捕获 flutter app的崩溃日志并上报

小灰灰 2023-01-07 01:30 755阅读 0赞

flutter 的崩溃日志收集主要有两个方面：

1.  flutter dart 代码的异常（包含app和framework代码两种情况，一般不会引起闪退，你猜为什么）
2.  flutter engine 的崩溃日志（一般会闪退）

### Flutter App 代码异常捕获 ###

人写的代码是无数异常交织起来的偶然产物，代码发生异常才是正常情况。

除了在关键的地方加上 `try-catch` 让它们变成已知异常之外，抓到未知异常才是真本事。

比如下面的一段代码中的`try-catch`是无效的：

<table> 
 <tbody> 
  <tr> 
   <td> <pre>1
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</pre> </td> 
   <td> <pre>try {
    Future.error("asynchronous surprise");
} catch (e){
    print(e)
}
</pre> </td> 
  </tr> 
 </tbody> 
</table>

好在，Dart 有一个 [`Zone`][Zone] 的概念，有点类似`sandbox`的意思。不同的 Zone 代码上下文是不同的互不影响，Zone 还可以创建新的子Zone。Zone 可以重新定义自己的`print`、`timers`、`microtasks`还有最关键的`how uncaught errors are handled` **未捕获异常的处理**

<table> 
 <tbody> 
  <tr> 
   <td> <pre>1
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</pre> </td> 
   <td> <pre>runZoned(() {
    Future.error("asynchronous error");
}, onError: (dynamic e, StackTrace stack) {
    reportError(e, stack);
});
</pre> </td> 
  </tr> 
 </tbody> 
</table>

在 `reportError` 里即可以进行上报处理（详见后面介绍）。

### Flutter framework 异常捕获 ###

<table> 
 <tbody> 
  <tr> 
   <td> <pre>1
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</pre> </td> 
   <td> <pre>FlutterError.onError = (FlutterErrorDetails details) {
    reportError(details.exception, details.stack);
};
</pre> </td> 
  </tr> 
 </tbody> 
</table>

该 error 一般是由 `Widget` 在 `build` 的时候抛出，如下：

<table> 
 <tbody> 
  <tr> 
   <td> <pre>1
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</pre> </td> 
   <td> <pre>@override
void performRebuild() {
  Widget built;
  try {
    built = build();
  } catch (e, stack) {
    built = ErrorWidget.builder(_debugReportException(ErrorDescription("building $this"), e, stack));
  } finally {
    _dirty = false;
  }
  try {
    _child = updateChild(_child, built, slot);
  } catch (e, stack) {
    built = ErrorWidget.builder(_debugReportException(ErrorDescription("building $this"), e, stack));
    _child = updateChild(null, built, slot);
  }
}
</pre> </td> 
  </tr> 
 </tbody> 
</table>

该代码有删减，具体请参看[framework.dart源码][framework.dart]。其中的`_debugReportException` 就是 FlutterError 的调用点：

<table> 
 <tbody> 
  <tr> 
   <td> <pre>1
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</pre> </td> 
   <td> <pre>FlutterErrorDetails _debugReportException(
  DiagnosticsNode context,
  dynamic exception,
  StackTrace stack, {
  InformationCollector informationCollector,
}) {
  final FlutterErrorDetails details = FlutterErrorDetails(
    exception: exception,
    stack: stack,
    library: 'widgets library',
    context: context,
    informationCollector: informationCollector,
  );
  FlutterError.reportError(details);
  return details;
}
</pre> </td> 
  </tr> 
 </tbody> 
</table>

### Flutter engine 异常捕获 ###

flutter engine 部分的异常，以Android 为例，主要为 `libfutter.so`发生的错误。

这部份可以直接交给native崩溃收集sdk来处理，比如 [firebase crashlytics][]、 [bugly][]、[xCrash][] 等等

### reportError 堆栈上报 ###

线上app 出现异常虽然捕获了，但只是打印出来是没办法解决问题，还需要把他上报到开发者能看到的地方。

上面提到了许多崩溃收集的sdk，以 bugly 为例，它支持自定义异常上报，我们只需将 dart 异常及堆栈通过 `MethodChannel`传递给 bugly sdk 即可。

Dart:

<table> 
 <tbody> 
  <tr> 
   <td> <pre>1
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</pre> </td> 
   <td> <pre>var channel = new MethodChannel("crash_handler");

Future&lt;void&gt; reportError(dynamic exception, StackTrace stack) async {
  try {
    return await channel.invokeMethod("report_error", &lt;String, dynamic&gt;{
      "type": exception.runtimeType.toString(), // exception type
      "message": exception.toString(),          // message
      "stack": stack.toString(),                // stacktrace
    });
  } catch(ignored) {
  }
}
</pre> </td> 
  </tr> 
 </tbody> 
</table>

Android Java代码如下：

<table> 
 <tbody> 
  <tr> 
   <td> <pre>1
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</pre> </td> 
   <td> <pre>public class CrashHandler implements MethodCallHandler {
  @Override
  public void onMethodCall(MethodCall call, Result result) {
    switch (call.method) {
      case "report_error":
        postFlutterExcetion(call.argument("type"), call.argument("message"), call.argument("stack"))
        result.success(true);
        break;
      default:
        result.notImplemented();
    }
  }
  
  static void postFlutterExcetion(String excpetionType, String excpetionMessage, String stack) {
    if (!CrashModule.hasInitialized()) return;
    CrashReport.postException(4, excpetionType, excpetionMessage, stack, null);
  }
}

// ...

MethodChannel(flutterView, "crash_handler").setMethodCallHandler(new CrashHandler())
</pre> </td> 
  </tr> 
 </tbody> 
</table>

iOS 类似的注册一个MethodChannel并在`handleMethodCall`中调用 Bugly 的`reportExceptionWithCategory`即可。

其它的sdk类似处理，此处略过不表。

### 堆栈还原 ###

收集到异常之后，需要查符号表(symbols)还原堆栈。下面以Android 端 bugly 收集到堆栈为一例：

<table> 
 <tbody> 
  <tr> 
   <td> <pre>1
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</pre> </td> 
   <td> <pre>1 #00 pc 00016998 /system/lib/libc.so (__memcpy_base+104) [armeabi-v7a::2b2dac1c583b68da2f7c58e7ed352851]
2 #01 pc 00158aed /data/app/com.netease.cartoonreader-1/lib/arm/libflutter.so [armeabi-v7a::2c9d8634bdb07ea641970181b0b00b84]
3 #02 pc 00138041 /data/app/com.netease.cartoonreader-1/lib/arm/libflutter.so [armeabi-v7a::2c9d8634bdb07ea641970181b0b00b84]
4 #03 pc 00139461 /data/app/com.netease.cartoonreader-1/lib/arm/libflutter.so [armeabi-v7a::2c9d8634bdb07ea641970181b0b00b84]
5 #04 pc 00013057 /system/lib/libutils.so (_ZN7android6Looper9pollInnerEi+530) [armeabi-v7a::ac423f49f579c99cfababb65014363e9]
6 #05 pc 00013127 /system/lib/libutils.so (_ZN7android6Looper8pollOnceEiPiS1_PPv+130) [armeabi-v7a::ac423f49f579c99cfababb65014363e9]
7 #06 pc 00007889 /system/lib/libandroid.so (ALooper_pollOnce+64) [armeabi-v7a::954c216fdf1faa9aa08f41bc27503a87]
8 #07 pc 001394fb /data/app/com.netease.cartoonreader-1/lib/arm/libflutter.so [armeabi-v7a::2c9d8634bdb07ea641970181b0b00b84]
9 #08 pc 001371eb /data/app/com.netease.cartoonreader-1/lib/arm/libflutter.so [armeabi-v7a::2c9d8634bdb07ea641970181b0b00b84]
10 #09 pc 00138441 /data/app/com.netease.cartoonreader-1/lib/arm/libflutter.so [armeabi-v7a::2c9d8634bdb07ea641970181b0b00b84]
11 #10 pc 0004185b /system/lib/libc.so (_ZL15__pthread_startPv+30) [armeabi-v7a::2b2dac1c583b68da2f7c58e7ed352851]
12 #11 pc 000192a5 /system/lib/libc.so (__start_thread+6) [armeabi-v7a::2b2dac1c583b68da2f7c58e7ed352851]
13 java:
14 [Failed to get Java stack]
</pre> </td> 
  </tr> 
 </tbody> 
</table>

首先需要确认该 flutter engine 所属版本号，在命令行执行：

<table> 
 <tbody> 
  <tr> 
   <td> <pre>1
</pre> </td> 
   <td> <pre>flutter --version
</pre> </td> 
  </tr> 
 </tbody> 
</table>

输出如下：

<table> 
 <tbody> 
  <tr> 
   <td> <pre>1
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</pre> </td> 
   <td> <pre>Flutter 1.5.4-hotfix.2 • channel stable • https://github.com/flutter/flutter.git
Framework • revision 7a4c33425d (9 weeks ago) • 2019-04-29 11:05:24 -0700
Engine • revision 52c7a1e849
Tools • Dart 2.3.0 (build 2.3.0-dev.0.5 a1668566e5)
</pre> </td> 
  </tr> 
 </tbody> 
</table>

可以看到 Engine 的 revision 为 **52c7a1e849**。

其次，在 [flutter infra][] 上找到对应cpu abi 的 *symbols.zip* 并下载 ：[https://console.cloud.google.com/storage/browser/flutter\_infra/flutter/52c7a1e849a170be4b2b2fe34142ca2c0a6fea1f/android-arm-release][https_console.cloud.google.com_storage_browser_flutter_infra_flutter_52c7a1e849a170be4b2b2fe34142ca2c0a6fea1f_android-arm-release]

解压后，可以得到带有符号信息的 debug so 文件—— libflutter.so，并将其放到文件夹 armeabi-v7a 下。如需要x86等的符号信息，类似操作。

<table> 
 <tbody> 
  <tr> 
   <td> <pre>1
2
</pre> </td> 
   <td> <pre>mkdir -p ~/Downloads/flutter-52c7a1e849/armeabi-v7a
unzip symbols.zip -d ~/Downloads/flutter-52c7a1e849/armeabi-v7a
</pre> </td> 
  </tr> 
 </tbody> 
</table>

使用 ndk-stack

Android 上手动还原 libflutter.so 堆栈，可以使用 NDK 提供的工具 `ndk-stack`

1.  将原始堆栈保存到 stack.txt 中，注意第一行要以 `*** *** *** *** *** *** *** *** *** *** *** *** *** *** *** ***` 开头
    
    <table> 
     <tbody> 
      <tr> 
       <td> <pre>1
    2
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    </pre> </td> 
       <td> <pre>*** *** *** *** *** *** *** *** *** *** *** *** *** *** *** ***
    1 #00 pc 00016998 /system/lib/libc.so (__memcpy_base+104) [armeabi-v7a::2b2dac1c583b68da2f7c58e7ed352851]
    2 #01 pc 00158aed /data/app/com.netease.cartoonreader-1/lib/arm/libflutter.so [armeabi-v7a::2c9d8634bdb07ea641970181b0b00b84]
    3 #02 pc 00138041 /data/app/com.netease.cartoonreader-1/lib/arm/libflutter.so [armeabi-v7a::2c9d8634bdb07ea641970181b0b00b84]
    4 #03 pc 00139461 /data/app/com.netease.cartoonreader-1/lib/arm/libflutter.so [armeabi-v7a::2c9d8634bdb07ea641970181b0b00b84]
    5 #04 pc 00013057 /system/lib/libutils.so (_ZN7android6Looper9pollInnerEi+530) [armeabi-v7a::ac423f49f579c99cfababb65014363e9]
    ...
    </pre> </td> 
      </tr> 
     </tbody> 
    </table>
2.  执行ndk-stack命令
    
    <table> 
     <tbody> 
      <tr> 
       <td> <pre>1
    </pre> </td> 
       <td> <pre>$ANDROID_NDK/ndk-stack -sym ~/Downloads/flutter-52c7a1e849/armeabi-v7a -dump stack.txt &gt; re-stack.txt
    </pre> </td> 
      </tr> 
     </tbody> 
    </table>

打开文件 re-stack.txt 即可看到还原后的堆栈：

<table> 
 <tbody> 
  <tr> 
   <td> <pre>1
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</pre> </td> 
   <td> <pre>********** Crash dump: **********
#00 0x00016998 /system/lib/libc.so (__memcpy_base+104) [armeabi-v7a::2b2dac1c583b68da2f7c58e7ed352851]
#01 0x00158aed /data/app/com.netease.cartoonreader-1/lib/arm/libflutter.so [armeabi-v7a::2c9d8634bdb07ea641970181b0b00b84]
fml::WriteAtomically(fml::UniqueObject&lt;int, fml::internal::os_unix::UniqueFDTraits&gt; const&amp;, char const*, fml::Mapping const&amp;)
/b/s/w/ir/k/src/out/android_release/../../flutter/fml/platform/posix/file_posix.cc:203:3
flutter::PersistentCacheStore(fml::RefPtr&lt;fml::TaskRunner&gt;, std::__1::shared_ptr&lt;fml::UniqueObject&lt;int, fml::internal::os_unix::UniqueFDTraits&gt; &gt;, std::__1::basic_string&lt;char, std::__1::char_traits&lt;char&gt;, std::__1::allocator&lt;char&gt; &gt;, std::__1::unique_ptr&lt;fml::Mapping, std::__1::default_delete&lt;fml::Mapping&gt; &gt;)::$_0::operator()()
/b/s/w/ir/k/src/out/android_release/../../flutter/shell/common/persistent_cache.cc:114:0
auto fml::internal::CopyableLambda&lt;flutter::PersistentCacheStore(fml::RefPtr&lt;fml::TaskRunner&gt;, std::__1::shared_ptr&lt;fml::UniqueObject&lt;int, fml::internal::os_unix::UniqueFDTraits&gt; &gt;, std::__1::basic_string&lt;char, std::__1::char_traits&lt;char&gt;, std::__1::allocator&lt;char&gt; &gt;, std::__1::unique_ptr&lt;fml::Mapping, std::__1::default_delete&lt;fml::Mapping&gt; &gt;)::$_0&gt;::operator()&lt;&gt;() const
/b/s/w/ir/k/src/out/android_release/../../flutter/fml/make_copyable.h:24:0
#02 0x00138041 /data/app/com.netease.cartoonreader-1/lib/arm/libflutter.so [armeabi-v7a::2c9d8634bdb07ea641970181b0b00b84]
fml::MessageLoopImpl::FlushTasks(fml::MessageLoopImpl::FlushType)
/b/s/w/ir/k/src/out/android_release/../../flutter/fml/message_loop_impl.cc:140:5
fml::MessageLoopImpl::RunExpiredTasksNow()
/b/s/w/ir/k/src/out/android_release/../../flutter/fml/message_loop_impl.cc:148:0
#03 0x00139461 /data/app/com.netease.cartoonreader-1/lib/arm/libflutter.so [armeabi-v7a::2c9d8634bdb07ea641970181b0b00b84]
fml::MessageLoopAndroid::OnEventFired()
/b/s/w/ir/k/src/out/android_release/../../flutter/fml/platform/android/message_loop_android.cc:92:5
fml::MessageLoopAndroid::MessageLoopAndroid()::$_0::operator()(int, int, void*) const
/b/s/w/ir/k/src/out/android_release/../../flutter/fml/platform/android/message_loop_android.cc:42:0
fml::MessageLoopAndroid::MessageLoopAndroid()::$_0::__invoke(int, int, void*)
/b/s/w/ir/k/src/out/android_release/../../flutter/fml/platform/android/message_loop_android.cc:40:0
#04 0x00013057 /system/lib/libutils.so (_ZN7android6Looper9pollInnerEi+530) [armeabi-v7a::ac423f49f579c99cfababb65014363e9]

...
</pre> </td> 
  </tr> 
 </tbody> 
</table>

bugly 自动还原堆栈

一个个崩溃堆栈手动还原多麻烦（噫 你怎么这么多崩溃），下载好 debug so 之后你也可以使用 bugly给的符号表上传工具上传到bugly上，文档见：[https://bugly.qq.com/docs/user-guide/symbol-configuration-android/?v=20181014122344\#\_4][https_bugly.qq.com_docs_user-guide_symbol-configuration-android_v_20181014122344_4]

输出符号表：

<table> 
 <tbody> 
  <tr> 
   <td> <pre>1
</pre> </td> 
   <td> <pre>java -jar buglySymbolAndroid.jar -i ~/Downloads/flutter-52c7a1e849/armeabi-v7a
</pre> </td> 
  </tr> 
 </tbody> 
</table>

将符号表上传之后，bugly 会自动将堆栈还原，如下图所示

使用 atos

iOS上的 Flutter 引擎崩溃堆栈还原步骤和 Android 类似，先下载对应的符号表(Flutter.dSYM.zip)，然后通过 `atos` 还原，如：

<table> 
 <tbody> 
  <tr> 
   <td> <pre>1
</pre> </td> 
   <td> <pre>atos -arch arm64 -o ~/Downloads/flutter_e1e6ced81d029258d449bdec2ba3cddca9c2ca0c_ios-release_Flutter.dSYM/Flutter.dSYM/Contents/Resources/DWARF/Flutter -l 0x000000010277c000 0x00000001027b91dc
</pre> </td> 
  </tr> 
 </tbody> 
</table>

输出：

<table> 
 <tbody> 
  <tr> 
   <td> <pre>1
</pre> </td> 
   <td> <pre>fml::MessageLoopDarwin::OnTimerFire(__CFRunLoopTimer*, fml::MessageLoopDarwin*) (in Flutter) (message_loop_darwin.mm:76)
</pre> </td> 
  </tr> 
 </tbody> 
</table>

本文完，如你更好的方案请不要犹豫快留言告诉我。

*这部分是给看到后面的读者的一个福利 <(▰˘◡˘▰)>*

如果你不想使用第三方的错误收集平台，可以用 [https://github.com/flutter/sentry][https_github.com_flutter_sentry] 和 [https://sentry.io][https_sentry.io]的[开源版][Link 1] 配合使用搭建自己的后台。另外我fork的版本 [https://github.com/yrom/sentry/tree/2.2.0-patch][https_github.com_yrom_sentry_tree_2.2.0-patch] 使用幸福感更高~。

[Zone]: https://github.com/dart-lang/sdk/blob/master/sdk/lib/async/zone.dart#L268
[framework.dart]: https://github.com/flutter/flutter/blob/master/packages/flutter/lib/src/widgets/framework.dart#L3926
[firebase crashlytics]: https://firebase.google.com/docs/crashlytics
[bugly]: https://bugly.qq.com/v2/
[xCrash]: https://github.com/iqiyi/xCrash/
[flutter infra]: https://console.cloud.google.com/storage/browser/flutter_infra/flutter/
[https_console.cloud.google.com_storage_browser_flutter_infra_flutter_52c7a1e849a170be4b2b2fe34142ca2c0a6fea1f_android-arm-release]: https://console.cloud.google.com/storage/browser/flutter_infra/flutter/52c7a1e849a170be4b2b2fe34142ca2c0a6fea1f/android-arm-release
[https_bugly.qq.com_docs_user-guide_symbol-configuration-android_v_20181014122344_4]: https://bugly.qq.com/docs/user-guide/symbol-configuration-android/?v=20181014122344#_4
[https_github.com_flutter_sentry]: https://github.com/flutter/sentry
[https_sentry.io]: https://sentry.io/
[Link 1]: https://github.com/getsentry/sentry
[https_github.com_yrom_sentry_tree_2.2.0-patch]: https://github.com/yrom/sentry/tree/2.2.0-patch