public void invalidateNamespace(String ns, long opTimeout)
      throws MemcachedException, InterruptedException, TimeoutException {
    String key = this.getNSKey(ns);
    this.incr(key, 1, System.currentTimeMillis(), opTimeout); // this method calls preProcessKey, which encodes ns
  }
...
private <T> Object get0(String key, final long timeout, final CommandType cmdType,
      final Transcoder<T> transcoder)
      throws TimeoutException, InterruptedException, MemcachedException {
    key = this.preProcessKey(key); // calls getNamespace
    byte[] keyBytes = ByteUtils.getBytes(key);
    ByteUtils.checkKey(keyBytes);
    return this.fetch0(key, keyBytes, cmdType, timeout, transcoder);
  }
...
public String getNamespace(String ns)
      throws TimeoutException, InterruptedException, MemcachedException {
    String key = this.keyProvider.process(this.getNSKey(ns));
    byte[] keyBytes = ByteUtils.getBytes(key);
    ByteUtils.checkKey(keyBytes);
    Object item = this.fetch0(key, keyBytes, CommandType.GET_ONE, this.opTimeout, this.transcoder); // get namespace without encoding
    while (item == null) {
      item = String.valueOf(System.nanoTime());
      boolean added = this.add0(key, 0, item, this.transcoder, this.opTimeout);
      if (!added) {
        item = this.fetch0(key, keyBytes, CommandType.GET_ONE, this.opTimeout, this.transcoder);
      }
    }
    String namespace = item.toString();
    if (!ByteUtils.isNumber(namespace)) {
      throw new IllegalStateException(
          "Namespace key already has value.The key is:" + key + ",and the value is:" + namespace);
    }
    return namespace;
  }