amazon-web-services - 错误: Unexpected server response: 502 on trying to connect to a lambda function through Amazon API gateway Websocket API

Question

我有一个简单的Node.js 10.x Lambda函数，在Lambda function console上进行测试时可以正常工作:

exports.handler = async (event) => {
    var msg = 'connected';
    return { 
        statusCode: 200, 
        body: { msg: msg}
    };
};

我通过他们的 API Gateway console创建了 WebSocket API ，并通过 LAMBDA_PROXY集成将其集成到其中:



当我尝试使用 wscat连接到它时，出现错误:

wscat -c "wss://awesomeid1.execute-api.us-west-2.amazonaws.com/dev"
error: Unexpected server response: 502

我该如何解决？

额外的问题:我们如何找到Websocket API连接错误的日志？

无法解决问题的相关链接:

502 internal server error response from API gateway from lambda function

AWS - Using @connections websocket call back url to send response from back-end(one-way) - API Gateway websocket protocol

AWS API Gateway error response generates 502 "Bad Gateway"

Answer 1

我找到了this answer的根本原因。基本上，使用Lambda代理集成时的，Lambda函数响应body值的需要为string 。我们需要使用JSON.stringify()或类似的东西:

exports.handler = async (event) => {
 var msg = 'connected';
 return { 
 statusCode: 200, 
 body: JSON.stringify({ msg: msg}) /*required on lambda proxy integration*/
 };
};

在Output Format of a Lambda Function for Proxy Integration部分上研究文档:

In Lambda proxy integration, API Gateway requires the backend Lambda function to return output according to the following JSON format

    "isBase64Encoded": true|false,
    "statusCode": httpStatusCode,
    "headers": { "headerName": "headerValue", ... },
    "multiValueHeaders": { "headerName": ["headerValue", "headerValue2", ...], ... },
    "body": "..." } 

[...]

The output body is marshalled to the frontend as the method response payload [...]

If the function output is of a different format, API Gateway returns a 502 Bad Gateway error response.

回答红利问题:

在添加新的IAM角色 AmazonAPIGatewayPushToCloudWatchLogs 并在其摘要页面上获取其ARN之后，我们可以按照以下步骤操作:

Set up API Logging Using the API Gateway Console

并看到服务器上的日志消息更具描述性:
Execution failed due to configuration error: Malformed Lambda proxy response