AWS Solutions Architect Professional 题目解析（5）

上周末因病歇了几天，今天终于缓过来了，来分享一道让我走了一些弯路，花了差不多1个小时找资料的题目。

The Solutions Architect manages a serverless application that consists of multiple API gateways, AWS Lambda functions, Amazon S3 buckets, and Amazon DynamoDB tables. Customers say that a few application components slow while loading dynamic images, and some are timing out with the "504 Gateway Timeout" error. While troubleshooting the scenario, the Solutions Architect confirms that DynamoDB monitoring metrics are at acceptable levels. Which of the following steps would be optimal for debugging these application issues? (Choose two.)

A. Parse HTTP logs in Amazon API Gateway for HTTP errors to determine the root cause of the errors.

B. Parse Amazon CloudWatch Logs to determine processing times for requested images at specified intervals.

C. Parse VPC Flow Logs to determine if there is packet loss between the Lambda function and S3.

D. Parse AWS X-Ray traces and analyze HTTP methods to determine the root cause of the HTTP errors.

E. Parse S3 access logs to determine if objects being accessed are from specific IP addresses to narrow the scope to geographic latency issues.

答案：BD

题目难度：中

题目解析：题干中明确提到“504 Gateway Timeout”错误。于是，我以此为关键字到AWS的网站上去搜索了一把，找到的文档涉及ELB，CloudFront等多个服务的504错误和解决方案，但就是没见到跟API Gateway有关的。

我又反复读了几遍题目和备选答案，确认504错误应该是跟API Gateway有关系。但是，为什么会找不到相关的文档呢？

根据之前备考的经验，我怀疑题目中的504错误会不会是一个干扰项？如果我跳出具体的错误代码和细节，着眼于整个API Gateway的性能监控，能不能找到正确的方向呢？

沿着这个思路，我又以API Gateway为关键词去AWS Developer Guide文档中寻找线索。果然找到一篇题目为“Tracing, Logging, and Monitoring an API Gateway API”的文档。

文档开篇第一句话就是“AWS X-Ray, AWS CloudTrail, and Amazon CloudWatch are tools that Amazon API Gateway developers can use to trace, log, and monitor API execution and management operations.”。

再回过头来对比备选答案，选项B和D自然应该是最符合要求。

参考：https://docs.aws.amazon.com/apigateway/latest/developerguide/monitoring_overview.html