Using HiTraceChain (C/C++)

Overview

HiTraceChain is a lightweight implementation of the cloud-based distributed call chain tracing on the device side. It allows the calls made in a service process to be traced, helping locating issues across threads, processes, and devices. With hiTraceChain, a unique ID is generated for a service process, passed throughout the service process, and associated with various output information (including application events, system time, and logs). During debugging and fault locating, you can use this unique ID to quickly correlate various information related to the service process. hiTraceChain provides APIs to implement call chain tracing throughout a service process. This can help you quickly obtain the run log for the call chain of a service process and locate faults across devices, processes, and threads.

Available APIs

The APIs for distributed call chain tracing are provided by the hiTraceChain module. For details, see Hitrace.

Example

1. Create a native C++ application in DevEco Studio. The project created by default contains the index.ets file, and a hello.cpp or napi_init.cpp file is generated in the entry\src\main\cpp directory. In this example, the generated file is hello.cpp. The code of index.ets is as follows. The function testNapi.add() defined in hello.cpp is called in onClick(). “` import hilog from ‘@ohos.hilog’; import testNapi from ‘libentry.so’;

   @Entry @Component struct Index { @State message: string = ‘Hello World’;

   build() {
       Row() {
       Column() {
           Text(this.message)
           .fontSize(50)
           .fontWeight(FontWeight.Bold)
           .onClick(() => {
               hilog.info(0x0000, 'testTag', 'Test NAPI 2 + 3 = %{public}d', testNapi.add(2, 3));
           })
       }
       .width('100%')
       }
       .height('100%')
   }
   

   }

2. Add the link of libhitrace_ndk.z.so to CMakeLists.txt.

   ”` // CMakeLists.txt #the minimum version of CMake. cmake_minimum_required(VERSION 3.4.1) project(MyApplication)

set(NATIVERENDER_ROOT_PATH ${CMAKE_CURRENT_SOURCE_DIR})

include_directories(${NATIVERENDER_ROOT_PATH} ${NATIVERENDER_ROOT_PATH}/include) add_library(entry SHARED hello.cpp) target_link_libraries(entry PUBLIC libace_napi.z.so libhitrace_ndk.z.so)

3. Include the hiTrace header file in the **hello.cpp** file.

    ```c++
    #include "hitrace/trace.h"
    ```

4. In **Add()** of **hello.cpp**, use **OH_HiTrace_BeginChain()** to start a trace and use **OH_HiTrace_EndChain()** to stop the trace.

    ```c++
    #include "napi/native_api.h"
    #include "hitrace/trace.h"
    static napi_value Add(napi_env env, napi_callback_info info)
    {
        // Start distributed tracing.
        OH_HiTrace_BeginChain("hitraceTest", HITRACE_FLAG_DEFAULT);
        // Stop distributed tracing. (This is for reference only. Set the start and stop points to match your case.)
        OH_HiTrace_EndChain();
        size_t requireArgc = 2;
        size_t argc = 2;
        napi_value args[2] = {nullptr};

        napi_get_cb_info(env, info, &argc, args , nullptr, nullptr);

        napi_valuetype valuetype0;
        napi_typeof(env, args[0], &valuetype0);

        napi_valuetype valuetype1;
        napi_typeof(env, args[1], &valuetype1);

        double value0;
        napi_get_value_double(env, args[0], &value0);

        double value1;
        napi_get_value_double(env, args[1], &value1);

        napi_value sum;
        napi_create_double(env, value0 + value1, &sum);

        return sum;

    }
    ```

5. Run the project, and an HAP application is generated on the device. Click "Hello World". The **Add()** function in **hello.cpp** will be called. View the trace log, which is as follows:
    ```text
    11-02 15:13:28.922  21519-21519  C02D03/HiTraceC                  com.example.hitracechaintest     I  [a92ab94c18e1341 0 0][dict]HiTraceBegin name:hitraceTest event flags:0x01.
    11-02 15:13:28.930  21519-21519  C02D03/HiTraceC                  com.example.hitracechaintest     I  [a92ab94c18e1341 324c3a3 0][dict]HiTraceEnd.

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