javascript 使用承诺 - 在失败处理程序中记录堆栈跟踪
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Using promises - Logging stack trace in fail handler
提问by dave
I am rather new to nodejs so I will explain in a bit more detail what I am trying to do.
我对 nodejs 比较陌生，所以我将更详细地解释我想要做什么。
I have a webserver. If a request fails I want to log the stack trace of that exception, but deliver a error page and not crash the server.
我有一个网络服务器。如果请求失败，我想记录该异常的堆栈跟踪，但提供错误页面而不是使服务器崩溃。
As an example, the function handling the requests:
例如，处理请求的函数：
var Q = require('q');
var requestHandler = function () {
// Here I get the data etc. that was requested. As this is not important, just a dummy here
Q.resolve()
// Now I answer the request
.then(function (data) {
// Dummy Code representing the sending of a response
console.log('sending response …');
console.log('oh no! an exception');
// Now an Exception occurs
throw new Error('You did something wrong!');
})
// If there was any error, show the error page instead
.fail(function (err) {
// Dummy Code representing the sending of the error page
console.log('sending error page');
// Additionally I want to write the error into a log file
console.error('You had an error: ', err);
})
// If there was an error in the .fail-handler, I deserve the server to crash
.done();
};
// A request comes in, I want to call my handler
requestHandler();
The console's output:
控制台的输出：
sending response …
oh no! an exception
sending error page
You had an error: [Error: You did something wrong!]
I can't see a way to access the stack trace. But when I throw an exception in the .fail-handler (or just omit the complete .fail-handler), I get a stack trace on the console (but I'd have to restart the server).
我看不到访问堆栈跟踪的方法。但是当我在 .fail-handler 中抛出一个异常（或者只是省略完整的 .fail-handler）时，我会在控制台上得到一个堆栈跟踪（但我必须重新启动服务器）。
So I guess my question is:
所以我想我的问题是：
How do I access the stack trace in a promise fail handler?
如何访问承诺失败处理程序中的堆栈跟踪？
EDIT: Any tips on how to improve the explanation are welcome, of course. If I didn't make myself clear, please let me know.
编辑：当然，欢迎提供有关如何改进解释的任何提示。如果我没有说清楚，请告诉我。
回答by Mariusz Nowak
Logging the error object won't print error's stack trace. You need to ask for it specifically:
记录错误对象不会打印错误的堆栈跟踪。你需要特别要求它：
console.error('You had an error: ', err.stack);
