如何从AWS Lambda函数返回错误集合/对象并映射到AWS API Gateway响应代码 [英] How to return error collection/object from AWS Lambda function and map to AWS API Gateway response code

问题描述

我正在尝试从AWS Lambda函数返回一个对象，而不是一个简单的字符串。

I am attempting to return an object from a AWS Lambda function instead of a simple string.

// ...
    context.fail({
        "email": "Email address is too short",
        "firstname": "First name is too short"
    });
// ...

我已经使用了 errorMessage 用于将错误响应映射到状态代码并且非常棒：

I have already used the errorMessage for mapping error responses to status codes and that has been great:

// ...
    context.fail('That "username" has already been taken.');
// ...

我只是想做一些AWS API Gateway买不起？

Am I simply trying to do something that the AWS API Gateway does not afford?

我也发现这篇文章有所帮助：有没有办法改变亚马逊API网关返回的http状态码？。

I have also already found this article which helped: Is there a way to change the http status codes returned by Amazon API Gateway?.

推荐答案

更新
从写作开始，lambda已更新调用签名，现在传递事件，上下文，回调。

而不是调用 context.done（错误，res）你应该使用 callback（err，res）。请注意，context.done的情况仍然适用于回调模式。

Instead of calling context.done(err, res) you should use callback(err, res). Note that what was true for context.done still applies to the callback pattern.

还应该在API网关代理和集成实现中添加这一点，这整个线程已经过时了。
如果您要将API Gateway与Lambda集成，我建议您阅读本文： http://docs.aws.amazon.com/apigateway/latest/developerguide/api-gateway-create-api-as-simple-proxy- for-lambda.html

Should also add that with API Gateways proxy and integration implementation this entire thread is pretty much obsolete. I recommend reading this article if you are integrating API Gateway with Lambda: http://docs.aws.amazon.com/apigateway/latest/developerguide/api-gateway-create-api-as-simple-proxy-for-lambda.html

首先，让我们先澄清一些事情。

First things first, let's clear a few things up.

context。完成（错误，结果）; 只是 context.fail（错误）; 和 context.success的包装器（响应）;
Lambda文档明确指出如果错误为非null则忽略结果：

context.done(error, result); is nothing but a wrapper around context.fail(error); and context.success(response); The Lambda documentation clearly states that result is ignored if error is non null:

如果使用RequestResponse（同步）调用类型调用Lambda函数，则该方法返回响应正文，如下所示：
如果错误为null，则设置为e响应结果的字符串表示的主体。这类似于context.succeed（）。
如果错误不为null，则将响应正文设置为error。
如果使用类型为error的单个参数调用该函数，则将在回应机构。
http：// docs。 aws.amazon.com/lambda/latest/dg/nodejs-prog-model-context.html

这是什么意味着无论你是使用失败/成功还是完成的组合都无关紧要，行为完全相同。

What this means is that it won't matter whether you use a combination of fail/success or done, the behaviour is exactly the same.

我已经测试了Lambda的每个可想到的响应处理组合以及API网关中的响应代码映射。

I have tested every thinkable combination of response handling from Lambda in combination with Response code mapping in API Gateway.

这些测试的结论是Lambda Error RegExp仅针对Lambda错误执行，即：您必须调用 context.done（错误）; 或 context.fail（错误）; 表示RegExp实际触发。

The conclusion of these tests are that the "Lambda Error RegExp" is only executed against a Lambda error, i.e: you have to call context.done(error);or context.fail(error); for the RegExp to actually trigger.

现在，这个呈现一个问题，已经注意到，Lambda接受你的错误并将其粘贴在一个对象中并调用 toString（）关于你提供的任何东西：

Now, this presents a problem as, has already been noted, Lambda takes your error and sticks it in an object and calls toString() on whatever you supplied:

{ errorMessage: yourError.toString() }

如果你提供了一个错误对象，你就会得到这个：

If you supplied an error object you'll get this:

{ errorMessage: "[object Object]" }

根本不是很有帮助。

到目前为止我找到的唯一解决方法是致电

The only workaround I have found thus far is to call

context.fail(JSON.stringify(error));

然后在我的客户端执行：

and then in my client do:

var errorObject = JSON.parse(error.errorMessage);

它不是很优雅但它有效。
作为我的错误的一部分，我有一个名为代码的属性。它看起来像这样：

It's not very elegant but it works. As part of my error I have a property called "code". It could look something like this:

{ 
    code: "BadRequest", 
    message: "Invalid argument: parameter name" 
}

当我对此对象进行字符串化时，我得到：

When I stringify this object I get:

"{\"code\":\"BadRequest\",\"message\":\"Invalid argument: parameter name\"}"

Lambda会将此字符串粘贴在errorMessage属性中响应，我现在可以安全地在API网关响应映射中找到。*BadRequest。* 。

Lambda will stick this string in the errorMessage property of the response and I can now safely grep for .*"BadRequest".* in the API Gateway response mapping.

这是一个非常黑的，可以解决两个奇怪的Lambda和API网关怪癖：

It's very much a hack that works around two somewhat strange quirks of Lambda and API Gateway:

1. 为什么Lambda坚持包装错误而不是只是按原样给b $ b吧？


2. 为什么API Gateway不允许我们在
   Lambda结果中grep，只有错误？

我正准备与亚马逊就这两个相当奇怪的行为开启一个支持案例。

I am on my way to open a support case with Amazon regarding these two rather odd behaviours.

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