为什么 API Gateway (Test) 不等待异步 lambda？

Question

我正在使用 Node.js (14.x) 在 AWS 上编写异步 lambda。此 lambda 由 API 网关调用（REST API、POST 方法、已启用 CORS）。

为了允许 API 网关调用异步 lambda，我在其集成请求中添加了以下 HTTP 标头：名称 = X-Amz-Invocation-Type 和映射自（值）= 'Event' as specified here。

当我运行测试时，我得到以下输出：

Execution log for request BLAH
Fri Mar 26 07:30:34 UTC 2021 : Starting execution for request: BLAH
Fri Mar 26 07:30:34 UTC 2021 : HTTP Method: POST, Resource Path: BLAH
Fri Mar 26 07:30:34 UTC 2021 : Method request path: {}
Fri Mar 26 07:30:34 UTC 2021 : Method request query string: {}
Fri Mar 26 07:30:34 UTC 2021 : Method request headers: {}
Fri Mar 26 07:30:34 UTC 2021 : Method request body before transformations: {
  "id": "BLAH",
  "recaptcha": "BLAH"
}
Fri Mar 26 07:30:34 UTC 2021 : Request validation succeeded for content type application/json
Fri Mar 26 07:30:34 UTC 2021 : Endpoint request URI: https://lambda.BLAH.amazonaws.com/2015-03-31/functions/arn:aws:lambda:BLAH:function:BLAH/invocations
Fri Mar 26 07:30:34 UTC 2021 : Endpoint request headers: {X-Amz-Date=BLAH, x-amzn-apigateway-api-id=BLAH, Accept=application/json, User-Agent=AmazonAPIGateway_BLAH, Host=lambda.BLAH.amazonaws.com, X-Amz-Content-Sha256=BLAH, X-Amzn-Trace-Id=Root=BLAH, x-amzn-lambda-integration-tag=BLAH, Authorization=*****BLAH*****, X-Amz-Source-Arn=arn:aws:execute-api:BLAH/test-invoke-stage/POST/BLAH, X-Amz-Invocation-Type=Event, X-Amz-Security-Token=BLAH [TRUNCATED]
Fri Mar 26 07:30:34 UTC 2021 : Endpoint request body after transformations: {
  "id": "BLAH",
  "recaptcha": "BLAH"
}
Fri Mar 26 07:30:34 UTC 2021 : Sending request to https://lambda.BLAH.amazonaws.com/2015-03-31/functions/arn:aws:lambda:BLAH:function:BLAH/invocations
Fri Mar 26 07:30:34 UTC 2021 : Received response. Status: 202, Integration latency: 34 ms
Fri Mar 26 07:30:34 UTC 2021 : Endpoint response headers: {Date=Fri, 26 Mar 2021 07:30:34 GMT, Content-Length=0, Connection=keep-alive, x-amzn-RequestId=BLAH, x-amzn-Remapped-Content-Length=0, X-Amzn-Trace-Id=root=BLAH;sampled=0}
Fri Mar 26 07:30:34 UTC 2021 : Endpoint response body before transformations: 
Fri Mar 26 07:30:34 UTC 2021 : Method response body after transformations: 
Fri Mar 26 07:30:34 UTC 2021 : Method response headers: {X-Amzn-Trace-Id=Root=BLAH;Sampled=0, Access-Control-Allow-Origin=*, Content-Type=application/json}
Fri Mar 26 07:30:34 UTC 2021 : Successfully completed execution

请注意，响应给出了Status: 202，并且没有响应正文。 无论我在 lambda 中放入什么代码，似乎都是这样。以下是我尝试过的几个基本示例：

// Load the AWS SDK for Node.js and set the region.
var AWS = require('aws-sdk');
AWS.config.update({region: 'BLAH'});

// Main function, responds to AWS API Gateway.
exports.handler = async function (event, context) {
    var response = {
        httpStatus : 200,
        message : "Success"
    };
    return JSON.stringify(response);
};

和

// Load the AWS SDK for Node.js and set the region.
var AWS = require('aws-sdk');
AWS.config.update({region: 'BLAH'});

// Main function, responds to AWS API Gateway.
exports.handler = async function (event, context) {
    var promise = new Promise(function(resolve, reject) {
        var response = {
            httpStatus : 200,
            message : "Success"
        };
        resolve(JSON.stringify(response));
    });
    return promise;
};

我确保部署了 API 和 Lambda。 如何获得非 202 状态（即让 API 网关等待异步 lambda）？

Answer 1

这是按预期工作的。 AWS docs on "Asynchronous invocation" 中的第二句话说：

当您异步调用函数时，您无需等待函数代码的响应。

如果您想要一个带有结果的响应，异步调用将不起作用。