AWS API网关总是返回502坏网关

Question

我在AWS中创建了一个简单的lambda函数，从DynamoDB返回列表。我还创建了API来触发lambda函数。当我在AWS控制台中进行测试时，该函数可以正常工作。但是当我在邮递员中测试这个功能时，我总是得到502坏网关下面的错误。({“消息”：“内部服务器错误”)}

以下是node.js中的函数：

const doc = require('dynamodb-doc');

const dynamo = new doc.DynamoDB();

/**
 * Provide an event that contains the following keys:
 *
 *   - operation: one of the operations in the switch statement below
 *   - tableName: required for operations that interact with DynamoDB
 *   - payload: a parameter to pass to the operation being performed
 */
exports.handler = async (event) => {

    const operation = event.operation;
    const payload = event.payload;

    if (event.tableName) {
        payload.TableName = event.tableName;
    }

    switch (operation) {
        case 'create':
            return await dynamo.putItem(payload).promise();
        case 'read':
            return await dynamo.getItem(payload).promise();
        case 'update':
            return await dynamo.updateItem(payload).promise();
        case 'delete':
            return await dynamo.deleteItem(payload).promise();
        case 'list':
            return await dynamo.scan(payload).promise();
        case 'echo':
            return payload;
        case 'ping':
            return 'pong';
        default:
            throw new Error(`Unrecognized operation "${operation}"`);
    }
};

下面是生成API网关端点的详细信息。

API endpoint: https://iabzqisam7.execute-api.us-east-1.amazonaws.com/test/moneyAppDynamoDBOperationsLambda
Authorization: NONE
Method: ANY
Resource path: /moneyAppDynamoDBOperationsLambda
Stage: test

下面是我如何尝试使用Postman测试API：

 Postman  URL(Get) : https://iabzqisam7.execute-api.us-east-1.amazonaws.com/test/moneyAppDynamoDBOperationsLambda

    Headers: Key: content-type, Value: application/json
    Body (raw) :
    {
        "operation": "list",
        "tableName": "Advertiser",
        "payload": {
            "TableName": "Advertiser"
        }
    }

它在AWS控制台中运行得非常好。

知道为什么我在从邮递员打API网关的时候一直收到502个坏网关错误吗？

Answer 1

502坏网关异常，通常用于从Lambda代理集成后端返回的不兼容输出，有时用于重负载导致的无序调用。

API getway输出不会告诉您问题与Lambda错误、API getway或策略问题有关。

API网关返回502，这意味着它不理解Lambda返回的输出，并给您{“message”：“内部服务器错误”} 502。

调试使用API getway上的启用日志记录

创建新的IAM角色，允许API将日志推送到CloudWatch。随函附上以下政策：

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Effect": "Allow",
            "Action": [
                "logs:CreateLogGroup",
                "logs:CreateLogStream",
                "logs:DescribeLogGroups",
                "logs:DescribeLogStreams",
                "logs:PutLogEvents",
                "logs:GetLogEvents",
                "logs:FilterLogEvents"
            ],
            "Resource": "*"
        }
    ]
}

信任策略：

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Sid": "",
      "Effect": "Allow",
      "Principal": {
        "Service": "apigateway.amazonaws.com"
      },
      "Action": "sts:AssumeRole"
    }
  ]
}

在API网关控制台->转到->添加API网关的ARN -CloudWatch日志记录角色->‘保存’

进入API的阶段。在“CloudWatch设置”下，选择“启用CloudWatch日志”。将“日志级别”设置为“信息”。选择“记录完整请求/响应数据”。

请检查日志和共享错误日志。

• How can I see AWS Gateway logs for external calls? 代理集成的Lambda函数的输出格式

如果函数输出是一种不同的格式或格式错误，API网关返回一个502坏网关错误响应。

• https://docs.aws.amazon.com/apigateway/latest/developerguide/set-up-lambda-proxy-integrations.html
• https://aws.amazon.com/premiumsupport/knowledge-center/malformed-502-api-gateway/。