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캐시 분산 잠금 원리 및 기본 사용법

2024-07-12

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분산 잠금 원리 및 용도

 

회전

  1.  public Map<String, List<Catelog2Vo>> getCatalogJsonFromDBWithRedisLock() {
  2.  
  3.         Boolean b = redisTemplate.opsForValue().setIfAbsent(Lock, Lock, Duration.ofMinutes(1));
  4.         if (!b) {
  5.             int i = 10;
  6.             while (i > 0) {
  7.                 Object result = redisTemplate.opsForValue().get(CATALOG_JSON);
  8.                 try {
  9.                     TimeUnit.MILLISECONDS.sleep(100);
  10.                 } catch (InterruptedException e) {
  11.                     throw new RuntimeException(e);
  12.                 }
  13.                 if (result != null) {
  14.                     System.out.println("命中缓存 db lock");
  15.                     return (Map<String, List<Catelog2Vo>>) result;
  16.                 }
  17.                 i--;
  18.             }
  19.             throw new RuntimeException("系统繁忙，请重新访问");
  20.         }
  21.  
  22.  
  23.         //1.查出所有1级分类
  24.         List<CategoryEntity> selectList = baseMapper.selectList(null);
  25.         /**
  26.          * 将数据库的多次查询变成一次
  27.          */
  28.         System.out.println("查询了数据库");
  29.  
  30.         //2. 封装数据
  31.         List<CategoryEntity> level1Category = selectList.stream().filter(s -> s.getParentCid().equals(0L)).collect(Collectors.toList());
  32.         Map<String, List<Catelog2Vo>> map = level1Category.stream().collect(Collectors.toMap(k -> k.getCatId().toString(), v -> {
  33.             //1.每一个的一级分类,查到1级分类的所有二级分类
  34.             List<CategoryEntity> categoryEntities = selectList.stream().filter(s -> s.getParentCid().equals(v.getCatId())).collect(Collectors.toList());
  35.  
  36.             List<Catelog2Vo> catelog2VoList = categoryEntities.stream().map(c -> {
  37.                 Catelog2Vo catelog2Vo = new Catelog2Vo();
  38.                 catelog2Vo.setId(c.getCatId().toString());
  39.                 catelog2Vo.setName(c.getName());
  40.                 catelog2Vo.setCatalog1Id(v.getCatId().toString());
  41.  
  42.                 List<CategoryEntity> categoryEntities1 = selectList.stream().filter(s -> s.getParentCid().equals(c.getCatId())).collect(Collectors.toList());
  43.                 List<Catelog2Vo.Catelog3Vo> collect = categoryEntities1.stream().map(c3 -> {
  44.                     Catelog2Vo.Catelog3Vo catelog3Vo = new Catelog2Vo.Catelog3Vo();
  45.                     catelog3Vo.setId(c3.getCatId().toString());
  46.                     catelog3Vo.setName(c3.getName());
  47.                     catelog3Vo.setCatalog2Id(c.getCatId().toString());
  48.                     return catelog3Vo;
  49.                 }).collect(Collectors.toList());
  50.  
  51.                 catelog2Vo.setCatalog3List(collect);
  52.  
  53.                 return catelog2Vo;
  54.             }).collect(Collectors.toList());
  55.  
  56.  
  57.             return catelog2VoList;
  58.         }));
  59.         if (map == null) {
  60.             /**
  61.              * 解决缓存穿透
  62.              */
  63.             map = new HashMap<>();
  64.         }
  65.         redisTemplate.opsForValue().set(CATALOG_JSON, map, Duration.ofDays(1));
  66.         redisTemplate.delete(Lock);
  67.         return map;
  68.     }

  1.  public Map<String, List<Catelog2Vo>> getCatalogJsonFromDBWithRedisLock() {
  2.         String uuid = UUID.randomUUID().toString();
  3.         Boolean b = redisTemplate.opsForValue().setIfAbsent(Lock, uuid, Duration.ofMinutes(1));
  4.         if (!b) {
  5.             int i = 10;
  6.             while (i > 0) {
  7.                 Object result = redisTemplate.opsForValue().get(CATALOG_JSON);
  8.                 try {
  9.                     TimeUnit.MILLISECONDS.sleep(100);
  10.                 } catch (InterruptedException e) {
  11.                     throw new RuntimeException(e);
  12.                 }
  13.                 if (result != null) {
  14.                     System.out.println("命中缓存 db lock");
  15.                     return (Map<String, List<Catelog2Vo>>) result;
  16.                 }
  17.                 i--;
  18.             }
  19.             throw new RuntimeException("系统繁忙，请重新访问");
  20.         }
  21.  
  22.  
  23.         //1.查出所有1级分类
  24.         List<CategoryEntity> selectList = baseMapper.selectList(null);
  25.         /**
  26.          * 将数据库的多次查询变成一次
  27.          */
  28.         System.out.println("查询了数据库");
  29.  
  30.         //2. 封装数据
  31.         List<CategoryEntity> level1Category = selectList.stream().filter(s -> s.getParentCid().equals(0L)).collect(Collectors.toList());
  32.         Map<String, List<Catelog2Vo>> map = level1Category.stream().collect(Collectors.toMap(k -> k.getCatId().toString(), v -> {
  33.             //1.每一个的一级分类,查到1级分类的所有二级分类
  34.             List<CategoryEntity> categoryEntities = selectList.stream().filter(s -> s.getParentCid().equals(v.getCatId())).collect(Collectors.toList());
  35.  
  36.             List<Catelog2Vo> catelog2VoList = categoryEntities.stream().map(c -> {
  37.                 Catelog2Vo catelog2Vo = new Catelog2Vo();
  38.                 catelog2Vo.setId(c.getCatId().toString());
  39.                 catelog2Vo.setName(c.getName());
  40.                 catelog2Vo.setCatalog1Id(v.getCatId().toString());
  41.  
  42.                 List<CategoryEntity> categoryEntities1 = selectList.stream().filter(s -> s.getParentCid().equals(c.getCatId())).collect(Collectors.toList());
  43.                 List<Catelog2Vo.Catelog3Vo> collect = categoryEntities1.stream().map(c3 -> {
  44.                     Catelog2Vo.Catelog3Vo catelog3Vo = new Catelog2Vo.Catelog3Vo();
  45.                     catelog3Vo.setId(c3.getCatId().toString());
  46.                     catelog3Vo.setName(c3.getName());
  47.                     catelog3Vo.setCatalog2Id(c.getCatId().toString());
  48.                     return catelog3Vo;
  49.                 }).collect(Collectors.toList());
  50.  
  51.                 catelog2Vo.setCatalog3List(collect);
  52.  
  53.                 return catelog2Vo;
  54.             }).collect(Collectors.toList());
  55.  
  56.  
  57.             return catelog2VoList;
  58.         }));
  59.         if (map == null) {
  60.             /**
  61.              * 解决缓存穿透
  62.              */
  63.             map = new HashMap<>();
  64.         }
  65.         redisTemplate.opsForValue().set(CATALOG_JSON, map, Duration.ofDays(1));
  66.         Object o = redisTemplate.opsForValue().get(Lock);
  67.         if (o != null && o.equals(uuid)) {
  68.             redisTemplate.delete(Lock);
  69.         }
  70.  
  71.         return map;
  72.     }

여전히 문제가 있습니다

전송 과정에 시간이 걸리므로 이때 KEY가 만료되면 다른 스레드가 들어와서 KEY를 생성한 후 이전 스레드로 데이터를 반환합니다. KEY가 삭제되면 다른 스레드에서 새로 추가한 키가 반환됩니다. 삭제되었습니다.

값 비교 가져오기 + 성공적으로 비교 삭제 = 원자적 작업

redis+lua 스크립트 구현

 public static final String Lock = "Lock";
  1.   public Map<String, List<Catelog2Vo>> getCatalogJsonFromDBWithRedisLock() {
  2.         String uuid = UUID.randomUUID().toString();
  3.         Boolean b = redisTemplate.opsForValue().setIfAbsent(Lock, uuid, Duration.ofMinutes(5));
  4.         if (!b) {
  5.             System.out.println("获取分布式锁失败，等待重试");
  6.             int i = 10;
  7.             while (i > 0) {
  8.                 Object result = redisTemplate.opsForValue().get(CATALOG_JSON);
  9.                 try {
  10.                     TimeUnit.MILLISECONDS.sleep(100);
  11.                 } catch (InterruptedException e) {
  12.                    e.printStackTrace();
  13.                 }
  14.                 if (result != null) {
  15.                     System.out.println("命中缓存 db lock");
  16.                     return (Map<String, List<Catelog2Vo>>) result;
  17.                 }
  18.                 i--;
  19.             }
  20.             throw new RuntimeException("系统繁忙，请重新访问");
  21.         }
  22.  
  23.  
  24.         //1.查出所有1级分类
  25.         /**
  26.          * 将数据库的多次查询变成一次
  27.          */
  28.         System.out.println("获取分布式锁成功");
  29.  
  30.         //2. 封装数据
  31.         Map<String, List<Catelog2Vo>> map = null;
  32.         try {
  33.             System.out.println("查询了数据库");
  34.             List<CategoryEntity> selectList = baseMapper.selectList(null);
  35.             List<CategoryEntity> level1Category = selectList.stream().filter(s -> s.getParentCid().equals(0L)).collect(Collectors.toList());
  36.             map = level1Category.stream().collect(Collectors.toMap(k -> k.getCatId().toString(), v -> {
  37.                 //1.每一个的一级分类,查到1级分类的所有二级分类
  38.                 List<CategoryEntity> categoryEntities = selectList.stream().filter(s -> s.getParentCid().equals(v.getCatId())).collect(Collectors.toList());
  39.  
  40.                 List<Catelog2Vo> catelog2VoList = categoryEntities.stream().map(c -> {
  41.                     Catelog2Vo catelog2Vo = new Catelog2Vo();
  42.                     catelog2Vo.setId(c.getCatId().toString());
  43.                     catelog2Vo.setName(c.getName());
  44.                     catelog2Vo.setCatalog1Id(v.getCatId().toString());
  45.  
  46.                     List<CategoryEntity> categoryEntities1 = selectList.stream().filter(s -> s.getParentCid().equals(c.getCatId())).collect(Collectors.toList());
  47.                     List<Catelog2Vo.Catelog3Vo> collect = categoryEntities1.stream().map(c3 -> {
  48.                         Catelog2Vo.Catelog3Vo catelog3Vo = new Catelog2Vo.Catelog3Vo();
  49.                         catelog3Vo.setId(c3.getCatId().toString());
  50.                         catelog3Vo.setName(c3.getName());
  51.                         catelog3Vo.setCatalog2Id(c.getCatId().toString());
  52.                         return catelog3Vo;
  53.                     }).collect(Collectors.toList());
  54.  
  55.                     catelog2Vo.setCatalog3List(collect);
  56.  
  57.                     return catelog2Vo;
  58.                 }).collect(Collectors.toList());
  59.  
  60.  
  61.                 return catelog2VoList;
  62.             }));
  63.             if (map == null) {
  64.                 /**
  65.                  * 解决缓存穿透
  66.                  */
  67.                 map = new HashMap<>();
  68.             }
  69.             redisTemplate.opsForValue().set(CATALOG_JSON, map, Duration.ofDays(1));
  70.  
  71.  
  72.         } catch (Exception e) {
  73.             e.printStackTrace();
  74.         } finally {
  75.             //lua脚本解锁
  76.             //如果获取key等于传过来的值，就执行删除操作,否则就不执行
  77.             String script="if redis.call('get',KEYS[1])==ARGV[1] then return redis.call('del',KEYS[1]) else return 0 end";
  78.             Long execute = redisTemplate.execute(new DefaultRedisScript<Long>(script, Long.class), Arrays.asList(Lock), uuid);
  79.             if (execute==1){
  80.                 System.out.println("原子删锁成功");
  81.             }else {
  82.                 System.out.println("原子删锁失败");
  83.             }
  84.         }
  85.  
  86.         return map;
  87.     }

단 한 명만 데이터베이스에 쿼리했습니다.

개인 프로필

그는 30년 이상 기술 연구에 전념해 왔으며, java, linux, javascript, php, css 등 다양한 언어에 능숙하며, 오픈 소스 분야에서 많은 공헌을 했습니다. 나중에 참조할 수 있도록 기술 개발의 일부 문제를 공유하는 개발자 문서 스테이션입니다.

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