jedis源码-分片路由

jedis分片相关的类有Sharded ShardInfo Jedis

ShardInfo ：

public abstract class ShardInfo<T> {
  private int weight;  //加权
  protected abstract T createResource();  //建立jedis链接实例
  public abstract String getName();
}

Sharded : 

public Sharded(List<S> shards, Hashing algo, Pattern tagPattern) {
    this.algo = algo;
    this.tagPattern = tagPattern;
    initialize(shards);  //shards 分片列表
  }

 

private void initialize(List<S> shards) {
    nodes = new TreeMap<Long, S>();

    for (int i = 0; i != shards.size(); ++i) {
      final S shardInfo = shards.get(i);
      if (shardInfo.getName() == null) 
        for (int n = 0; n < 160 * shardInfo.getWeight(); n++) {  //把一个分片分红160个节点，存起来
              nodes.put(this.algo.hash("SHARD-" + i + "-NODE-" + n), shardInfo);
        }
     else 
       for (int n = 0; n < 160 * shardInfo.getWeight(); n++) {
           nodes.put(this.algo.hash(shardInfo.getName() + "*" + shardInfo.getWeight() + n), shardInfo);
      }
      resources.put(shardInfo, shardInfo.createResource());  // 建立jedis链接实例，存起来，因此  resources 是对redis实例的缓存
    }
  }

当执行读写操做时要根据key从resources里取出一个jedis实例 获取jedis实例分为两个步，重点是 经过key 从nodes节点里找到一个分片

public S getShardInfo(byte[] key) {
    SortedMap<Long, S> tail = nodes.tailMap(algo.hash(key));  /默认的hash算法，
    if (tail.isEmpty()) {
        return nodes.get(nodes.firstKey()); //有序的map，即便返回多个值，经过取first也能保证每次取到    的结果是一个
    }
    return tail.get(tail.firstKey());
  }