diff --git a/hbase-endpoint/src/main/java/org/apache/hadoop/hbase/client/coprocessor/AggregationClient.java b/hbase-endpoint/src/main/java/org/apache/hadoop/hbase/client/coprocessor/AggregationClient.java
index cde7d41d9c9..d2363425fee 100644
--- a/hbase-endpoint/src/main/java/org/apache/hadoop/hbase/client/coprocessor/AggregationClient.java
+++ b/hbase-endpoint/src/main/java/org/apache/hadoop/hbase/client/coprocessor/AggregationClient.java
@@ -49,7 +49,6 @@ import org.apache.hadoop.hbase.client.Scan;
 import org.apache.hadoop.hbase.client.Table;
 import org.apache.hadoop.hbase.coprocessor.ColumnInterpreter;
 import org.apache.hadoop.hbase.ipc.CoprocessorRpcUtils;
-import org.apache.hadoop.hbase.ipc.ServerRpcController;
 import org.apache.hadoop.hbase.protobuf.ProtobufUtil;
 import org.apache.hadoop.hbase.protobuf.generated.AggregateProtos.AggregateRequest;
 import org.apache.hadoop.hbase.protobuf.generated.AggregateProtos.AggregateResponse;
@@ -59,6 +58,8 @@ import org.apache.hadoop.hbase.util.Pair;
 
 import com.google.protobuf.ByteString;
 import com.google.protobuf.Message;
+import com.google.protobuf.RpcCallback;
+import com.google.protobuf.RpcController;
 
 /**
  * This client class is for invoking the aggregate functions deployed on the
@@ -81,12 +82,59 @@ import com.google.protobuf.Message;
  * </ul>
  * <p>Call {@link #close()} when done.
  */
-@InterfaceAudience.Private
+@InterfaceAudience.Public
 public class AggregationClient implements Closeable {
   // TODO: This class is not used.  Move to examples?
   private static final Log log = LogFactory.getLog(AggregationClient.class);
   private final Connection connection;
 
+  /**
+   * An RpcController implementation for use here in this endpoint.
+   */
+  static class AggregationClientRpcController implements RpcController {
+    private String errorText;
+    private boolean cancelled = false;
+    private boolean failed = false;
+
+    @Override
+    public String errorText() {
+      return this.errorText;
+    }
+
+    @Override
+    public boolean failed() {
+      return this.failed;
+    }
+
+    @Override
+    public boolean isCanceled() {
+      return this.cancelled;
+    }
+
+    @Override
+    public void notifyOnCancel(RpcCallback<Object> arg0) {
+      throw new UnsupportedOperationException();
+    }
+
+    @Override
+    public void reset() {
+      this.errorText = null;
+      this.cancelled = false;
+      this.failed = false;
+    }
+
+    @Override
+    public void setFailed(String errorText) {
+      this.failed = true;
+      this.errorText = errorText;
+    }
+
+    @Override
+    public void startCancel() {
+      this.cancelled = true;
+    }
+  }
+
   /**
    * Constructor with Conf object
    * @param cfg
@@ -160,13 +208,13 @@ public class AggregationClient implements Closeable {
         new Batch.Call<AggregateService, R>() {
           @Override
           public R call(AggregateService instance) throws IOException {
-            ServerRpcController controller = new ServerRpcController();
+            RpcController controller = new AggregationClientRpcController();
             CoprocessorRpcUtils.BlockingRpcCallback<AggregateResponse> rpcCallback =
                 new CoprocessorRpcUtils.BlockingRpcCallback<AggregateResponse>();
             instance.getMax(controller, requestArg, rpcCallback);
             AggregateResponse response = rpcCallback.get();
-            if (controller.failedOnException()) {
-              throw controller.getFailedOn();
+            if (controller.failed()) {
+              throw new IOException(controller.errorText());
             }
             if (response.getFirstPartCount() > 0) {
               ByteString b = response.getFirstPart(0);
@@ -248,13 +296,13 @@ public class AggregationClient implements Closeable {
 
           @Override
           public R call(AggregateService instance) throws IOException {
-            ServerRpcController controller = new ServerRpcController();
+            RpcController controller = new AggregationClientRpcController();
             CoprocessorRpcUtils.BlockingRpcCallback<AggregateResponse> rpcCallback =
                 new CoprocessorRpcUtils.BlockingRpcCallback<AggregateResponse>();
             instance.getMin(controller, requestArg, rpcCallback);
             AggregateResponse response = rpcCallback.get();
-            if (controller.failedOnException()) {
-              throw controller.getFailedOn();
+            if (controller.failed()) {
+              throw new IOException(controller.errorText());
             }
             if (response.getFirstPartCount() > 0) {
               ByteString b = response.getFirstPart(0);
@@ -323,13 +371,13 @@ public class AggregationClient implements Closeable {
         new Batch.Call<AggregateService, Long>() {
           @Override
           public Long call(AggregateService instance) throws IOException {
-            ServerRpcController controller = new ServerRpcController();
+            RpcController controller = new AggregationClientRpcController();
             CoprocessorRpcUtils.BlockingRpcCallback<AggregateResponse> rpcCallback =
                 new CoprocessorRpcUtils.BlockingRpcCallback<AggregateResponse>();
             instance.getRowNum(controller, requestArg, rpcCallback);
             AggregateResponse response = rpcCallback.get();
-            if (controller.failedOnException()) {
-              throw controller.getFailedOn();
+            if (controller.failed()) {
+              throw new IOException(controller.errorText());
             }
             byte[] bytes = getBytesFromResponse(response.getFirstPart(0));
             ByteBuffer bb = ByteBuffer.allocate(8).put(bytes);
@@ -388,14 +436,14 @@ public class AggregationClient implements Closeable {
         new Batch.Call<AggregateService, S>() {
           @Override
           public S call(AggregateService instance) throws IOException {
-            ServerRpcController controller = new ServerRpcController();
+            RpcController controller = new AggregationClientRpcController();
             // Not sure what is going on here why I have to do these casts. TODO.
             CoprocessorRpcUtils.BlockingRpcCallback<AggregateResponse> rpcCallback =
                 new CoprocessorRpcUtils.BlockingRpcCallback<AggregateResponse>();
             instance.getSum(controller, requestArg, rpcCallback);
             AggregateResponse response = rpcCallback.get();
-            if (controller.failedOnException()) {
-              throw controller.getFailedOn();
+            if (controller.failed()) {
+              throw new IOException(controller.errorText());
             }
             if (response.getFirstPartCount() == 0) {
               return null;
@@ -456,13 +504,13 @@ public class AggregationClient implements Closeable {
         new Batch.Call<AggregateService, Pair<S, Long>>() {
           @Override
           public Pair<S, Long> call(AggregateService instance) throws IOException {
-            ServerRpcController controller = new ServerRpcController();
+            RpcController controller = new AggregationClientRpcController();
             CoprocessorRpcUtils.BlockingRpcCallback<AggregateResponse> rpcCallback =
                 new CoprocessorRpcUtils.BlockingRpcCallback<AggregateResponse>();
             instance.getAvg(controller, requestArg, rpcCallback);
             AggregateResponse response = rpcCallback.get();
-            if (controller.failedOnException()) {
-              throw controller.getFailedOn();
+            if (controller.failed()) {
+              throw new IOException(controller.errorText());
             }
             Pair<S, Long> pair = new Pair<S, Long>(null, 0L);
             if (response.getFirstPartCount() == 0) {
@@ -560,13 +608,13 @@ public class AggregationClient implements Closeable {
         new Batch.Call<AggregateService, Pair<List<S>, Long>>() {
           @Override
           public Pair<List<S>, Long> call(AggregateService instance) throws IOException {
-            ServerRpcController controller = new ServerRpcController();
+            RpcController controller = new AggregationClientRpcController();
             CoprocessorRpcUtils.BlockingRpcCallback<AggregateResponse> rpcCallback =
                 new CoprocessorRpcUtils.BlockingRpcCallback<AggregateResponse>();
             instance.getStd(controller, requestArg, rpcCallback);
             AggregateResponse response = rpcCallback.get();
-            if (controller.failedOnException()) {
-              throw controller.getFailedOn();
+            if (controller.failed()) {
+              throw new IOException(controller.errorText());
             }
             Pair<List<S>, Long> pair = new Pair<List<S>, Long>(new ArrayList<S>(), 0L);
             if (response.getFirstPartCount() == 0) {
@@ -676,13 +724,13 @@ public class AggregationClient implements Closeable {
         new Batch.Call<AggregateService, List<S>>() {
           @Override
           public List<S> call(AggregateService instance) throws IOException {
-            ServerRpcController controller = new ServerRpcController();
+            RpcController controller = new AggregationClientRpcController();
             CoprocessorRpcUtils.BlockingRpcCallback<AggregateResponse> rpcCallback =
                 new CoprocessorRpcUtils.BlockingRpcCallback<AggregateResponse>();
             instance.getMedian(controller, requestArg, rpcCallback);
             AggregateResponse response = rpcCallback.get();
-            if (controller.failedOnException()) {
-              throw controller.getFailedOn();
+            if (controller.failed()) {
+              throw new IOException(controller.errorText());
             }
 
             List<S> list = new ArrayList<S>();