public class MultiLevelCache {
    private Cache<String, String> jvmCache;
    private Jedis redis;

    public MultiLevelCache() {
        jvmCache = Caffeine.newBuilder()
             .maximumSize(100)
             .build();
        redis = new Jedis("localhost", 6379);
    }

    public String getProductName(String productId) {
        // 首先嘗試從 JVM 本地緩存獲取
        String productName = jvmCache.getIfPresent("product:" + productId + ":name");
        if (productName == null) {
            // 若 JVM 本地緩存未命中，嘗試從 Redis 緩存獲取
            productName = redis.get("product:" + productId + ":name");
            if (productName!= null) {
                // 將 Redis 中命中的數(shù)據(jù)更新到 JVM 本地緩存
                jvmCache.put("product:" + productId + ":name", productName);
            } else {
                // 若 Redis 緩存未命中，從數(shù)據(jù)庫獲取
                productName = fetchFromDatabase(productId);
                if (productName!= null) {
                    // 將數(shù)據(jù)存儲(chǔ)到 Redis 緩存
                    redis.set("product:" + productId + ":name", productName);
                    // 同時(shí)存儲(chǔ)到 JVM 本地緩存
                    jvmCache.put("product:" + productId + ":name", productName);
                }
            }
        }
        return productName;
    }

    private String fetchFromDatabase(String productId) {
        // 模擬從數(shù)據(jù)庫讀取數(shù)據(jù)，這里使用 MySQL 示例代碼
        MySQLDataAccess mySQLDataAccess = new MySQLDataAccess();
        return mySQLDataAccess.fetchProductName(productId);
    }

    public static void main(String[] args) {
        MultiLevelCache cache = new MultiLevelCache();
        String productName = cache.getProductName("1");
        System.out.println("Product Name: " + productName);
    }
}
class MySQLDataAccess {
    private static final String JDBC_URL = "jdbc:mysql://localhost:3306/your_database";
    private static final String JDBC_USER = "username";
    private static final String JDBC_PASSWORD = "password";

    public String fetchProductName(String productId) {
        String productName = null;
        try (Connection connection = DriverManager.getConnection(JDBC_URL, JDBC_USER, JDBC_PASSWORD)) {
            String query = "SELECT name FROM products WHERE id =?";
            try (PreparedStatement preparedStatement = connection.prepareStatement(query)) {
                preparedStatement.setInt(1, Integer.parseInt(productId));
                try (ResultSet resultSet = preparedStatement.executeQuery()) {
                    if (resultSet.next()) {
                        productName = resultSet.getString("name");
                    }
                }
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return productName;
    }
}

-- 在 Nginx 配置文件中
http {
    lua_shared_dict my_cache 10m;  -- 定義一個(gè) 10MB 的共享字典

    server {
        location /cache {
            content_by_lua_block {
                local cache = ngx.shared.my_cache
                local key = ngx.var.arg_key
                local value = cache:get(key)
                if value == nil then
                    -- 從 Redis 獲取數(shù)據(jù)
                    local redis = require "resty.redis"
                    local red = redis:new()
                    red:connect("localhost", 6379)
                    value = red:get(key)
                    red:close()
                    if value ~= nil then
                        cache:set(key, value)  -- 將數(shù)據(jù)存儲(chǔ)到本地緩存
                    end
                end
                ngx.say(value)
            }
        }
    }
}

public class RedisCacheConsistency {
    public static void main(String[] args) {
        Jedis jedis = new Jedis("localhost", 6379);
        String key = "product:1:price";
        // 先更新數(shù)據(jù)庫（這里省略數(shù)據(jù)庫更新代碼）
        // 立即刪除緩存
        jedis.del(key);
        // 延時(shí) 500 毫秒后再次刪除緩存，確保臟數(shù)據(jù)清除
        new Thread(() -> {
            try {
                TimeUnit.MILLISECONDS.sleep(500);
                jedis.del(key);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }).start();
        jedis.close();
    }
}

public class LocalCacheConsistency {
    // 本地緩存
    private Cache<String, String> cache;
    // 模擬的數(shù)據(jù)庫訪問服務(wù)
    private DatabaseService databaseService;
    // 定時(shí)任務(wù)執(zhí)行器
    private ScheduledExecutorService executorService;

    public LocalCacheConsistency() {
        // 初始化本地緩存，設(shè)置最大容量和過期時(shí)間
        cache = Caffeine.newBuilder()
              .maximumSize(100)
              .expireAfterWrite(1, TimeUnit.MINUTES)
              .build();
        databaseService = new DatabaseService();
        // 創(chuàng)建定時(shí)任務(wù)執(zhí)行器
        executorService = Executors.newSingleThreadScheduledExecutor();
        // 啟動(dòng)定時(shí)刷新任務(wù)
        startCacheRefreshTask();
    }

    // 從本地緩存獲取數(shù)據(jù)
    public String get(String key) {
        return cache.getIfPresent(key);
    }

    // 存儲(chǔ)數(shù)據(jù)到本地緩存
    public void put(String key, String value) {
        cache.put(key, value);
    }

    // 從數(shù)據(jù)庫獲取數(shù)據(jù)并更新本地緩存
    public void refreshCache(String key) {
        String value = databaseService.fetchData(key);
        if (value!= null) {
            cache.put(key, value);
        }
    }

    // 啟動(dòng)定時(shí)刷新緩存任務(wù)
    private void startCacheRefreshTask() {
        executorService.scheduleAtFixedRate(() -> {
            // 這里可以根據(jù)實(shí)際情況選擇要刷新的緩存鍵，例如全部刷新或只刷新部分熱點(diǎn)鍵
            // 這里假設(shè)我們要刷新所有緩存鍵，你可以修改為更具體的邏輯
            refreshAllCacheKeys();
        }, 0, 30, TimeUnit.SECONDS); // 每 30 秒刷新一次
    }

    // 刷新所有緩存鍵
    private void refreshAllCacheKeys() {
        // 假設(shè)緩存鍵的前綴是 "product:"，這里可以根據(jù)具體業(yè)務(wù)進(jìn)行修改
        for (int i = 1; i <= 100; i++) {
            String key = "product:" + i;
            refreshCache(key);
        }
    }

    // 模擬的數(shù)據(jù)庫服務(wù)
    private static class DatabaseService {
        public String fetchData(String key) {
            // 這里可以實(shí)現(xiàn)具體的數(shù)據(jù)庫查詢邏輯，這里僅作模擬
            System.out.println("Fetching data from database for key: " + key);
            return"Value for " + key;
        }
    }
}