redis实战第十五篇 redis cluster的批处理中ask重定向解决方案

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ask重定向现象请参考【传送门】

分别使用mget和pipline做批处理
1.使用mget批量获取，如果存在重定向问题，会抛出异常。

    @Testpublic void testMget(){JedisCluster jedis = RedisClusterUtil.getJedis();List<String> results = null;results = jedis.mget("user:{info}:id","user:{info}:age");for(String res:results){System.out.println(res);}results = jedis.mget("user:{info}:id","user:{info}:age","user:{info}:name","user:{info}:email");for(String res:results){System.out.println(res);}}

返回结果如下所示，第一次mget执行成功，是因为两个键都迁移完成，第二次获取失败是因为存在ask重定向问题。

232132
20redis.clients.jedis.exceptions.JedisDataException: TRYAGAIN Multiple keys request during rehashing of slot

2.使用pipline做批量处理

@Testpublic void testPiplione(){//创建JedisCluster时，节点地址可以只填写部分，集群内部可以通过cluster nodes获取所有节点信息JedisSlotBasedConnectionHandler connectionHandler = new JedisCluster(new HostAndPort("192.168.0.31",6380),1000,1000,5,"1234@abcd",new JedisPoolConfig()){public JedisSlotBasedConnectionHandler getConnectionHandler() {return (JedisSlotBasedConnectionHandler) super.connectionHandler;}}.getConnectionHandler();List<String> keys = Arrays.asList("user:{info}:id","user:{info}:age","user:{info}:name","user:{info}:email");Jedis jedis = connectionHandler.getConnectionFromSlot(JedisClusterCRC16.getSlot(keys.get(3)));try {Pipeline pipelined = jedis.pipelined();for (String key : keys) {pipelined.get(key);}List<Object> results = pipelined.syncAndReturnAll();for (Object result : results) {System.out.println(result);}} finally {jedis.close();}}

批处理结果如下，当存在重定向问题时，pipline不会抛出异常，而是直接返回异常对象，并且成功迁移的键能获取到值。

redis.clients.jedis.exceptions.JedisAskDataException: ASK 5642 192.168.0.33:6380
redis.clients.jedis.exceptions.JedisAskDataException: ASK 5642 192.168.0.33:6380
peter
132132@163.com

基于异常结果对象，可以获取到对应的重定向节点信息，根据获取到的节点信息获取连接再次发送请求。

@Testpublic void testPiplione2(){JedisSlotBasedConnectionHandler connectionHandler = new JedisCluster(new HostAndPort("192.168.0.31",6380),1000,1000,5,"1234@abcd",new JedisPoolConfig()){public JedisSlotBasedConnectionHandler getConnectionHandler() {return (JedisSlotBasedConnectionHandler) super.connectionHandler;}}.getConnectionHandler();List<String> keys = Arrays.asList("user:{info}:id","user:{info}:age","user:{info}:name","user:{info}:email");Jedis jedis = connectionHandler.getConnectionFromSlot(JedisClusterCRC16.getSlot(keys.get(3)));try {Pipeline pipelined = jedis.pipelined();for (String key : keys) {pipelined.get(key);}List<Object> results = pipelined.syncAndReturnAll();for (int i =0 ; i<keys.size() ; i++) {// 键顺序和结果顺序，Pipeline严格按照键发送的顺序返回结果，即使出现异常也是如此Object result = results.get(i);//判断是否是异常结果对象if (result != null && result instanceof JedisAskDataException) {JedisAskDataException askException = (JedisAskDataException) result;//根据异常结果对象获取节点信息HostAndPort targetNode = askException.getTargetNode();//根据节点信息获取jedis连接Jedis targetJedis = connectionHandler.getConnectionFromNode(targetNode);try {// 执行askingtargetJedis.asking();// 获取key并执行String key = keys.get(i);String targetResult = targetJedis.get(key);System.out.println(targetResult);} finally {targetJedis.close();}} else {System.out.println(result);}}}finally {jedis.close();}}

以下是执行结果，可以看出pipline可以根据返回的异常结果对象，获取ask重定向节点信息，发送ask请求，获取返回结果，这点和mget不一样，mget出现ask重定向问题时会直接抛出异常。