Examples: unify command line flags (#32456)

1. All greeter servers now support flag `--port` to customize the listen
port.
2. All client implementation now have `--target` flag to specify the
server location.
3. ABSL is used to parse the flags to reduce the amount of boilerplate
code in the examples.

Fixes: #26989

examples/cpp/helloworld/BUILD

@@ -21,6 +21,8 @@ cc_binary(
     deps = [
         "//:grpc++",
         "//examples/protos:helloworld_cc_grpc",
+        "@com_google_absl//absl/flags:flag",
+        "@com_google_absl//absl/flags:parse",
     ],
 )
 
@@ -31,6 +33,8 @@ cc_binary(
     deps = [
         "//:grpc++",
         "//examples/protos:helloworld_cc_grpc",
+        "@com_google_absl//absl/flags:flag",
+        "@com_google_absl//absl/flags:parse",
     ],
 )
 
@@ -41,6 +45,8 @@ cc_binary(
     deps = [
         "//:grpc++",
         "//examples/protos:helloworld_cc_grpc",
+        "@com_google_absl//absl/flags:flag",
+        "@com_google_absl//absl/flags:parse",
     ],
 )
 
@@ -51,6 +57,8 @@ cc_binary(
     deps = [
         "//:grpc++",
         "//examples/protos:helloworld_cc_grpc",
+        "@com_google_absl//absl/flags:flag",
+        "@com_google_absl//absl/flags:parse",
     ],
 )
 
@@ -74,6 +82,9 @@ cc_binary(
         "//:grpc++",
         "//:grpc++_reflection",
         "//examples/protos:helloworld_cc_grpc",
+        "@com_google_absl//absl/flags:flag",
+        "@com_google_absl//absl/flags:parse",
+        "@com_google_absl//absl/strings:str_format",
     ],
 )
 
@@ -84,6 +95,9 @@ cc_binary(
     deps = [
         "//:grpc++",
         "//examples/protos:helloworld_cc_grpc",
+        "@com_google_absl//absl/flags:flag",
+        "@com_google_absl//absl/flags:parse",
+        "@com_google_absl//absl/strings:str_format",
     ],
 )
 
@@ -95,6 +109,9 @@ cc_binary(
         "//:grpc++",
         "//:grpc++_reflection",
         "//examples/protos:helloworld_cc_grpc",
+        "@com_google_absl//absl/flags:flag",
+        "@com_google_absl//absl/flags:parse",
+        "@com_google_absl//absl/strings:str_format",
     ],
 )
 

examples/cpp/helloworld/CMakeLists.txt

@@ -58,12 +58,14 @@ target_link_libraries(hw_grpc_proto
 
 # Targets greeter_[async_](client|server)
 foreach(_target
-  greeter_client greeter_server 
-  greeter_callback_client greeter_callback_server 
+  greeter_client greeter_server
+  greeter_callback_client greeter_callback_server
   greeter_async_client greeter_async_client2 greeter_async_server)
   add_executable(${_target} "${_target}.cc")
   target_link_libraries(${_target}
     hw_grpc_proto
+    absl::flags
+    absl::flags_parse
     ${_REFLECTION}
     ${_GRPC_GRPCPP}
     ${_PROTOBUF_LIBPROTOBUF})

examples/cpp/helloworld/Makefile

@@ -17,15 +17,15 @@
 HOST_SYSTEM = $(shell uname | cut -f 1 -d_)
 SYSTEM ?= $(HOST_SYSTEM)
 CXX = g++
-CPPFLAGS += `pkg-config --cflags protobuf grpc`
+CPPFLAGS += `pkg-config --cflags protobuf grpc absl_flags absl_flags_parse`
 CXXFLAGS += -std=c++14
 ifeq ($(SYSTEM),Darwin)
-LDFLAGS += -L/usr/local/lib `pkg-config --libs --static protobuf grpc++`\
+LDFLAGS += -L/usr/local/lib `pkg-config --libs --static protobuf grpc++ absl_flags absl_flags_parse`\
            -pthread\
            -lgrpc++_reflection\
            -ldl
 else
-LDFLAGS += -L/usr/local/lib `pkg-config --libs --static protobuf grpc++`\
+LDFLAGS += -L/usr/local/lib `pkg-config --libs --static protobuf grpc++ absl_flags absl_flags_parse`\
            -pthread\
            -Wl,--no-as-needed -lgrpc++_reflection -Wl,--as-needed\
            -ldl
@@ -38,7 +38,7 @@ PROTOS_PATH = ../../protos
 
 vpath %.proto $(PROTOS_PATH)
 
-all: system-check greeter_client greeter_server greeter_async_client greeter_async_client2 greeter_async_server greeter_callback_client greeter_callback_server 
+all: system-check greeter_client greeter_server greeter_async_client greeter_async_client2 greeter_async_server greeter_callback_client greeter_callback_server
 
 greeter_client: helloworld.pb.o helloworld.grpc.pb.o greeter_client.o
 	$(CXX) $^ $(LDFLAGS) -o $@
@@ -70,7 +70,7 @@ greeter_callback_server: helloworld.pb.o helloworld.grpc.pb.o greeter_callback_s
 	$(PROTOC) -I $(PROTOS_PATH) --cpp_out=. $<
 
 clean:
-	rm -f *.o *.pb.cc *.pb.h greeter_client greeter_server greeter_async_client greeter_async_client2 greeter_async_server greeter_callback_client greeter_callback_server 
+	rm -f *.o *.pb.cc *.pb.h greeter_client greeter_server greeter_async_client greeter_async_client2 greeter_async_server greeter_callback_client greeter_callback_server
 
 
 # The following is to test your system and ensure a smoother experience.

examples/cpp/helloworld/greeter_async_client.cc

@@ -20,6 +20,9 @@
 #include <memory>
 #include <string>
 
+#include "absl/flags/flag.h"
+#include "absl/flags/parse.h"
+
 #include <grpc/support/log.h>
 #include <grpcpp/grpcpp.h>
 
@@ -29,6 +32,8 @@
 #include "helloworld.grpc.pb.h"
 #endif
 
+ABSL_FLAG(std::string, target, "localhost:50051", "Server address");
+
 using grpc::Channel;
 using grpc::ClientAsyncResponseReader;
 using grpc::ClientContext;
@@ -100,12 +105,15 @@ class GreeterClient {
 };
 
 int main(int argc, char** argv) {
+  absl::ParseCommandLine(argc, argv);
   // Instantiate the client. It requires a channel, out of which the actual RPCs
-  // are created. This channel models a connection to an endpoint (in this case,
-  // localhost at port 50051). We indicate that the channel isn't authenticated
-  // (use of InsecureChannelCredentials()).
-  GreeterClient greeter(grpc::CreateChannel(
-      "localhost:50051", grpc::InsecureChannelCredentials()));
+  // are created. This channel models a connection to an endpoint specified by
+  // the argument "--target=" which is the only expected argument.
+  std::string target_str = absl::GetFlag(FLAGS_target);
+  // We indicate that the channel isn't authenticated (use of
+  // InsecureChannelCredentials()).
+  GreeterClient greeter(
+      grpc::CreateChannel(target_str, grpc::InsecureChannelCredentials()));
   std::string user("world");
   std::string reply = greeter.SayHello(user);  // The actual RPC call!
   std::cout << "Greeter received: " << reply << std::endl;

examples/cpp/helloworld/greeter_async_client2.cc

@@ -21,6 +21,9 @@
 #include <string>
 #include <thread>
 
+#include "absl/flags/flag.h"
+#include "absl/flags/parse.h"
+
 #include <grpc/support/log.h>
 #include <grpcpp/grpcpp.h>
 
@@ -30,6 +33,8 @@
 #include "helloworld.grpc.pb.h"
 #endif
 
+ABSL_FLAG(std::string, target, "localhost:50051", "Server address");
+
 using grpc::Channel;
 using grpc::ClientAsyncResponseReader;
 using grpc::ClientContext;
@@ -121,12 +126,15 @@ class GreeterClient {
 };
 
 int main(int argc, char** argv) {
+  absl::ParseCommandLine(argc, argv);
   // Instantiate the client. It requires a channel, out of which the actual RPCs
-  // are created. This channel models a connection to an endpoint (in this case,
-  // localhost at port 50051). We indicate that the channel isn't authenticated
-  // (use of InsecureChannelCredentials()).
-  GreeterClient greeter(grpc::CreateChannel(
-      "localhost:50051", grpc::InsecureChannelCredentials()));
+  // are created. This channel models a connection to an endpoint specified by
+  // the argument "--target=" which is the only expected argument.
+  std::string target_str = absl::GetFlag(FLAGS_target);
+  // We indicate that the channel isn't authenticated (use of
+  // InsecureChannelCredentials()).
+  GreeterClient greeter(
+      grpc::CreateChannel(target_str, grpc::InsecureChannelCredentials()));
 
   // Spawn reader thread that loops indefinitely
   std::thread thread_ = std::thread(&GreeterClient::AsyncCompleteRpc, &greeter);

examples/cpp/helloworld/greeter_async_server.cc

@@ -21,6 +21,10 @@
 #include <string>
 #include <thread>
 
+#include "absl/flags/flag.h"
+#include "absl/flags/parse.h"
+#include "absl/strings/str_format.h"
+
 #include <grpc/support/log.h>
 #include <grpcpp/grpcpp.h>
 
@@ -30,6 +34,8 @@
 #include "helloworld.grpc.pb.h"
 #endif
 
+ABSL_FLAG(uint16_t, port, 50051, "Server port for the service");
+
 using grpc::Server;
 using grpc::ServerAsyncResponseWriter;
 using grpc::ServerBuilder;
@@ -49,8 +55,8 @@ class ServerImpl final {
   }
 
   // There is no shutdown handling in this code.
-  void Run() {
-    std::string server_address("0.0.0.0:50051");
+  void Run(uint16_t port) {
+    std::string server_address = absl::StrFormat("0.0.0.0:%d", port);
 
     ServerBuilder builder;
     // Listen on the given address without any authentication mechanism.
@@ -164,8 +170,9 @@ class ServerImpl final {
 };
 
 int main(int argc, char** argv) {
+  absl::ParseCommandLine(argc, argv);
   ServerImpl server;
-  server.Run();
+  server.Run(absl::GetFlag(FLAGS_port));
 
   return 0;
 }

examples/cpp/helloworld/greeter_callback_client.cc

@@ -22,6 +22,9 @@
 #include <mutex>
 #include <string>
 
+#include "absl/flags/flag.h"
+#include "absl/flags/parse.h"
+
 #include <grpcpp/grpcpp.h>
 
 #ifdef BAZEL_BUILD
@@ -30,6 +33,8 @@
 #include "helloworld.grpc.pb.h"
 #endif
 
+ABSL_FLAG(std::string, target, "localhost:50051", "Server address");
+
 using grpc::Channel;
 using grpc::ClientContext;
 using grpc::Status;
@@ -89,32 +94,13 @@ class GreeterClient {
 };
 
 int main(int argc, char** argv) {
+  absl::ParseCommandLine(argc, argv);
   // Instantiate the client. It requires a channel, out of which the actual RPCs
   // are created. This channel models a connection to an endpoint specified by
   // the argument "--target=" which is the only expected argument.
+  std::string target_str = absl::GetFlag(FLAGS_target);
   // We indicate that the channel isn't authenticated (use of
   // InsecureChannelCredentials()).
-  std::string target_str;
-  std::string arg_str("--target");
-  if (argc > 1) {
-    std::string arg_val = argv[1];
-    size_t start_pos = arg_val.find(arg_str);
-    if (start_pos != std::string::npos) {
-      start_pos += arg_str.size();
-      if (arg_val[start_pos] == '=') {
-        target_str = arg_val.substr(start_pos + 1);
-      } else {
-        std::cout << "The only correct argument syntax is --target="
-                  << std::endl;
-        return 0;
-      }
-    } else {
-      std::cout << "The only acceptable argument is --target=" << std::endl;
-      return 0;
-    }
-  } else {
-    target_str = "localhost:50051";
-  }
   GreeterClient greeter(
       grpc::CreateChannel(target_str, grpc::InsecureChannelCredentials()));
   std::string user("world");

examples/cpp/helloworld/greeter_callback_server.cc

@@ -20,6 +20,10 @@
 #include <memory>
 #include <string>
 
+#include "absl/flags/flag.h"
+#include "absl/flags/parse.h"
+#include "absl/strings/str_format.h"
+
 #include <grpcpp/ext/proto_server_reflection_plugin.h>
 #include <grpcpp/grpcpp.h>
 #include <grpcpp/health_check_service_interface.h>
@@ -30,6 +34,8 @@
 #include "helloworld.grpc.pb.h"
 #endif
 
+ABSL_FLAG(uint16_t, port, 50051, "Server port for the service");
+
 using grpc::CallbackServerContext;
 using grpc::Server;
 using grpc::ServerBuilder;
@@ -53,8 +59,8 @@ class GreeterServiceImpl final : public Greeter::CallbackService {
   }
 };
 
-void RunServer() {
-  std::string server_address("0.0.0.0:50051");
+void RunServer(uint16_t port) {
+  std::string server_address = absl::StrFormat("0.0.0.0:%d", port);
   GreeterServiceImpl service;
 
   grpc::EnableDefaultHealthCheckService(true);
@@ -75,7 +81,7 @@ void RunServer() {
 }
 
 int main(int argc, char** argv) {
-  RunServer();
-
+  absl::ParseCommandLine(argc, argv);
+  RunServer(absl::GetFlag(FLAGS_port));
   return 0;
 }

examples/cpp/helloworld/greeter_client.cc

@@ -20,6 +20,9 @@
 #include <memory>
 #include <string>
 
+#include "absl/flags/flag.h"
+#include "absl/flags/parse.h"
+
 #include <grpcpp/grpcpp.h>
 
 #ifdef BAZEL_BUILD
@@ -28,6 +31,8 @@
 #include "helloworld.grpc.pb.h"
 #endif
 
+ABSL_FLAG(std::string, target, "localhost:50051", "Server address");
+
 using grpc::Channel;
 using grpc::ClientContext;
 using grpc::Status;
@@ -72,32 +77,13 @@ class GreeterClient {
 };
 
 int main(int argc, char** argv) {
+  absl::ParseCommandLine(argc, argv);
   // Instantiate the client. It requires a channel, out of which the actual RPCs
   // are created. This channel models a connection to an endpoint specified by
   // the argument "--target=" which is the only expected argument.
+  std::string target_str = absl::GetFlag(FLAGS_target);
   // We indicate that the channel isn't authenticated (use of
   // InsecureChannelCredentials()).
-  std::string target_str;
-  std::string arg_str("--target");
-  if (argc > 1) {
-    std::string arg_val = argv[1];
-    size_t start_pos = arg_val.find(arg_str);
-    if (start_pos != std::string::npos) {
-      start_pos += arg_str.size();
-      if (arg_val[start_pos] == '=') {
-        target_str = arg_val.substr(start_pos + 1);
-      } else {
-        std::cout << "The only correct argument syntax is --target="
-                  << std::endl;
-        return 0;
-      }
-    } else {
-      std::cout << "The only acceptable argument is --target=" << std::endl;
-      return 0;
-    }
-  } else {
-    target_str = "localhost:50051";
-  }
   GreeterClient greeter(
       grpc::CreateChannel(target_str, grpc::InsecureChannelCredentials()));
   std::string user("world");

examples/cpp/helloworld/greeter_server.cc

@@ -20,6 +20,10 @@
 #include <memory>
 #include <string>
 
+#include "absl/flags/flag.h"
+#include "absl/flags/parse.h"
+#include "absl/strings/str_format.h"
+
 #include <grpcpp/ext/proto_server_reflection_plugin.h>
 #include <grpcpp/grpcpp.h>
 #include <grpcpp/health_check_service_interface.h>
@@ -38,6 +42,8 @@ using helloworld::Greeter;
 using helloworld::HelloReply;
 using helloworld::HelloRequest;
 
+ABSL_FLAG(uint16_t, port, 50051, "Server port for the service");
+
 // Logic and data behind the server's behavior.
 class GreeterServiceImpl final : public Greeter::Service {
   Status SayHello(ServerContext* context, const HelloRequest* request,
@@ -48,8 +54,8 @@ class GreeterServiceImpl final : public Greeter::Service {
   }
 };
 
-void RunServer() {
-  std::string server_address("0.0.0.0:50051");
+void RunServer(uint16_t port) {
+  std::string server_address = absl::StrFormat("0.0.0.0:%d", port);
   GreeterServiceImpl service;
 
   grpc::EnableDefaultHealthCheckService(true);
@@ -70,7 +76,7 @@ void RunServer() {
 }
 
 int main(int argc, char** argv) {
-  RunServer();
-
+  absl::ParseCommandLine(argc, argv);
+  RunServer(absl::GetFlag(FLAGS_port));
   return 0;
 }