name s.domain.com;

    location ~ ^/([a-zA-Z0-9]{6,8})$ {
        set $short_code $1;

        # 查詢Redis
        redis_pass redis_cluster;
        redis_query GET url:$short_code;

        # 命中則直接302跳轉(zhuǎn)
        if ($redis_value != "") {
            add_header Cache-Control "private, max-age=86400";
            return 302 $redis_value;
        }

        # 未命中轉(zhuǎn)發(fā)到后端
        proxy_pass http://backend;
    }
}

// Netty HTTP連接池配置
publicclass HttpConnectionPool {
    privatefinal EventLoopGroup group = new NioEventLoopGroup();
    privatefinal Bootstrap bootstrap = new Bootstrap();
    
    public HttpConnectionPool() {
        bootstrap.group(group)
            .channel(NioSocketChannel.class)
            .option(ChannelOption.SO_KEEPALIVE, true)
            .handler(new HttpClientInitializer());
    }
    
    public Channel getChannel(String host, int port) throws InterruptedException {
        return bootstrap.connect(host, port).sync().channel();
    }
    
    // 使用示例
    public void redirect(ChannelHandlerContext ctx, String longUrl) {
        Channel channel = getChannel("target.com", 80);
        channel.writeAndFlush(new DefaultFullHttpRequest(
            HttpVersion.HTTP_1_1, 
            HttpMethod.GET, 
            longUrl
        ));
        // 處理響應(yīng)...
    }
}

public class RedirectController {
    @GetMapping("/{shortCode}")
    @SentinelResource(
        value = "redirectService", 
        fallback = "fallbackRedirect",
        blockHandler = "blockRedirect"
    )
    public ResponseEntity redirect(@PathVariable String shortCode) {
        // 跳轉(zhuǎn)邏輯...
    }
    
    // 熔斷降級(jí)方法
    public ResponseEntity fallbackRedirect(String shortCode, Throwable ex) {
        return ResponseEntity.status(503)
            .body("服務(wù)暫時(shí)不可用");
    }
    
    // 限流處理方法
    public ResponseEntity blockRedirect(String shortCode, BlockException ex) {
        return ResponseEntity.status(429)
            .body("請(qǐng)求過于頻繁");
    }
}

public int determineDbShard(String shortCode) {
    // 取短碼首字母的ASCII值
    int ascii = (int) shortCode.charAt(0);
    // 分16個(gè)庫
    return ascii % 16;
}

public int determineTableShard(String shortCode) {
    // 取短碼的CRC32值
    CRC32 crc32 = new CRC32();
    crc32.update(shortCode.getBytes());
    // 每庫1024張表
    return (int) (crc32.getValue() % 1024);
}