HBASE-6104. Require EXEC permission to call coprocessor endpoints. Add missing file

git-svn-id: https://svn.apache.org/repos/asf/hbase/trunk@1553347 13f79535-47bb-0310-9956-ffa450edef68

hbase-server/src/main/java/org/apache/hadoop/hbase/coprocessor/EndpointObserver.java

@@ -0,0 +1,65 @@
+/*
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.hadoop.hbase.coprocessor;
+
+import java.io.IOException;
+
+import org.apache.hadoop.classification.InterfaceAudience;
+import org.apache.hadoop.classification.InterfaceStability;
+import org.apache.hadoop.hbase.Coprocessor;
+import org.apache.hadoop.hbase.HBaseInterfaceAudience;
+
+import com.google.protobuf.Message;
+import com.google.protobuf.Service;
+
+/**
+ * Coprocessors implement this interface to observe and mediate endpoint invocations
+ * on a region.
+ */
+@InterfaceAudience.LimitedPrivate(HBaseInterfaceAudience.COPROC)
+@InterfaceStability.Evolving
+public interface EndpointObserver extends Coprocessor {
+
+  /**
+   * Called before an Endpoint service method is invoked.
+   * The request message can be altered by returning a new instance. Throwing an
+   * exception will abort the invocation.
+   * Calling {@link org.apache.hadoop.hbase.coprocessor.ObserverContext#bypass()} has no
+   * effect in this hook.
+   * @param ctx the environment provided by the region server
+   * @param service the endpoint service
+   * @param methodName the invoked service method
+   * @param request the request message
+   * @return the possibly modified message
+   * @throws IOException
+   */
+  Message preEndpointInvocation(ObserverContext<RegionCoprocessorEnvironment> ctx, Service service,
+      String methodName, Message request) throws IOException;
+
+  /**
+   * Called after an Endpoint service method is invoked. The response message can be
+   * altered using the builder.
+   * @param ctx the environment provided by the region server
+   * @param service the endpoint service
+   * @param methodName the invoked service method
+   * @param request the request message
+   * @param responseBuilder the response message builder
+   * @throws IOException
+   */
+  void postEndpointInvocation(ObserverContext<RegionCoprocessorEnvironment> ctx, Service service,
+      String methodName, Message request, Message.Builder responseBuilder) throws IOException;
+
+}