private ByteBuffer getBlobBuffer() throws IOException {
    // Find server with the blob
    for (ReplicaId replicaId : blobId.getPartition().getReplicaIds()) {
      MockServer server =
          mockServerLayout.getMockServer(replicaId.getDataNodeId().getHostname(), replicaId.getDataNodeId().getPort());
      if (server.getBlobs().containsKey(blobId.getID())) {
        return getBlobBufferFromServer(server);
      }
    }
    return null;
  }
@return the ByteBuffer for the blob contents on a server that hosts the partition.
@throws IOException
ambry-router/src/test/java/com/github/ambry/router/GetBlobOperationTest.java