Redis问题整理

Redis问题总结

1、单点登录的两个项目cookie不一致

由于在配置自定义Cookie的时候

@Bean("shiroCookie")
    public SimpleCookie simpleCookie(){
        SimpleCookie simpleCookie = new SimpleCookie();
        simpleCookie.setName("shiroCookie");
        simpleCookie.setPath("/demo");
        //防止xss读取cookie
        simpleCookie.setHttpOnly(true);
        //关闭浏览器后失效
        simpleCookie.setMaxAge(-1);
        return simpleCookie;
    }

里面有一个setPath("/demo");意思是说，这个Cookie的域是 项目路径/demo的，没法和其他的项目共享Cookie，把它设置成

simpleCookie.setPath("/");

或者不设置，默认的也是/，即可解决。

2、访问不到6379端口

1、在redis.conf文件中，把 bind 127.0.0.1注释，把protected-mode的值改成yes

2、关闭防火墙systemctl stop firewalld.service

3、redisTemplate无法操作多节点

自定义一个ConnectionFactory

@Bean
    public JedisConnectionFactory jedisConnectionFactory() {
        List<String> clusterNodes = Arrays.asList("123.57.95.134:6379");
        return new JedisConnectionFactory(new RedisClusterConfiguration(clusterNodes));
    }

只需要添加一个节点的ip，它会自动寻找其他节点。

然后自定义一个RedisTemplate

@Bean
    public RedisTemplate<Object, Object> redisTemplate(RedisConnectionFactory redisConnectionFactory) {
        RedisTemplate<Object, Object> redisTemplate = new RedisTemplate<>();
        redisTemplate.setConnectionFactory(jedisConnectionFactory());
        GenericJackson2JsonRedisSerializer json = new GenericJackson2JsonRedisSerializer();
        redisTemplate.setValueSerializer(json);
        redisTemplate.setKeySerializer(new StringRedisSerializer());
        return redisTemplate;
    }

把JedisConnectionFactory注入进redisTemplate即可。

4、提示无法连接到Redis服务器

问题描述：

key能够存取

但是在进行存取操作时总会提示

解决办法：

SpringBoot默认使用的是lettuce来对Redis进行操作，而代码中使用的是RedisTemplate，所以把lettuce包排除即可。

<dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-redis</artifactId>
            <exclusions>
                <exclusion>
                    <groupId>io.lettuce</groupId>
                    <artifactId>lettuce-core</artifactId>
                </exclusion>
            </exclusions>
        </dependency>

5、获取key所在的节点

刚开始想实现的效果是存入某个key，然后返回：key添加成功，节点是xxx。看了JedisCluster的方法，redisTemplate的方法，Jedis的方法，都没有找到能够返回的。在百度，谷歌查资料也没有找到具体的说明。

后面想到可以根据key去计算slot的值，然后根据分片的配置。

怎么计算？我查看了Redis源码里面的算法

package redis.clients.jedis.util;

import redis.clients.jedis.exceptions.JedisClusterOperationException;

/**
 * CRC16 Implementation according to CCITT standard Polynomial : 1021 (x^16 + x^12 + x^5 + 1) See <a
 * href="http://redis.io/topics/cluster-spec">Appendix A. CRC16 reference implementation in ANSI
 * C</a>
 */
public final class JedisClusterCRC16 {
  private static final int[] LOOKUP_TABLE = {0x0000, 0x1021, 0x2042, 0x3063, 0x4084, 0x50A5,
          0x60C6, 0x70E7, 0x8108, 0x9129, 0xA14A, 0xB16B, 0xC18C, 0xD1AD, 0xE1CE, 0xF1EF, 0x1231,
          0x0210, 0x3273, 0x2252, 0x52B5, 0x4294, 0x72F7, 0x62D6, 0x9339, 0x8318, 0xB37B, 0xA35A,
          0xD3BD, 0xC39C, 0xF3FF, 0xE3DE, 0x2462, 0x3443, 0x0420, 0x1401, 0x64E6, 0x74C7, 0x44A4,
          0x5485, 0xA56A, 0xB54B, 0x8528, 0x9509, 0xE5EE, 0xF5CF, 0xC5AC, 0xD58D, 0x3653, 0x2672,
          0x1611, 0x0630, 0x76D7, 0x66F6, 0x5695, 0x46B4, 0xB75B, 0xA77A, 0x9719, 0x8738, 0xF7DF,
          0xE7FE, 0xD79D, 0xC7BC, 0x48C4, 0x58E5, 0x6886, 0x78A7, 0x0840, 0x1861, 0x2802, 0x3823,
          0xC9CC, 0xD9ED, 0xE98E, 0xF9AF, 0x8948, 0x9969, 0xA90A, 0xB92B, 0x5AF5, 0x4AD4, 0x7AB7,
          0x6A96, 0x1A71, 0x0A50, 0x3A33, 0x2A12, 0xDBFD, 0xCBDC, 0xFBBF, 0xEB9E, 0x9B79, 0x8B58,
          0xBB3B, 0xAB1A, 0x6CA6, 0x7C87, 0x4CE4, 0x5CC5, 0x2C22, 0x3C03, 0x0C60, 0x1C41, 0xEDAE,
          0xFD8F, 0xCDEC, 0xDDCD, 0xAD2A, 0xBD0B, 0x8D68, 0x9D49, 0x7E97, 0x6EB6, 0x5ED5, 0x4EF4,
          0x3E13, 0x2E32, 0x1E51, 0x0E70, 0xFF9F, 0xEFBE, 0xDFDD, 0xCFFC, 0xBF1B, 0xAF3A, 0x9F59,
          0x8F78, 0x9188, 0x81A9, 0xB1CA, 0xA1EB, 0xD10C, 0xC12D, 0xF14E, 0xE16F, 0x1080, 0x00A1,
          0x30C2, 0x20E3, 0x5004, 0x4025, 0x7046, 0x6067, 0x83B9, 0x9398, 0xA3FB, 0xB3DA, 0xC33D,
          0xD31C, 0xE37F, 0xF35E, 0x02B1, 0x1290, 0x22F3, 0x32D2, 0x4235, 0x5214, 0x6277, 0x7256,
          0xB5EA, 0xA5CB, 0x95A8, 0x8589, 0xF56E, 0xE54F, 0xD52C, 0xC50D, 0x34E2, 0x24C3, 0x14A0,
          0x0481, 0x7466, 0x6447, 0x5424, 0x4405, 0xA7DB, 0xB7FA, 0x8799, 0x97B8, 0xE75F, 0xF77E,
          0xC71D, 0xD73C, 0x26D3, 0x36F2, 0x0691, 0x16B0, 0x6657, 0x7676, 0x4615, 0x5634, 0xD94C,
          0xC96D, 0xF90E, 0xE92F, 0x99C8, 0x89E9, 0xB98A, 0xA9AB, 0x5844, 0x4865, 0x7806, 0x6827,
          0x18C0, 0x08E1, 0x3882, 0x28A3, 0xCB7D, 0xDB5C, 0xEB3F, 0xFB1E, 0x8BF9, 0x9BD8, 0xABBB,
          0xBB9A, 0x4A75, 0x5A54, 0x6A37, 0x7A16, 0x0AF1, 0x1AD0, 0x2AB3, 0x3A92, 0xFD2E, 0xED0F,
          0xDD6C, 0xCD4D, 0xBDAA, 0xAD8B, 0x9DE8, 0x8DC9, 0x7C26, 0x6C07, 0x5C64, 0x4C45, 0x3CA2,
          0x2C83, 0x1CE0, 0x0CC1, 0xEF1F, 0xFF3E, 0xCF5D, 0xDF7C, 0xAF9B, 0xBFBA, 0x8FD9, 0x9FF8,
          0x6E17, 0x7E36, 0x4E55, 0x5E74, 0x2E93, 0x3EB2, 0x0ED1, 0x1EF0,};

  private JedisClusterCRC16(){
    throw new InstantiationError( "Must not instantiate this class" );
  }

  public static int getSlot(String key) {
    if (key == null) {
      throw new JedisClusterOperationException("Slot calculation of null is impossible");
    }

    key = JedisClusterHashTagUtil.getHashTag(key);
    // optimization with modulo operator with power of 2 equivalent to getCRC16(key) % 16384
    return getCRC16(key) & (16384 - 1);
  }

  public static int getSlot(byte[] key) {
    if (key == null) {
      throw new JedisClusterOperationException("Slot calculation of null is impossible");
    }

    int s = -1;
    int e = -1;
    boolean sFound = false;
    for (int i = 0; i < key.length; i++) {
      if (key[i] == '{' && !sFound) {
        s = i;
        sFound = true;
      }
      if (key[i] == '}' && sFound) {
        e = i;
        break;
      }
    }
    if (s > -1 && e > -1 && e != s + 1) {
      return getCRC16(key, s + 1, e) & (16384 - 1);
    }
    return getCRC16(key) & (16384 - 1);
  }

  /**
   * Create a CRC16 checksum from the bytes. implementation is from mp911de/lettuce, modified with
   * some more optimizations
   * @param bytes
   * @param s
   * @param e
   * @return CRC16 as integer value See <a
   *         href="https://github.com/xetorthio/jedis/pull/733#issuecomment-55840331">Issue 733</a>
   */
  public static int getCRC16(byte[] bytes, int s, int e) {
    int crc = 0x0000;

    for (int i = s; i < e; i++) {
      crc = ((crc << 8) ^ LOOKUP_TABLE[((crc >>> 8) ^ (bytes[i] & 0xFF)) & 0xFF]);
    }
    return crc & 0xFFFF;
  }

  public static int getCRC16(byte[] bytes) {
    return getCRC16(bytes, 0, bytes.length);
  }

  public static int getCRC16(String key) {
    byte[] bytesKey = SafeEncoder.encode(key);
    return getCRC16(bytesKey, 0, bytesKey.length);
  }
}

突然发现里面有方法

public static int getSlot(byte[] key)
public static int getSlot(String key)

于是一气呵成