一、首先下载代码

GitHub - open-telemetry/opentelemetry-cpp: The OpenTelemetry C++ Client

// git config --global https.proxy 'socks5://127.0.0.1:1081'
// git config --global http.proxy 'socks5://127.0.0.1:1081'
git clone --recursive https://github.com/open-telemetry/opentelemetry-cpp.git
git submodule update --init

在子模块下载过程中，始终报错，试了好几次，之后用手机作为热点，搞定了

二、编译流程

mkdir build && cd build
cmake ../

1) 报错：

CMake Error at /usr/share/cmake-3.10/Modules/FindPackageHandleStandardArgs.cmake:137 (message):
  Could NOT find GTest (missing: GTEST_LIBRARY GTEST_MAIN_LIBRARY)
Call Stack (most recent call first):
  /usr/share/cmake-3.10/Modules/FindPackageHandleStandardArgs.cmake:378 (_FPHSA_FAILURE_MESSAGE)
  /usr/share/cmake-3.10/Modules/FindGTest.cmake:196 (FIND_PACKAGE_HANDLE_STANDARD_ARGS)
  CMakeLists.txt:398 (find_package)

说是无法找到GTEST模块，

解决方法：

sudo apt-get install libgtest-dev
cd
cd /usr/src/gtest
sudo cmake CMakeLists.txt 
sudo make 
sudo cp *.a /usr/lib

会拷贝2个文件到系统目录；

2） 还是报错：

-- Building for architecture ARCH=x64
Trying to use local nlohmann::json from submodule
-- Using the single-header code from /usr/local/soft/ot/third_party/nlohmann-json/single_include/
-- Found GTest: /usr/lib/libgtest.a  
GTEST_INCLUDE_DIRS   = /usr/include
GTEST_BOTH_LIBRARIES = /usr/lib/libgtest.a;/usr/lib/libgtest_main.a
CMake Error at CMakeLists.txt:405 (find_package):
  Could not find a package configuration file provided by "benchmark" with
  any of the following names:

    benchmarkConfig.cmake
    benchmark-config.cmake

  Add the installation prefix of "benchmark" to CMAKE_PREFIX_PATH or set
  "benchmark_DIR" to a directory containing one of the above files.  If
  "benchmark" provides a separate development package or SDK, be sure it has
  been installed.


-- Configuring incomplete, errors occurred!
See also "/usr/local/soft/ot/build/CMakeFiles/CMakeOutput.log".
See also "/usr/local/soft/ot/build/CMakeFiles/CMakeError.log".

那就接着安装一个：

sudo apt install cmake
git clone https://github.com/google/benchmark.git
git clone https://github.com/google/googletest.git  benchmark/googletest
mkdir build && cd build
cmake -DCMAKE_BUILD_TYPE=RELEASE ..
make -j4
make install

备注：一定要在子目录放置一个GTEST，不然还是不能编译；编译后要install一下，设置环境变量，拷贝配置文件过去；

3） 报错，说找不到CURL，示例程序要用；

解决：

sudo apt-get update
sudo apt install curl
apt-get install libcurl4-openssl-dev

4）报错：Unknown CMake command "add_compile_definitions".

我是ubuntn18.04，用的cmake是3.10版本，

 安装cmake 3.14

1.下载

wget https://cmake.org/files/v3.14/cmake-3.14.5.tar.gz

2.解压
tar -xzvf cmake-3.14.5.tar.gz
cd cmake-3.14.5/

3.编译

这一步可能需要很长时间，依次输入

./bootstrap
make -j8
sudo make install

安装后测试cmake

cmake --version
CMake Error: Could not find CMAKE_ROOT !!!
CMake has most likely not been installed correctly.
Modules directory not found in
/usr/local/share/cmake-3.10
cmake version 3.10.2
还是不对，需要设置一下：

但是我没有设置，

直接使用目录运行

/usr/loca/bin/cmake ../

这时可以了，不报错了；

5） 编译

make -j8

 理论行可以运行测试了。

三、再次编译

默认的编译导出器只有流方式，需要添加一个选项

/usr/local/bin/cmake -DWITH_OTLP=ON ../

这时报了一个错误：

Please set them or make sure they are set and tested correctly in the CMake files:
GMOCK_LIB

可以参考：GTEST GMOCK使用入门-使用源码编译gtest gmock的方法_zishuijing_dd的博客-CSDN博客

我的方式是比较暴力，从third目录直接把googletest拷贝到自己的一个目录，然后编译并安装，然后就有了libgmock.a

再次执行cmake就不报错了！

cmake -DCMAKE_POSITION_INDEPENDENT_CODE=ON    -DWITH_OTLP=ON  ../

#不用使用make命令

cmake --build . --target all

四、运行

./example_otlp_http http://10.128.6.99:4318/v1/traces