Koa.js：集中式错误处理

Question

我通过 Mongoose 使用 Koa.js 和 MongoDB。我想知道如何实现一个完美的集中式错误处理机制。

例如，我编写的通过 Mongoose 连接到 MongoDB 的函数存在一些问题。这就是为什么我收到以下错误。但是，我想捕获此错误并以集中方式处理它。意思是，我希望所有错误和警告（无论来自应用程序的哪个部分）都由我的应用程序中的一个函数处理，该函数将记录它。

warning.js:18 (node:11776) UnhandledPromiseRejectionWarning: Unhandled promise rejection (rejection id: 1): MongoNetworkError: failed to connect to server [127.0.0.1:27017] on first connect [MongoNetworkError: read ECONNRESET]
    writeOut @ warning.js:18
    output @ warning.js:69
    process.on @ warning.js:100
    emitOne @ events.js:116
    emit @ events.js:211
    (anonymous) @ warning.js:74
    _combinedTickCallback @ next_tick.js:131
    _tickCallback @ next_tick.js:180
    TickObject (async)
    init @ inspector_async_hook.js:22
    emitInitNative @ async_hooks.js:472
    emitInitScript @ async_hooks.js:388
    nextTick @ next_tick.js:270
    process.emitWarning @ warning.js:146
    emitWarning @ promises.js:75
    emitPendingUnhandledRejections @ promises.js:95
    _tickCallback @ next_tick.js:189
    Show 11 more blackboxed frames

warning.js:18 (node:11776) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.
    writeOut @ warning.js:18
    output @ warning.js:69
    process.on @ warning.js:100
    emitOne @ events.js:116
    emit @ events.js:211
    (anonymous) @ warning.js:74
    _combinedTickCallback @ next_tick.js:131
    _tickCallback @ next_tick.js:180
    TickObject (async)
    init @ inspector_async_hook.js:22
    emitInitNative @ async_hooks.js:472
    emitInitScript @ async_hooks.js:388
    nextTick @ next_tick.js:270
    process.emitWarning @ warning.js:146
    emitWarning @ promises.js:78
    emitPendingUnhandledRejections @ promises.js:95
    _tickCallback @ next_tick.js:189
    Show 11 more blackboxed frames

warning.js:18 (node:11776) UnhandledPromiseRejectionWarning: Unhandled promise rejection (rejection id: 2): MongoNetworkError: failed to connect to server [127.0.0.1:27017] on first connect [MongoNetworkError: read ECONNRESET]
    writeOut @ warning.js:18
    output @ warning.js:69
    process.on @ warning.js:100
    emitOne @ events.js:116
    emit @ events.js:211
    (anonymous) @ warning.js:74
    _combinedTickCallback @ next_tick.js:131
    _tickCallback @ next_tick.js:180
    TickObject (async)
    init @ inspector_async_hook.js:22
    emitInitNative @ async_hooks.js:472
    emitInitScript @ async_hooks.js:388
    nextTick @ next_tick.js:270
    process.emitWarning @ warning.js:146
    emitWarning @ promises.js:75
    emitPendingUnhandledRejections @ promises.js:95
    _tickCallback @ next_tick.js:189
    Show 11 more blackboxed frames

Answer 1

以下代码将确保任何未处理的承诺错误或任何未捕获的错误，如果未在本地处理，将得到处理：

app.use(async (ctx, next) => {
  try {
    await next();
  } catch (err) {
    ctx.status = err.status || 500;
    ctx.body = err.message;
    ctx.app.emit('error', err, ctx);
  }
});

...

someUnhandledError();

...


process.on("unhandledRejection", (reason: string) => {
  // I just caught an unhandled promise rejection,
  // let's throw it here so my central error handler can catch it
  throw new AppError(reason, 500);
});

process.on('uncaughtException', (error: Error) => {
  // I just received an error that was never handled, time to handle it
  // by throwing it so my error handling middleware can catch it
  throw new AppError("Error", 500)
});

app.on('error', (err, ctx) => {
  // centralized error handling:
  // console.log(error)
  // write error to log file
});

app.listen(3000);

注意：这里使用的AppError 类是扩展Error 类的自定义类。

Answer 2

在 Koa wiki 中有一个关于错误处理的部分：https://github.com/koajs/koa/wiki/Error-Handling

他们建议使用错误处理程序中间件作为应用程序中的第一个中间件，这样下游抛出的任何错误都会冒泡到它上面。

他们来自 wiki 的示例：

app.use(async (ctx, next) => {
  try {
    await next();
  } catch (err) {
    ctx.status = err.status || 500;
    ctx.body = err.message;
    ctx.app.emit('error', err, ctx);
  }
});

app.on('error', (err, ctx) => {
  /* centralized error handling:
   *   console.log error
   *   write error to log file
   *   save error and request information to database if ctx.request match condition
   *   ...
  */
});