private IOException badResponse(String debug) {
    return new IOException(String.format("Invalid result for request %s. Will be retried", debug));
  }
For describing the actual asynchronous rpc call.
<p/>
Typically, you can use lambda expression to implement this interface as

<pre>
(c, s, d) -&gt; s.xxx(c, your request here, d)
</pre>
hbase-client/src/main/java/org/apache/hadoop/hbase/client/AbstractRpcBasedConnectionRegistry.java