documentation: new server reflection tutorial

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+# gRPC Server Reflection Tutorial
+
+gRPC Server Reflection provides information about publicly-accessible gRPC
+services on a server, and assists clients at runtime with constructing RPC
+requests and responses without precompiled service information. It is used by
+the gRPC command line tool (gRPC CLI), which can be used to introspect server
+protos and send/receive test RPCs. Reflection is only supported for
+proto-based services.
+
+## Enable Server Reflection
+
+gRPC-Java Server Reflection is implemented by
+`io.grpc.protobuf.service.ProtoReflectionService` in the `grpc-services`
+package. To enable server reflection, you need to add the
+`ProtoReflectionService` to your gRPC server.
+
+For example, to enable server reflection in
+`examples/src/main/java/io/grpc/examples/helloworld/HelloWorldServer.java`, we
+need to make the following changes:
+
+```diff
+--- a/examples/build.gradle
++++ b/examples/build.gradle
+@@ -27,6 +27,7 @@ def grpcVersion = '1.1.0-SNAPSHOT' // CURRENT_GRPC_VERSION
+ dependencies {
+   compile "io.grpc:grpc-netty:${grpcVersion}"
+   compile "io.grpc:grpc-protobuf:${grpcVersion}"
++  compile "io.grpc:grpc-services:${grpcVersion}"
+   compile "io.grpc:grpc-stub:${grpcVersion}"
+
+   testCompile "junit:junit:4.11"
+diff --git a/examples/src/main/java/io/grpc/examples/helloworld/HelloWorldServer.java b/examples/src/main/java/io/grpc/examples/helloworld/HelloWorldServer.java
+index ce1158a4..788bcc62 100644
+--- a/examples/src/main/java/io/grpc/examples/helloworld/HelloWorldServer.java
++++ b/examples/src/main/java/io/grpc/examples/helloworld/HelloWorldServer.java
+@@ -33,6 +33,7 @@ package io.grpc.examples.helloworld;
+
+ import io.grpc.Server;
+ import io.grpc.ServerBuilder;
++import io.grpc.protobuf.service.ProtoReflectionService;
+ import io.grpc.stub.StreamObserver;
+
+ import java.io.IOException;
+@@ -51,6 +52,7 @@ public class HelloWorldServer {
+     int port = 50051;
+     server = ServerBuilder.forPort(port)
+         .addService(new GreeterImpl())
++        .addService(ProtoReflectionService.getInstance())
+         .build()
+         .start();
+     logger.info("Server started, listening on " + port);
+```
+
+In the following examples, we assume you have made these changes to
+enable reflection in `HelloWorldServer.java`.
+
+## gRPC CLI
+
+After enabling server reflection in a server application, you can use gRPC
+CLI to get information about its available services. gRPC CLI is written
+in C++. Instructions on how to build gRPC CLI can be found at
+[command_line_tool.md](https://github.com/grpc/grpc/blob/master/doc/command_line_tool.md).
+
+## Use gRPC CLI to check services
+
+First, build and start the `hello-world-server`:
+
+```sh
+$ cd examples/
+$ ./gradlew installDist
+$ build/install/examples/bin/hello-world-server
+```
+
+Open a new terminal and make sure you are in the directory where the `grpc_cli`
+binary is located:
+
+```sh
+$ cd <grpc-cpp-directory>/bins/opt
+```
+
+### List services
+
+`grpc_cli ls` command lists services and methods exposed at a given port:
+
+- List all the services exposed at a given port
+
+  ```sh
+  $ ./grpc_cli ls localhost:50051
+  ```
+
+  output:
+  ```sh
+  helloworld.Greeter
+  grpc.reflection.v1alpha.ServerReflection
+  ```
+
+- List one service with details
+
+  `grpc_cli ls` command inspects a service given its full name (in the format of
+  \<package\>.\<service\>). It can print information with a long listing format
+  when `-l` flag is set. This flag can be used to get more details about a
+  service.
+
+  ```sh
+  $ ./grpc_cli ls localhost:50051 helloworld.Greeter -l
+  ```
+
+  output:
+  ```sh
+  filename: helloworld.proto
+  package: helloworld;
+  service Greeter {
+    rpc SayHello(helloworld.HelloRequest) returns (helloworld.HelloReply) {}
+  }
+
+  ```
+
+### List methods
+
+- List one method with details
+
+  `grpc_cli ls` command also inspects a method given its full name (in the
+  format of \<package\>.\<service\>.\<method\>).
+
+  ```sh
+  $ ./grpc_cli ls localhost:50051 helloworld.Greeter.SayHello -l
+  ```
+
+  output:
+  ```sh
+    rpc SayHello(helloworld.HelloRequest) returns (helloworld.HelloReply) {}
+  ```
+
+### Inspect message types
+
+We can use`grpc_cli type` command to inspect request/response types given the
+full name of the type (in the format of \<package\>.\<type\>).
+
+- Get information about the request type
+
+  ```sh
+  $ ./grpc_cli type localhost:50051 helloworld.HelloRequest
+  ```
+
+  output:
+  ```sh
+  message HelloRequest {
+    optional string name = 1[json_name = "name"];
+  }
+  ```
+
+### Call a remote method
+
+We can send RPCs to a server and get responses using `grpc_cli call` command.
+
+- Call a unary method
+
+  ```sh
+  $ ./grpc_cli call localhost:50051 SayHello "name: 'gRPC CLI'"
+  ```
+
+  output:
+  ```sh
+  message: "Hello gRPC CLI"
+  ```