Method getReplicas

lib/metadata/index.js:304–336

* Gets the host list representing the replicas that contain the given partition key, token or token range. * * It uses the pre-loaded keyspace metadata to retrieve the replicas for a token for a given keyspace. * When the keyspace metadata has not been loaded, it returns null. *

(keyspaceName, token)

   * @returns {Array}
   */
  getReplicas(keyspaceName, token) {
    if (!this.ring) {
      return null;
    }
    if (Buffer.isBuffer(token)) {
      token = this.tokenizer.hash(token);
    }
    if (token instanceof TokenRange) {
      token = token.end;
    }
    let keyspace;
    if (keyspaceName) {
      keyspace = this.keyspaces[keyspaceName];
      if (!keyspace) {
        // the keyspace was not found, the metadata should be loaded beforehand
        return null;
      }
    }
    let i = utils.binarySearch(this.ring, token, (t1, t2) => t1.compare(t2));
    if (i < 0) {
      i = ~i;
    }
    if (i >= this.ring.length) {
      //it circled back
      i = i % this.ring.length;
    }
    const closestToken = this.ringTokensAsStrings[i];
    if (!keyspaceName) {
      return [this.primaryReplicas[closestToken]];
    }
    const replicas = this._getKeyspaceReplicas(keyspace);
    return replicas[closestToken];
  }

  /**
   * Gets the token ranges that define data distribution in the ring.