gRPC库C++构建及示例_vlambda技术博客

vlambda
2021-02-24

gRPC库C++构建及示例

gRPC is a modern, open source, high-performance remote procedure call (RPC) framework that can run anywhere. gRPC enables client and server applications to communicate transparently, and simplifies the building of connected systems.

C++开发者做什么事情都不太容易,网络编程原本已经很艰难了,想要使用gRPC来降低难度,库构建又是一道坎儿.这里展示如何在残酷的网络环境下使用CMake构建gRPC库,并附带示例验证库构建结果.

如何下载`gRPC`库源代码?

gRPC自身内容很庞大,依赖也比较复杂,如果使用Github下载,耗时费力不说,还容易中断.所幸Gitee上提供了部分镜像仓库,可以将gRPC库自身内容快速拉取下来:

git clone -b v1.34.0 https://gitee.com/mirrors/grpc-framework.git grpc

注意,目前在Gitee上只能找到gRPC依赖的部分"官方"镜像仓库,网友提供的镜像仓库较旧,因而只能构造v1.34.0版本.通过上述指令可以将v1.34.0版本的gRPC代码下载到grpc目录.

[submodule "third_party/zlib"]
	path = third_party/zlib
	url = https://github.com/madler/zlib
	# When using CMake to build, the zlib submodule ends up with a
	# generated file that makes Git consider the submodule dirty. This
	# state can be ignored for day-to-day development on gRPC.
	ignore = dirty

使用了zlib,在Gitee上搜索其代码仓库为https://gitee.com/mirrors/zlib,可以使用如下指令clone:

git clone https://gitee.com/mirrors/zlib.git

因而替换成:

[submodule "third_party/zlib"]
	path = third_party/zlib
	#url = https://github.com/madler/zlib
	url = https://gitee.com/mirrors/zlib.git
	# When using CMake to build, the zlib submodule ends up with a
	# generated file that makes Git consider the submodule dirty. This
	# state can be ignored for day-to-day development on gRPC.
	ignore = dirty

通过这种方法可以找到部分依赖库的最新镜像仓库,但是有一些找不到最新的,例如protobuf等库,用户local-grpc提供了gRPC依赖的全部代码仓库,可以使用这些仓库(注意代码不是同步镜像,导致gRPC只能构造相应版本),其中protobuf链接为:

https://gitee.com/local-grpc/protobuf.git

这里将.gitmodules修改为如下内容即可:

[submodule "third_party/zlib"]
	path = third_party/zlib
	#url = https://github.com/madler/zlib
	url = https://gitee.com/mirrors/zlib.git
	# When using CMake to build, the zlib submodule ends up with a
	# generated file that makes Git consider the submodule dirty. This
	# state can be ignored for day-to-day development on gRPC.
	ignore = dirty
[submodule "third_party/protobuf"]
	path = third_party/protobuf
	#url = https://github.com/google/protobuf.git
	url = https://gitee.com/local-grpc/protobuf.git
[submodule "third_party/googletest"]
	path = third_party/googletest
	#url = https://github.com/google/googletest.git
	url = https://gitee.com/local-grpc/googletest.git
[submodule "third_party/benchmark"]
	path = third_party/benchmark
	#url = https://github.com/google/benchmark
	url = https://gitee.com/mirrors/google-benchmark.git
[submodule "third_party/boringssl-with-bazel"]
	path = third_party/boringssl-with-bazel
	#url = https://github.com/google/boringssl.git
	url = https://gitee.com/mirrors/boringssl.git
[submodule "third_party/re2"]
	path = third_party/re2
	#url = https://github.com/google/re2.git
	url = https://gitee.com/local-grpc/re2.git
[submodule "third_party/cares/cares"]
	path = third_party/cares/cares
	#url = https://github.com/c-ares/c-ares.git
	url = https://gitee.com/mirrors/c-ares.git
	branch = cares-1_12_0
[submodule "third_party/bloaty"]
	path = third_party/bloaty
	#url = https://github.com/google/bloaty.git
	url = https://gitee.com/local-grpc/bloaty.git
[submodule "third_party/abseil-cpp"]
	path = third_party/abseil-cpp
	#url = https://github.com/abseil/abseil-cpp.git
	url = https://gitee.com/mirrors/abseil-cpp.git
	branch = lts_2020_02_25
[submodule "third_party/envoy-api"]
	path = third_party/envoy-api
	#url = https://github.com/envoyproxy/data-plane-api.git
	url = https://gitee.com/local-grpc/data-plane-api.git
[submodule "third_party/googleapis"]
	path = third_party/googleapis
	#url = https://github.com/googleapis/googleapis.git
	url = https://gitee.com/mirrors/googleapis.git
[submodule "third_party/protoc-gen-validate"]
	path = third_party/protoc-gen-validate
	#url = https://github.com/envoyproxy/protoc-gen-validate.git
	url = https://gitee.com/local-grpc/protoc-gen-validate.git
[submodule "third_party/udpa"]
	path = third_party/udpa
	#url = https://github.com/cncf/udpa.git
	url = https://gitee.com/local-grpc/udpa.git
[submodule "third_party/libuv"]
	path = third_party/libuv
	#url = https://github.com/libuv/libuv.git
	url = https://gitee.com/mirrors/libuv.git

使用如下指令拉取gRPC所有依赖:

cd grpc
git submodule update --init

如果你希望使用CMake的FetchContent模块将gRPC整合到自身工程中,可以将上述步骤下载完成的完整源代码打包成压缩包,存放在自己的ftp等服务器上,然后使用如下Python脚本计算出SHA512:

import sys
import hashlib

# BUF_SIZE is totally arbitrary, change for your app!
BUF_SIZE = 65536  # lets read stuff in 64kb chunks!

sha512 = hashlib.sha512()
with open(sys.argv[1], 'rb') as f:
    while True:
        data = f.read(BUF_SIZE)
        if not data:
            break
        sha512.update(data)
print("SHA512: {0}".format(sha512.hexdigest()))

以压缩包完整/相对路径为参数,执行上述脚本,复制得到的SHA512内容,然后在你工程的CMakeLists.txt中以如下方式使用:

include(FetchContent)

FetchContent_Declare(
   gRPC
   URL  "gRPC源码压缩包服务器路径"
   URL_HASH SHA512= "gRPC源码压缩包的SHA512"
   ##DOWNLOAD_DIR可以根据需要修改
   DOWNLOAD_DIR ${CMAKE_SOURCE_DIR}/external/downloads/spdlog
)
set(FETCHCONTENT_QUIET OFF)
FetchContent_MakeAvailable(gRPC)

##工程中库使用方式
target_link_libraries(YourTarget grpc++)

注意在之前要安装必备的依赖,例如nasm.

不过上述使用方式构建时速度特别慢,以下展示如何直接构建出gRPC库,并安装到指定路径.

如何构建`gRPC`库

首先需要安装必要的依赖,例如在Windows上需要以下内容:

Visual Studio 2015或 Visual Studio 2017
Git
CMake
nasm,并且配置到 PATH环境变量中
可选的 Ninja

CMake的使用方式大同小异,这里以Windows为例展示,首先要进行配置,假设已经处于源代码路径中:

cmake -S . -B .build -G"Visual Studio 15 2017" -T v141 -A x64 -DgRPC_INSTALL=ON -DgRPC_BUILD_TESTS=OFF -DgRPC_BUILD_CSHARP_EXT=OFF -DCMAKE_INSTALL_PREFIX="安装路径"

上述配置使用的是Visual Studio 2017及对应工具集,64位构建,使能安装动作,禁止构造测试用例和C#扩展,并指定了安装路径.如果使用的是Visual Studio 2015则替换成Visual Studio 14 2015.

然后通过如下指令构建并安装:

cmake --build .build --target install --config Release

经过一段时间的等待,在安装路径就可以看到构建出的结果了.

这里需要说明的是,gRPC无法将Debug和Release等多个配置安装到同一位置.开发者只能选择构建某一配置,然后在使用时工程构建也只能使用这一配置,通常可以选择Release构造,如果面临调试需求,可以选择RelWithDebInfo,即上述指令修改位:

cmake --build .build --target install --config RelWithDebInfo

上述**.build**路径为官方示例建议的路径,可以自行修改,但无必要.

经过上述操作,在安装路径下就有了可以使用的gRPC库了.下面来看一下如何使用它.

如何运行`Hello World`

在gRPC源代码的\examples\cpp\helloworld路径下有如下代码文件:

greeter_server.cc
greeter_client.cc
greeter_async_server.cc
greeter_async_client.cc
greeter_async_client2.cc

在\examples\protos下有对应的helloworld.proto文件.

将上述文件拷贝到示例目录,例如helloworld目录下,并添加CMakeList.txt工程配置,最终目录结构如下:

greeter_server.cc
greeter_client.cc
greeter_async_server.cc
greeter_async_client.cc
greeter_async_client2.cc
helloworld.proto
CMakeLists.txt

将CMakeLists.txt修改为类似如下内容:

cmake_minimum_required(VERSION 3.15)
#工程名,可自行修改
project(grpc-examples CXX)

#以下三个find_package需要添加,否则找不到对应的target会报错
find_package(Threads REQUIRED)#注意不要加CONFIG
find_package(protobuf CONFIG REQUIRED)
find_package(gRPC CONFIG REQUIRED)

##添加共享的静态库,包含helloworld.proto中定义的RPC协议代码
add_library(helloworld)
target_sources(helloworld
	PRIVATE "helloworld.proto"
)

##生成helloworld.proto对应的C++代码
protobuf_generate(TARGET helloworld LANGUAGE cpp)

##获取proto的grpc插件
get_target_property(grpc_cpp_plugin_location gRPC::grpc_cpp_plugin LOCATION)

##生成helloworld.proto对应的gRPC-C++代码,以此来支持gRPC协议
protobuf_generate(TARGET helloworld LANGUAGE grpc GENERATE_EXTENSIONS .grpc.pb.h .grpc.pb.cc PLUGIN "protoc-gen-grpc=${grpc_cpp_plugin_location}")

target_link_libraries(helloworld
    PRIVATE gRPC::grpc++
)

##上述protobuf_generate将自动生成的代码存放于该位置,需要添加到include路径
target_include_directories(helloworld
    PUBLIC  ${CMAKE_CURRENT_BINARY_DIR}
)

##遍历列表创建应用程序
foreach(_target
    greeter_client greeter_server
    greeter_async_client greeter_async_client2 greeter_async_server)
    add_executable(${_target} "${_target}.cc")
    target_link_libraries(${_target}
        PRIVATE helloworld 
                gRPC::grpc++ gRPC::grpc++_reflection
    )
endforeach()

这里需要强调,官方文档在Windows下构建存在问题,必须添加gRPC::grpc++_reflection依赖,否则构建示例会报如下错误.

无法解析的外部符号 "void __cdecl grpc::reflection::InitProtoReflectionServerBuilderPlugin(void)

CMake的protobuf_generate模块可以用来辅助代码生成动作,开发者只需要将.proto文件作为源代码添加到target中,然后protobuf_generate会根据配置自动生成对应代码,在.proto文件发生变化时能够自动刷新.详细信息参见gRPC and Plugin support in CMake.

在输出目录找到生成的应用程序,例如greeter_server.exe:

./greeter_server.exe

然后启动客户端:

./greeter_client.exe

客户端输出如下内容并退出:

Greeter received: Hello world

现在就可以查阅官方教程来学习gRPC了.

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