Merge pull request #15816 from jtattermusch/dedup_cpp_routeguide

Deduplicate C++ routeguide

examples/cpp/cpptutorial.md

@@ -1,488 +0,0 @@
-# gRPC Basics: C++
-
-This tutorial provides a basic C++ programmer's introduction to working with
-gRPC. By walking through this example you'll learn how to:
-
-- Define a service in a `.proto` file.
-- Generate server and client code using the protocol buffer compiler.
-- Use the C++ gRPC API to write a simple client and server for your service.
-
-It assumes that you are familiar with
-[protocol buffers](https://developers.google.com/protocol-buffers/docs/overview).
-Note that the example in this tutorial uses the proto3 version of the protocol
-buffers language, which is currently in alpha release: you can find out more in
-the [proto3 language guide](https://developers.google.com/protocol-buffers/docs/proto3)
-and see the [release notes](https://github.com/google/protobuf/releases) for the
-new version in the protocol buffers Github repository.
-
-## Why use gRPC?
-
-Our example is a simple route mapping application that lets clients get
-information about features on their route, create a summary of their route, and
-exchange route information such as traffic updates with the server and other
-clients.
-
-With gRPC we can define our service once in a `.proto` file and implement clients
-and servers in any of gRPC's supported languages, which in turn can be run in
-environments ranging from servers inside Google to your own tablet - all the
-complexity of communication between different languages and environments is
-handled for you by gRPC. We also get all the advantages of working with protocol
-buffers, including efficient serialization, a simple IDL, and easy interface
-updating.
-
-## Example code and setup
-
-The example code for our tutorial is in [examples/cpp/route_guide](route_guide).
-You also should have the relevant tools installed to generate the server and
-client interface code - if you don't already, follow the setup instructions in
-[INSTALL.md](../../INSTALL.md).
-
-## Defining the service
-
-Our first step is to define the gRPC *service* and the method *request* and
-*response* types using
-[protocol buffers](https://developers.google.com/protocol-buffers/docs/overview).
-You can see the complete `.proto` file in
-[`examples/protos/route_guide.proto`](../protos/route_guide.proto).
-
-To define a service, you specify a named `service` in your `.proto` file:
-
-```protobuf
-service RouteGuide {
-   ...
-}
-```
-
-Then you define `rpc` methods inside your service definition, specifying their
-request and response types. gRPC lets you define four kinds of service method,
-all of which are used in the `RouteGuide` service:
-
-- A *simple RPC* where the client sends a request to the server using the stub
-  and waits for a response to come back, just like a normal function call.
-
-```protobuf
-   // Obtains the feature at a given position.
-   rpc GetFeature(Point) returns (Feature) {}
-```
-
-- A *server-side streaming RPC* where the client sends a request to the server
-  and gets a stream to read a sequence of messages back. The client reads from
-  the returned stream until there are no more messages. As you can see in our
-  example, you specify a server-side streaming method by placing the `stream`
-  keyword before the *response* type.
-
-```protobuf
-  // Obtains the Features available within the given Rectangle.  Results are
-  // streamed rather than returned at once (e.g. in a response message with a
-  // repeated field), as the rectangle may cover a large area and contain a
-  // huge number of features.
-  rpc ListFeatures(Rectangle) returns (stream Feature) {}
-```
-
-- A *client-side streaming RPC* where the client writes a sequence of messages
-  and sends them to the server, again using a provided stream. Once the client
-  has finished writing the messages, it waits for the server to read them all
-  and return its response. You specify a client-side streaming method by placing
-  the `stream` keyword before the *request* type.
-
-```protobuf
-  // Accepts a stream of Points on a route being traversed, returning a
-  // RouteSummary when traversal is completed.
-  rpc RecordRoute(stream Point) returns (RouteSummary) {}
-```
-
-- A *bidirectional streaming RPC* where both sides send a sequence of messages
-  using a read-write stream. The two streams operate independently, so clients
-  and servers can read and write in whatever order they like: for example, the
-  server could wait to receive all the client messages before writing its
-  responses, or it could alternately read a message then write a message, or
-  some other combination of reads and writes. The order of messages in each
-  stream is preserved. You specify this type of method by placing the `stream`
-  keyword before both the request and the response.
-
-```protobuf
-  // Accepts a stream of RouteNotes sent while a route is being traversed,
-  // while receiving other RouteNotes (e.g. from other users).
-  rpc RouteChat(stream RouteNote) returns (stream RouteNote) {}
-```
-
-Our `.proto` file also contains protocol buffer message type definitions for all
-the request and response types used in our service methods - for example, here's
-the `Point` message type:
-
-```protobuf
-// Points are represented as latitude-longitude pairs in the E7 representation
-// (degrees multiplied by 10**7 and rounded to the nearest integer).
-// Latitudes should be in the range +/- 90 degrees and longitude should be in
-// the range +/- 180 degrees (inclusive).
-message Point {
-  int32 latitude = 1;
-  int32 longitude = 2;
-}
-```
-
-## Generating client and server code
-
-Next we need to generate the gRPC client and server interfaces from our `.proto`
-service definition. We do this using the protocol buffer compiler `protoc` with
-a special gRPC C++ plugin.
-
-For simplicity, we've provided a [Makefile](route_guide/Makefile) that runs
-`protoc` for you with the appropriate plugin, input, and output (if you want to
-run this yourself, make sure you've installed protoc and followed the gRPC code
-[installation instructions](../../INSTALL.md) first):
-
-```shell
-$ make route_guide.grpc.pb.cc route_guide.pb.cc
-```
-
-which actually runs:
-
-```shell
-$ protoc -I ../../protos --grpc_out=. --plugin=protoc-gen-grpc=`which grpc_cpp_plugin` ../../protos/route_guide.proto
-$ protoc -I ../../protos --cpp_out=. ../../protos/route_guide.proto
-```
-
-Running this command generates the following files in your current directory:
-- `route_guide.pb.h`, the header which declares your generated message classes
-- `route_guide.pb.cc`, which contains the implementation of your message classes
-- `route_guide.grpc.pb.h`, the header which declares your generated service
-  classes
-- `route_guide.grpc.pb.cc`, which contains the implementation of your service
-  classes
-
-These contain:
-- All the protocol buffer code to populate, serialize, and retrieve our request
-  and response message types
-- A class called `RouteGuide` that contains
-   - a remote interface type (or *stub*) for clients to call with the methods
-     defined in the `RouteGuide` service.
-   - two abstract interfaces for servers to implement, also with the methods
-     defined in the `RouteGuide` service.
-
-
-<a name="server"></a>
-## Creating the server
-
-First let's look at how we create a `RouteGuide` server. If you're only
-interested in creating gRPC clients, you can skip this section and go straight
-to [Creating the client](#client) (though you might find it interesting
-anyway!).
-
-There are two parts to making our `RouteGuide` service do its job:
-- Implementing the service interface generated from our service definition:
-  doing the actual "work" of our service.
-- Running a gRPC server to listen for requests from clients and return the
-  service responses.
-
-You can find our example `RouteGuide` server in
-[route_guide/route_guide_server.cc](route_guide/route_guide_server.cc). Let's
-take a closer look at how it works.
-
-### Implementing RouteGuide
-
-As you can see, our server has a `RouteGuideImpl` class that implements the
-generated `RouteGuide::Service` interface:
-
-```cpp
-class RouteGuideImpl final : public RouteGuide::Service {
-...
-}
-```
-In this case we're implementing the *synchronous* version of `RouteGuide`, which
-provides our default gRPC server behaviour. It's also possible to implement an
-asynchronous interface, `RouteGuide::AsyncService`, which allows you to further
-customize your server's threading behaviour, though we won't look at this in
-this tutorial.
-
-`RouteGuideImpl` implements all our service methods. Let's look at the simplest
-type first, `GetFeature`, which just gets a `Point` from the client and returns
-the corresponding feature information from its database in a `Feature`.
-
-```cpp
-  Status GetFeature(ServerContext* context, const Point* point,
-                    Feature* feature) override {
-    feature->set_name(GetFeatureName(*point, feature_list_));
-    feature->mutable_location()->CopyFrom(*point);
-    return Status::OK;
-  }
-```
-
-The method is passed a context object for the RPC, the client's `Point` protocol
-buffer request, and a `Feature` protocol buffer to fill in with the response
-information. In the method we populate the `Feature` with the appropriate
-information, and then `return` with an `OK` status to tell gRPC that we've
-finished dealing with the RPC and that the `Feature` can be returned to the
-client.
-
-Now let's look at something a bit more complicated - a streaming RPC.
-`ListFeatures` is a server-side streaming RPC, so we need to send back multiple
-`Feature`s to our client.
-
-```cpp
-Status ListFeatures(ServerContext* context, const Rectangle* rectangle,
-                    ServerWriter<Feature>* writer) override {
-  auto lo = rectangle->lo();
-  auto hi = rectangle->hi();
-  long left = std::min(lo.longitude(), hi.longitude());
-  long right = std::max(lo.longitude(), hi.longitude());
-  long top = std::max(lo.latitude(), hi.latitude());
-  long bottom = std::min(lo.latitude(), hi.latitude());
-  for (const Feature& f : feature_list_) {
-    if (f.location().longitude() >= left &&
-        f.location().longitude() <= right &&
-        f.location().latitude() >= bottom &&
-        f.location().latitude() <= top) {
-      writer->Write(f);
-    }
-  }
-  return Status::OK;
-}
-```
-
-As you can see, instead of getting simple request and response objects in our
-method parameters, this time we get a request object (the `Rectangle` in which
-our client wants to find `Feature`s) and a special `ServerWriter` object. In the
-method, we populate as many `Feature` objects as we need to return, writing them
-to the `ServerWriter` using its `Write()` method. Finally, as in our simple RPC,
-we `return Status::OK` to tell gRPC that we've finished writing responses.
-
-If you look at the client-side streaming method `RecordRoute` you'll see it's
-quite similar, except this time we get a `ServerReader` instead of a request
-object and a single response. We use the `ServerReader`s `Read()` method to
-repeatedly read in our client's requests to a request object (in this case a
-`Point`) until there are no more messages: the server needs to check the return
-value of `Read()` after each call. If `true`, the stream is still good and it
-can continue reading; if `false` the message stream has ended.
-
-```cpp
-while (stream->Read(&point)) {
-  ...//process client input
-}
-```
-Finally, let's look at our bidirectional streaming RPC `RouteChat()`.
-
-```cpp
-  Status RouteChat(ServerContext* context,
-                   ServerReaderWriter<RouteNote, RouteNote>* stream) override {
-    std::vector<RouteNote> received_notes;
-    RouteNote note;
-    while (stream->Read(&note)) {
-      for (const RouteNote& n : received_notes) {
-        if (n.location().latitude() == note.location().latitude() &&
-            n.location().longitude() == note.location().longitude()) {
-          stream->Write(n);
-        }
-      }
-      received_notes.push_back(note);
-    }
-
-    return Status::OK;
-  }
-```
-
-This time we get a `ServerReaderWriter` that can be used to read *and* write
-messages. The syntax for reading and writing here is exactly the same as for our
-client-streaming and server-streaming methods. Although each side will always
-get the other's messages in the order they were written, both the client and
-server can read and write in any order — the streams operate completely
-independently.
-
-### Starting the server
-
-Once we've implemented all our methods, we also need to start up a gRPC server
-so that clients can actually use our service. The following snippet shows how we
-do this for our `RouteGuide` service:
-
-```cpp
-void RunServer(const std::string& db_path) {
-  std::string server_address("0.0.0.0:50051");
-  RouteGuideImpl service(db_path);
-
-  ServerBuilder builder;
-  builder.AddListeningPort(server_address, grpc::InsecureServerCredentials());
-  builder.RegisterService(&service);
-  std::unique_ptr<Server> server(builder.BuildAndStart());
-  std::cout << "Server listening on " << server_address << std::endl;
-  server->Wait();
-}
-```
-As you can see, we build and start our server using a `ServerBuilder`. To do this, we:
-
-1. Create an instance of our service implementation class `RouteGuideImpl`.
-1. Create an instance of the factory `ServerBuilder` class.
-1. Specify the address and port we want to use to listen for client requests
-   using the builder's `AddListeningPort()` method.
-1. Register our service implementation with the builder.
-1. Call `BuildAndStart()` on the builder to create and start an RPC server for
-   our service.
-1. Call `Wait()` on the server to do a blocking wait until process is killed or
-   `Shutdown()` is called.
-
-<a name="client"></a>
-## Creating the client
-
-In this section, we'll look at creating a C++ client for our `RouteGuide`
-service. You can see our complete example client code in
-[route_guide/route_guide_client.cc](route_guide/route_guide_client.cc).
-
-### Creating a stub
-
-To call service methods, we first need to create a *stub*.
-
-First we need to create a gRPC *channel* for our stub, specifying the server
-address and port we want to connect to without SSL:
-
-```cpp
-grpc::CreateChannel("localhost:50051", grpc::InsecureChannelCredentials());
-```
-
-Now we can use the channel to create our stub using the `NewStub` method
-provided in the `RouteGuide` class we generated from our `.proto`.
-
-```cpp
-public:
- RouteGuideClient(std::shared_ptr<Channel> channel, const std::string& db)
-     : stub_(RouteGuide::NewStub(channel)) {
-   ...
- }
-```
-
-### Calling service methods
-
-Now let's look at how we call our service methods. Note that in this tutorial
-we're calling the *blocking/synchronous* versions of each method: this means
-that the RPC call waits for the server to respond, and will either return a
-response or raise an exception.
-
-#### Simple RPC
-
-Calling the simple RPC `GetFeature` is nearly as straightforward as calling a
-local method.
-
-```cpp
-  Point point;
-  Feature feature;
-  point = MakePoint(409146138, -746188906);
-  GetOneFeature(point, &feature);
-
-...
-
-  bool GetOneFeature(const Point& point, Feature* feature) {
-    ClientContext context;
-    Status status = stub_->GetFeature(&context, point, feature);
-    ...
-  }
-```
-
-As you can see, we create and populate a request protocol buffer object (in our
-case `Point`), and create a response protocol buffer object for the server to
-fill in. We also create a `ClientContext` object for our call - you can
-optionally set RPC configuration values on this object, such as deadlines,
-though for now we'll use the default settings. Note that you cannot reuse this
-object between calls. Finally, we call the method on the stub, passing it the
-context, request, and response. If the method returns `OK`, then we can read the
-response information from the server from our response object.
-
-```cpp
-std::cout << "Found feature called " << feature->name()  << " at "
-          << feature->location().latitude()/kCoordFactor_ << ", "
-          << feature->location().longitude()/kCoordFactor_ << std::endl;
-```
-
-#### Streaming RPCs
-
-Now let's look at our streaming methods. If you've already read [Creating the
-server](#server) some of this may look very familiar - streaming RPCs are
-implemented in a similar way on both sides. Here's where we call the server-side
-streaming method `ListFeatures`, which returns a stream of geographical
-`Feature`s:
-
-```cpp
-std::unique_ptr<ClientReader<Feature> > reader(
-    stub_->ListFeatures(&context, rect));
-while (reader->Read(&feature)) {
-  std::cout << "Found feature called "
-            << feature.name() << " at "
-            << feature.location().latitude()/kCoordFactor_ << ", "
-            << feature.location().longitude()/kCoordFactor_ << std::endl;
-}
-Status status = reader->Finish();
-```
-
-Instead of passing the method a context, request, and response, we pass it a
-context and request and get a `ClientReader` object back. The client can use the
-`ClientReader` to read the server's responses. We use the `ClientReader`s
-`Read()` method to repeatedly read in the server's responses to a response
-protocol buffer object (in this case a `Feature`) until there are no more
-messages: the client needs to check the return value of `Read()` after each
-call. If `true`, the stream is still good and it can continue reading; if
-`false` the message stream has ended. Finally, we call `Finish()` on the stream
-to complete the call and get our RPC status.
-
-The client-side streaming method `RecordRoute` is similar, except there we pass
-the method a context and response object and get back a `ClientWriter`.
-
-```cpp
-    std::unique_ptr<ClientWriter<Point> > writer(
-        stub_->RecordRoute(&context, &stats));
-    for (int i = 0; i < kPoints; i++) {
-      const Feature& f = feature_list_[feature_distribution(generator)];
-      std::cout << "Visiting point "
-                << f.location().latitude()/kCoordFactor_ << ", "
-                << f.location().longitude()/kCoordFactor_ << std::endl;
-      if (!writer->Write(f.location())) {
-        // Broken stream.
-        break;
-      }
-      std::this_thread::sleep_for(std::chrono::milliseconds(
-          delay_distribution(generator)));
-    }
-    writer->WritesDone();
-    Status status = writer->Finish();
-    if (status.IsOk()) {
-      std::cout << "Finished trip with " << stats.point_count() << " points\n"
-                << "Passed " << stats.feature_count() << " features\n"
-                << "Travelled " << stats.distance() << " meters\n"
-                << "It took " << stats.elapsed_time() << " seconds"
-                << std::endl;
-    } else {
-      std::cout << "RecordRoute rpc failed." << std::endl;
-    }
-```
-
-Once we've finished writing our client's requests to the stream using `Write()`,
-we need to call `WritesDone()` on the stream to let gRPC know that we've
-finished writing, then `Finish()` to complete the call and get our RPC status.
-If the status is `OK`, our response object that we initially passed to
-`RecordRoute()` will be populated with the server's response.
-
-Finally, let's look at our bidirectional streaming RPC `RouteChat()`. In this
-case, we just pass a context to the method and get back a `ClientReaderWriter`,
-which we can use to both write and read messages.
-
-```cpp
-std::shared_ptr<ClientReaderWriter<RouteNote, RouteNote> > stream(
-    stub_->RouteChat(&context));
-```
-
-The syntax for reading and writing here is exactly the same as for our
-client-streaming and server-streaming methods. Although each side will always
-get the other's messages in the order they were written, both the client and
-server can read and write in any order — the streams operate completely
-independently.
-
-## Try it out!
-
-Build client and server:
-```shell
-$ make
-```
-Run the server, which will listen on port 50051:
-```shell
-$ ./route_guide_server
-```
-Run the client (in a different terminal):
-```shell
-$ ./route_guide_client
-```

examples/cpp/route_guide/README.md

@@ -0,0 +1,6 @@
+# gRPC Basics: C++ sample code
+
+The files in this folder are the samples used in [gRPC Basics: C++][],
+a detailed tutorial for using gRPC in C++.
+
+[gRPC Basics: C++]:https://grpc.io/docs/tutorials/basic/c.html