public static Optional<ServerCall<?>> getCurrentServerCallWithCellScanner() {
    return getCurrentCall().filter(c -> c instanceof ServerCall)
      .filter(c -> c.getCellScanner() != null).map(c -> (ServerCall<?>) c);
  }
Just return the current rpc call if it is a {@link ServerCall} and also has {@link CellScanner}
attached.
<p/>
Mainly used for reference counting as {@link CellScanner} may reference non heap memory.
hbase-server/src/main/java/org/apache/hadoop/hbase/ipc/RpcServer.java