背景
随着项目使用量的增长，前期为解决高峰请求设置大量缓存应对的方式对单一Redis的压力越来越大，经常收到大量报警，网络IO占用很大，因此打算进行Redis分片，将流量较均衡分散到多台Redis上。
目标
- 支持多Redis数据源；
- 支持@Cacheable/@CachePut/@CacheEvict缓存注解；
方案
基于jedis的ShardedJedis扩展开发，因其可以根据Jedis j = getShard(key)将key较均匀的分散到各个实例中（具体选择过程可看代码详解，大致就是初始化的会根据实例数及各实例的权重，将每个实例分成权重值*160个虚拟节点并做成TreeMap存储，再加一个map2存储实例和配置的映射，每次getShard(key)先去虚拟节点map找到符合的虚拟节点对应的实例，再从map2获取实例的配置信息），我们所要做的工作就是进行封装，包括模版、管理器、缓存等（ShardedJedisTemplate、ShardedJedisCache、ShardedJedisCacheManager）；
详细代码
- 首先是yml配置，配置遵循一个格式
redis://xxxx@localhost:6379/9,9表示的db索引值
redis:
jedisInfos:
- host: redis://localhost:37379/0
connectionTimeout: 3000
pool:
max-total: 10 # 连接池最大连接数
max-idle: 10 # 连接池中的最大空闲连接
min-idle: 5 # 连接池中的最小空闲连接
max-wait-millis: 2000 # 连接池最大阻塞等待时间（使用负值表示没有限制）- jedis配置信息类，用于读取yml中的配置信息并注入bean（这边主要就是配置格式注意下，根据自己需求可以添加需要用的字段）
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.context.annotation.Configuration;
import redis.clients.jedis.JedisPoolConfig;
import java.util.List;
/**
* 多节点配置类
* jedis配置信息
*/
@Configuration
@ConfigurationProperties(prefix = "redis")
public class ShardedJedisProperties {
private List<JedisInfo> jedisInfos;
private JedisPoolConfig pool;
//ignore getter/setter
public static class JedisInfo {
private int connectionTimeout;
//host被URI解析，模版格式为 "redis://xxxx@localhost:6379/9"; 9为db
private String host;
//ignore getter/setter
}
}- jedis连接工厂的配置，这边主要就是用到上面的jedis的配置信息
import redis.clients.jedis.ShardedJedis;
import redis.clients.jedis.ShardedJedisPool;
/**
* 连接工厂
*/
public class ShardedJedisConnectionFactory {
private ShardedJedisPool shardedJedisPool;
/**
* 获取连接
*/
public ShardedJedis getConnection() {
return shardedJedisPool.getResource();
}
//ignore partial getter/setter
}- 自定义jedis模版（ShardedJedisTemplate）,下面只提供部分代码，只是对所有的
ShardedJedis做了一层简单封装获取工厂连接，（注意某些参数有时候是byte[]有时候是string，自行对key进行转换）。
import org.springframework.data.redis.serializer.RedisSerializer;
import org.springframework.util.Assert;
import redis.clients.jedis.*;
import java.util.*;
public class ShardedJedisTemplate<K, V> {
private ShardedJedisConnectionFactory factory;
private RedisSerializer keySerializer;
private RedisSerializer valueSerializer;
//ignore getter/setter
/**
* 设置单个值
*
* @param key
* @param value
* @return
*/
public String set(String key, String value) {
try (ShardedJedis shardedJedis = factory.getConnection()) {
return shardedJedis.set(key, value);
}
}
/**
* 获取单个值
*
* @param key
* @return
*/
public String get(String key) {
try (ShardedJedis shardedJedis = factory.getConnection()) {
return shardedJedis.get(key);
}
}
}- 自定义cache，毕竟需要支持缓存注解
import org.apache.commons.lang3.ArrayUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.cache.Cache;
import org.springframework.cache.support.SimpleValueWrapper;
import org.springframework.data.redis.cache.DefaultRedisCachePrefix;
import org.springframework.data.redis.serializer.GenericJackson2JsonRedisSerializer;
import org.springframework.data.redis.serializer.RedisSerializer;
import org.springframework.data.redis.serializer.SerializationException;
import org.springframework.data.redis.serializer.StringRedisSerializer;
import org.springframework.util.Assert;
import java.util.concurrent.Callable;
public class ShardedJedisCache implements Cache {
private static final Logger log = LoggerFactory.getLogger(ShardedJedisCache.class);
private ShardedJedisTemplate shardedJedisTemplate;
private String name;
private RedisSerializer keySerializer;
private RedisSerializer valueSerializer;
private long defaultExpiration = 0;
public ShardedJedisCache(String name, ShardedJedisTemplate shardedJedisTemplate) {
this.name = name;
this.shardedJedisTemplate = shardedJedisTemplate;
this.keySerializer = shardedJedisTemplate.getKeySerializer() == null ?
new StringRedisSerializer() : shardedJedisTemplate.getKeySerializer();
this.valueSerializer = shardedJedisTemplate.getValueSerializer() == null ?
new GenericJackson2JsonRedisSerializer() : shardedJedisTemplate.getValueSerializer();
}
@Override
public ValueWrapper get(Object key) {
// log.debug("======get from cache '{}' by key : {} ======", name, key);
try {
byte[] computeKey = computeKey(key);
byte[] bs = shardedJedisTemplate.get(computeKey);
return (bs == null ? null : new SimpleValueWrapper(deserializeValue(bs)));
} catch (SerializationException e) {
log.error("cache get error", e);
return null;
}
}
@Override
public <T> T get(Object key, Class<T> type) {
ValueWrapper wrapper = this.get(key);
return wrapper == null ? null : (T) wrapper.get();
}
@Override
public <T> T get(Object key, Callable<T> callable) {
ValueWrapper wrapper = this.get(key);
return wrapper == null ? null : (T) wrapper.get();
}
@Override
public void put(Object key, Object value) {
// log.debug("======put to cache '{}' with key : {} ======", name, key);
byte[] k = computeKey(key);
byte[] v = rawValue(value);
shardedJedisTemplate.setAndExpire(k, v, defaultExpiration);
}
@Override
public ValueWrapper putIfAbsent(Object key, Object value) {
// log.debug("======put to cache '{}' with key : {} ======", name, key);
byte[] k = computeKey(key);
byte[] v = rawValue(value);
String s = shardedJedisTemplate.setAndExpire(k, v, defaultExpiration);
return (s == null ? null : new SimpleValueWrapper(s));
}
@Override
public void evict(Object key) {
// log.info("======delete from cache '{}' by key : {} ======", name, key);
shardedJedisTemplate.del(computeKey(key));
}
@Override
public void clear() {
}
/**
* 加前缀和分隔符 默认:
* 在cacheName和key之间加分隔符
* 有兴趣可以看看{@link DefaultRedisCachePrefix}
*
* @return
* @paramkey
*/
private byte[] computeKey(Object key) {
byte[] bytes = rawKey(key);
return ArrayUtils.addAll((name.concat(":")).getBytes(), bytes);
}
/**
* 设置Key失效时间
*
* @param key
*/
private void expires(byte[] key) {
shardedJedisTemplate.expire(key, defaultExpiration);
}
/**
* key转字节
*
* @param key
* @return
*/
@SuppressWarnings("unchecked")
private byte[] rawKey(Object key) {
Assert.notNull(key, "non null key required");
if (keySerializer == null && key instanceof byte[]) {
return (byte[]) key;
}
return keySerializer.serialize(key);
}
/**
* value转字节
*
* @param value
* @return
*/
@SuppressWarnings("unchecked")
private byte[] rawValue(Object value) {
if (valueSerializer == null && value instanceof byte[]) {
return (byte[]) value;
}
return valueSerializer.serialize(value);
}
@SuppressWarnings("unchecked")
private Object deserializeValue(byte[] value) {
if (valueSerializer == null) {
return value;
}
return valueSerializer.deserialize(value);
}- 自定义jedis缓存管理器（ShardedJedisCacheManager）,这样Spring就不会自行创建RedisCacheManager了，一次注解缓存就可生效了，其实注解都可以指定manager，即可以同时存在多个manager，但期望统一，没必要多个。
import org.springframework.cache.Cache;
import org.springframework.cache.CacheManager;
import org.springframework.data.redis.serializer.GenericJackson2JsonRedisSerializer;
import org.springframework.data.redis.serializer.RedisSerializer;
import org.springframework.data.redis.serializer.StringRedisSerializer;
import java.util.*;
/**
* cacheManager实现类
*/
public class ShardedJedisCacheManager implements CacheManager {
private final ConcurrentMap<String, Cache> cacheMap = new ConcurrentHashMap<>(16);
private volatile Set<String> cacheNames;
private long defaultExpiration;
private Map<String, Long> expires;
private ShardedJedisTemplate<Object, Object> shardedJedisTemplate;
public ShardedJedisCacheManager(ShardedJedisTemplate<Object, Object> shardedJedisTemplate) {
this(shardedJedisTemplate, Collections.emptySet());
}
public ShardedJedisCacheManager(ShardedJedisTemplate<Object, Object> shardedJedisTemplate, Set<String> cacheNames) {
this.shardedJedisTemplate = shardedJedisTemplate;
this.cacheNames = cacheNames;
this.defaultExpiration = 0L;
}
@Override
public Cache getCache(String name) {
Cache cache = cacheMap.get(name);
if (cache != null) {
return cache;
}
synchronized (this.cacheMap) {
cache = this.cacheMap.get(name);
if (cache == null) {
cache = createCache(name);
}
return cache;
}
}
//可能需要一个预加载 问题不大
private Cache createCache(String cacheName) {
ShardedJedisCache cache = new ShardedJedisCache(cacheName, shardedJedisTemplate);
cache.setDefaultExpiration(this.computeExpiration(cacheName));
if (cacheNames == null || cacheNames.size() == 0) {
cacheNames = new LinkedHashSet<>();
}
cacheNames.add(cacheName);
cacheMap.put(cacheName, cache);
return cache;
}
@Override
public Collection<String> getCacheNames() {
return cacheNames;
}
//ignore partial getter/setter
protected long computeExpiration(String name) {
Long expiration = null;
if (this.expires != null) {
expiration = this.expires.get(name);
}
return expiration != null ? expiration : this.defaultExpiration;
}
}- 配置类，将前面自定义的注册bean
import com.google.common.collect.Lists;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.data.redis.serializer.GenericJackson2JsonRedisSerializer;
import org.springframework.data.redis.serializer.StringRedisSerializer;
import redis.clients.jedis.JedisShardInfo;
import redis.clients.jedis.ShardedJedisPool;
import java.util.List;
/**
* jedis连接池的基本配置
*
* @author bbcui
*/
@Configuration
public class ShardedJedisConfiguration {
@Autowired
private ShardedJedisProperties shardedJedisProperties;
public static final String SHARDED_JEDIS_POOL = "shardedJedisPool";
public static final String SHARDed_REDIS_CONNECTION_FACTORY = "shardedRedisConnectionFactory";
public static final String SHARDed_REDIS_TEMPLATE = "shardedRedisTemplate";
@Bean(name = SHARDED_JEDIS_POOL)
public ShardedJedisPool shardedJedisPool() {
List<JedisShardInfo> jedisShardInfoList = Lists.newArrayList();
JedisShardInfo jedisShardInfo;
for (ShardedJedisProperties.JedisInfo jedisInfo : shardedJedisProperties.getJedisInfos()) {
jedisShardInfo = new JedisShardInfo(jedisInfo.getHost());
jedisShardInfo.setConnectionTimeout(jedisInfo.getConnectionTimeout());
jedisShardInfoList.add(jedisShardInfo);
}
return new ShardedJedisPool(shardedJedisProperties.getPool(), jedisShardInfoList);
}
@Bean(name = SHARDed_REDIS_CONNECTION_FACTORY)
public ShardedJedisConnectionFactory shardRedisConnectionFactory(@Qualifier(SHARDED_JEDIS_POOL) ShardedJedisPool shardedJedisPool) {
return new ShardedJedisConnectionFactory(shardedJedisPool);
}
@Bean(name = SHARDed_REDIS_TEMPLATE)
public ShardedJedisTemplate shardRedisTemplate(@Qualifier(SHARDed_REDIS_CONNECTION_FACTORY) ShardedJedisConnectionFactory shardedJedisConnectionFactory) {
ShardedJedisTemplate shardedJedisTemplate = new ShardedJedisTemplate();
shardedJedisTemplate.setFactory(shardedJedisConnectionFactory);
shardedJedisTemplate.setKeySerializer(new StringRedisSerializer());
shardedJedisTemplate.setValueSerializer(new GenericJackson2JsonRedisSerializer());
return shardedJedisTemplate;
}
}- 再包装一层 提供一个统一的使用入口 （部分代码省略）
@Configuration
@EnableCaching
@EnableAutoConfiguration
public class CacheConfig extends CachingConfigurerSupport {
/**
* 拼接符
*/
private static final String SPLICE = ":";
@Autowired
private ShardedJedisTemplate shardedJedisTemplate;
/**
* 注入bean
*/
@Bean(name = “shardRedisCacheManager”)
@Override
public ShardedJedisCacheManager cacheManager() {
// 自定义缓存名对应的过期时间
Map<String, Long> expires = ImmutableMap.<String, Long>builder()
.put(CacheConfig.CacheNames.CACHE_30SECS, TimeUnit.SECONDS.toSeconds(30))
.put(CacheConfig.CacheNames.CACHE_5MINS, TimeUnit.MINUTES.toSeconds(5))
.build();
ShardedJedisCacheManager manager = new ShardedJedisCacheManager(shardedJedisTemplate);
//默认30分钟
manager.setDefaultExpiration(TimeUnit.MINUTES.toSeconds(30));
manager.setExpires(expires);
return manager;
}
@Bean
@Override
public KeyGenerator keyGenerator() {
return (target, method, params) -> {
StringBuilder sb = new StringBuilder("cache:");
sb.append(target.getClass().getName());
sb.append(method.getName());
for (Object obj : params) {
if (obj != null) {
sb.append(obj.toString());
}
}
return sb.toString();
};
}
}import com.google.common.collect.Lists;
import com.google.common.collect.Sets;
import com.lianjia.kaoqin.saas.common.utils.DateUtil;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.cache.Cache;
import org.springframework.data.redis.core.RedisTemplate;
import org.springframework.data.redis.core.script.DefaultRedisScript;
import org.springframework.stereotype.Component;
import java.util.*;
import java.util.concurrent.TimeUnit;
/**
* 额外的缓存操作工具
* 使用shardedJedis，分片分流缓存，支持springCache注解，对外的get、put等接口都用shardedJedis；
*/
@Component
public class CacheUtil {
private static ShardedJedisCacheManager shardedJedisCacheManager;
private static ShardedJedisTemplate shardedJedisTemplate;
private static RedisTemplate redisTemplate;
private static DefaultRedisScript<Number> redisluaScript;
/**
* spring启动时，自动初始化redisCacheManager和redisTemplate
* <p>
* 使用时不再需要进行初始操作
*/
@Autowired
public CacheUtil(@Qualifier(value = CacheConfig.SHARD_REDIS_CACHE_MANAGER) ShardedJedisCacheManager shardedJedisCacheManager,
@Qualifier(value = ShardedJedisConfiguration.SHARDed_REDIS_TEMPLATE) ShardedJedisTemplate shardedJedisTemplate,
RedisTemplate redisTemplate,
@Qualifier(value = "redisluaScript") DefaultRedisScript defaultRedisScript) {
this.shardedJedisCacheManager = shardedJedisCacheManager;
this.shardedJedisTemplate = shardedJedisTemplate;
this.redisTemplate = redisTemplate;
this.redisluaScript = defaultRedisScript;
}
/**
* 缓存数据
*/
public static void put(String cache, Object key, Object value) {
shardedJedisCacheManager.getCache(cache).put(key, value);
}
/**
* 删除缓存
*/
public static void evict(String cache, Object key) {
shardedJedisCacheManager.getCache(cache).evict(key);
}
/**
* 查询缓存
*/
public static <T> T get(String cache, Object key) {
Object val = shardedJedisCacheManager.getCache(cache).get(key);
if (val instanceof Cache.ValueWrapper) {
return (T) ((Cache.ValueWrapper) val).get();
} else {
return null;
}
}
/**
* 缓存数据
*/
public static void put(Object key, Object value, long timeout, TimeUnit timeUnit) {
shardedJedisTemplate.setex(key, (int) TimeUnit.SECONDS.convert(timeout, timeUnit), value);
}
}总结
原理较简单，本质就是自行封装一些类，但是有部分缺陷，ShardedJedis命令较少一些，可能会觉得这么麻烦还不如直接用集群，反正都有一些命令不支持（DBA不让玩），自己业务内定义分流策略可能会更好，这是DBA说的，所以只能简单做个分片了。实践下来，基本能较均匀的分流，性能没有可见的影响（hash）。
虽然key的分布比较均衡，但不代表各个实例的使用率（比如一些指标，请求量、网络IO等）差不多，因为存在一些热点key。。。这部分需要综合考虑是否使用本地缓存来解决了，但是本地缓存的引入会使得系统更加复杂，如何保证数据的一致性又成了新的挑战，建议本地缓存必要用的话存储一些只读的或者更新频率极低的数据。
项目后来仍然保留了RedisTemplate用作一些特殊场景，比如执行一些限流脚本等。。。
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